dnv-rp-j203: geological storage of carbon dioxide

RECOMMENDED PRACTICE

DET NORSKE VERITAS AS

The electronic pdf version of this document found through http://www.dnv.com is the officially binding version

DNV-RP-J203

Geological Storage of Carbon Dioxide

APRIL 2012

This document has been amended since the main revision (April 2012), most recently in July 2013.

See “Changes” on page 3.

© Det Norske Veritas AS April 2012

Any comments may be sent by e-mail to [email protected]

This service document has been prepared based on available knowledge, technology and/or information at the time of issuance of this document, and is believed to reflect the best ofcontemporary technology. The use of this document by others than DNV is at the user's sole risk. DNV does not accept any liability or responsibility for loss or damages resulting fromany use of this document.

FOREWORD

DNV is a global provider of knowledge for managing risk. Today, safe and responsible business conduct is both a licenseto operate and a competitive advantage. Our core competence is to identify, assess, and advise on risk management. Fromour leading position in certification, classification, verification, and training, we develop and apply standards and bestpractices. This helps our customers safely and responsibly improve their business performance. DNV is an independentorganisation with dedicated risk professionals in more than 100 countries, with the purpose of safeguarding life, propertyand the environment.

DNV service documents consist of among others the following types of documents:

— Service Specifications. Procedural requirements.

— Standards. Technical requirements.

— Recommended Practices. Guidance.

The Standards and Recommended Practices are offered within the following areas:

A) Qualification, Quality and Safety Methodology

B) Materials Technology

C) Structures

D) Systems

E) Special Facilities

F) Pipelines and Risers

G) Asset Operation

H) Marine Operations

J) Cleaner Energy

O) Subsea Systems

U) Unconventional Oil & Gas


Amended July 2013 see note on front cover Recommended Practice DNV-RP-J203, April 2012

Changes –

CHANGES – CURRENT

General

This is a new document.

Amendment July 2013

— An editorial correction has been made in the first row of Table 5-1.



Contents –

CONTENTS

CHANGES – CURRENT .................................................................................................................................. 3

1. Preface..................................................................................................................................................... 5

2. Introduction............................................................................................................................................ 52.1 General......................................................................................................................................................52.2 Objective ...................................................................................................................................................52.3 Approach...................................................................................................................................................52.4 Scope.........................................................................................................................................................52.5 Users .........................................................................................................................................................62.6 Relationship to other codes.......................................................................................................................62.7 Structure of this document ........................................................................................................................7

3. Definitions and abbreviations ............................................................................................................... 83.1 Definitions.................................................................................................................................................83.2 Abbreviations..........................................................................................................................................123.3 Verbal Forms ..........................................................................................................................................12

4. Storage Site Screening and Appraisal................................................................................................ 134.1 Introduction.............................................................................................................................................134.2 Screening.................................................................................................................................................134.3 Appraisal ................................................................................................................................................17

5. Permitting ............................................................................................................................................. 265.1 Introduction.............................................................................................................................................265.2 Permit context and requirements (Step 1, Figure 5-1)............................................................................265.3 Risk performance targets (Step 2, Figure 5-1)........................................................................................275.4 Storage Permit application (Step 3, Figure 5-1) .....................................................................................275.5 Closure Permit application (alternative Step 3, Figure 5-1) ...................................................................325.6 Evaluate completeness (Step 4, Figure 5-1) ...........................................................................................345.7 Submit application (Step 5, Figure 5-1)..................................................................................................34

6. Risk management................................................................................................................................. 356.1 Introduction.............................................................................................................................................356.2 Risk management context .......................................................................................................................356.3 Risk Assessment .....................................................................................................................................376.4 Risk treatment .........................................................................................................................................396.5 Risk management review and documentation ........................................................................................40

7. Well qualification ................................................................................................................................. 417.1 Introduction.............................................................................................................................................417.2 Set requirements in qualification basis ...................................................................................................427.3 Risk assessment for well qualification....................................................................................................437.4 Plan well qualification & select qualification activities .........................................................................457.5 Evaluate likelihood of success ................................................................................................................467.6 Evaluate need for modifications .............................................................................................................477.7 Update qualification basis.......................................................................................................................477.8 Initial Well Qualification Report ............................................................................................................477.9 Execute well qualification activities .......................................................................................................477.10 Performance Assessment ........................................................................................................................487.11 Requirements met?..................................................................................................................................487.12 Final Well Qualification Report..............................................................................................................48

Appendix A. Subsurface Data ...................................................................................................................... 49

Appendix B. Generic failure modes for well integrity

under exposure to Carbon Dioxide............................................................................................................... 54



Sec.1 Preface –

1 Preface

The main objective of this Recommended Practice (RP) is to provide a systematic approach to the selection,qualification and management of geological storage sites for carbon dioxide (CO2). This RP specifies what, inDNV’s opinion, is the best industry practice for that purpose.

This RP may be used as a basis for verification and is considered applicable worldwide.

2 Introduction

2.1 General

There is growing consensus that global warming and climate change are the anthropogenic results ofgreenhouse gas emissions from the combustion of fossil fuels, such as natural gas, oil and coal. The world'spopulation is steadily growing, as are its energy needs. It is expected that a significant part of the world's futureneed for electrical energy and heat will come from burning of fossil fuels, implying increased CO2 emissionsto the atmosphere.

Carbon Capture and Storage (CCS) offers an opportunity to mitigate global warming and associated negativeimpacts by capturing and storing CO2 that would otherwise be emitted to the atmosphere. CCS refers to theprocess of capturing CO2 from large point sources, such as fossil fuel power plants, cement factories, oilrefineries, or iron and steel mills, and injecting and isolating the captured CO2 in deep geological formations.

For CCS to be effective the geological formations into which CO2 is injected must be carefully selected andqualified to ensure that they can provide long-term containment of injected CO2 streams.

2.2 Objective

This RP provides users with systematic procedures and performance requirements for assessing and verifyingthe suitability of storage sites and projects for environmentally safe, long-term geological storage of injectedCO2 streams. This includes assessment and verification of monitoring and risk management plans tailored tothe characteristics of each storage site.

2.3 Approach

This RP applies the principles of Technology Qualification given in DNV-RP-A203 to managing the technicalrisks related to CO2 geological storage. Technology Qualification is a methodology developed by DNV forreducing the risk and uncertainty associated with implementation of new technology. The following principlesshall control the qualification process:

— specifications and performance requirements shall be clearly defined, quantified and documented— a qualification plan shall be developed to evaluate fulfilment of the specified requirements— threats to the performance requirements shall be identified— tailored threat identification should be carried out for novel elements where the uncertainty is most

significant— the relevance of individual threats shall be determined based on their risk— risk assessments shall be executed and documented in a transparent and traceable way— risk assessments shall be used to evaluate the appropriateness of requirements and to guide decision making— the qualification process and the evaluation of fulfilment of performance requirements shall be

documented.

2.4 Scope

2.4.1 General

This RP defines performance requirements and procedures for the following:

— the selection and qualification of geological storage sites for long-term storage of CO2— the documentation of storage site characterization and storage site development plans as a basis for permit

applications/reviews— risk management throughout life cycle of CO2 geological storage projects, from initial screening and

storage site selection through to storage site closure and preparation for post-closure stewardship— monitoring and storage performance verification— well assessment and management planning— storage site closure and preparation for post-closure stewardship.

Where the term CO2 is used in the guideline, it assumes that carbon dioxide is pressurized; may or may notcontain water; exists either as a liquid, super critical fluid or a gas; and also includes carbon dioxide dissolvedin water contained in the injection zone.



Sec.2 Introduction –

2.4.2 Qualification requirements

The following qualification requirements are summarized in tables throughout the document:

— Table 4-1: Requirements to potential storage sites that should be included in the Screening Basis.— Table 4-3: Requirements to prospective storage sites that shall be included in the Appraisal Basis (in

addition those listed in Table 4-1).— Table 5-2: Requirements for storage site closure.— Table 5-3: Requirements for the Storage Development Plan.— Table 5-1: Requirements for the Monitoring Plan.

2.4.3 Exclusions

This RP does not include performance requirements or recommended procedures for:

— the selection and qualification of hydrocarbon fields for enhanced recovery by CO2 injection— the capture of CO2 and its transportation from source to storage site— management of surface facilities and well operations (injection wells, production wells, monitoring wells)— accounting of CO2 emissions avoided— CO2 injection and storage in un-mineable coal beds, basalt formations, shales, and salt caverns— underground storage in materials involving the use of any form of engineered containers.

2.4.4 Application

This RP may be applied as a basis for verification and risk-based decision making, including but not limited to:

— guidance and quality assurance of storage site planning and development— demonstration of compliance with industry best practice— implementation of regulations— independent assessment and verification— stakeholder communication.

The requirements in this RP shall be subordinate to local regulations.

2.5 Users

Users of this RP may typically be:

— an operator— a regulator— an independent verifier— an investor or other financial stakeholder.

2.6 Relationship to other codes

Generic qualification procedures for new technology are given in DNV-RP-A203. While these procedurescover a generic approach, the present document describes how these principles shall be applied to qualify andmanage CO2 geological storage sites.

Only the storage component of the CCS value chain from the injection zone up to and including the CO2injection well heads is addressed in this RP. Elements of the capture and (pipeline) transport components of theCCS chain are given in DNV-RP-J201 and DNV-RP-J202, respectively.

This RP incorporates and combines the guidance given in the following two documents:

— CO2QUALSTORE – Guideline for Selection and Qualification of Sites and Projects for CO2 GeologicalStorage of CO2 (2010).

— CO2WELLS – Guideline for the Risk Management of Existing Wells at CO2 Geological Storage Sites(2011).

These two guidelines were the final deliverables from joint industry projects whereas this RP has beendeveloped, and will be maintained, by DNV.



Sec.2 Introduction –

2.7 Structure of this document

Figure 2-1Life cycle diagram for a CO2 geological storage project showing decision gates (diamonds) and permits (stars). Thesections within this RP are shown underneath the relevant life cycle stages as grey bars.

This document is structured around the generic decision gate model for a CO2 storage site, as shown in Fig.2-1. The decision gate model covers the life cycle of a CO2 geological storage project. Decision gates 2, 4 and 8are designed to precede an operator’s application for an exploration permit, storage permit and transfer ofresponsibility permit, or their equivalents.

This RP contains the following sections:

— Section 4: Storage Site Screening and Appraisal— Section 5: Permitting— Section 6: Risk Management— Section 7: Well Qualification.

5 6 74 8

Screening Design Construct Operate Close

1 2 3

Initiate

Project

Select

Prospective Sites

Select

Storage Site

Storage Permit

applicationInitiate

Construction

Initiate CO2

Injection

Qualify for

Site ClosureDecommision

TOR

Screening & Appraisal

EP – Exploration Permit

SP – CO2 Storage Permit

TOR – Transfer of Responsibility

PermittingAppraisalEP SP

Permitting

Risk Management

Well Qualification

Permitting



Sec.3 Definitions and abbreviations –

3 Definitions and abbreviations

3.1 Definitions

Term Definition

Accounting and Reporting Plan

One component of a Storage Development Plan. It is a document that describes how an operator shall account for and report avoided emissions of CO2 for regulators and/or emissions trading schemes. The content and structure of the Accounting and Reporting plan is not described in this document because this is expected to be prescribed by regulations and/or requirements of an emissions trading scheme.

Acid gas Natural gas or gas mixture which contains significant amounts of hydrogen sulfide (H2S) and/or CO2.

Appraisal Communication Plan

A plan that describes how the operator intends to communicate with the relevant stakeholders that influenced the requirements in the Appraisal Basis

Appraisal Basis A document that defines the requirements to be fulfilled during the project Appraisal stage in order to be qualified to apply for a Storage Permit.

Appraisal Plan A document that describes the scope of each step in the Appraisal stage and the activities to be carried out.

Appraisal Risk Assessment Report

A report that documents the activities undertaken during the Appraisal stage risk assessment.

Appraisal stage The second project life cycle stage in a CO2 geological storage project.

Appraisal Report A report that documents the activities undertaken during the Appraisal stage, which storage sites are qualified to apply for a Storage Permit and the evidence for making this decision.

Biosphere Realm of living organisms in the atmosphere, on the ground, in the oceans and seas, in surface waters, and in the subsurface at depths above which water salinity is less than limits defined for groundwater. See also Groundwater.

Capacity Accumulated mass of CO2 that can be injected into injection zone(s) while maintaining storage integrity.

Capillary entry pressure The capillary pressure at which the non-wetting phase starts to displace the wetting phase, usually brine, contained in the largest pore throat within a water-wet formation.

Carbon dioxide (CO2) Non-polar chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom (O=C=O).

Cement plug Volume of cement slurry placed in a wellbore which, once in a solid state, shall function as a well barrier.

Characterization Report A report that documents the storage site characterization activities that have been carried out, which storage sites remain prospective and that the storage site characterization is sufficient to support the selection of a final storage site.

Closure see Storage site closure.

Closure Basis A document that defines the requirements to be fulfilled during the project Closure stage in order to be able to regard a storage site as qualified for Closure.

Closure Plan One component of a Storage Development Plan. It is a document that describes closure requirements for a given storage site and the qualification process that shall be used to demonstrate fulfillment of these requirements.

Closure Permit Written decision issued by a designated regulatory authority authorizing closure of a CO2 storage site.

Closure Qualification Statement

One component of a Storage Closure application. It is a document that includes a description of the Closure Basis, an Environmental Statement for storage site closure, a Storage Performance Forecast for storage site closure, a Monitoring Plan for storage site closure and an updated Closure Plan.

CO2 Carbon dioxide. As used in this RP it assumes that carbon dioxide is pressurized; may or may not contain water; exists either as a liquid, super critical fluid or a gas; and also includes carbon dioxide dissolved in water contained in the reservoir.

CO2 geological storage CO2 injection accompanied by storage of injected CO2 streams in a geological formation.

CO2 geological storage project

Component of a carbon capture and storage project that includes site screening, selection and appraisal, permitting, design and construction of site facilities, well drilling, operation of CO2 geological storage, storage site closure (including well and facilities abandonment), and post-closure. It also includes monitoring during all project phases.

CO2 injection Well operation injecting a CO2 stream into a designated injection zone.

CO2 plume Dispersing volume of CO2 stream not dissolved in resident formation fluids.

CO2 stream A flow of substances which consists of a sufficiently high fraction of CO2 and sufficiently low concentrations of other substances to meet specifications of streams permitted for long-term CO2 geological storage.




Communication Plan One component of a Storage Development Plan. It is a document that shall describe when and how the operator shall communicate with project stakeholders including providing information about environmental impact and risk treatment.

Consequence Outcome of an event affecting objectives

Consequence category A subject of concern for which risk is evaluated and managed, for example human health and safety, environmental protection and storage site performance.

Containment Prevention of leakage at rates or in total mass sufficient to cause adverse impact.

Corrective control Mitigative control intended to limit the scale and duration of unintended consequences, such as leakage or pressure build-up in unintended zones or above desired levels, and to restore the integrity of a storage site and/or the quality of economic or environmental receptors that have been affected by the CO2 geological storage project.

Dense phase conditions Conditions for which CO2 will be in a liquid or supercritical phase.

Economic receptor Subsurface domain or formation that is or has potential to be an economic resource, e.g., hydrocarbon reservoirs, coal seams, formations with high geothermal energy conversion potential, mineral resources, etc.

Elevated pressure Pressure sufficient to cause movement of formation fluids from the storage complex through a high permeable pathway into an economic or environmental receptor above the storage complex.

Environmental receptor Biosphere, surface area above storage site or other subsurface domain or formation designated for conservation purposes that may be polluted or negatively impacted by the CO2 geological storage project.

Environmental Statement One component of a Storage Development Plan. It is a document that documents the outcome of an Environmental Impact Assessment or an equivalent process.

Event Discrete occurrence or change of a particular set of circumstances over a short period of time.

Event-consequence scenario

Chain of circumstances upon which a consequence with negative impact on a risk category may arise as a result of the event.

Failure mechanism The physical, chemical or other process that may lead to, or has led to, a failure.

Failure mode Potential or observed manner of failure on a specified level of a well component or system of components.

Flowline A surface pipeline carrying an injection or production stream that connects the wellhead to a manifold or to injection or production facilities, such as a compressor.

Formation fluid Fluid or gas occupying pore-space in a geological formation.

Fracture A crack or surface of breakage within rock not related to foliation or cleavage in metamorphic rock along which there has been no movement.

Geological fault A displacement of rocks along a shear surface. The surface along which displacement occurs is called the fault plane (often a curved surface).

Geomechanical stability Prevention of adverse impact caused by induced seismicity, fracturing or earth deformation as a result of CO2 injection.

Geosphere The solid earth below the ground surface and bottom of rivers and water bodies on land, and below the sea bottom offshore.

Groundwater Water located beneath the ground surface and characterized by having low concentrations of dissolved salts and other total dissolved solids.

Impact hypothesis Concise statement of the expected consequences – both positive and negative – to the risk categories of the storage site contingent upon execution of the risk management plan.

Injection and Operating Plan

One component of a Storage Development Plan. It is a document that includes the final Well Engineering Concept and final Well Qualification Report for each well at a storage site and describes the following characterisitics; i) the expected injection forecast, ii) the expected variation in delivered well performance and iii) well operating procedures.

Injection zone A geologic formation, group of formations, or part of a formation into which CO2 is or will be injected for the purpose of long-term storage.

Injectivity (1) The possible CO2 injection rate that can be achieved through a specified well subject to (bottom-hole or other) injection pressure constraints.

Injectivity (2) The possible CO2 injection rate for a given storage site that can be achieved subject to reservoir pressure or other injection pressure constraints.

Leakage Measurable release of CO2 stream constituents or displaced formation fluid from a storage complex that detrimentally impacts an economic or environmental receptor as a result of project activity.

Leakage pathway Natural or engineered feature or combination of features through which CO2 stream constituents or formation fluids displaced by CO2 injection can potentially migrate outside of the storage complex. For example geological faults, wells, permeable horizons, outcrops and spill points.

Term Definition




Level of risk Magnitude of a risk or combination of risks, expressed in terms of the combination of consequences and their likelihood.

Likelihood Chance of something happening expressed either qualitatively or quantitatively and described using general terms or mathematically, such as a probability or a frequency over a given time period.

Life cycle of a storage site Time span from initial planning and execution of storage site screening to post-closure stewardship phase (see Storage site closure).

Long-term Minimum period of retention of injected CO2-streams in subsurface geological formations necessary for CO2 geological storage to be considered an effective and environmentally safe climate change mitigation option.

Mitigative control Risk control to prevent or reduce adverse effects of events.

Modelling Report A report that documents the activities undertaken during the modelling step of the Appraisal stage and the results obtained.

Monitoring Measurement and surveillance activities necessary for ensuring safe and reliable CO2 geological storage.

Monitoring Plan One component of a Storage Development Plan. It is a document that describes the monitoring objectives, targets, techniques and activities for a storage site.

Monitoring target A measurable physical property or characteristic at a given location that can provide an indicator of compliance or non-compliance with defined requirements for storage site performance.

Operator Natural or legal, private or public person, business organization(s) or government entity who operates and controls the CO2 geological storage operation or to whom decisive power over the storage operation has been delegated according to regulations.

Overburden Sedimentary succession (stratigraphic column) overlying a reference underground formation.

Plug and Abandon Action taken to ensure permanent isolation of fluids and pressures from exposed permeable zones along well trajectory by installation of well barriers, usually cement plugs.

Passive control Risk control naturally inherent in the CO2 geological storage site or in the engineered components associated with the system.

Performance margin Margin to non-compliance with performance requirements.

Performance requirement Requirement used to evaluate the success of a performance assessment.

Permeability Measure of the ability of a soil or rock to transmit fluids.

Porosity Ratio of the volume of void pore space in the rock relative to the bulk volume of the rock.

Preventive control Risk control to prevent or reduce the likelihood of an event.

Qualification A process of providing the evidence that a technology or CO2 storage site will function within specific limits with an acceptable level of confidence.

Regulator Relevant national, state or provincial authority and/or international regulatory body.

Risk Effect of uncertainty on objectives. Risk may be expressed in terms of a combination of a likelihood of occurrence of an event and the associated severity of potential consequences that may arise as a result of the event.

Risk analysis Process to comprehend the nature of risk and determine the level of risk.

Risk assessment Overall process of risk identification, risk analysis and risk evaluation.

Risk control Measure or inherent characteristic whose purpose is to reduce risk.

Risk evaluation Process of comparing the results of risk analysis with the evaluation risk criteria to determine whether the risk and/or its magnitude are/is acceptable or tolerable.

Risk evaluation criteria Terms of reference against which the significance of a risk is evaluated. Note that this definition is equivalent to the definition of ‘risk criteria’ in ISO 31000.

Risk identification Process of finding, recognizing and describing risks.

Risk Management Plan One component of a Storage Development Plan. It is a document that describes how risks to a storage site shall be managed in the Operate and Close stages of a project.

Risk owner Person or entity with the accountability and authority to manage the risk.

Risk performance target For a specified risk, the target level of risk to be achieved through implementation of a prescribed risk treatment.

Risk scenario Combination of a threat-event scenario and possible event-consequence scenarios.

Risk treatment Process to modify risk through implementation of risk controls.

Seal Relatively impermeable rock, commonly shale, anhydrite or salt that forms a barrier or seal above and around reservoir rock so that fluids cannot migrate beyond the reservoir. The permeability of a seal capable of retaining fluids through geologic time is typically in the range 10-6 to 10-8 Darcies.

Term Definition




Screening Basis A document that defines the requirements to be fulfilled during the project Screening stage in order to be able to regard a storage site as prospective and thereby qualified for appraisal.

Screening Plan A document that describes the scope of each step in the Screening stage and the activities to be carried out.

Screening stage The first project life cycle stage in a CO2 geological storage project.

Screening Report A report that documents the activities undertaken during the Screening stage presents the evidence for selecting prospective storage sites that qualify for appraisal.

Significant event Circumstance or set of circumstances with potential to have significant impact on a consequence category.

Significant risk Risk whose magnitude must be reduced through implementation of appropriate risk treatment to maintain alignment with project objectives.

Spill point Structurally lowest point in a structural trap that can retain buoyant fluids.

Stakeholder Individual, group of individuals, or organization whose interests are substantially affected by the project. Stakeholders can include employees, shareholders, community residents, suppliers, customers, non-governmental organizations, governments, regulators, labour unions, and other individuals or groups.

Storage complex Subsurface volume delineated by the operator and approved by the regulator for the purpose of environmentally safe long-term containment of injected CO2 streams.

Storage Development Plan A generic term used in this document to refer to the package of documentation that an operator shall submit to a regulator in order to apply for a Storage Permit. Comparable to a Plan for Development and Operations for hydrocarbon fields. DNV recognises that the name of this document and required content may vary depending on jurisdiction.

Storage integrity Ability of storage complex to provide long-term containment and geomechanical stability when CO2 geological storage operations are managed in accordance with the Injection and Operating Plan.

Storage Performance Forecast

One component of a Storage Development Plan. It is a document that provides a scenario-based storage performance forecast that demonstrates the suitability of the Injection and Operating Plan in meeting the storage site performance requirements defined in the Appraisal Basis.

Storage permit Written decision issued by a designated regulatory authority authorizing CO2 injection by an operator into a specified injection zone for the purpose of permanent containment within a defined CO2 geological storage complex, and which specifies the conditions under which CO2 injection and storage operations may take place.

Storage site Storage complex and the wells and surface facilities associated with the operation, monitoring and risk management of the storage site.

Storage site closure Milestone in the CO2 geological storage project after cessation of CO2 injection upon which operation changes from actively managing risks through cycles of modelling, monitoring and risk assessments, to a post-closure stewardship phase focusing on providing continued assurance that risks are maintained at an acceptable level.

Stratigraphic column Sedimentary succession of geological formations in region of interest for CO2 geological storage.

Technical Appraisal Plan A document that shall describe how storage site characterization and modelling activities will be performed for each prospective storage site in order to provide the technical basis for the storage site and well engineering concept selection.

Threat Element which alone or in combination has the intrinsic potential to give rise to risk.

Threat-event scenario Chain of circumstances upon which the threat may cause the event to occur.

Verification Confirmation by examination and provision of objective evidence that specified requirements have been fulfilled, usually a quality assurance process of determining compliance with a regulation, standard or specification.

Well barrier Envelope of one or several dependent components preventing fluids or gases from flowing unintentionally between geological formations or to the surface.

Well component Individual pieces of equipment which are joined together as part of well construction.

Well Engineering Concept A document that describes the well engineering solution for new and existing wells at concept level for a prospective storage site.

Well integrity The ability of a well to perform its required function effectively and efficiently whilst preventing uncontrolled release of formation fluids along the wellbore throughout the life of the well.

Well Qualification The process of providing the evidence that a given well will function within specific limits with an acceptable level of confidence.

Well Qualification Basis A document that defines the requirements to be fulfilled during the qualification of a given well, including a description of the current status of the well, the well performance requirements, the well specification and the critical parameters.

Term Definition




3.2 Abbreviations

3.3 Verbal Forms

For verification of compliance with this RP, the following definitions of the verbal forms, shall, should andmay are applied:

Well Qualification Report A report that documents the activities performed during Well Qualification, the fitness for purpose of a given well and the defined margins against specified failure modes or performance targets.

Wellbore The physical hole that makes up the well.

ALARP As Low as Reasonably Practicable

CCS Carbon Capture and Storage

CO2 Carbon Dioxide

HSE Health, Safety and Environment.

Shall: indicates a mandatory requirement to be followed for fulfilment or compliance with the present RP.

Should: indicates a recommendation that a certain course of action is preferred or particularly suitable.

May: indicates permission, or an opinion, which is permitted as a part of conformance with the RP.

Term Definition



Sec.4 Storage Site Screening and Appraisal –

4 Storage Site Screening and Appraisal

4.1 Introduction

This chapter describes the recommended procedure for identifying potential storage sites in a given region,screening those that are prospective and developing one or more to a level of maturity suitable for beginningthe process of applying for a Storage Permit at Milestone M3 in Figure 2-1.

4.2 Screening

4.2.1 General

The purpose of storage site screening is to evaluate the potential for CO2 geological storage in a given region.

The following steps represent a generic recommendation of screening activities applicable to any region. Thescope of the steps is expected to vary between regions depending on the quality and quantity of existing data.

The output from storage site screening should be a list of potential storage sites that fulfil the operator’srequirements laid down in the Screening Basis. The screening process shall be documented in a ScreeningReport.

4.2.2 Screening Basis

The purpose of the Screening Basis is to provide a common set of requirements against which all potentialstorage sites will be assessed at Milestone M2 in Figure 2-1.

The Screening Basis document should include a list of requirements that a storage site should fulfil in order tobe regarded as prospective and qualify for appraisal. These requirements should at least include those listed inTable 4-1.

The Screening Basis document should also describe the context in which the screening activity is taking place.The context may be described by the following:

— the locations of the current or planned sources of CO2— the mass rates and composition of the CO2 streams from these sources— the expected rates of supply and the lifetime of the CO2 sources— the natural environment such as meteorology, surface/marine environment, biosphere, hydrosphere and

geosphere in as far as it may interact with the storage complex or potential leaks from the complex— historical, existing or planned uses of the subsurface in the region, such as:

— groundwater extraction— oil or gas production— geothermal energy extraction— acid gas disposal— natural gas storage— waste disposal

— historical, existing or planned land use in the region for onshore storage sites, such as:

— population centres (taking into account demographic trends)

Table 4-1 Requirements to potential storage sites that should be included in the Screening Basis

1) A quantitative requirement for minimum total capacity (tonnes)

2) A quantitative requirement for minimum annual injectivity (tonnes/year)

3) A requirement for documented evidence of the following positive indicators of long-term containment:

a) depth: sufficient depth of injection zone to achieve CO2 dense phase conditions (> 300 kg/m3 at reservoir conditions)

b) seal: presence of laterally extensive seal above the injection zone to prevent flow communication with economic and/or environmental receptors

c) wells: confidence that well integrity can be established and maintained in existing wells that penetrate the primary seal and will be exposed to CO2 or pressure changes

d) geological faults:

i) sufficiently stable geological environment to give confidence that containment will not be jeopardized by natural tectonic activity

ii) absence of existing flow-paths along geological faults that penetrate the storage complex

4) A requirement for documented evidence of the following positive indicators of the potential to monitor and deploy risk treatment:

a) legal availability of the storage site over the expected life cycle

b) physical accessibility to the storage site over the expected life cycle




— industrial developments— agriculture— transport infrastructure such as roads and railways— industrial infrastructure such as pipelines and power lines

— protected and sensitive areas such as:

— nature reserves (on land or marine)— indigenous reserves— military areas— drinking water sources

— the social and cultural context around a storage site, including public perceptions of CO2 geological storageand related issues in the region

— the legal and regulatory environment for CO2 geological storage in the region— the expectations of the operator, regulators and stakeholders to the screening process.

4.2.3 Screening Plan

The purpose of the Screening Plan is to describe the scope of each screening step and the activities to be carriedout.

The planned activities should be appropriate for the type of data that will be used and the level of detail requiredfor comparison against the requirements set out in the Screening Basis.

The Screening Plan document should describe the following:

— the data that will be used for screening— where this data will be obtained— how this data will be used to identify potential storage sites— how storage capacity will be calculated— how existing wells will be identified and risk assessed— how other potential leakage risks will be identified and risk assessed— how potential conflicts with other sub-surface resources or land-use claims will be identified— how the location of potential storage sites will be evaluated with respect to the location of CO2 sources— which stakeholders will be involved or informed during the screening process— stakeholder’s needs for information and involvement, providing the rationale for the communication

strategy and for future engagement— how legal and physical accessibility to storage sites will be assessed.

4.2.4 Data Collection and Review

The purpose of this step is to collect and review data in order to identify potential storage sites.

This activity may primarily be based on data available from existing sources, but acquisition of new datathrough early-stage appraisal activities may be needed in data poor areas. An operator should consider thelikelihood of getting necessary public support for undertaking CO2 storage in a given region, which may entailpublic surveys and stakeholder interviews.

Data review should identify geological structures that demonstrate the potential to comply with therequirements in the Screening Basis and document these as potential storage sites.

Examples of the types of data that may be collected and the information that may be derived from each aregiven in Appendix A.

Guidance note:

For regions with a large number of possible storage sites, this step may require an iterative approach that may useindicative storage site screening requirements as a first step. Such requirements may be used to rank storage sitesaccording to suitability for CO2 storage. Geographical Information System tools and datasets may be utilized tofacilitate recording and visualization of such ranking parameters.

The main purpose of screening requirements is to enable compilation of aggregate ranking scores indicative of storagesite suitability to help accelerate and guide the screening process by rapidly identifying the most promising areas forCO2 geological storage. Screening requirements should not be interpreted as thresholds for elimination of prospectswith unfavorable characteristics. The suitability of a potential storage site will ultimately need to be demonstratedthrough detailed storage site-specific assessments. To this end, storage sites with certain unfavorable characteristicsmay in the end still prove to be suitable.

Furthermore, while generic screening requirements may be applied to assign indicative suitability scores, additionalrequirements may be added to reflect the purpose of the storage site, including potential social, cultural, technical oreconomic constraints. For further information about screening requirements see:

IEA Greenhouse Gas R&D Programme (IEA GHG). 2009. CCS Site Characterisation Criteria, Report No. 2009/10.Cheltenham. United Kingdom.

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4.2.5 Uncertainty Assessment

4.2.5.1 General

The purpose of this step is to assess the level of uncertainty related to each potential storage site that wasidentified in the preceding step.

The quality and quantity of the available evidence for and against meeting the requirements laid down in theScreening Basis should be assessed for each potential storage site.

Critical pieces of missing information that would reduce the uncertainty for a given storage site should also beidentified and recorded for use in developing an eventual Appraisal Plan.

4.2.5.2 Capacity

Initial estimates of storage capacity can be obtained using a number of different methods that span a range ofcomplexities. Three broad groups of capacity estimation methods are volumetric methods, analytical or semi-analytical methods, and numerical reservoir simulation methods. For these categories the uncertainty attachedto capacity estimates may be assessed by using the following approaches:

— for volumetric based capacity estimation methods the uncertainty may be reflected by providingconservative and optimistic estimates of the volumetric fraction of the pore-space that can be filled withCO2. For closed contour structures the capacity is usually not more than 1-2 percent of the accessible pore-volume due to limits on pressure build-up. (Note that this ratio may be significantly increased if thereservoir has been depleted by hydrocarbon production). Other factors, such as preferential flow paths andinternal flow barriers, may further reduce the capacity.

— for capacity estimation methods that include modelling of the CO2 plume movement and pressure build-upin an analytical or semi-analytical fashion it may be possible to do sensitivity analysis of the primaryuncertain parameters that describe the pore volume of the target storage formation and possible degree offilling with CO2

— if three-dimensional reservoir simulations are applied to estimate capacity, then the level of uncertaintymay be estimated by simulating a limited number of scenarios, including best-case and worst casescenarios.

The level of uncertainty will also be reflected by the complexity of the method used to estimate capacity andthe reliability and resolution of the data from which the storage capacity has been estimated.

4.2.5.3 Reservoir injectivity

Early estimates of reservoir injectivity may be based on permeability measurements or calculations fromregional well-logs or production/injectivity data of existing wells in the injection zone. The uncertainty inreservoir injectivity is often related to the availability of well-logs in the vicinity of the proposed storage site.

Other key uncertainty factors with regards to reservoir injectivity are the potential for compartments or flowbaffles in the target formation and the effect of near-well geochemical reactions that may limit the sustainedinjectivity of a given well. These factors are, however, generally difficult to assess at the screening stage unlessthe storage site has been subject to oil or gas development.

4.2.5.4 Containment

At the screening stage containment is typically assessed based on the formation type, depth, thickness, andlateral extent of the primary seal above the target storage formation, as well as the density, depth, age, dataavailability and drilling, construction and abandonment procedures for active and abandoned wells in theregion. Consideration should also be given to the potential for natural or induced seismic events to createleakage pathways.

Key containment uncertainties relate to the degree and certainty of knowledge about these parameters and thecontribution from the four different trapping mechanisms (structural, capillary, solubility, and mineraltrapping) during the life cycle of the storage site. To evaluate the significance of the uncertainties, theredundancies in the containment system (for example the presence of multiple geological seals and number ofindependent well barriers) should be taken into account.

Guidance note:

Assessment of injectivity is also partly a commercial consideration since lack of reservoir injectivity can often bemanaged by increasing the number of injection wells.

Depending on the availability of data, the assessment of the requirements defined in the Screening Basis may entailacquisition of data not readily available (e.g., through drilling and collecting logs from an appraisal well) anddedicated modelling efforts. The need for acquisition of additional data should balance the benefit of reducinguncertainty against the cost of the data acquisition. Similarly the need for and scope of modelling efforts at this stageshould reflect the need for sufficiently robust assessments of capacity, injectivity and containment characteristics tosupport the prioritization of storage sites for further characterization.





4.2.6 Risk Assessment

The purpose of this step is to develop an initial risk register for each potential storage site within the contextof the preceding uncertainty assessment.

The initial risk register should be used for comparison in the following selection step and should be suitable forindependent audit and verification.

See Sec.6.3 for a risk assessment method description tailored to potential storage sites.

See Sec.7.3 for specific considerations with respect to existing wells.

This step represents the first risk assessment for the storage sites being screened and the resulting risk registershould form the basis for documenting the history of successive risk assessments. An electronic risk databaseis recommended over a simple spreadsheet in order to keep track of changes over time and manage actions andresponsibilities related to individual risks or groups of risks.

The risk register should describe the methodologies and tools applied to assess and manage risks, define theconsequence categories and describe the risk evaluation criteria for each consequence category tuned to thescope and objectives of the project. The risk evaluation criteria can entail the use of qualitative or quantitativelikelihood and consequence classes.

For each identified risk, the initial risk register should contain the following information from the riskassessment:

— a description of the potential causes and consequences of the risk — the estimated likelihood and severity of potential consequences before risk treatment— preferred risk controls— the estimated likelihood and severity of potential consequences after preferred risk controls are

implemented together with an explanation of the basis for the risk evaluation— the names of the people assigned with responsibility to implement preferred risk controls— the risk owner.

Revisions to the risk register should be documented in a transparent and traceable way. This includesdocumenting the basis and rationale for revisions, the date that specific revisions were made, and by whom.The risk register should also track the effect of implemented risk treatment, also when the effect is inaccordance with prior assessments of its effectiveness.

4.2.7 Milestone M2: Screening Report and Selection of Prospective Storage Sites

The purpose of this step is to select prospective storage sites from a ranked list of potential sites and documentthe screening process in a Screening Report.

Each storage site should be evaluated against the requirements in the Screening Basis. The screening activitiesshould be evaluated against those described in the Screening Plan and the check-list in Table 4-2. The followingcomponents should be collated in a Screening Report, which should highlight uncertainties and constraints thatmight be put on injection at each storage site:

— Screening Basis document— Screening Plan document— data collection and review findings— uncertainty assessment findings— risk assessment findings— evaluation against the requirements in the Screening Basis.

If the evaluations are positive for a storage site then it should be regarded as prospective and thereby qualifiedfor storage site appraisal.

If more than one storage site is prospective, the operator should take into account the results of the precedinguncertainty and risk assessments in order to prioritise subsequent appraisal work.




4.3 Appraisal

4.3.1 General

The purpose of this stage is to appraise prospective storage sites in detail and develop a well engineeringconcept that provides the required capacity, injectivity and containment.

Appraisal should be carried out for a portfolio of prospective storage sites in order to minimise the risk of notdiscovering a suitable storage site in a given area.

The storage site appraisal process shall provide an operator with enough technical information to determinewhich storage sites remain prospective at Milestone M3 in Figure 2-1 and select the best candidate. Theappraisal process shall be documented in an Appraisal Report.

If successful, the appraisal process shall provide the information required to compile a robust Storage Permitapplication.

Table 4-2 Screening check-listL

egal,

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tory

, so

cial

an

d

com

mer

cial

1Is the regulatory process and the requirements for CO2 geological storage in the target region understood by the relevant competent personnel?

2Have all applicable legal and regulatory constraints been identified, e.g., surface/subsurface access and ownership, areas excluded from storage, trans-boundary issues and access for future field studies, such as seismic surveys?

3Have all social and cultural constraints that may impede the likelihood of project approval/acceptance been identified and assessed, including public perceptions of CO2 geological storage and related issues in the region?

4 Have all potential conflicts of use of the surface and subsurface at the target region been identified?

5Have the sources, volumes and compositions of the CO2 streams to be injected and stored been adequately defined?

6 Have opportunities for cost-effective transport from source to sink been adequately assessed?

Geo

log

y a

nd

En

vir

on

men

tal

7

Has the stratigraphy at each storage site been compiled and documented?Have all potential storage reservoirs, primary seals and formations that may represent a conflict of interest been identified? For example hydrocarbon or groundwater bearing formations.Have structural and isopach maps of injection and confining zones been examined? For example regional cross sections and tectonic maps.Has the regional hydrogeology been studied?

8Has sufficient data on the injection zone(s) been compiled and reviewed, including depth, thickness, reservoir dip, lithology, pressure, temperature, porosity, permeability, salinity, mineralogy, interstitial shale content and potential rock-fluid interactions?

9Has sufficient data on each confining zone been compiled and reviewed, including depth, thickness, areal extent, lithology, capillary pressure data, and other factors that may affect integrity of the confining zone(s)?

10Does the data reviewed on the confining zone(s) (for example fracture strength) provide adequate confidence in the ability to ensure containment of injected CO2 streams to enable the decision to invest in further storage site characterization?

11Are the contributions from the four trapping mechanisms adequately understood at this stage of the project?

12Has storage capacity and injectivity of each potential storage site been estimated and the level of uncertainty in these estimates been quantified?

13Have all existing wells within each of the delineated areas for the potential storage sites been identified and the corresponding well completion logs and well records been obtained?

14Has the industrial history of the potential storage sites been reviewed, e.g., mining, groundwater production, disposal of waste, natural and town gas storage, well abandonment history?

15 Have all environmental and economic receptors surrounding the potential storage site been identified?

16Has relevant environmental data required for screening been acquired and reviewed, e.g., maps or regional groundwater, surface water, sensitive terrestrial and marine ecosystems, and land use (for onshore storage sites)?

17Ability to monitor the storage site: has it been established that there are no obvious barriers to effective monitoring?

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k

18 Have all relevant consequence categories been defined?

19 Are the project specific risk evaluation criteria for the respective consequence categories appropriate?

20Does the risk register comprehensively document how risks have been assessed for each element of concern?

21Is the basis and rationale for the evaluation of identified risks documented in a sufficiently transparent way to support differentiation of potential storage sites based on legal, regulatory, technical, commercial, social and cultural factors?




The following steps represent a generic recommendation of appraisal activities applicable to any region. Thescope of the steps is expected to vary between regions depending on the quality and quantity of existing data.

4.3.2 Appraisal Basis

The purpose of the Appraisal Basis is to provide a common set of requirements against which all prospectivestorage sites will be assessed at Milestone M3.

The Appraisal Basis document shall include the requirements listed in Table 4-1 and Table 4-3 as a minimum:

The Appraisal Basis document should also describe the context in which the appraisal activity is taking place.The context may be described through any additional requirements to the appraisal process imposed by, forexample, the following:

— the Storage Permit— drilling and well related permits— pipeline and surface infrastructure permits— the operator’s internal management processes— other commercial stakeholders in the storage site — independent verification — operators of subsurface developments above or below the injection zone, or of nearby subsurface

developments that may experience pressure communication originating from the planned storage operation— emissions trading schemes in which the project wishes to participate— financial investors— local communities and landowners.

To ensure that the requirements imposed by any of the above are understood and properly accounted for in theappraisal process, the operator should consult with representatives from each group of stakeholders that isconsidered relevant for the Appraisal stage.

4.3.3 Appraisal Plan

4.3.3.1 General

The purpose of the Appraisal Plan is to describe the intended appraisal activities at each prospective storagesite, the scope of each of the following steps and the activities that the operator intends to carry out in each step.

The activities shall be appropriate for the type of data that will be used and the level of detail required forcomparison against the requirements set out in the Appraisal Basis. The Appraisal Plan shall include twocomponents:

— a Technical Appraisal Plan— an Appraisal Communication Plan.

4.3.3.2 Technical Appraisal Plan

This document shall describe how storage site characterization and modelling activities will be performed foreach prospective storage site in order to provide the technical basis for the storage site and well engineeringconcept selection.

The Technical Appraisal Plan shall take into account the knowledge gained during storage site screening andinclude:

— a description of additional data needs in order to demonstrate compliance with the requirements in theAppraisal Basis.

Table 4-3 Requirements to prospective storage sites that shall be included in the Appraisal Basis (in addition those listed in Table 4-1)

5) A requirement for a documented Well Engineering Concept that shall:

a) enable storage of required volumes of CO2

b) enable storage at required rates of injection

c) provide long-term containment along new and existing wellbores

6) A requirement for documented evidence that sufficient baseline data can be acquired prior to start of CO2 injection operations to enable differentiation of changes in environmental receptors attributable to CO2 injection from changes attributable to pre-injection background variation or to natural or other anthropogenic sources

7) A requirement for documented evidence that surface and subsurface conditions shall allow implementation of comprehensive and cost-effective monitoring capable of detecting possible deviations from planned operations sufficiently early to allow for timely implementation of risk treatment

8) A requirement for evidence that simulation models exist that have sufficient spatial and temporal resolution to provide a basis for:

a) risk management of the storage site during normal operations

b) closure of the storage site following demonstration of conformance with monitoring observations




— a description of how the additional data needs shall be met— a description of how modelling studies shall provide an understanding of CO2 trapping mechanisms and

their interaction and reliability (for example structural trapping, residual CO2 (capillary) trapping,solubility trapping and mineral trapping)

— a description of how the level of uncertainty attached to the requirements in the Appraisal Basis shall bemodelled and quantified through sensitivity studies or scenario analyses

— a description of how all relevant environmental receptors at each storage site shall be identified— a description of how the environmental impact limits of the receptors will be determined with respect to

pressure dispersion and potential ingress by CO2 , dissolved solids or other displaced gas or fluid resultingfrom the storage operations

— a description of how existing wells will be qualified, if present— a description of the baseline monitoring data that will be collected and how this data provides a basis for

assessing storage site performance against the requirements in the Appraisal Basis— a preliminary definition of the vertical and lateral boundaries of the storage complex and injection zone at

each prospective storage site.

Storage complex and injection zone definition

The purpose of defining the storage complex and injection zone in the Technical Appraisal Plan is to focus thesite characterization efforts, though it is recognized that these definitions may be modified in light of the sitecharacterization results.

Vertical boundaries shall be defined such that the storage complex includes, at least, the injection zone and theprimary seal. If economic or environmental receptors are present below the injection zone, then the storagecomplex shall also include a zone below the injection zone that separates the injection zone from thesereceptors.

Lateral boundaries shall be defined such that confidence can be established that the CO2 plume will becontained within the storage complex throughout the project life cycle.

Guidance note:

An operator shall determine if execution of the Technical Appraisal Plan shall require exploration type permits forconducting, for example, seismic data acquisition or drilling and well testing.


Appraisal Communication Plan

The Appraisal Communication Plan shall describe how the operator intends to communicate with the relevantstakeholders that influenced the requirements in the Appraisal Basis.

Executing the communication plan shall help an operator gain an understanding of any preferences theregulator may have for which storage site to select.

The Appraisal Communication Plan shall:

— demonstrate that the operator has the ability and ambition to manage the selected storage site in a safe andresponsible way and in compliance with regulations

— describe the operator’s understanding of CO2 storage opportunities and risks in the region based on thefindings from storage site screening

— describe the requirements that the operator has included in the Appraisal Basis.

The Appraisal Communication Plan may define different communication goals for different stakeholders. Forexample the last two bullet points above may only be relevant for the regulator.

Guidance note:

Stakeholder communication and consultation during storage site appraisal shall aim to provide interested parties withobjective, factual, relevant and understandable information about CCS in general and about the project in particular,including the nature and degree of understanding of known or perceived risks. In particular, stakeholdercommunication and consultation shall aim to ensure that stakeholder’s perceptions of risks and their values, attitudes,needs, assumptions, and concerns that may impact storage site and injection concept selection are identified, recorded,adequately understood and appropriately considered.


4.3.4 Characterization

The purpose of this step is to perform the appraisal activities detailed in the Appraisal Plan in order tocharacterize the storage sites with respect to the requirements in the Appraisal Basis.

This step represents the initial phase of storage site characterization, which shall be iteratively improvedthroughout the life cycle of a storage site in order to support proper and continuous risk management. Unlikethe Data Collection and Review step during screening, this step may involve the acquisition and analysis ofnew data in order to determine the relevant physical properties of a given storage site.




Examples of the types of data that may be acquired and the information that may be derived from each are givenin Appendix A.

The operator shall produce a storage site Characterization Report that documents the following:

— the storage site characterization activities that have been carried out, a description of the data that has beenselected and of its quality, and the operator’s conclusions from this work

— that storage site characterization has been conducted in accordance with the principles listed in theintroduction to this section

— which storage sites remain prospective and why others may no longer be considered— the resources (personnel and tools) applied to perform the storage site characterization activities, including

the expertise of the personnel involved— the objective and nature of any consultation process with regulators or external stakeholders — any natural or industrial analogues that have been used as references to underpin the suitability of a

prospective storage site, including any differences in the analogy that may lead to misinterpretation of theanalysis

— the storage site characterization is sufficient to support the storage site selection decision at Milestone M3in Figure 2-1.

A synopsis of the Characterization Report should be made available to external stakeholders.

During the life cycle of a storage site the Characterization Report shall be updated as new data becomesavailable and shall be reviewed for completeness and accuracy prior to or during successive risk assessments.

4.3.5 Modelling

4.3.5.1 General

The purpose of this step is to predict the future performance of a given storage site through numericalmodelling that shall simulate as closely as possible the physical processes relevant to CO2 storage.

Storage site modelling shall:

— be appropriate and relevant to the requirements in the Appraisal Basis— provide information that supports risk analysis— be fit for purpose in order to predict hydrodynamic, geochemical, thermal and geomechanical effects of the

CO2 injection and storage operations.

This step shall include the following activities:

— construction of a digital three-dimensional geological model (or a set of such models) for each prospectivestorage site

— flow modelling using a set of digital three-dimensional numerical simulation models that are consistent withthe geological model(s) and suited to evaluate possible CO2 flow scenarios, effects of trappingmechanisms, the pressure and temperature response over time, and the effectiveness of risk treatmentoptions

— geochemical modelling of potential geochemical effects on injection zone (capacity and injectivity),primary seal (containment), and wells (well integrity and need for risk treatment)

— geomechanical modelling of pressure- or temperature-induced stress changes that can impact the integrityof the primary seal or wells, the magnitude of ground surface deformation, and the potential frequency andmagnitude of any induced seismicity

— compilation of a storage site Modelling Report that includes a description of how the coupling betweenmodels is handled. This description should address coupled flow and geomechanical effects on pressureand temperature behaviour and geochemical alteration of porosity and permeability that may impact flowand injectivity.

4.3.5.2 Geological model

The geological model(s) shall include a digital, three dimensional description of the following characteristics:

— overburden stratigraphy and hydrogeology including pressures and fluid compositions— areal and vertical limits of all formations within storage complex, including, if applicable, the hydraulic

connected pore space within which the injection zone is located and pressure communication can bemeasured

— existing wells that penetrate the storage complex— economic or environmental receptors above and below storage complex— structure of the physical trap (geometry of interface between the injection zone and the primary seal)— geomechanical and geochemical properties of the injection zone and primary seal— net porosity and permeability of all permeable geological formations within the storage complex— geological faults or structural features in the storage complex that may represent a risk to long-term

containment.




The geological model should have an appropriate spatial resolution to provide a basis for creating flow,geochemical and geomechanical simulation models suited to capture the relevant physical processes and meettheir intents as outlined in Sections 4.3.5.3, 4.3.5.4, and 4.3.5.5 below.

Uncertainties associated with geological models shall be assessed. Focus shall be put on assessing uncertaintyrelated to features and parameters that have an impact on the requirements in the Appraisal Basis. Whenassessing the uncertainty span, the operator shall identify and evaluate best-case and worst-case scenarios. Theoperator shall also state what efforts will be made during eventual operation of a storage site to reduce theuncertainty in the geological model further by calibrating parameters with observations.

4.3.5.3 Flow modelling

Flow modelling shall provide quantitative and auditable predictions of the following:

— subsurface movement, extent and fate (trapping mechanism) of injected CO2 streams— subsurface movement and fate of formation fluids that will be displaced by CO2 injection— pressure build-up as a result of the CO2 injection and storage operation over time— evolution of temperature distribution in injection zone over time— effectiveness of secondary structural trapping and capillary and dissolution trapping— effectiveness of risk treatment options— parameter sensitivities (influence of parameter perturbations on predictions)— detection thresholds for monitoring measurements to enable timely implementation of risk treatment.

Flow modelling shall also provide a basis for the following:

— calibration of the geological model and CO2 flow parameters against observations (for example frominjection tests)

— design and evaluation of well engineering concepts (for example the number and type of wells, wellspacing, etc.)

— design and layout of monitoring and performance requirements for monitoring technologies (sensitivitiesand spatial and temporal resolution and coverage).

Multiple numerical flow simulations shall be performed based on different geo-statistical representations of thegeology in order to allow estimation of variability of the key output parameters. The spatial and temporalresolution of the simulation models shall be designed to reflect the reliability of the data, and to capture theflow processes at spatial and temporal scales relevant for:

— demonstrating compliance with the requirements in the Appraisal Basis— supporting risk analysis activities— demonstrating the permanence of storage.

Guidance note:

It could give a misleading impression of the predictive ability of the model to perform high-resolution simulations ifthere is substantial uncertainty in the geological description. The preferred resolution will, however, depend on thecapabilities of simulators available, and also on the resolution of the geological model.

A variety of simulators can be employed for numerical simulation of CO2 geological storage. In general, simulationresults shall be reproducible. However, different simulators may produce different results, depending on the physicalmodel (e.g., two-phase flow model or compositional flow model) and the numerical algorithms that are used in thesimulations. Thus, in order to allow verification of simulation results, the operator shall be ready to specify whichsimulator has been employed and make all assumptions, variables and input data available.


4.3.5.4 Geochemical modelling

The main objective of geochemical modelling for CO2 geological storage is to enhance the understanding ofpotential geochemical effects on storage capacity, injectivity and containment. To this end, geochemicalmodels shall be built to provide insights into the chemical reactivity of the following components of the storagesite:

— the injection zone (for evaluation of potential effects on capacity and injectivity)— primary seal (for evaluation of potential effects on containment)— wells that may experience contact with CO2 or CO2-charged formation fluids (to evaluate the potential for

degradation of well integrity and the need for associated risk treatment).— The geochemical modelling shall be performed for in-situ pressure and temperature conditions and account

for pressure and temperature changes predicted from flow modelling.

Guidance note:

The composition of the CO2 stream to be injected shall be defined by the operator prior to modelling geochemicalreactions.





Chemical reactivity of the injection zone

Geochemical modelling of the injection zone shall be carried out and may assume that flow is transportdominated and provide data related to:

— the initial geochemical characteristics of the injection zone at in-situ pressure and temperature— effect of geochemical interactions (dehydration, dissolution and precipitation reactions) with the CO2

stream on storage capacity and injectivity— change in formation fluid composition and phase behavior.

Chemical reactivity of the primary seal

Geochemical modelling of the primary seal shall be carried out and may assume diffusion dominated transportin the matrix and flow dominated transport along discontinuities. The geochemical modelling of the primaryseal may provide information related to:

— the initial geochemical characteristics of the primary seal at in-situ pressure and temperature— potential geochemical reactions (and extent of chemical reactivity) between the injected CO2 stream or a

CO2 charged formation fluid and the rocks and minerals in the primary seal— the significance of geochemical reactions on the capacity of the primary seal to ensure long-term

containment.

Chemical reactivity of materials in wells

Analysis and geochemical modelling shall be performed for wells that may be exposed to CO2-saturated brineor water-saturated CO2 to assess the potential impact of geochemical reactions on well material integrity. Wellsfound prone to develop defects that present a significant risk to well integrity shall be studied further todetermine the need for priority monitoring and risk treatment. The process of assessing risk contributions fromwells and identifying appropriate risk treatment is further described in Sec.7.

4.3.5.5 Geomechanical modelling

The operator shall carry out geomechanical modelling to determine the potential for the following effects at agiven storage site:

— pressure- or temperature-induced stress changes to impact the integrity of the primary seal and thesignificance of any potential geomechanical effects relative to long-term containment (for exampletemperature induced stress changes around the injection wellbore)

— ground surface deformation (e.g., heave) and potential for induced seismicity as a result of CO2 injectionand storage operations and the respective significance relative to geomechanical stability.

In areas that have been subject to previous subsurface developments (oil and gas production, natural gasstorage, geothermal energy conversion, etc.) that may have induced stress effects on the storage complex, thegeomechanical modelling must also address historical pressure- and temperature induced stress changes as wellas changes predicted for the CO2 injection operations.

The geomechanical earth model to be used shall include, at least, a simplified representation of the overburdenand a more detailed representation of the storage complex.

The geometry of the geomechanical earth model shall be based on the spatial distribution of strata asrepresented in the project’s geological model (see Sec.4.3.5.2).

The strata in the model shall be populated with the mechanical properties and in-situ stresses that shall havebeen determined during the Site Characterization step.

4.3.5.6 Modelling Report

This report shall document the results of the modelling step and provide relevant input to the risk assessmentand Well Engineering Concept.

4.3.6 Risk Assessment

The purpose of this step is to assess the risks associated with each prospective storage site with respect to therequirements in the Appraisal Basis and in light of the Site Characterization and modelling results.

The findings of this risk assessment shall be documented in an Appraisal Risk Assessment Report and recordedin the project risk register that was recommended to be established during Storage Site Screening (Sec.1.5).These findings shall be used to support decisions about the completeness of the Appraisal stage and thequalification of prospective storage sites for Storage Permit application.

See Sec.6.3 for a risk assessment method description tailored to potential storage sites.

See Sec.7.3 for specific considerations with respect to existing wells.

The risk assessment criteria shall be consistent with the requirements in the Appraisal Basis such thatacceptability or tolerability of all risks indicates compliance with these requirements.




4.3.7 Appraisal Review

The purpose of this step is to review the completeness of the Appraisal process and determine if thecharacteristics of each storage site are adequately understood to support the qualification of one or morestorage sites for Storage Permit application. The findings shall be documented in an Appraisal reviewdocument.

The operator shall assess if the level of understanding of each prospective storage site is sufficient to enable acomprehensive evaluation of compliance with the Appraisal Basis requirements, and if so, carry out thisevaluation. These actions may lead to one of the following outcomes, which shall be documented in theAppraisal review document:

— if the operator concludes that there is insufficient understanding of a given storage site, then furthercharacterization work, modelling and risk assessment shall be carried out until a sufficient level ofunderstanding is reached. The Appraisal Basis and Plan shall also be reviewed to determine if they areappropriately defined and have been adequately executed for the storage site(s) in question

— if the operator concludes that there is sufficient understanding of a given storage site, but the evaluationagainst the Appraisal Basis requirements is negative, then the storage site in question shall not qualify toapply for a Storage Permit

— if the operator concludes that there is sufficient understanding of a given storage site and the evaluationagainst the Appraisal Basis requirements is positive, then the storage site in question shall qualify to applyfor a Storage Permit.

If more than one prospective storage site qualifies for a Storage Permit application, then the operator may rankthese storage sites based on the findings of the preceding risk assessment. Such a ranking shall:

— include consideration of legal and regulatory compliance, cost, schedule, reputation, system performanceand public support even if these factors are not defined as consequence categories

— favour storage sites with natural inherent storage integrity higher than storage sites that require a largerdegree of engineering work to provide storage integrity

— use a consistent set of risk evaluation criteria. For example, the performance in terms of cost should takeinto account both anticipated baseline costs (pipeline costs, drilling and construction costs, monitoring,land access, etc.) and additional costs stemming from potential consequences of identified risks.

Ranking criteria shall be documented and the results may be summarized in a tabular format such as that shownin Table 4-4.

Documenting the relative rank of sites in this manner is not necessarily suited for identifying a preferred storagesite, but may help detect higher risk storage sites. Tabulating relative ranks as illustrated in Table 4-4 may alsoprovide a good basis for discussing with the regulator and key stakeholders the rationale for selection of apreferred storage site among a list of prospective ones that satisfy the selection requirements.

If one or more prospective storage sites are found to have significantly higher risks than others, then an operatormay decide to exclude these from the qualification process before studying potential well engineering concepts.

4.3.8 Well Engineering Concept

The purpose of this step is to identify the most appropriate well engineering solution for new and existing wellsat each prospective storage site at a conceptual design level.

An operator shall document a Well Engineering Concept that includes a description of the following:

— the location and type of new wells required (for example; injectors, producers, monitoring wells)— the location and type of existing wells to be re-used— the location of abandoned wells — sub-surface trajectories— conceptual design of completions— approximate flow rates and total volumes for each injector— surface flow line geometry— pressure envelopes for each well.

For existing wells the operator shall:

Table 4-4 Example ranking of prospective storage sites based on risk assessment findings during the Appraisal stage.

Consequence categories Site 1 Site 2 Site 3 Site 4

HSE 1 4 2 3

Cost 3 2 1 4

Schedule 4 1 2 3

Storage Performance 1 4 3 2




— specify which wells penetrate the storage complex— specify which wells provide part of an identified leakage pathway— specify which wells are predicted by reservoir modelling to be exposed to elevated pressure and the

pressure ranges— specify which wells have the highest potential to leak — specify the maximum CO2 volumes at risk of leakage from each such well— specify which wells fall into the following categories:

— active or suspended wells that do not require conversion for continued use— active or suspended wells that do require conversion for continued use— active or suspended wells to be plugged and abandoned prior to CO2 injection— wells previously plugged and abandoned

— provide an Initial Well Qualification Report for each well (see Sec.7.8).

In addition to down-hole considerations, the operator shall also describe the following:

— surface accessibility to well locations and corresponding required pipeline infrastructure— scenario-based predictions of CO2 plume and pressure distribution during the life cycle of a given storage

site for a given well engineering concept — cost predictions for the implementation and operation of a given well engineering concept— cost predictions for construction and operation of required flowline infrastructure.

The last two bullet points above shall be considered when evaluating the economic feasibility of a storage siteand well engineering concept. The preceding bullet points shall be considered when evaluating the technicalfeasibility.

If a technically and economically feasible well engineering concept cannot be identified for a given storage site,then the storage site in question shall not qualify to apply for a Storage Permit.

4.3.9 Monitoring and Risk Management Planning

The purpose of this step is to determine if appropriate monitoring and risk management can be carried out ata given storage site and maintained during the project life cycle.

Preliminary Monitoring and Risk Management Plans shall be developed for each prospective storage site forwhich one or more technically and economically feasible well engineering concepts have been identified.

A preliminary Risk Management Plan shall:

— be designed to manage the risks identified and assessed in the preceding Risk Assessment step (Sec.2.5)— include a preliminary risk treatment plan that shall describe how each identified risk can be controlled and

maintained at acceptable levels — describe monitoring and modelling activities required to support risk management, including timely

implementation of risk treatment.

A preliminary Monitoring Plan shall:

— describe the purpose of monitoring during each project phase— describe monitoring targets and technology performance requirements for each monitoring target

(sensitivity and spatial and temporal resolution and coverage)— include the design (technologies and procedures), objectives (monitoring targets and associated technology

sensitivities) and layout (spatial and temporal resolution and coverage) of activities in a tentative base casemonitoring plan

— include the design, objectives and layout of a contingency monitoring plan designed to deal with situationsoutside the envelope of expected system performance

— comply with the requirements for a Monitoring Plan described in Sec.5.4.7.

If the preliminary monitoring and risk management plans cannot provide confidence that all selectionrequirements shall be met and maintained for a given storage site, then the storage site in question shall notqualify to apply for a Storage Permit.

4.3.10 Milestone M3: Appraisal Report and Storage Site Selection

The purpose of this step is to evaluate which storage sites are qualified to apply for a Storage Permit and toselect one or more for further development. The appraisal process shall be documented in an Appraisal Report.

Storage sites and associated well engineering concepts that remain prospective shall be evaluated against therequirements in the Appraisal Basis. In addition the appraisal activities should be evaluated against thosedescribed in the Appraisal Plan. This evaluation process shall be documented in an auditable and transparentmanner by collating the following components in an Appraisal Report:

— Appraisal Basis document




— Appraisal Plan document— Characterization Report— Modelling Report— Appraisal Risk Assessment Report— Appraisal review document— Well Engineering Concept document— Preliminary Risk Management Plan— Preliminary Monitoring Plan— Evaluation against the Appraisal Basis and Appraisal Plan.

If the evaluation is positive then the storage site in question shall be regarded as qualified to apply for a StoragePermit.

If more than one storage site is qualified to apply for a Storage Permit, the operator may select one or more forfurther development. This selection process shall take into account the results of the preceding evaluation andthe operator shall document the selection criteria used, the conclusions reached and the evidence that supportsthose conclusions.

Prior to selection the operator shall provide the relevant regulator with an opportunity to comment on theselection criteria to be used.



Sec.5 Permitting –

5 Permitting

5.1 Introduction

This chapter describes a procedure for developing CO2 storage and closure permit applications. The termstorage permit is used generically in this chapter to cover the following:

— a new storage permit— the renewal of an existing storage permit— the transfer from one type of permit to another type (for example from enhanced oil production by CO2

injection to CO2 storage)— the registration of a project in a regulated scheme that requires reporting of mass of CO2 emissions avoided.

This procedure addresses a number of common requirements that shall typically be met by an operator and anumber of generic documents that may vary in scope or name between jurisdictions.

Guidance note:

Exploration Permits are not described in this RP (for example to conduct seismic data acquisition or drilling and welltesting). This is due to variations in requirements between jurisdictions and the similarity to established practice inhydrocarbon exploration.


The operator shall carry out steps 1, 2, 3 and 5 from Figure 5-1 when applying for a CO2 storage or closurepermit. Step 4 should be carried out by the regulator or an entity acting on behalf of the regulator.

Figure 5-1Procedure for developing CO2 storage and closure permit applications

5.2 Permit context and requirements (Step 1, Figure 5-1)

The operator shall describe the context and requirements, as defined below, in a permitting plan that alsodescribes how the operator intends to fulfil these requirements.

The context of the permit application shall be defined by documenting all of the following:

— the type of permit or application:

— a new storage permit— the renewal of an existing storage permit— the transfer from one type of permit to another type (for example from enhanced oil production to CO2

storage)— the registration of a project in an regulated scheme that requires reporting of mass of CO2 emissions

avoided— a closure permit.

— the status of storage site characterization— the operational history of the site and any previous permits— the Risk Management context (see Sec.6.2)— the expectations from regulators and stakeholders to the permit application process.

Permit application requirements shall be defined by documenting all of the following:

— relevant regulatory requirements— relevant requirements for reporting of mass of CO2 emissions avoided— requirements imposed by the operator.

If the objective is to transfer from one type of permit to another type of permit, then the rationale for the needor desire to change the regulatory status of the project shall be explained, and the differences in the respectiveregulatory frameworks shall be highlighted.

Step 1

Document

permit context

and requirements

Step 2

Define risk

performance targets

with regulator

Step 3

Develop or update

storage or closure

permit application

Step 4

Verify

completeness

Step 5

Submit

applicationYes

No




5.3 Risk performance targets (Step 2, Figure 5-1)

The operator shall specify acceptable risk performance targets for all significant risks (see Sec.6.4).

The specification of a risk performance target shall include:

— the target level of risk— the risk treatment and/or inherent characteristics of a storage site that shall reduce and maintain the risk at

or below this level— the expected and low-end likelihood that the specified risk treatment will be effective in meeting the target

level of risk— the rationale and analysis behind the risk evaluation

Risk performance targets shall be relevant to the permit context and requirements described in the previousstep. Targets for storage operations shall be updated for storage site closure (see Table 5-2).

The following three stage process should be followed in order to reach agreement between the operator and theregulator(s) about acceptable risk performance targets. Further iterations of this process may be required ifagreement is not forthcoming.

— operator proposes risk performance targets for a given storage site and well engineering concept— operator documents additional or alternative risk treatment options that have not been selected and the

rationale for this decision— operator and regulator discuss if target risk level is acceptable and if the prescribed risk treatment plan is

sufficiently robust with respect to targeted levels of risk. This may include consideration of the cost-effectiveness and practicability of alternative risk treatment options relative to the proposed risk treatmentoption.

Guidance note:

Quantitative risk assessments use quantitative criteria reflecting the likelihood of occurrence times the severity ofconsequence (e.g., in terms of deaths per year) to determine the acceptability of risks. Such risk assessments requiresufficient relevant statistics or empirical data to enable a quantification of likelihood and consequence, whichgenerally will not be available for CO2 storage sites since each site will have its unique characteristics. The term “riskperformance target” should therefore be interpreted as a risk acceptance criterion in a qualitative sense.

For instance, the likelihood of loss of containment cannot generally be quantified based on available statistics orempirical data, but can nevertheless be assessed and evaluated based on a careful examination of the geologicalcharacteristics, the outputs from tailored modelling activities, and the way the site will be managed to control reservoirpressure and CO2 plume migration. However, this evaluation will inevitably be associated with a certain degree ofuncertainty, as our knowledge of the subsurface is imperfect. Thus, to address this uncertainty and provide assurancethat the risk of loss of containment is sufficiently low, a site-specific risk treatment plan that accounts for allreasonably likely eventualities must be developed, and its effectiveness assessed.

For this example, the risk treatment would typically entail the use of monitoring to provide early-warning signs, andimplementation of appropriate responses to avoid loss of containment. Hence, the likelihood of loss of containmentwould be the likelihood that all natural (e.g., geological seals) and engineered (detection plus response) risk controlsfail.

Similarly, risk treatment plans should address ways to prevent adverse consequences if loss of containment occurs,and to enable prediction of the severity of the consequences. Hence, while it may not be possible to put a number onthe initial risk of loss of containment, it is possible to qualitatively evaluate the effectiveness of a risk treatment planand use this evaluation to provide a high level of assurance that a risk performance target will be met.


5.4 Storage Permit application (Step 3, Figure 5-1)

5.4.1 General

For Closure Permit application see Sec.5.5.

The application for a new Storage Permit should take the form of a Storage Development Plan, comparable toa Plan for Development and Operations for hydrocarbon fields. The term Storage Development Plan is used ina generic sense and DNV recognises that the name of this document and required content may vary dependingon jurisdiction. The recommendations given below are designed to fulfil all potential requirements.

The application for renewal of a storage permit, transfer of usage of a storage site or registration in a regulatedscheme that requires reporting of mass of CO2 emissions avoided, is expected to have a smaller scope than theapplication for a new storage permit. For these cases the operator shall identify the relevant parts of this sectionand use them as required.

A Storage Development Plan should include the following components:

1) a storage site Characterization Report

2) an Injection and Operating Plan




3) an Environmental Statement

4) a Storage Performance Forecast

5) a Risk Management Plan

6) a Monitoring Plan

7) a Communication Plan

8) a storage site Closure Plan

9) an Accounting and Reporting Plan.

These components are described in the following sections.

Guidance note:

The Storage Development Plan can be a compilation of a set of documents that together contain the informationoutlined in the subsections below, i.e., it is not required to be a single stand-alone document. In fact, some parts of theStorage Development Plan may need to be submitted separately (e.g., the Environmental Statement), and some partswill be frequently updated throughout the project, while others will typically be largely unchanged. This suggests thatthe “Storage Development Plan” should be loosely interpreted as a compilation of various reports and plans thatcombined provide the necessary technical information necessary for evaluating the eligibility of a project to achievea Storage Permit.

The content and structure of the Accounting and Reporting plan is not described because this is expected to beprescribed by regulations and/or requirements of an emissions trading scheme.


5.4.2 Characterization Report

See Sec.4.3.4.

5.4.3 Injection and Operating Plan

The Injection and Operating Plan shall be designed to meet the storage site performance requirements definedin the Appraisal Basis (Sec.4.3.2). The plan shall include a final version of the Well Engineering Concept (seeSec.4.3.8) and a Final Well Qualification Report for each existing well that is relevant to the storage site (seeSec.7.12).

The Injection and Operating Plan shall also describe:

— expected injection forecast including variability in rate — the expected variation in delivered well performance— well operating procedures, including HSE procedures and contingency plans for shut-ins and well failures.

5.4.4 Environmental Statement

An Environmental Statement shall represent the outcome of an Environmental Impact Assessment or anequivalent process required by environmental regulations. The operator shall review the relevantenvironmental policy, legal and administrative framework within which the statement is prepared, includingall relevant regulations at a local, national and international level that could affect the storage site.

This step highlights some additional considerations with respect to a CO2 storage site that an operator shalladdress:

— identify environmental receptors that may be affected by risks in the risk register for a given storage site,for example:

— air quality or marine environment (onshore/offshore)— soil or shallow sediments— surface water— groundwater— wetlands and floodplains— flora and fauna.

— identify the timescales required for restitution of local ecological resources — describe the state of the environmental receptors prior to commencement of CO2 storage— describe and predict possible environmental impacts of risks described in the risk register. Impacts shall be

specified in a quantitative, semi-quantitative or qualitative way with respect to frequency, duration andmagnitude

— define threshold values for degrees of impact significance for these receptors— define relevant risk treatment and the modelling performed to assess the effectiveness of these measures— describe monitoring targets and performance requirements for monitoring technologies (sensitivities and

spatial and temporal resolution and coverage) needed to ensure timely implementation of appropriate risktreatment.




5.4.5 Storage Performance Forecast

This document shall provide a scenario-based storage performance forecast that demonstrates the suitability ofthe Injection and Operating Plan in meeting the storage site performance requirements defined in the AppraisalBasis (Sec.4.3.2).

The operator shall carry out the following activities and describe the results in the Storage PerformanceForecast:

— identify the parameters from the Appraisal modelling step (Sec.4.3.5) that may influence the risks identifiedin the Appraisal Risk Assessment step (Sec.4.3.6)

— perform sensitivity analyses of these modelling parameters — model and predict base-case and high-end rates, cumulative volumes and timing of CO2 or displaced

formation fluids (including associated contaminants such as hydrocarbons or heavy metals) that may leakfrom the storage complex and reach an environmental receptor as identified in the EnvironmentalStatement

— model and predict potential cumulative leakage of CO2 to atmosphere for each scenario that involves apotential for leakage (CO2 escaping from the storage complex will be assumed to eventually enter theatmosphere)

— describe risk treatment options to reduce the risk of environmental impacts and leakage to atmosphere— define monitoring targets in terms of the following:

— how they shall be used as indicators of a deviation from expected storage performance— their location — when and how the physical properties of the monitoring target may change— the required detection thresholds to enable timely implementation of risk treatment.

5.4.6 Risk Management Plan

The operator shall document how the risk management process described in Sec.6 shall be applied to a givenstorage site in the Operate and Close stages of a project. The plan shall make reference to:

— the storage site performance requirements defined in the Appraisal Basis (Sec.4.3.2)— the storage site risk register updated during the Appraisal Risk Assessment (Sec.4.3.6)— the environmental receptors described in the Environmental Statement (Sec.5.4.4)— the monitoring targets and risk treatment described in the Storage Performance Forecast (Sec.5.4.5)— the Monitoring Plan (Sec.5.4.7).

The risk management plan shall include a description of the following:

— the organizational procedures and practices to be applied to risk management, including assignment ofresponsibilities

— the delegation of responsibilities, functions, and relationships among organizations and individuals toensure diligent and timely execution, monitoring and review of risk management activities

— a schedule for performing iterative risk assessments and activities supporting the risk assessments— the consequence categories to be used— risk evaluation criteria for each consequence category tuned to the scope and objectives of the project— risk tolerability/acceptance thresholds— risk treatment plans that describe how risks will be controlled and maintained at acceptable levels— a robust contingency plan and associated costs for controlling a sufficiently broad range of conceivable but

unexpected circumstances that can represent a risk to consequence categories, including worst-casescenarios

— how the monitoring plan is designed to support risk management activities— how the site-specific modelling and simulation activities incorporate new monitoring results and is

designed to evaluate effects of uncertainties and support the risk analysis— how the risk assessment methodology considers and accounts for uncertainty in site conditions and

processes that influence the performance of the storage site— a plan for iterative review and revision of project risk register based on updated modelling and monitoring

results— a schedule and process to map, monitor, review and document the risk management process— a schedule and process for external communication/consultation with regards to risk management— an impact hypothesis, including where and when any impacts may occur, and how any anticipated

consequences to consequence categories are weighed against the benefits of the project. The impacthypothesis shall be formulated in a brief and concise way suitable for stakeholder communication.

Guidance note:

Risk treatment entails the process to implement risk controls to prevent, mitigate and correct situations that may causeunwanted consequences, i.e., it encompasses the implementation of preventive, mitigative and corrective controls. Allof these types of measures should be adequately considered for each risk, and the combined effect of the prescribedrisk treatment should build confidence that risks will be controlled and maintained at acceptable or tolerable levels.




The implementation of risk treatment should follow a three decision logic comprised of: (i) the detection of acircumstance that signals the need to implement risk treatment; (ii) assessment and selection of an appropriatetreatment to address the situation; and, (iii) the implementation of the selected risk treatment. This procedure shouldbe followed by an assessment of the effect of the implemented risk treatment, whether the residual level of risk isacceptable or tolerable, and, if not, an assessment and selection of additional risk treatment (see also Section 6.4).

It can be constructive to discuss risk tolerance/acceptability thresholds for key risks with regulators and stakeholders.To this end, the operator may apply the ALARP principle (risks should be reduced as low as reasonably practicable)as a structuring element for discussions to illuminate the paired concepts of (i) risk tolerance and (ii) practicability ofpotential risk treatment (in terms of cost, time, effort, likelihood of success, and secondary risks potentially entailedby the risk treatment).


5.4.7 Monitoring Plan

5.4.7.1 General

The following steps represent a generic recommendation for developing a Monitoring Plan to be included in aStorage Permit application.

Updates may be required for the renewal of a Storage Permit and shall be required for a Closure Permitapplication (Sec.5.5). Such updates shall be obtained by iterating on each step of the process below while takingnew information into account.

5.4.7.2 Define objectives

The operator shall specify the monitoring objectives for a given storage site in the Monitoring Plan.

These objectives shall include:

— to monitor storage site performance in terms of health, safety and the environment in order to detect earlysigns of potential impacts and maintain proper control of identified risks

— to verify predictive models and provide a basis for calibration and updating of models in order to enhancecapability to predict future performance

— to measure the quantity of CO2 stored at a site— to locate and verify the containment of the injected CO2 within the storage complex.

Site specific objectives shall also be added as appropriate.

5.4.7.3 Describe context

The operator shall establish the context for a Monitoring Plan in order to demonstrate that the plan fulfils:

— regulatory requirements— emissions trading requirements (if applicable)

— international precedents set by other CO2 storage sites.

The context shall be established by identifying regulations and precedents that are relevant to a given projectand documenting why others may not be. For example, monitoring activities carried out by other projects forresearch purposes may not be proven or suitable.

5.4.7.4 Specify monitoring targets

The operator shall re-iterate the monitoring targets specified in the following two documents:

— the Environmental Statement (Sec.5.4.4)— the Storage Performance Forecast (Sec.5.4.5)

These monitoring targets shall have been identified by the Risk Assessment that was carried out during theAppraisal stage (Sec.4.3.6). The method for identifying monitoring targets is described in Sec.6.3.3 (RiskAnalysis).

For each monitoring target the operator shall specify:

— the physical property to be measured— the location(s) at which the physical property shall be measured— the frequency or time intervals at which the physical property shall be measured— the natural variability of physical property (temporal and spatial)— the detection thresholds required to satisfy the specified monitoring objectives (for example, protection of

other operator’s hydrocarbon and mineral rights, groundwater, sensitive flora and fauna within thebiosphere/marine biosphere and leakage to atmosphere).




5.4.7.5 Screen monitoring techniques

There exist a large number of monitoring techniques that can be applied to CO2 storage sites, but not all willbe technically feasible for any given site. This will be determined by, amongst other factors:

— the location (onshore/offshore)— the terrain and land use (onshore)— water depth and seafloor conditions (offshore)— the depth of the injection zone— the lithology of the storage complex and overburden — the sensitivity and reliability of a given technique.

The operator shall identify the techniques that are technically feasible at a given site and document thetechniques that were found to be technically inappropriate. This will demonstrate to a regulator the full list oftechniques that was considered.

Guidance note:

A best practice manual for monitoring, verification and accounting of CO2 stored in deep geologic formations hasbeen developed by the U.S. Department of Energy National Energy Technology laboratory. This reference containsa comprehensive list of potential monitoring techniques that may be applied:

U.S. Department of Energy National Energy Technology Laboratory, Best Practices for: Monitoring, Verificationand Accounting of CO2 stored in Deep Geologic Formations, (2009).


5.4.7.6 Select monitoring techniques

While all of the feasible techniques could be applied to the site in question, this does not mean to say that theyshould be. The usefulness of the data generated by the techniques will differ, as will their cost of deploymentand environmental impact.

The operator should apply and document a qualitative cost-benefit analysis in order to rank the techniquesaccording to the information benefit they bring to the project, bearing in mind the performance targets that havebeen set. For example, the techniques may fall into one of the following four categories:

— high benefit and low cost – should be selected and may be used more frequently— high benefit and high cost – should be selected, but may be limited to focused applications and used less

frequently— low benefit and low cost – may be selected— low benefit and high cost – should not be selected.

The rationale for the operator’s selection shall be documented and techniques that have been dismissed due tolack of technical feasibility, inadequate sensitivity/reliability or low benefit relative to cost shall be documentedtogether with their reasons for rejection.

5.4.7.7 Plan monitoring activities

The operator shall describe the following in the Monitoring Plan:

— procedures for documenting monitoring activities, procedures and results— the schedule and process for reviewing, updating and documenting changes to the monitoring plan to adapt

to changes in objectives or circumstances or to incorporate lessons learnt or changes to best practices— the baseline against which monitoring measurements will be compared, which shall include observed and

expected temporal trends and fluctuations— the design (technologies and procedures), objectives (monitoring targets and associated technology

sensitivities) and layout (spatial and temporal resolution and coverage) of activities in base case monitoringplan

— the assumptions and expected conditions (base case scenario) for which the monitoring plan is designed— the design, layout and objectives of a contingency monitoring plan designed to deal with situations outside the

envelope of expected system performance, which may include additional monitoring to design and evaluaterisk treatment, and possibly the establishment of a consultation panel of independent qualified experts.

5.4.7.8 Evaluate completeness

The purpose of this step is to check that the Monitoring Plan is complete, fit for purpose and in compliance withregulations. The operator may employ an external party to perform this step in order to obtain an unbiasedviewpoint.

The operator or external party shall perform the following activities:

— check the status of the permit application with respect to the objectives defined in Sec.5.4.7.1— check compliance with relevant regulations (may take the form of a dialogue with the regulator)— check compliance with relevant standards, codes or guidelines




— conduct further technical studies to quantify particular aspects of the qualitative cost-benefit analysis in theprevious step, if required

— check the fitness-for-purpose of the Monitoring Plan according to the requirements in Table 5-1.

5.4.8 Communication Plan

The operator shall develop a Communication Plan for responding to significant events. The plan shall bedesigned to facilitate understanding among internal and external stakeholders of the nature of the risks posedby the event, including its possible causes, their potential consequences and risk treatment.

The plan shall describe when and how the operator will carry out the following actions:

— communicate to regulators, stakeholders and the public that a significant event has taken place — provide information about risk treatment— communicate impact on the environment and/or economic resources, if any— evaluate the effectiveness of the communication.

5.4.9 Closure Plan

The operator shall develop a storage site Closure Plan that describes closure requirements for a given storagesite and the qualification process that shall be used to demonstrate fulfillment of these requirements.

In addition, the operator shall include a plan for long-term stewardship in the Closure Plan that includes thefollowing components:

— plans for monitoring activities (design, layout and objectives), as required by applicable regulation, todetect signs of leakage at the surface or in subsurface environmental or economic receptors

— a description of risk treatment to address the most likely events identified from the closure qualificationprocess, which shall include fluid migration (CO2 or otherwise) via wells

— plans to notify future land and resource owners of the storage site and remaining subsurface infrastructure— a description of the entity responsible for undertaking the long-term stewardship plan.

5.5 Closure Permit application (alternative Step 3, Figure 5-1)

5.5.1 General

The application for a Closure Permit, if applicable, should take the form of a Closure Qualification Statementthat includes the following components:

— a description of the Closure Basis— an Environmental Statement for storage site closure— a Storage Performance Forecast for storage site closure— a Monitoring Plan for storage site closure— an Updated Closure Plan.

These components are described in the following sections and represent the output of a qualification processfor storage site closure.

This qualification process shall be carried out by the operator in order to provide sufficient evidence that agiven site shall fulfil the closure requirements. The process shall follow a structured and transparent approachaiming to show how the operator has managed risks within acceptable levels during the project.

Table 5-1 Requirements for the Monitoring Plan

1Designed to monitor storage site performance in terms of health, safety and the environment in order to detect early signs of potential impacts and maintain proper control of identified risks.

2Designed to verify predictive models and provide a basis for calibration and updating of models in order to enhance capability to predict future performance.

3 Designed to verify the mass of CO2 stored.

4 Designed to demonstrate requirements for site closure, if applicable.

5Designed to provide regulators and stakeholders with confidence that the storage site is adequately understood and remains suitable for CO2 geological storage.

6

Designed to identify trends that may lead to deviations in site performance beyond agreed limits sufficiently early (accepted by the operator and the regulator) to allow either:

— timely implementation of appropriate changes to the Site Development Plan— timely and safe shut-down of CO2 injection.

7Includes procedures for the Monitoring Plan to be periodically reviewed and revised as needed to support pro-active risk management and adapt to changing project circumstances and advances in technology or best practices.

8 Allocates responsibility and accountability for timely and diligent execution of the monitoring activities.

9Includes procedures for evaluating the monitoring activities and processes against defined performance requirements.




The qualification process may be initiated when the operator has concluded, based on a preliminary assessment,that the requirements for site closure according to applicable regulations have been met.

5.5.2 Closure Basis

The Closure Basis shall include a list of requirements that shall be fulfilled in order for the storage site to beclosed. These requirements shall include, at least, the requirements listed in Table 5-2.

The Closure Basis document should also describe the context in which the closure qualification activity istaking place. The context may be described through any additional requirements to the closure qualificationprocess imposed by, for example, the following:

— the Storage Permit— the Closure Permit— surface infrastructure decommissioning regulations— well abandonment regulations— the operator’s internal management processes— other commercial stakeholders in the storage site — independent verification — operators of subsurface developments above or below the injection zone, or of nearby subsurface

developments that may experience pressure communication originating from the planned storage operation— emissions trading schemes in which the project wishes to participate— financial investors— local communities and landowners.

To ensure that the requirements imposed by any of the above are understood and properly accounted for in theclosure qualification process, the operator should consult with representatives from relevant stakeholders.

5.5.3 Environmental Statement for storage site closure

The operator shall update the Environmental Statement from Sec.5.4.4 with respect to:

— any natural changes to the storage site and surrounding environment— any man-made changes to the storage site and surrounding environment (not related to the CO2 storage

activities)— any changes to the storage site and surrounding environment resulting from the CO2 storage activities— any changes to environmental monitoring targets or their threshold values— any changes to environmental regulations— potential impacts from storage site decommissioning.

5.5.4 Storage Performance Forecast for storage site closure

The operator shall update the Storage Performance Forecast from Sec.5.4.5 with respect to historicalperformance data. This step shall help fulfil the following closure requirements:

— provide the evidence that the storage site is well understood and that performance can be predicted afterclosure (Requirement 1 in Table 5-1)

— define a limited number of key monitoring targets that may be used to provide assurance of long-termcontainment (Requirement 4 in Table 5-1).

Relevant historical data that shall be compiled during this step includes:

— operational logs that document the history of storage site operations— monitoring logs that document and map the history of the monitoring and verification activities— an updated risk register documenting how risks have been assessed and managed throughout the life cycle

of the storage site, including description of reasons for upgrading or downgrading risks during the life cycleof the storage site

— description of how key uncertainties have been analyzed and managed throughout the life cycle of thestorage site, and review of key decisions made in light of these uncertainties

— compilation of risk performance targets, including a record of changes made during the life cycle of thestorage site and a description of the reasons for these changes

Table 5-2 Requirements for storage site closure

1) A requirement for documented evidence that the storage site is sufficiently understood to predict its future performance:

a) actual storage performance during the injection phase of the project has been consistent with the initial and updated Storage Performance Forecasts

b) actual storage performance after the cessation of injection has been consistent with the updated Storage Performance Forecasts.

2) Further risk treatment is not required.

3) All wells that penetrate the storage complex have adequate well integrity.

4) Assurance of long-term containment can be maintained by observation of a limited number of key monitoring targets.




— compilation of results and conclusions drawn from monitoring, modelling and risk assessments to supportdemonstration of compliance with site closure requirements, including description of how geomechanicaland flow simulation models have been calibrated or adjusted

— historical storage performance relative to predictions from modelling and simulation.

Consistency of actual and predicted storage performance shall be demonstrated by:

— a converging trend between the comparisons over time

— model calibrations by history matching no longer alter the understanding of the storage site characteristicsin a way that significantly influences the performance predictions

— the uncertainty band on the predictions of CO2 plume migration and pressure development is withinacceptable limits.

5.5.5 Monitoring Plan for storage site closure

The operator shall update the Monitoring Plan (Sec.5.4.7) with respect to the revised list of key monitoringtargets defined in the updated Storage Performance Forecast (Sec.5.5.1.4).

5.5.6 Updated Closure Plan

The operator shall update the Closure Plan from Sec.5.4.9 with respect to:

— any updates to the closure requirements

— the revised list of key monitoring targets defined in the updated Storage Performance Forecast (Sec.5.4.5)

— any updates to risk treatment due to advances in technology

— any changes to stakeholder composition (for example by change of land ownership).

5.6 Evaluate completeness (Step 4, Figure 5-1)

The purpose of this step is to check that the permit application is complete, fit for purpose and in compliancewith regulations. The operator should perform the following activities:

— check the status of the permit application with respect to the requirements described in Step 1 (Sec.5.2)

— check compliance with relevant regulations

— check compliance with relevant standards, codes or guidelines

— check the fitness-for-purpose of the permit application.

In the case that the permit application is a Storage Development Plan, then the requirements in Table 5-3 shallbe used to check its fitness-for-purpose.

5.7 Submit application (Step 5, Figure 5-1)

The operator should submit the application in question according to the requirements specified in Step 1(Sec.5.2).

Table 5-3 Requirements for a Storage Development Plan

1 Storage Development Plan is tailored to the unique characteristics of the storage site.

2The Characterization Report provides a sufficiently detailed and reliable description of the storage site to demonstrate and confirm the suitability of the storage site for environmentally safe long-term CO2 geological storage.

3The Injection and Operating Plan documents the technical and economic feasibility of the CO2 injection operations.

4The Environmental Statement describes all potential consequences to environmental receptors that may stem from the risks in the risk register, and documents the analysis that is used to determine impact significance thresholds for these receptors.

5The results of predictive modelling that are documented in the Storage Performance Forecast are based on the Injection and Operating Plan.

6The Storage Performance Forecast provides sufficient understanding of containment and performance risks to form a robust basis for design of the Monitoring and Risk Management Plans.

7The predictive models used by the operator are capable of demonstrating adequate conformance with observations to sustain CO2 injection operations (support renewal of storage permit) and allow for timely site closure.

8 The Risk Management Plan is suitable for the storage site and will ensure that risks are appropriately managed.

9The Monitoring Plan gives assurance that risks can be controlled at “acceptable” levels (see requirements in Table 5-1).

10The Communication Plan is appropriate to the level of knowledge about CO2 geological storage in general and the CCS project in particular among relevant stakeholders, and is suited to address the concerns that may arise.



Sec.6 Risk management –

6 Risk management

6.1 Introduction

The purpose of risk management is to ensure that opportunities and risks related to the geological storage ofCO2 at a given site are effectively managed in an accurate, balanced, transparent and traceable way. Therecommended risk management process is modified from ISO 31000 to take account of specific considerationsfor CO2 geological storage and is illustrated in Figure 6-1.

Figure 6-1Recommended risk management process for CO2 geological storage.

This process is designed to:

— run in parallel with the project life cycle stages in Figure 2-1— provide CO2 storage operators with decision support at key project milestones— reduce cost and schedule risks during storage site Screening and Appraisal— improve storage performance during the Operate stage— increase the likelihood of obtaining Storage and Closure Permits in a timely manner.

The process steps shown in Figure 6-1 are described below.

6.2 Risk management context

6.2.1 General

The operator shall establish the context of their risk management process by:

— defining the project objectives (Sec.6.2.2)— defining the responsibilities for and within the risk management process— defining the scope of the risk management process (Sec.6.2.3)— identifying and specifying the decisions that have to be made— defining the consequence categories to be used (Sec.6.2.4)— defining the risk evaluation criteria to be used (Sec.6.2.5).

6.2.2 Project objectives

The operator shall define objectives for the project in question that are aligned with organisational goals.Whereas goals may be high level statements that provide an overall context for what the operator is trying toachieve, the objectives shall describe the specific, tangible results that a given project will deliver.

Project objectives shall be specific, measurable, achievable, realistic and time limited.

6.2.3 Scope

Table 6-1 describes internal and external factors that an operator shall take into account when defining thescope of the risk management process.

Establish

context

Assess risks:• Identify• Analyze• Evaluate

Plan and

assess risk

treatment

Monitor, review and document

Iterate &

calibrate




6.2.4 Consequence categories

Risks may be usefully grouped into categories according to the nature of their consequences. The consequencecategories for risk management of a CO2 storage site shall include the following:

— human health and safety— environmental protection— storage site containment— storage site performance.

The consequence categories should also include the following:

— legal and regulatory compliance— cost— schedule— reputation.

An operator may use additional categories as appropriate.

Stakeholder views and risk perceptions shall be adequately understood and appropriately considered whenspecifying consequence categories. To this end, stakeholders’ values, assumptions, capabilities, and concernsthat may impact decisions based on risk considerations or hinder the achievement of objectives shall beidentified and recorded.

6.2.5 Risk evaluation criteria

The operator shall define risk evaluation criteria to be used to evaluate the significance of risk. The criteria shallbe aligned with the project objectives and may be derived from regulations, standards, recommended practicesor other requirements.

The operator shall consider the following factors when defining risk evaluation criteria for a CO2 storage site:

Table 6-1 Internal and external factors affecting the risk management context.

En

vir

on

men

t, r

eso

urc

es,

infr

ast

ruct

ure

an

d s

ub

surf

ace

d

evel

op

men

ts1 Natural environment: meteorology, surface/marine environment (ecology, wildlife, botanic, parks

and reserves, etc.), biosphere, hydrosphere, and geosphere (including geology, hydrogeology, geochemistry, tectonics and seismicity).

2 Resources: groundwater, hydrocarbon and mineral reserves, coal seams, geothermal energy.

3 Infrastructure and facilities: buildings, transportation corridors (roads, railroads, pipelines, etc.), power distribution lines, oil and gas production and processing facilities, wells, groundwater reservoirs.

4 Subsurface developments: hydrocarbon production, mineral extraction, mining, waste disposal, natural gas storage, acid gas disposal, geothermal energy conversion.

Soci

al,

cu

ltu

ral,

p

oli

tica

l a

nd

ec

on

om

ical

5 Demographic, historical and cultural factors that can influence how the project will affect or be viewed by stakeholders.

6 Political elements and trends that may influence the perception and/or financing of a storage site.

7 Geographic and temporal economic factors, including possible effects of the project upon the local economy.

Leg

al,

reg

ula

tory

, a

nd

in

du

stry

p

ract

ice

8 Relevant directives, acts and regulations applicable to storage sites and any active initiatives to introduce new or modify existing directives, acts or regulations.

9 Relevant codes, standards, protocols and guidelines that may serve to guide risk management and facilitate demonstration of compliance with regulations, acts and directives.

10 Manuals that document current industry practice and guide cost-effective implementation of CO2 storage technology and in accordance with best industry practice.

Op

era

tor

an

d

pro

ject

res

ou

rces

11 Economic ownership, contributions and liabilities for each component in the CCS system.

12 Operator’s responsibility and authority limitation, including its resources and commitment to risk management.

13 Experience of the organizations involved in the project to address risks through the development and implementation of a comprehensive risk management plan.

14 Available resources, capacities and capabilities for performing isolated functions with respect to the storage site and for integration across all project components in the project and in the total CCS system.




— the distinction between risks to performance and containment (commercial versus environmental criteriafor example)

— the timeframe of reference for a given risk (different for operational and post-closure risks, amongst others) — how likelihood may be defined (qualitatively or quantitatively as a probability or frequency)— the views of stakeholders (for example commercial partners)— how combinations of multiple risks may be linked together to create risk scenarios (for example leakage of

formation fluids to surface along an abandoned well).— the level at which a given risk becomes acceptable or tolerable (for example the frequency values that

correspond to the three regions in Figure 6-2).

The level of a risk may be unacceptable, tolerable or broadly acceptable:

— unacceptable – risks cannot be justified except in extraordinary circumstances— tolerable or as low as reasonably practicable (ALARP) – risks are tolerable if further risk reduction is

impracticable or the costs of additional risk reducing measures are disproportionate to the improvementgained;

— broadly acceptable – no need for detailed effort to demonstrate that risks are reduced ALARP.

These levels are illustrated in Figure 6-2.

Figure 6-2Levels of risk that should be used to establish risk evaluation criteria

6.3 Risk Assessment

6.3.1 General

The operator shall assess risks using the three stage approach described below.

6.3.2 Risk identification

The operator shall perform a comprehensive risk identification process that considers all relevant risks, anddocuments in a transparent, traceable and consistent manner which threats, events and consequences have beenconsidered.

The risk identification process shall be tailored to the relevant stage of development for a project, for exampleScreening risk assessment (Sec.4.2.6) or Appraisal risk assessment (Sec.4.3.6).

The following activities shall be performed:

— identification of threats to the consequence categories established in the risk management context(Sec.6.2.4).

— identification of additional threats related to novel aspects of the project, for example:

— unique features of the storage site under consideration— technical or organisational aspects that are outside the operator’s experience.

— identification and description of risk scenarios for each threat containing:

— one or more threat-event scenarios— one or more event-consequence scenarios.

— comparison of identified risk scenarios with an acknowledged database of threats, events and consequences

Unacceptable

Region

Broadly Acceptable

or Negligible Region

Tolerable or

ALARP Region

Risks cannot be justified

except in extraordinary

circumstances

Tolerable only if risk

reduction is impracticable

or if the cost is grossly

disproportionate to the

improvement gained

No need for detailed effort

to demonstrate ALARP




— description of environmental and economic receptors that may be negatively impacted by potential loss ofcontainment or geomechanical responses to the CO2 injection and storage operations.

— identification of interdependencies between different risk scenarios, including potential for cascadingeffects that may increase likelihood of occurrence or severity of consequences.

6.3.3 Risk Analysis

Risk analysis aims to enhance the understanding of risks, including the nature of the risk itself, the likelihoodof occurrence and the severity of potential consequences to the relevant consequence categories for each risk.The risk analysis shall:

— be technically defensible and based on best available knowledge or scientific reasoning— assess the span of possible system performance scenarios, and evaluate risk treatment options — provide the technical basis for evaluating risks, and, whenever practically feasible, assess and quantify the

degree of uncertainty in the level of risk.

Where sufficient and demonstrably relevant data can be obtained, quantification of likelihood and consequenceshall be based on appropriate scientific reasoning or auditable statistics and/or calculations. Otherwise,quantification shall be based upon the documented judgment of experts who are qualified in terms of applicableprofessional expertise and project knowledge.

Care shall be exercised to ensure that the results of the risk evaluation exhibit reasonable accuracy. Ifsignificant uncertainty related to risk magnitude exists, relative to the risk evaluation criteria, then the degreeof uncertainty shall be modelled through sensitivity studies or scenario analyses and be used to providereasonable uncertainty bands.

Guidance note:

The operator shall distinguish between the following two broad categories of uncertainty that are relevant togeological storage sites:

— uncertainty associated with the description of the storage site including the site characteristics, engineeredcomponents, and natural processes and their interaction with the environment

— the degree to which the conceptual and mathematical models are representative of the actual system.


The operator shall document in a transparent, traceable and consistent manner how each of the followingactivities has been performed in the risk analysis process:

— analysis of likelihood of occurrence for each identified risk scenario— analysis of severity of potential consequences to the consequence categories for each identified risk

scenario— analysis of uncertainty in the likelihood of occurrence and severity of potential consequences for each risk

scenario— identification of measures to reduce or manage uncertainty that can influence the risk evaluation and/or

selection of risk treatment, and assessment of the effectiveness of these measures— identification and visualization of risk controls in an event-focused way:

— preventive controls that may be applied to threat-event scenarios— mitigative controls (including corrective controls) that may be applied to event-consequence scenarios

(see Figure 6-3 for an example)

— assessment of the uncertainty associated with the effectiveness of risk controls— identification of monitoring targets and performance requirements for monitoring technologies

(sensitivities and spatial and temporal resolution and coverage) required for timely implementation ofappropriate risk treatment

— identification of data requirements and modelling and simulation studies to be performed to support the riskanalysis

— analysis of cumulative likelihood that the respective risk events may occur— analysis of cumulative likelihood that significant negative impact to the respective consequence categories

may occur.




Figure 6-3Example of risk control visualisation that may be used to support risk analysis

6.3.4 Risk evaluation

The purpose of risk evaluation is to use the outcome of risk analysis to assist in making decisions about whichrisks need treatment and their order of priority.

Risk evaluation determines the significance and tolerability/acceptability of risks and sets the performancerequirements for risk treatment. The planning of risk treatment actions is described in Sec.6.4.

The operator shall document in a transparent, traceable and consistent manner how each of the followingactivities has been performed for each risk in the project risk register:

— identification of risks that require treatment based on the results of risk analysis— prioritization of these risks — documentation of the level of risk prior to risk treatment— specification of the target risk levels to be achieved by risk treatment.

6.4 Risk treatment

Risk treatment involves selecting one or more options for modifying risks and implementing those options.

The operator shall develop a risk treatment plan for the relevant risks that were identified and prioritized duringrisk evaluation. This plan shall document in a transparent, traceable and consistent manner how each of thefollowing activities has been performed for a selected risk:

— identification of the risk treatment options that are

— cost-effective— do not introduce other significant risks that outweigh potential benefits of the treatment

— evaluation of the following risk treatment options in order of preference:

— avoid risk— remove threat— reduce likelihood— reduce consequences— share the risk with another party or parties— retain and tolerate the risk by informed decision

— prioritization of risk treatment options, including the order in which risk controls shall be implemented— specification of risk performance targets for all significant risks including:

— target risk levels— planned risk treatment to control and maintain the risk at or below this level

— evaluation of uncertainty attached to risk levels, both pre-mitigation and post-mitigation:

— in the case that significant uncertainty exists, the operator shall explain how uncertainty is taken intoaccount and defend why the risk treatment plan is robust with respect to targeted risk levels

— planning of contingency measures for managing conceivable, but unexpected circumstances or incidentsthat carry risks or give rise to negative impacts to consequence categories.

Following implementation of risk treatment the operator shall evaluate the level of risk in order to determineif a given risk performance target has been met (see Sec.6.5).

Threat –Event Scenario Event

Threa

t

Event–Consequence Scenario Consequence 3

Passive

contro

l 1

Passive

contro

l 2

Active

contro

l 2

Active

co

ntro

l 1

Preventive controls Mitigative controls

Event–Consequence Scenario

Event–Consequence Scenario Consequence 2

Consequence 1




Risk treatment plans shall be reviewed and revised as required in order to ensure that risks remain acceptablethroughout the life cycle of the storage site.

6.5 Risk management review and documentation

6.5.1 General

The risk assessment results shall be revisited as required to ensure that changes in the context for riskmanagement are detected in a timely manner, and that the risk management plan continues to be suitable forthe storage site.

Reviews of the risk management process shall be executed on a regular basis and documented in a transparentand traceable manner throughout the life cycle of a storage site. The responsibilities for monitoring and reviewshall be clearly defined.

6.5.2 Process

The monitoring and review of the risk management process shall evaluate compliance with the followingrequirements:

— risk controls are effective and efficient, and implemented as needed in a timely manner— data is gathered as needed to improve risk assessment and management— lessons learnt from successes and failures are documented and analysed— changes in the context are detected in a timely manner, including changes to consequence categories, risk

evaluation criteria and the risk itself which can require revision of risk treatments and priorities— emerging risks are identified in a timely manner— progress in implementing risk treatment plans is measured against risk performance targets — the results of monitoring and review are recorded and externally and internally reported as appropriate and

are used as an input to the review of the risk management plan.

6.5.3 Transparency

The risk evaluation criteria for each consequence category shall be documented. For all consequence categoriesother than those that involve strictly the operator’s interests, the risk acceptability/tolerance thresholds shall bespecified. For consequence categories that involve strictly the operator’s interests, these thresholds should bespecified.

The operator shall document and describe monitoring and modelling outputs that form a basis for the riskassessments, the assumptions and references for the modelling studies, and implications of monitoringtechnology limitations on the risk assessment results.

6.5.4 Traceability

The results of risk assessments shall be recorded in a consistent manner so that risk assessments are comparableover time. The risk owners shall be documented. Changes in assumptions and design of modelling andmonitoring plans shall be documented and justified. If different risk assessment methodologies have beenapplied, it shall be demonstrated how the results of updated assessments compare with the most recentassessment. If the results of an updated risk assessment deviate significantly from the prior assessment, thereasons for the differences shall be documented.



Sec.7 Well qualification –

7 Well qualification

7.1 Introduction

Well Qualification, in the context of this RP, refers to the process of providing the evidence that a given wellwill function within specific limits with an acceptable level of confidence when exposed to the effects of CO2storage. The operator shall apply this process to:

— plugged and abandoned wells that shall continue to provide formation fluid containment

— active or suspended wells that shall be plugged and abandoned prior to CO2 storage operations

— active wells that shall retain their original function during CO2 storage operations before final plugging andabandonment

— active wells that shall have a modified function during CO2 storage operations before final plugging andabandonment.

In addition the operator may apply this process to the design of new wells.

The current status of existing wells that may be exposed to the effects of CO2 storage shall have beenestablished during the Screening and Appraisal stage risk assessments. The task of well qualification is then to:

— identify risks to the future performance and reliability of a given well (failure modes and mechanisms)

— reduce these risks in a systematic manner by targeted qualification activities (for example by testing andanalysis)

— design monitoring activities that shall trigger specified risk reduction measures in the future.

The steps in the well qualification process are shown in Figure 7-1.

Figure 7-1Flow diagram illustrating the well qualification process with respect to the milestones shown in Figure 2-1

Execute well qualification activities

Assess results against

requirements

Set requirements in

qualification basis

Perform risk assessment

for well qualification

Evaluate need

for modifications

No

Yes

Plan well qualification &

select qualification activities

Modify q

ualifica

tion b

asis

Requirements met?

Yes

No

Evaluate likelihood

of success

Current status of

existing wells from risk

assessment

Initial Well

Qualification

ReportM3

Final Well

Qualification Report

M4




The result of well qualification is a Well Qualification Report that shall document the fitness for purpose of agiven well and define margins against specified failure modes or performance targets. The qualification resultsmay be used:

— as an acceptance for use of an existing well for a CO2 storage application— for comparison between solutions for a given well— as input in the evaluation of the reliability of a CO2 geological storage site that the well may be part of— as an assurance of well integrity.

The following principles shall apply to well qualification:

— a qualification strategy shall be developed to bring a well from its current state to a defined target state orto assess the present condition of the well

— specifications and requirements shall be clearly defined, quantified and documented— the performance margins and the margins to failure shall be established based on recognised methods— failure modes that are not identified may pose a risk to the successful use of the well; this residual risk shall

be managed by ensuring the relevant competencies are used (see Table 7-1) and by challenging the criticalassumptions during the course of qualification

— the qualification process shall be based on a systematic, risk based approach and performed by aqualification team possessing all required competencies

— when service experience is used as proof of fulfilment of the specifications, then evidence of thatexperience shall be collated and checked

— the work shall be documented and traceable— an iterative approach is recommended when uncertainties are very large— the typical quality assurance system for drilling, completing, and abandonment of a well shall be an integral

part of the qualification process.

7.2 Set requirements in qualification basis

7.2.1 General

The operator shall specify the qualification requirements for a given well in the Well Qualification Basisdocument that shall include:

— a description of the current status of the well based on the findings of the Screening and Appraisal riskassessments (Sec.4.3.6)

— the well performance requirements (Sec.7.2.2)— the well specification (Sec.7.2.3)— the critical parameters list for the well (Sec.7.4.2).

7.2.2 Well performance requirements

The well performance requirements shall:

— define how the well will be used— define the environment that it is intended for— specify requirements such as acceptance criteria, performance expectations and qualification targets— include requirements throughout the extended life cycle of the well.

The well performance requirements shall reflect the storage site requirements specified in the Appraisal Basis(Sec.4.3.2). Examples of well performance requirements are:

Table 7-1 Competencies that a well qualification team shall possess.

Discipline Expertise/knowledge required

Well engineering Procedures for drilling, construction and permanent abandonment of wells

Materials/corrosion Characteristics of materials in well construction and their susceptibility to corrosion

Cements Chemical and physical properties of different cement typesInterpretation of cement evaluation logs

Geochemistry Geochemical interactions between injected or resident fluids, well materials, cements, rocks and fluids in the near wellbore environment

Geomechanics Potential geomechanical impacts on well cements and the near wellbore environment that may stem from CO2 storage operations

Well integrity Well integrity management and CO2 specific well integrity issues

Storage site characterization

Storage site characteristicsPotential effects on the near-well environment if the site is or will be used for CO2 geological storage (i.e., predicted changes in pressure, temperature and exposure to CO2 or fluids charged with CO2 or other constituents in the CO2 stream)

HSE HSE management and requirements in applicable regulations




— reliability requirements related to selected functions— sustained annulus pressure limits— completion string leak rate limits— wear/corrosion tolerances within the completion string— casing corrosion rate limits.

7.2.3 Well specification

The well specification shall be described as completely and unambiguously as possible through text, drawings,reports and other relevant documents. It is important that the well integrity criteria are stated and that allrelevant interfaces are clearly defined. The specification shall identify all phases of the well’s life and allrelevant main parameters.

Well specification may include, for example:

— well description, schematic and formation boundaries and lithology types along the well— functional requirements— permit requirements— health, safety and environmental requirements— well integrity criteria— operation and maintenance, monitoring and abandonment principles— completion and interfacing with surface facilities.

The specification and functional requirements shall be quantitative and complete. In case quantitative measuresare not available for some of the requirements (for example, no cement evaluation log available) thequalification can be carried out for a best estimate, but as soon as the target requirements can be quantified theyshall be entered into the well qualification basis and the implication of these new values shall evaluated.

7.3 Risk assessment for well qualification

7.3.1 General

The operator shall carry out an assessment of well integrity risks with respect to:

— the current status of the well (from Screening and Appraisal stage Risk Assessments, see Sec.4.3.6)— the future function of the well (as specified in the Qualification Basis, see Sec.7.2)— the critical parameters list (see Sec.7.4.2)— the well component classification (see Sec.7.3.2.3).

The output from this risk assessment shall be a failure mode register containing identified failure modes andfailure mechanisms ranked according to their risk level. This register should be integrated with the overall riskregister or database for the storage site in question.

7.3.2 Risk identification

7.3.2.1 General

See Sec.6.3.2 for a general risk identification method description.

See Appendix A for examples of the types of well integrity data that should be collected and the informationthat may be derived from each.

The operator shall conceptually subdivide the well into distinct and manageable components for riskidentification. See Appendix B for examples of components and their failure modes and mechanisms.

When performing this step the operator shall take into account:

— well operations— well suspension— well abandonment— external failure modes for a well (not included in Appendix B), such as geological faulting— the underlying failure mechanisms that could lead to failure modes.

Well integrity risks for existing wells include both:

— existing inherent risks without CO2 storage— additional risks caused by CO2 storage.

The latter is a function of the likelihood of:

— a well being exposed to the effects of CO2 storage (reservoir dynamics)— well integrity failure in the event of such exposure.

The likelihood of the former will be a function of the CO2 storage volume that is defined for a given storage




site and used to estimate capacity in the screen stage and is not discussed further in this step. The likelihood ofthe latter is discussed further with respect to the direct effects on the near-well environment if the storage siteshall be used for CO2 geological storage. This includes:

— predicted effects of changes in pressure— predicted effects of temperature changes— predicted effects of exposure to CO2 or fluids charged with CO2 or other constituents in the CO2 stream.

Where the term CO2 is used in the guideline, it assumes that carbon dioxide is pressurized; may or may notcontain water; exists either as a liquid, super critical fluid or a gas; and also includes carbon dioxide dissolvedin water contained in the reservoir.

Predicted effects of changes in pressure may extend beyond the area of legal control of a project developer inwhich case a mitigation plan may have to be put in place.

A number of co-components may typically be associated with industrial CO2 streams, such as those listedbelow. The well qualification issues related to these are not specifically addressed in this RP, but may behandled by the same qualification methodology:

— cracking and fouling associated with H2S either present in the injection stream or released in the geologicalformation by CO2

— nitrogen and argon; these are non-condensable and will alter the vaporization and condensation propertiesof the CO2 stream

— oxygen; this may increase corrosion rates— hydrogen; this may limit materials of construction— trace components, such as seal oil from compressors.

7.3.2.2 Special considerations for well integrity under exposure to CO2

Corrosion of carbon steel pipe and degradation of cement: the dominating failure mechanism related to long-term exposure to CO2 or CO2 saturated formation fluids is anticipated to be corrosion of carbon steel pipe anddegradation of cement. The probability of failure modes resulting from these failure mechanisms will dependon the corrosion and degradation rates that are assumed. It is understood that international research anddevelopment work continues in order to reach an industry consensus on how to predict these rates in a reliablemanner.

Elastomers: routinely used as sealing elements and can be found in surface and downhole valves, packers anddownhole seals. CO2 presents additional challenges to elastomer design. Elastomers shall resist explosivedecompression (rapid gas-decompression) and be qualified appropriately (refer to, for example NORSOK M-710). Elastomer performance and properties change with time and they shall be avoided as part of the primaryabandonment barrier design.

CO2 as a refrigerant: designers shall be aware of the refrigerant properties of carbon dioxide. Large pressuredrop over a short distance will cause flowing CO2 temperatures to drop significantly. Materials of constructionshall ensure that toughness of metals and flexibility of elastomers (durometer) are maintained for both normaland abnormal flow conditions. Low temperatures can also freeze annulus fluids and cause additional tubingcontraction, for example unstable flow regime down the tubing in low pressure reservoirs.

The temperature range could therefore be greater than normally experienced in a conventional oil and gasinjection well and may cause considerable expansion/contraction and additional loads on the well.

Blow-down considerations: blow-down of CO2 in liquid or super critical phase is a challenge. In addition tothe low temperatures, dry ice can form which may land locally and create hazards, or in extreme cases causeerosion of the vent pipework. Design of wireline and coiled tubing systems and operations shall take this intoconsideration, for example by displacing the CO2 with nitrogen before de-pressurisation. This operational needalso exists with downhole safety valve testing and this may be the dimensioning case for surface pressurecontrol equipment.

Annulus management: the qualification process shall examine the management of the annulus condition duringthe injection phase to detect well integrity problems early and prevent corrosion of casing and tubing. Conditionmonitoring of the annulus during the injection phase could include pressure monitoring, measurement of top-up volumes, sampling of annulus fluids, and pressure-volume measurements.

7.3.2.3 Well component classification

The operator may choose to classify well components according to common failure mechanisms in order tofacilitate the process of risk identification.

Well component classification is a qualitative process that shall make use of a failure mechanism (such ascorrosion) that is common to the components in question. In the case of corrosion then the well componentsshall be classified according to the corrosion resistance of their materials and their degree of expected exposureto a corrosive environment. In examining the well components it may be beneficial to group them into sub-systems (such as the lower completion) prior to performing the classification.




An example of such a rating system is shown in Table 7-2. The term ‘technical uncertainty’ relates to thepotential incompatibility or poor performance of components, whereas the term ’technical challenges’ relatesto components of known incompatibility with CO2 and where performance can be modelled.

A well component or sub-system rated as Class 1 in this example shall be proven to be of no particular concernfor the application in question through documentation of tests, calculations and analysis. Such components donot require qualification and shall be handled through the regular design process.

A well component or sub-system rated as between Class 2 to Class 3 in this example has an increased degreeof technical uncertainty. Components falling into these classes shall be qualified according to the work processdescribed in this document.

Components falling into Class 4 likely require modification (see Sec.7.6).

7.3.3 Risk analysis

See Sec.6.3.3 for a general risk analysis method description.

The operator shall make use of quantitative measures of likelihood and consequence where this is supportedby the available data.

7.3.4 Risk evaluation

See Sec.6.3.4 for a general risk evaluation method description.

The operator shall distinguish between the following three qualitative risk classes as a minimum:

— low risk – failure modes that do not require qualification and may be adequately resolved by qualifiedpersonnel

— medium risk – non-critical failure modes that require qualification to reduce their risk— high risk – critical failure modes that require qualification to reduce their risk.

The operator shall establish a failure mode register for tracking the status of each failure mode and mechanismthroughout the qualification process. The risk evaluation shall be updated as new information arises and failuremodes with low risk should not be deleted from the list. This system shall include:

— all identified failure modes and mechanisms— a probability estimate for each failure mode to occur— the basis for the probability estimate tracing documentation revisions and implementation of mitigating

actions— the degree of CO2 implications to which the failure mode relates (Class 2 to 4 from Table 7-2) in order to

focus on the important components.

7.4 Plan well qualification & select qualification activities

7.4.1 General

The operator shall develop a plan that describes the qualification methods that shall be applied to reduce therisk(s) to well integrity.

Development of the well qualification plan shall include:

— high level planning to implement the overall qualification process— analysis and selection of qualification activities to provide the evidence needed for each failure mode— development of the reasoning that connects the evidence produced by the qualification activities to the

requirements set in the qualification basis

Table 7-2 Example classification system for the corrosion resistance of well components

Corrosion resistance

High Medium Low

Exp

osu

re t

o C

O2

corr

osi

on

Low 1 2 3

Medium 2 3 4

High 3 4 4

Where:

Class 1 represents no technical uncertainties;

Class 2 represents new technical uncertainties;

Class 3 represents new technical challenges;

Class 4 represents demanding technical challenges.




— development of detailed specifications of the qualification activities.

The detailed specifications of qualification activities shall explicitly specify:

— the evidence to be produced by each qualification activity— the failure modes that evidence relates to— the reasoning that relates the pieces of evidence to the failure modes— the reasoning that relates the evidence to the requirements specified in the qualification basis— success criteria for this evidence to demonstrate fulfilment of the qualification requirements.

The well qualification plan shall be revised as necessary.

7.4.2 Critical parameters list

The purpose of the critical parameters list is to document the vital governing parameters affecting the failuremechanisms, for example the parameters affecting the rate of casing corrosion, such as material composition,temperature, chemical composition of fluids, etc.

Hence, at the conclusion of the well qualification process, the boundary limits for the parameters and itemsgiven in the critical parameters list will represent the qualified limits or operating envelope within which thewell is considered qualified.

The operator shall determine governing parameters for critical failure mechanisms. The critical parameters listshall specify such governing parameters, and include their limits/boundaries within the scope of thequalification. Further, this list shall also specify the main concerns and uncertainties with the given parameters.

7.4.3 Selection of qualification activities

Qualification activities shall be selected in order to meet the requirements given in the qualification basis.

If a quantitative reliability target is stated in the qualification basis, then a quantitative reliability method isrequired to document fulfillment of the requirement, for example by determination of a lifetime probabilitydensity distribution for the relevant failure modes.

For each failure mode of concern, it shall be determined if the failure mechanisms can be modelled byrecognised and generally accepted methods. Then a detailed plan for the qualification activities can beestablished, for example, by use of existing standards or industry practices.

The following methods can be used, separately or in combination, to provide qualification evidence:

— failure mode avoidance, such as operational procedures or design changes— analysis or engineering judgement of previous documented experience with similar equipment and

operating conditions— analytical methods such as handbook solutions, methods from existing standards, empirical correlations or

mathematical formulas— numerical methods, such as process simulation models, computational fluid dynamics, finite element

modelling, coupled geomechanical and reservoir simulation modelling, corrosion models, etc— experimental methods, scale model testing, identification or verification of critical parameters and their

sensitivities.

Qualification activities may consist of qualitative and quantitative methods, analysis and testing. A typicalqualification program may include a combination of the following activities:

— material corrosion resistance, historical data, corrosion prediction models, testing— documenting field history, quantitative/ qualitative evaluation of failure history of wells in a field with

similar wells and exposure— assess documented industry practice with the specific well components— predictive modelling of CO2 movement and possible contact with components that might degrade if exposed

to either CO2 or CO2-saturated brines, and modelling to estimate degradation processes, rates and end points.

7.5 Evaluate likelihood of success

The operator should evaluate the likelihood of success for achieving qualification of a well in a qualitativemanner based on the technical challenges and the available time for qualification.

The operator may also perform a more sophisticated assessment of the total likelihood of success for all wellsas function of time. Such an assessment requires that both the probability of a successful outcome for eachactivity and the uncertainty in the durations are estimated.

An economic assessment of the qualification activities may be carried out following the same principles, wherethe time parameter is replaced by costs. This requires that cost estimates with uncertainties are estimated foreach qualification activity.

In the event that further development of a storage site is anticipated then a project developer shall considerinitiating baseline monitoring of existing wells at the earliest possible opportunity.




7.6 Evaluate need for modifications

Modifications of the well and/or the qualification basis may be considered if the likelihood of successfulqualification is low and/or the associated time and cost are high.

If the estimated likelihood of success is unacceptable and required modifications are excessively costly, thewell shall not be considered for further qualification and the storage site containing such a well shall beeliminated from the list of potential storage sites at Milestone M3.

7.7 Update qualification basis

The objective of this step is to update the qualification basis in light of new information that may come to lightduring the qualification process. Modification to the well qualification basis shall have a defined purpose, suchas:

— change of intended well function (possibly in order to avoid a particular failure mode)— reduction of the probability of occurrence or consequence of failure mode to an acceptable level— reduction of the total well cost.

Any modifications to the well qualification basis imply that the well qualification steps need to be updated. Theupdate may range from a limited update of parameters or risk data to major re-design of the well. In either casedocumentation is required in order to maintain traceability of the process.

7.8 Initial Well Qualification Report

The operator shall document the well qualification findings for each well thus far in the process in an InitialWell Qualification Report. The purpose of this report is to support the selection of a storage site and theoperator shall include this report in the Well Engineering Concept (Sec.4.3.8).

An Initial Well Qualification Report for each well shall describe:

— the required qualification activities — the likelihood of successful qualification— time and cost estimates for completion of well qualification.

7.9 Execute well qualification activities

7.9.1 General

The operator shall execute the well qualification activities specified in the Initial Well Qualification Reportaccording to industry recognised standards and document any assumptions made.

7.9.2 Failure mode detection

Failure modes detected during execution of the qualification activities (quality control qualification test,acceptance tests or later operations) shall be recorded and documented. The documentation shall include thedate detected, the description of the failure mode, other observation and the identity of the originator.

When a failure mode is detected in the qualification process, the occurrence of the failure mode shall beevaluated with regard to the three following cases:

— will occur within the expected frequency of occurrence according to the analysis— will occur with a higher frequency— has not been considered.

In the second case the basic assumption for the frequency of occurrence shall be re-evaluated. This re-evaluation shall include implications for any models used.

In the third case there shall be an evaluation stating if the failure mode is an artefact that need not be consideredor if it was missed and must be included in the qualification.

7.9.3 Collection and documentation of data

The documented evidence from the execution of the qualification activities shall enable the performanceassessment step to be carried out. The failure mode register from Sec.7.3.4 shall be used to follow up the datacollection and the qualification of the well.

7.9.4 Ensuring traceability of data

The operator shall establish an “audit trail” in order to ensure the traceability of data throughout thequalification process. Data shall be organized in such a manner that there is a clear link between the steps ofthe qualification process, from the qualification basis to performance assessment. It shall be possible to tracethe threads that have been identified, how they have been addressed (test, analysis, previous experience, etc.),what evidence has been developed (test and analysis reports), and how that evidence meets requirements in thewell qualification basis.




This step provides an opportunity for independent review of the qualification conclusions and will enable reuseof evidence in future projects, for example qualification of other wells or the same wells for a different use.

A fit for purpose electronic database should be used to enhance the traceability of data as described above.

7.10 Performance Assessment

The operator shall assess if the well qualification has been successful by comparing the available evidenceagainst the requirements specified in the well qualification basis.

If the performance assessment concludes that some requirements are not met, risk control options(modifications to the well) and further qualification activities shall be identified. This may include tighteningof the operating envelope for the well or enhanced inspection, workover and intervention strategies to meet therequirements based on the existing evidence. If none of these options are feasible, the well cannot be qualifiedagainst the well qualification basis.

Performance assessments may also be performed at defined points in time during operation to confirm that theoperations are within the assumptions for qualification stated in the Qualification Basis.

Key steps in the performance assessment are to:

— interpret the evidence to account for simplifications and assumptions made when the evidence wasgenerated and limitations and approximations in the methods used

— confirm that the qualification activities have been carried out and that the risk criteria have been met. A keypart of this confirmation is to carry out a gap analysis to ensure that the qualification evidence for eachidentified failure mode meets the specified risk criteria

— perform a sensitivity analysis of relevant parameter effects— assess the confidence that has been built based upon the qualification evidence through the qualification

activities. This shall consider the extent to which test specifications have independently reviewed and testwitnessed by an independent party

— compare the failure probability or performance margin for each identified failure mode of concern with therequirements in the qualification basis. Evidence shall be propagated from individual technologycomponents to the requirements specified for the entire system covered by the qualification.

The assessment findings may be represented as safe service envelopes such that a wider range of operatingconditions is covered than those specified in the well qualification basis. This can greatly simplify qualificationfor modified operating conditions.

7.11 Requirements met?

Depending on the findings of the previous step the operator shall decide on the need to modify the qualificationbasis.

7.12 Final Well Qualification Report

The operator shall document the well qualification findings for each well in a Final Well Qualification Report.This report shall be included in the Injection and Operating Plan (Sec.5.4.3) within the Storage Permitapplication (Sec.5.4).

A Final Well Qualification Report for each well shall document whether or not:

— the qualification activities stated in the Initial Well Qualification Report have been completed— the acceptance criteria for the qualification activities have been met — the functional requirements and target reliability as stated in the qualification basis have been met.



App.A Subsurface Data –

APPENDIX A SUBSURFACE DATA

Table A-1 Examples of relevant subsurface data and the information that may be derived from each.

Data type Information derived

Sei

smic

Regional seismology

Records of earthquake magnitudes, locations and depths

- background levels of natural seismicity.

Maximum ground motion velocities and displacements

- magnitude and orientation of regional stress field.

Regional 2D seismic lines

Time and depth migrated seismic sections

- regional structural cross sections

- lateral distance to subcrop/outcrop of formations

- regional map of lateral continuity of the primary seal.

Field specific 2D and 3D

seismic

Time and depth migrated 2D sections and 3D volumes

- detailed structural imaging

- location, orientation and throw of geological faults

- 3D time and depth formation horizon maps

- large-scale vertical and horizontal reservoir stratigraphic features, particularly unconformities, erosional surfaces and heterogeneity

- detailed, local map of lateral continuity of the primary seal.




Wel

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Petrophysical well log data

Resistivity/Conductivity logging

- formation resistivity

- indication of porosity

- indication of pore-fluid

- indication of permeability, if resistivity/ conductivity data with varying depth of investigation are available.

Gamma ray logging- rock characterization

- formation boundaries.

Spontaneous Potential logging- boundaries of permeable formations

- well correlation

Neutron/Density

- stratigraphy

- lithology

- depositional environment

- porosity

- permeability

- indication of pore fluid.

Temperature logging - temperature.

Caliper/dip logging - orientation of stress field.

Sonic logging

- porosity

- lithology

- rock matrix mechanical properties and related parameters for seismic survey processing.

Micro-resistivity, Downhole video imaging

- orientation of ‘breakouts’ from wellbore, orientation and spacing of fractures or other weak planes, indications of magnitude and orientation of principal stresses.

Well test data

Leak-off tests, short or extended- fracture initiation pressure in the zone for which the leak-off is being applied, pressure communication between zones.

Production and or injection followed by a shut-in pressure buildup (for production test) or shut-in pressure “falloff” (for injection test)

- effective reservoir permeability in zone near wellbore, formation damage near wellbore, qualitative indication of flow “boundaries”. For small connected reservoir volumes, can also indicate overall connected reservoir volume if test lasts long enough.

Interference tests, i.e. pressure measurement in neighboring wells at least one of which is either producing or injecting

- effective reservoir permeability in zone between wellbores, qualitative indication of flow “boundaries”. For small connected reservoir volumes, can also indicate overall connected reservoir volume if test lasts long enough.

Downhole fluid sampling data

- composition and variability of the formation fluids, particularly the presence of natural CO2, natural inert components or other important components that might react with the injected CO2 in: - the injection zone - other permeable units in the storage complex - the first permeable unit overlying the storage complex, if present.

Table A-1 Examples of relevant subsurface data and the information that may be derived from each. (Continued)





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Core plug test data

- capillary pressure as a function of saturation, for the relevant CO2 and formation fluid system in the injection zone, including residual (irreducible) water and CO2 saturations

- porosity

- relative permeability

- capillary entry pressure of the primary seal

- type of pore fluid

- characterization of clay minerals, tendency of isolated clay particles to be released and potentially cause plugging

- mineralogy of the rocks in the storage complex, including composition of the carbonates, clays and feldspars if present

- deformation properties of formations including Poisson’s ratio and Young’s modulus with appropriate spatial variations

- thermal properties including thermal expansion coefficient, specific heat capacity, thermal conductivity.






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Well integrity data

Well coordinates - number and location of wells.

Well schematics - as built construction.

Drilling reports including drilling fluid reports

- well construction

- quality of execution

- problem areas

- wear points.

Open hole log data including calliper logs- geological formation and hole condition prior to setting casing.

Cement evaluation logs - cement position and quality.

Cement placement data including centralizer programme

- cement position and quality.

Cement design and related laboratory reports

- mechanical and chemical properties of cement.

Well completion logs- tubular connection and jewellery depths

- condition of the above.

Dates of spudding, workovers and abandonment

- age of equipment

- history of the well.

Description of materials and cements used - mechanical and chemical properties.

Results of mechanical integrity tests performed on the well

- geological formation strength

- cement quality.

Annulus pressure/fluid sampling- integrity of casing and well barriers

- seal leak rates.

Visual inspection of the sealed top of the abandoned wellbore with possible bubble tests

- integrity of the abandonment.

Records of leak tests performed before abandonment

- integrity of the abandonment.

Other information such as the presence or absence of sustained casing pressure

- integrity of casing and well barriers.

List of operators (drilling operator, well operator, logging operator, etc.)

- sources of further information.

Track record of relevant regulatory changes regarding drilling and abandonment practices

- gaps with respect to current regulations.

Geomechanical history of the field including subsidence

- stress/strain/shear history of the well.

Industrial history of the area including drilling, injection, production and mining

- history of external factors on the well.

Records of temperature and pressure and composition of formation fluids over time

- reservoir history

- wellbore chemical exposure history.






No

n-t

ech

nic

al

da

ta

Conflict of interest

Hydrocarbon reservoirs, mineral resources, coal seams and geothermal energy extraction potential in zones above and below intended storage formation that may be impacted by CO2 geological storage project, and the status and ownership of these zones.

- hydrocarbon exploration and production developments.

Ownership and status of intended storage formation.

Surface infrastructure and facilities (buildings, transportation corridors (roads, railroads, pipelines and pipeline right-of-ways, etc.), power distribution lines, oil and gas production and processing facilities, groundwater reservoirs, etc.)

Subsurface infrastructure and facilities (wells, mines, waste repositories, gas storage sites, acid gas disposal sites, etc.)

Map of zones containing protected groundwater or zones with groundwater which are used in other subsurface development, and for which pressure depletion/build-up may impact or be impacted by the planned CO2 geological storage project.

- groundwater usage.

Existing pipelines and pipeline right-of-ways.

- pipelines.

Stakeholder map and plan to carry out a stakeholder assessment

- mapping of stakeholders and assessment of public perceptions of CO2 geological storage.

Map of protected or reserved areas

- assessment of legal and physical accessibility to injection zones.

Map of access pathways (pipeline right-of-ways and location of roads and other infrastructure needed for operation of CO2 geological storage project.

Regulatory

Applicable legislation, regulations and directives and initiatives to introduce new or modify existing legislation regulations and directives.

- regulatory restrictions, e.g., environmental regulations, trans-border transportation/migration issues.

EnvironmentalClimate, atmosphere and meteorology, ecology, wildlife, plants, parks and reserves

- surface and marine environment.

Societal

Demography and historical factors that can influence how the project will affect and be viewed by the local population. - demography and political, cultural and economic

environment.Political, cultural and regional economic circumstances that may influence the success of the project





App.B Generic failure modes for well integrity under exposure to Carbon Dioxide –

APPENDIX B GENERIC FAILURE MODES FOR WELL INTEGRITY

UNDER EXPOSURE TO CARBON DIOXIDE

Table B-1 Generic check-list of failure modes and failure mechanisms for wells under exposure to carbon dioxide (CO2).

No. Well Component Failure mode Failure mechanism

1 Well

1.01 Any part of the well

Misjudgment of status

- missing critical data - poor data.

2 Upper Completion

2.01 Production packer (including seal assemblies)

Material yields or cracks

- materials of construction lose their mechanical strength and begin to yield (hot), or brittle fracture if subjected to very cold conditions - materials on construction do not have capacity to resist pressure forces.

2.02 Material degradation

- compatibility with CO2 and other trace products in fluid stream - degradation under chemical stimulus - H2S cracking (corrosion) (Consider if H2 is likely).

2.03 Unreliable material performance

- explosive decompression - improper hardness at all conditions - degradation under chemical stimulus or under production fluid conditions.

2.04 Slipping - thermal expansion (or contraction) of tubing places additional load on locking mechanism - locks attempt to hold on to a worn or corroded casing wall - unstable well flow cycles material to fatigue failure.

2.05 Tubing and jewelry

Material degradation

- corrosion from fluids or from annulus souring - erosion (high flow rates, wireline intervention, tubing movement).

2.06 Material yields (cracks)

- pressure and temperature causes metal to yield - unstable flow causes fatigue - improper tubing movement causes buckling or necking.

2.07 Tools stuck downhole

- tubing and liner not in gauge.

2.08 Completion String Couplings


- corrosion from fluids or from annulus souring - erosion (high flow rates, wireline intervention, tubing movement).


- pressure and temperature causes metal to yield - unstable flow causes fatigue - improper tubing movement causes buckling or necking.

2.10 Seal fails - improper coupling connection used for CO2 service (no metal to metal) - improper assembly of coupling - coupling damaged before or during make-up - coupling backs off - corrosion cell within coupling threads - couplings back-off during running (rotation).

2.11 Surface controlled subsurface safety valve (SCSSV)


- corrosion from fluids - erosion (wireline intervention, high flow rates) - elastomer explosive decompression - elastomer degradation under fluids - elastomer hardness poor under certain conditions.


- materials on construction do not have capacity to resist pressure forces or remain ductile at certain temperatures.

2.13 Control line failure - control line blockage - control line disconnects from coupling - control line breaks owing to fatigue - control line is eroded by rubbing.




2.14 Wellhead & Christmas Tree

Material degradation, or unreliable material performance

- explosive decompression - improper hardness at all conditions - degradation under chemical stimulus - degradation under production fluid conditions.


- materials of construction lose their mechanical strength and begin to yield (hot), or - Brittle fracture if subjected to very cold conditions - materials on construction do not have capacity to resist pressure forces.

2.16 Corrosion of metal from inside

- thinning of pressure envelope owing to corrosion - embrittlement if H2S is present and not to NACE standard.

2.17 Cracks from cathodic protection; Corrosion from the environment; loss of containment

- hydrogen embrittlement- external corrosion.

2.18 Stress from piping on tree

- piping and tree movements place unacceptable stress on wellhead- “water Hammer”.

2.19 Stress from well supporting structure and environment

- structural events and tree movements place unacceptable stress on wellhead.

3 Lower Completion

3.01 Open hole - uncased

CO2 is not injected in the zone of interest

- thief zone.

3.02 Sand control Equipment failures - materials incompatibility - deterioration of equipment - mechanical failures of equipment.

3.03 Stimulation Fracture of cap rock

- hydraulic fracture job.

4 Casing/Liner/Cement

4.01 Casing/Liner Material Degrades - corrosion from annulus fluids (aerobic or anaerobic) - corrosion from reservoir fluids; (only for the production string) - embrittlement from sour annulus.


- materials on construction do not have capacity to resist pressure forces or remain ductile at certain temperatures; (this only applies to the strings that actually see the CO2).

4.03 Tools stuck downhole

- tubing and liner not in gauge.

4.04 Connections Material degradation

- corrosion from annulus fluids (aerobic or anaerobic) - corrosion from reservoir fluids - embrittlement from sour (H2S) annulus.


- materials of construction do not have capacity to resist pressure forces or remain ductile at certain temperatures - local stress associated with rock movements place excessive stress load on casing causing collapse - drilling dog-leg adds additional stress

4.06 Seal fails - coupling incorrectly installed - rock movement stresses pull couplings apart (axial) or collapse (pressure) - coupling backs off during running (rotation).

4.07 Conductor Corrosion of surface conductor onshore and platform wells

- collapse under weight.

4.08 Hydraulic damage of foundation soils around surface conductor

- collapse under weight.

Table B-1 Generic check-list of failure modes and failure mechanisms for wells under exposure to carbon dioxide (CO2). (Continued)





4.09 Cement Leak behind casing - CO2 degradation of cement - H2S degradation of cement - magnesium chloride degradation - thermal cracking and/or de-bonding (micro-annulus between cement and casing) due to Joule-Thomson effect during injection into, e.g., depleted gas reservoir - pre-existing channels in cement - pre-existing micro-annulus between casing and cement.

4.10 Cracked cement and casing and/or de-bonding

- different relative movement along wellbore due to subsidence of reservoir and/or expansion due to injection (e.g. “shear, kink, collapse”).

4.11 Poor cement job - centralisers did not function properly, mud wiper trip before cementing did not remove mud residue effectively.

4.12 Damaged cement across reservoir interval

- pressure tests (higher pressures) - temperature and pressure cycling - acids, chelators, stimulation.

5 Annuli

5.01 Frozen well - leak to annulus - cold fluid entering tubing.

6 Injection system

6.01 Unintended phase change in the wellbore

- both gas and dense phase CO2 present in the wellbore.

6.02 Equipment failures - pipeline specs inconsistent with material specs of well.

6.03 Tubing shocks - fluctuations due to start up (phase transition).

Table B-1 Generic check-list of failure modes and failure mechanisms for wells under exposure to carbon dioxide (CO2). (Continued)


dnv-rp-j203: geological storage of carbon dioxide

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