petrohysics level 2

EVALUATION – LEVEL 2 PETROLEUM CONSULTING – PETROPHYSICS ASSESSMENT GUIDE

Prepared By: Approval Global Business Unit

Petroleum Consulting

CAP Technical

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Document Number GL-GEC-TD-L4-04.IG01

Document Classification Controlled

Document Level L5

Revision NO. 000

Issue Date 16 Jan 2014

1

1.0 Purpose / How to Use This Guide

The information in this guide should be used by a Qualified Assessor or Qualified Supervisor to prepare for and conduct an assessment. This guide contains the questions that will be asked by the assessor and potential answers. The answers provided lay out the basic responses expected. However, answers that appear in lists / bullets are not exhaustive and responses from the employee should be validated per the discretion and experience of the assessor. The assessor should ask questions based on the scope of the day to day work taken on by the employee. Failure to provide a satisfactory answer to a question based on a Performance Criteria will result in the Employee being marked as “Not Yet Competent” for that specific criterion. Please ensure that all Mandatory Courses (including CBT’s) are complete prior to proceeding with assessments. When asked to “Identify and Explain” the employee should be able to identify the piece of equipment and clearly state its purpose and function.

2.0 Assessment Methods There are 4 methods of assessment in the Weatherford Competence Assurance Process. Each Unit of a Competency Standard has been marked with the required assessment method. These are the globally recommended methods for the assessment of that unit. As the weCAN method of assessment is the strongest and most robust, all units may be assessed through weCAN at any time.

3.0 Evidence Guidance A record of the assessment (known as evidence) is required to be uploaded into the Employee Connect system to prove the competency assurance as per the Competence Assurance Process (CAP) Document One set of evidence may be uploaded against a single element or against a single competence unit. Individual evidence does not need to be uploaded against individual performance criteria; however, the evidence at element or unit level must be sufficient and robust enough to demonstrate competence for each performance criteria. One set of evidence is NOT acceptable against more than one unit of competency for any assessment method other than Fast Track. The following listed criteria are generic requirements and self-descriptive, assessment of these items will be at the discretion of a competent Qualified Assessor or Qualified Supervisor, as applicable, in accordance with CAP.




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INDEX OF UNITS Sr No

Path Unit

1

Petrophysical Data Acquisition

2

Lithology

3

Shale Effects

4

Porosity

5

Statistical Analysis

6

Saturation

7

Permeability

8

Pore Pressure

9

Nuclear Resonance

10

Wellbore Imaging

11

Borehole Acoustics

12

Integration of Core and Log Data

13

Cased Hole Log Evaluation

14

Quantitative Seismic Studies

15

Petroleum Geology

16

Well Operations




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Unit 1 - Petrophysical Data Acquisition This unit is about the fundamentals of Petrophysics, understanding the value of information process and optimal tools used to meet customer challenges. The employee will be assessed in the elements relevant to the tasks he/she undertakes. Element 1 – Petrophysical Acquisition Planning

Sr. No.

Assessment Definitions Performance Definitions Critical Tasks

1 Compare the differences of log data, core data, test data and mud logging data.

Compare: Log data:

- continuous reading of data with excellent depth control

- limitations: derived measurement of formation parameters

Core data:

- extremely detailed and accurate assessment of the rock and fluids

- limitations: time consuming, slow, and expensive so the data sets are limited

Test data:

- measures pressure and flow rate at a single depth interval

- limitations: since it measures at a single point, it makes it slow and expensive to get comprehensive data sets

Mud logging data:

- direct measurement of the drill bit cuttings, results are very quick and accurate

- limitations: sample rate is large, which limits the detailed output, and the depth control is poor so the placement of the samples has low confidence

2 Prepare a sales support presentation for wireline and LWD logging that can be presented to a customer.

Provide: a personally created sales

support presentation that presents solutions to customer challenges for a specific client and focuses on how

our solution meets or met the customer‘s needs/challenges. Highlight the merits of the presentation to the Assessor, listing the customer’s needs that were identified, the answer product that was created and how it met or will meet the need.




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3

Prepare a post-job Answer Product presentation for wireline and LWD logging that can be presented to a customer.

Provide: a personally created post-

job Answer Product presentation that describes the processing and results on a specific well and focuses on how the results meet or met the customer‘s need. Highlight the merits of the presentation to the Assessor, listing specifics of the processing and results and how the results met or will meet the need.,

4

Explain optimal logging suite for specific customer needs or challenges using non-standard logging tools (imaging, shear slowness, formation testing, and NMR).

Explain: Given a list of customer challenges, provide the optimal non-standard logging tool for the challenge. Porosity in difficult or unknown lithology. Qualifying pore sizes and trapped fluids. (tool: NMR)

Understanding of natural fracture patterns. Direction of well bore breakout due to formation stress. (tool: Imaging)

Understanding properties needed for optimizing hydraulic fracturing. (tool: Shear Slowness)

Quantifying ability of formation to flow. Determination of formation pressure. (tool: Formation Testing)




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UNIT 2 – Lithology This unit is about the properties and measurements used to identify lithology. The employee will be assessed in the elements relevant to the tasks he/she undertakes. Element 1 – Discrimination of Reservoir/Non-Reservoir

Sr. No. Assessment Definitions Performance Definitions Critical Tasks

1

Identify reservoir zones in complex lithologies and structural settings using full suite of petrophysical tools (including well test information).

Identify: reservoir zones in a Complex Lithology Answer Product and explain how the measurements support the interpretation. Answer Product to be provided by Assessor or employee. Minimum log requirements should include triple combo data, acoustics, pressure tests for minimum three lithologies (i.e., shale, limestone, dolomite) depending on region.

Element 2 – Lithology Identification using Logs


1 Determine a complex lithology (more complex than sand shale) using appropriate lithology logs.

Determine: the lithology in a Complex Lithology Answer Product and explain how the measurements support the interpretation. Answer Product to be provided by Assessor or employee. Minimum log requirements should include triple combo data, acoustics, and one specific lithology dependent measurement for minimum three lithologies (i.e., shale, limestone, dolomite) depending on region. (Assessor note: “appropriate” is dependent on region / area; lithology dependent measurement is also dependent on region)




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UNIT 3 – Shale Effects This unit is about the effect of shale on porosity and how to determine shaliness using logs. The employee will be assessed in the elements relevant to the tasks he/she undertakes. Element 1 – Shale Nature and Effects


1 Identify the nature of various clays and shales, describe the difference between a clay and a shale.

Identify: Clays:

- fill well space - destroy the wellbore Clays: general term including many

combinations of one or more clay minerals with traces of metal oxides and organic matter. Clay minerals:

four main groups: kaolinite, montmorillionite-smectite, illite, chlorite Nature: Montmorillionite-smectite and

illite are expansive clay minerals, which mean they change their volume with an increase of water content (swelling). This can lead to wellbore collapse. Clay minerals are part of shales. Shales: Clay is a group of minerals

that may form shale in a laminated environment or mudstone in a non-laminated environment. Shale: fine-grained clastic

sedimentary rock composed of a mix of clay minerals, silt-sized particles and other minerals (like quartz or calcite). Shale is characterized by breaks along thin laminae or parallel layering.




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UNIT 4 – Porosity This unit is about porosity tools and how they are used to determine and calculate porosity. The employee will be assessed in the elements relevant to the tasks that he/she undertakes. Element 1 – Porosity Tools


1 Identify reasons for abnormal log response in porosity tool measurements.

Identify reasons: Density: Tool fails to maintain pad

contact or connection to the formation. The mud cake becomes too thick to correct and the use of barite in the mud causes the density to read in error. Neutron: Borehole fluid may become

gaseous or foam. Sonic: Borehole fluid may become

gaseous or foam. If formation becomes fractured or rough, the returning signal will have low amplitude.

Element 2 – Porosity Determination


1 Demonstrate differences between effective and total porosity systems.

1. Show the calculations for determining effective porosity from total porosity.

2. Explain how each is different. 3. Use log analysis software to create

an effective porosity curve from a data set.

4. Show how changes in the log measurements influence the effective porosity.

2

Reconcile log derived connected and non-connected porosity with core measurements (incl. thin sections).

Deliver a plot with core and log values and explain the steps taken to achieve porosity normalization. 1. Employee must provide log

(minimum triple combo data) 2. Provide core data for the interval of

interest (i.e., porosity from cores) 3. Provide thin sections of the core 4. Explain connection between log

data, calculated porosity from core and visual interpretation of thin sections




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3 Tie in and compare shaly sand porosity values between logs and cores.

Deliver a plot with core and log values and explain the steps taken to achieve core corrected porosity. 1. Employee must provide log

(minimum triple combo data) 2. Provide core data for the interval of

interest (i.e., porosity from cores) 3. Explain connection between log

data, calculated porosity from core 4. Correct the log based porosity to

match core porosity 5. Create a plot with core corrected

porosity




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UNIT 5 – Statistical Analysis This unit is about understanding the basic concept of errors in statistical log analysis and how they react to measurements (expand or restrict). The employee will be assessed in the elements relevant to the tasks that he/she undertakes. Element 1 – Statistical Log Analysis


1 Explain the error minimization approach to porosity determination from logs.

Explain: Every measurement has an error bar; when you combine the measurements, you either expand or restrict the error.




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UNIT 6 – Saturation This unit is about the resistivity and conductivity principles, including how to determine levels of resistivity and the effects of porosity, shale and carbonates in water saturation. The employee will be assessed in the elements relevant to the tasks that he/she undertakes. Element 1 – Saturation Determination


1 Assess and quantify the impact of shaly sand models on water saturation.

1. Use recent data set from region to calculate water saturation values in minimum of three models

2. Explain the difference in the outcomes – which model is best for the area.

3. State which model is the most appropriate for the logging environment and why.

Example models may include: Simandoux, Indonesian, and dual-water (Assessor note: upload output as evidence)

2

Reconcile results of oil/gas differentiation from log data with other evidence (e.g. mud logs, well tests etc.).

1. Produce an interpretation log that identifies oil and gas.

2. Explain how the non-log data supports the interpretation.

3. Suggest reasons for differences between the log data and non-log data.

Example: If there is a mud log with a gas show, but no indication on the log, explain why both can be valid but different.

3 Describe methods for independent determination of "m" (porosity exponent) in carbonates.

Describe: Provide evidence of a literature study or search on local/regional methods. Support or compare findings through discussion with assessor. Findings should include, but are not limited to: - Geographic validity (if MENA,

literature should be based on MENA geography)

- Geologic validity (if old carbonates, literature should be based on old carbonates)




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4 Describe methods for interpreting lateral and vertical continuity and other reservoir properties.

Describe:

Method for interpreting lateral and vertical continuity requires datasets from various wells Example: look at the data sets, identify the reservoir zones on the data sets and identify basic differences between reservoir zones in data logs (i.e., oil/water contact, oil only, etc.) Method for interpreting reservoir properties requires different data from different wells, such as… image data for structural information and pressure distribution test; fluid samples or lab analysis; core samples for sedimentalogical analysis; normal log data for petrophysical analysis.




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UNIT 7 – Permeability This unit is about defining the basics of permeability. The employee will be assessed in the elements relevant to the tasks he/she undertakes. Element 1 –Permeability Estimation from Standard and Specialized Logs


1 Determine permeability from porosity and irreducible water saturation.

1. Create a permeability log from porosity.

2. Account for effects of irreducible water saturation and tortuosity.

3. Implement a solution to determine true permeability that includes either NMR or core analysis (or both).

4. Deliver a log with porosity, a calculated permeability and a corrected permeability.

2 Generate a moved oil plot.

1. Find the appropriate dataset. 2. Produce a moved oil plot. 3. Discuss effect of the input

parameters on the output.

3 Describe factors that contribute to mobility.

Describe: reasons for lack of fluid flow; include effects of fluid viscosity, permeability, porosity and tortuosity.

Element 2 –Formation Testing Evaluation


1 Define fluid contacts and calculate fluid density.

1. Produce a log from a pressure test gradient

2. Identify fluid contact depth 3. Calculate fluid densities above and

below the contact 4. Interpret fluid type (water, oil, gas)

2

Explain method for pulling quality tester fluid using acquisition techniques (how to pull a clean sample).

Explain: monitoring flow line fluid

resistivity, density, and optical characteristics to determine best conditions for pulling sample; give example of the process, techniques used (watch as resistivity goes down, crack the valve once you have formation water, take the sample, etc.)




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UNIT 8 – Pore Pressure This unit is about abnormal pressures and their impact on logs. The employee will be assessed in the elements relevant to the tasks that he/she undertakes. Element 1 – Pore Pressure Prediction


1

Outline how abnormal pressures are created, and describe the impact of abnormal pressures zones on logs.

Outline: Abnormal pressures:

- pressure that deviates from the normal pressure gradient

- could be created from drilling, depletion or geological factors

Impact on logs: potential change in

resistivity, sonic, density, neutron




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UNIT 9 – Nuclear Resonance This unit is about NMR principles, tools, data and properties. The employee will be assessed in the elements relevant to the tasks that he/she undertakes. Element 1 – NMR Logging


1 Describe NMR principles: proton recession, and relaxation in porous media.

Describe: Two main principles of NMR are proton recession and proton relaxation. Proton Recession: Before logging,

the protons in the formation fluids are randomly oriented. When the tool passes through the formation, the tool generates magnetic fields that activate those protons. First, the tool’s permanent magnetic field aligns, or polarizes, the spin axes of the protons in a particular direction. Then the tool’s oscillating field is applied to tip these protons away from their new equilibrium position. Proton Relaxation: When the

oscillating field is subsequently removed, the protons begin tipping back, or relaxation, toward the original direction in which the static magnetic field aligned them. Specified pulse sequences are used to generate a series of so-called spin echoes, which are measured by the NMR logging tool and are displayed on logs as spin-echo trains. These spin-echo trains constitute the raw NMR data. Decay Spectrum: The amplitude of

the spin-echo-train decay can be fit very well by a sum of decaying exponentials, each with a different decay constant. The set of all the decay constants forms the decay spectrum or transverse-relaxation-time (T2) distribution. Properly defined, the area under the T2-distribution curve is equal to the initial amplitude of the spin-echo train. Hence, the T2 distribution can be directly calibrated in terms of porosity.




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2 Describe the NMR response to pore size, free fluid, trapped water, permeability, and water cut.

Describe: T2 values are related to

pore sizes; a T2 value can be selected below which the corresponding fluids are expected to reside in small pores and above which the corresponding fluids are expected to reside in larger pores. This T2 value is called the T2 cutoff (T2cutoff). Clay-bound water, capillary-bound water (trapped water), and movable (free) water occupy different pore sizes and locations. Hydrocarbon fluids differ from brine in their locations in the pore space, usually occupying the larger pores. They also differ from each other and brine in viscosity and diffusivity. NMR logging uses these differences to characterize the fluids (water cut) in the pore space. The T2 distribution describes the pore size distribution, which can be used to determine permeability.

3 Describe NMR tools, the similarities, differences and operational issues.

Describe: Pad or Mandrel tools – both align

and recess hydrogen; both follow normal NMR principles Pad tool measures only a small

sample on one side of the borehole Mandrel tools measure larger

vertical resolution, but greater volume of investigation; more susceptible to borehole environment Operational issues: limits to

borehole salinity

4 Define NMR permeability determination.

Describe: NMR relaxation properties of rock samples are dependent on porosity, pore size, pore-fluid properties and mineralogy. The NMR estimate of permeability is based on theoretical models that show that permeability increases with both increasing porosity and increasing pore size. Two related kinds of permeability models have been developed. The free-fluid or Coates model can be applied in formations containing water and/or hydrocarbons. The Average-T2 model can be applied to formations containing only water.




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Measurements on core samples are necessary to refine these models and produce a model customized for local use.

5 Define bound water vs free water.

Define: Bound water - water that is

chemically attached to clay molecules Free water is free to circulate in the

pore space

6

Describe NMR saturation techniques and interpretation including appropriate applications and limitations.

Describe: The NMR data and the

deep resistivity data are integrated to determine whether producible water is in the virgin zone, or whether an interval with high water saturation may actually produce water-free hydrocarbons. Applications:

- Obtain lithology independent porosity

- Capture clay bound and capillary bound water

- Obtain a more accurate water saturation calculation because free and trapped water is identified

Limitation:

- Must have understanding of T2 cutoff




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UNIT 10 – Wellbore Imaging This unit is about the tools used in wellbore imaging and the types of features and faults that can be identified on image logs. The employee will be assessed in the elements relevant to the tasks he/she undertakes. Element 1 – Interpretation of Borehole Images and Dip Meter Data


1 Identify and explain fractures on image logs.

1. Produce an image log from an appropriate dataset

2. Select a section of the log 3. Identify and characterize a

minimum of three types of fractures (Examples: resistive fractures, conductive fractures, borehole drilling induced fractures, etc. )

2 Compare image log output to core photography.

1. Produce a core photo integration log

2. Indicate the common features between the image and the core photo

(Examples of common features include: fractures, cross-bedding, grain size, etc.)

3 Interpret structural dip in routine situations and recognize more complex relationships.

Interpret: provide an image or dip

interpretation on an appropriate dataset and be able to explain the geological reasons for changes in dip. (Example: unconformities, faults, folds, etc.)

4 Sketch cross sections using dip plots including structure and faults.

Sketch: using the same data set as

Sr. No. 3, draw the cross section in 2D and 3D (Assessor note: upload output)

5 Correlate image data with other fracture indicators.

Correlate: using typical image log and another piece of evidence identify where both are same and where they differ; provide reasons why they differ. Sample statements: - Acoustics requires large, deep

fractures in order to be seen. - Imaging can detect fractures that

are very small. - Cores may have fractures due to

core handling. - Images require resistive differences




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between fracture and formation.

(Assessor note: employee may use sample from an acoustic log or core)

6

Compare computer generated auto-dip versus hand-picked dips from an image and explain differences.

1. Generate a hand-picked log and an auto-dip log

2. Show similarities 3. Explain differences On the surface auto-dip and hand-picked dips may look the same; however, auto-dip may generate dips of non-features, such as noise, and hand-picked requires analyst who can differentiate between valid and invalid data.




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UNIT 11 – Borehole Acoustics This unit is about the value of borehole acoustics measurements and how to identify basic characteristics in compressional and shear data. The employee will be assessed in the elements relevant to the tasks he/she undertakes. Element 1 – Anisotrophy and Mechanical Data


1 Create anisotrophy answer product and discuss geological causes of stress anisotrophy.

Create: an answer product demonstrating shear anisotropy. Include fast and slow shear and the direction of anisotropy. Intrinsic anisotropy is caused by the crystalline structure of the rock having different mechanical properties in different directions. Stress-based anisotropy is a change in mechanical properties with direction caused by external forces acting on the rock – usually tectonic.

2 Create mechanical properties from acoustics and density, state limits of acceptable data.

Create: a standard mechanical

properties log which includes: triple-combo data, acoustics, and calculated Young’s modulus, Poisson’s ratio and brittleness. Limits:

Poisson’s ration between 0 and 0.5. Vp/Vs ratio greater than 1, normally between 1.4 and 2.0.




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UNIT 12 – Integration of Core and Log Data This unit is about integrating core analysis with various types of log data and tools/techniques that are used during the process. The employee will be assessed in the elements relevant to the tasks that he/she undertakes. Element 1 – Analyze and Integrate Routine Core Analysis


1 Outline techniques for measurement of porosity, permeability and saturation.

1. Full size core is drilled. 2. In lab, Gamma Ray of core is

measured 3. Core plugs are taken at specified

depths 4. Dean-Stark method determines

core plug porosity and saturations, grain and bulk densities.

5. Flowing inert gas (N2 or He) through the core provides permeability.

2

Interpret routine core analysis data (porosity, permeability, grain-density and saturation) to derive reservoir properties, lithology, and fluid content.

1. Obtain a routine core analysis report

2. Interpret data (show porosity, density, saturation)

3. Derive reservoir properties, lithology and fluid

4. Explain the methodology (steps and reasoning) of the interpretation

Element 2 – Analyze and Integrate Special Core Analysis


1

Describe usage of special core analysis to determine electrical properties (m, n, Qv) and procedures to assure quality.

Describe: M: Several core plugs are obtained

and cleaned and dried of fluids. The plugs are flushed with water of various salinities and the plug resistivity is measured. The porosity is plotted against the resistivity ratio (Ro/Rw) on logarithmic scale. The slope is M and the value at 100% porosity is A. N: Core plugs are flushed with fluids

of varying saturation and the resistivity index (Rt/Ro) is measured. Values are plotted in log-log scale. The slope of the line through the points and (1,1) is N. Qv: Conductometric titration is a




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technique for estimating the cation-exchange capacity (Qv) of a sample by measuring the conductivity of the sample during titration. The technique includes crushing the end pieces of a core sample and mixing it for some time in a solution like barium acetate, during which all the cation-exchange sites are replaced by barium (Ba++) ions. The solution is then titrated with another solution, such as MgSO4, while observing the change in conductivity as the magnesium (Mg++) ions replace the Ba++ ions.

2 Explain importance of capillary pressure and wettability.

Explain: Capillary Pressure: The capillary

pressure curve is important for understanding saturation distribution in the reservoir and affects imbibition and multiphase fluid flow through the rock. Capillary pressure is the pressure required to push the non-wetting fluid into the pore spaces. Rocks have a distribution of pore throat sizes, so as more pressure is applied to the non-wetting phase, increasingly smaller pore openings are invaded. Wettability: Wettability is the

preference of a solid to contact one liquid or gas, known as the wetting phase (preferred fluid), rather than another liquid or gas. The wetting phase will tend to spread on the solid surface and a porous solid will tend to imbibe (draw in) the wetting phase, in both cases displacing the non-wetting phase. Rocks can be water-wet, oil-wet or intermediate-wet.

3

Describe how special core analysis can determine relative permeability curves and residual saturations.

Describe: Using a core plug, first water and then oil is injected until steady state is reached, measuring permeability with each fluid. The residual oil and water saturations are determined. The data is plotted on a perm vs saturation graph. The equations help the reservoir engineer understand the manner in which the formation will flow.

http://www.glossary.oilfield.slb.com/en/Terms/r/reservoir.aspx

http://www.glossary.oilfield.slb.com/en/Terms/i/imbibition.aspx

http://www.glossary.oilfield.slb.com/en/Terms/m/multiphase_fluid_flow.aspx

http://www.glossary.oilfield.slb.com/en/Terms/p/pore_throat.aspx

http://www.glossary.oilfield.slb.com/en/Terms/p/pore_throat.aspx

http://www.glossary.oilfield.slb.com/en/Terms/p/porous.aspx

http://www.glossary.oilfield.slb.com/en/Terms/w/water-wet.aspx

http://www.glossary.oilfield.slb.com/en/Terms/o/oil-wet.aspx

http://www.glossary.oilfield.slb.com/en/Terms/o/oil-wet.aspx




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Element 3 – Analyze and Integrate Petrography and Mineralogy Data


1 Define thin section and x-ray diffraction.

Define: Thin Section: A thin sliver of rock is

cut from the sample with a diamond saw and ground optically flat. It is then mounted on a glass slide and then ground smooth using progressively finer abrasive grit until the sample is only 30 μm thick. When placed between two polarizing filters set at right angles to each other, the optical properties of the minerals in the thin section alter the color and intensity of the light as seen by the viewer. As different minerals have different optical properties, most rock forming minerals can be easily identified. XRF: a method used for determining

the atomic and molecular structure of a crystal, in which the crystalline atoms cause a beam of X-rays to diffract into many specific directions. The mean positions of the atoms in the crystal can be determined, as well as their chemical bonds, their disorder and various other information. XRF is used to determine the mineralogy of the sample.

2 Describe scanning electron microscopy.

Describe: Scanning Electron Microscope (SEM): a type of

electron microscope that produces images of a sample by scanning it with a focused beam of electrons. The electrons interact with atoms in the sample, producing various signals that can be detected and that contain information about the sample's surface topography and composition.

http://en.wikipedia.org/wiki/Diamond_saw

http://en.wikipedia.org/wiki/Diamond_saw

http://en.wikipedia.org/wiki/Microscope_slide

http://en.wikipedia.org/wiki/Micrometre

http://en.wikipedia.org/wiki/Crystal

http://en.wikipedia.org/wiki/Atom

http://en.wikipedia.org/wiki/X-rays

http://en.wikipedia.org/wiki/Diffraction

http://en.wikipedia.org/wiki/Chemical_bond

http://en.wikipedia.org/wiki/Entropy

http://en.wikipedia.org/wiki/Electron_microscope

http://en.wikipedia.org/wiki/Electron

http://en.wikipedia.org/wiki/Topography




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UNIT 13 – Cased Hole Log Evaluation This unit is about common tools used in cement bond evaluation and the basic principles and measurements of production logging. The employee will be assessed in the elements relevant to the tasks that he/she undertakes. Element 1 – Zone Isolation and Pipe Integrity


1 Characterize cement quality behind casing without gas present.

1. Obtain a bond log that demonstrates bonded intervals and free pipe

2. Interpret the CBL 3. Explain where the cement job is

good and where it is poor 4. Provide reasoning to support the

interpretation (Assessor note: The employee needs to point out intervals of good cement, free pipe and top of cement on a bond log/CBL.)

2 Characterize cement quality with sector-bond or ultra-sonic scanner.

1. Obtain a bond log that demonstrates bonded intervals and channeling

2. Interpret the SBT/ERS 3. Explain where the cement job is

good and where it is poor 4. Provide reasoning to support the

interpretation (Assessor note: The employee needs to point out intervals of good cement, free pipe, top of cement, and channeling on a sector bond or ultra-sonic scanner.)

Element 2 – Evaluate Cased Hole Logs for Reservoir Surveillance


1 Outline procedure and objectives of periodic logging for hydrocarbon/ water discrimination.

Outline: Time-dependent logging: log the

well periodically, every few months; calculate water saturation. Objective: monitor the depth of the

oil-water contact and the water saturation over time as production and tertiary recovery is done.




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2 Describe the physics of pulsed neutron logging.

Describe: An electrical neutron

generator produces bursts of neutrons. The neutrons enter the formation and interact with material in the rock and fluids. The tools measure gamma rays that are released as the neutrons are captured by the formation. The tool measures porosity and sigma. Sigma responds closely to resistivity.

3 Describe the physics of induced gamma spectroscopy carbon/oxygen.

Describe: The tool works similar to pulsed neutron logging except the energy spectrum of the resultant gamma rays are measured. This energy spectrum determines which minerals are present in the formation. Also known as carbon-oxygen logging.

Element 3 – Evaluate Cased Hole Logs for Inflow Performance


1 Interpret flowmeters, fluid density, water cut, and temperature profiles in producing stream.

1. Obtain a field production log 2. Identify intervals of no flow, inflow,

and outflow (if appropriate) 3. Explain reasoning for interpretation Sample reasoning statements: - A no flow zone will have constant

spinner velocity, gradient temperature profile.

- An inflow zone will have increasing spinner velocity uphole.




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UNIT 14 – Quantitative Seismic Studies This unit is about the fundamentals of working with seismic data. The employee will be assessed in the elements relevant to the tasks that he/she undertakes. Element 1 – Generate Well Synthetics


1 Describe the application of log data to seismic data.

Describe: Acoustic log data, which is depth-based, is tied in seismic data, which is time-based. Acoustic log data has a higher resolution than seismic data; therefore, logging data is used to improve and update the seismic model.

Element 2 – Model Seismic Amplitudes


1 Describe the fundamentals of reflection seismology and its use in oilfield exploration.

Describe: Reflection seismology

uses the principles of seismology to estimate the properties of the Earth's subsurface from reflected seismic waves. When a seismic wave travelling through the Earth encounters an interface between two materials with different acoustic impedances, some of the wave energy will reflect off the interface and some will refract through the interface. At its most basic, the seismic reflection technique consists of generating seismic waves and measuring the time taken for the waves to travel from the source, reflect off an interface and be detected by an array of receivers (or geophones) at the surface. Knowing the travel times from the source to various receivers, and the velocity of the seismic waves, a geophysicist then attempts to reconstruct the path of the waves in order to build model of the subsurface.

http://en.wikipedia.org/wiki/Seismology

http://en.wikipedia.org/wiki/Earth

http://en.wikipedia.org/wiki/Reflection_(physics)

http://en.wikipedia.org/wiki/Seismic_wave

http://en.wikipedia.org/wiki/Seismic_wave

http://en.wikipedia.org/wiki/Reflection_(physics)

http://en.wikipedia.org/wiki/Refraction

http://en.wikipedia.org/wiki/Geophone




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The goal of seismic interpretation is to obtain a coherent geological story from the map of processed seismic reflections. The aim of this is to produce structural maps that reflect the spatial variation in depth of certain geological layers. Using theses maps hydrocarbon traps can be identified and models of the subsurface can be created that allow volume calculations to be made.




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UNIT 15 – Petroleum Geology This unit is about common well operations, quality control and well design. The employee will be assessed in the elements relevant to the tasks he/she undertakes. Element 1 – Stratigraphic Seal Occurrence and Effectiveness


1 Define and list requirements for a hydrocarbon seal.

Define: A hydrocarbon trap is formed when the upwards movement of the hydrocarbon is trapped below a rock layer that is impermeable to the hydrocarbon. Structural traps are formed as a result of changes in the structure of the subsurface due to processes such as folding and faulting, leading to the formation of domes, anticlines, and folds. The seal must be spatially large enough to hold an economic quantity of hydrocarbon beneath. The permeability of the seal must be less than the permeability required for the hydrocarbon below to flow. And the seal must be mechanically strong enough to hold the pressure below without fracturing. Further, the seal must have been in place before the migration of the hydrocarbon and remained in place and effective since migration.

Element 2 – Sedimentation and Poro-perm Distribution


1 Describe the relationship between rock properties, porosity, permeability, and saturation.

Describe: Rocks that are well sorted with large grains will have large pores, high porosity, high permeability, and have a low residual saturation. Rocks that are poorly sorted with smaller grains will have small pores, low permeability, and high residual saturation.

http://en.wikipedia.org/wiki/Structural_trap

http://en.wikipedia.org/wiki/Dome_(geology)

http://en.wikipedia.org/wiki/Anticline

http://en.wikipedia.org/wiki/Geological_fold




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Element 3 – Stratigraphic Trap Analysis


1 List the elements contributing to an effective stratigraphic trap.

List: Stratigraphic traps are formed as a result of lateral and vertical variations in the thickness, texture, porosity or lithology of the reservoir rock. Examples of this type of trap are an unconformity trap, a lens trap and a reef trap. The requirements of a stratigraphic trap are the same as a structural trap. Stratigraphic traps depend on the buoyancy force of the fluid to be overcome by the capillary force of the seal medium.

Element 4 – Principles of Diagenesis


1

Explain the chemical and physical principles of diagenetic processes, including the effects of mineralogy, rock water interaction, pressure and temperature.

Explain: Diagenesis is changes to sedimentary rocks during and after rock formation. It is any chemical, physical, or biological change undergone by sediment after its initial deposition at temperatures and pressures less than that required for the formation of metamorphic rocks.

After deposition, sediments are compacted as they are buried beneath successive layers of sediment which increase overburden pressure. They are cemented by minerals that precipitate from formation water.

Grains of sediment, rock fragments and fossils can be replaced by other minerals during diagenesis. Porosity usually decreases during diagenesis, except in cases such as dissolution of minerals and dolomitization.

2

Establish the basic differences between diagenesis in carbonates vs. siliclastics and the implications that these differences have for reservoir quality and complexity.

Describe: Siliclastic sedimentary rocks are composed of silicate minerals that were transported by moving fluids and were deposited when these fluids came to rest. In clastic rocks, diagenesis by temperature and pressure affect the porosity of the rock. The rock’s mineral structure is not usually affected.

http://en.wikipedia.org/wiki/Stratigraphy

http://en.wikipedia.org/wiki/Porosity

http://en.wikipedia.org/wiki/Lithology

http://en.wikipedia.org/w/index.php?title=Unconformity_trap&action=edit&redlink=1

http://en.wikipedia.org/w/index.php?title=Lens_trap&action=edit&redlink=1

http://en.wikipedia.org/w/index.php?title=Reef_trap&action=edit&redlink=1

http://en.wikipedia.org/wiki/Sedimentary_rocks

http://en.wikipedia.org/wiki/Sediment

http://en.wikipedia.org/wiki/Metamorphic_rocks

http://en.wikipedia.org/wiki/Solution

http://en.wikipedia.org/wiki/Rock_(geology)

http://en.wikipedia.org/wiki/Fossil


http://en.wikipedia.org/wiki/Solvation

http://en.wikipedia.org/wiki/Dolomitization




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Carbonate rocks are primarily composed of carbonate minerals such as limestone, which is composed of calcite, and dolostone, which is composed of the mineral dolomite. Carbonates are precipitated out of minerals in the water. Because the minerals in carbonates can be affected by the formation water, diagenesis affects the mineral composition and the presence of organic matter. These chemical factors plus the temperature and pressure affect carbonate rocks.

Element 5 – Nature of Carbonate Porosity and its Evolution


1 Define and characterize carbonate pore systems geologically and petrophysically.

Define: Porosity in carbonate rocks has two sources.

Primary (matrix supported) porosity is formed at time of deposition and is the void space between grains of matrix rock.

Secondary porosity is formed after deposition and is caused by diagenesis of the rock by chemical, biological, and mechanical changes to the rock.

2

Describe the basic differences between carbonate and siliclastic pore systems and discuss the implications relative to reservoir characteristics.

Describe: Porosity in siliclastic rock is almost exclusively primary porosity.

Carbonates can contain a large percentage of secondary porosity.

There is normally a string relationship between porosity and permeability in siliclastics. Due to a large amount of secondary porosity, the relationship does not hold true for carbonates.

3 Describe the concept of carbonate porosity evolution through time.

Describe: Carbonate primary porosity is formed during deposition. Chemical interactions between the rock and the formation water cause organic matter to be dissolved and cause changes in the mineral content. Over time, the secondary porosity of the rock increases as diagenesis occurs. Primary porosity can be quite small compared to total porosity after diagenesis.

4 Define the link between diagenesis and porosity in carbonates.

Define: Secondary porosity is caused by diagenesis of the rock by chemical, biological, and mechanical changes to the rock.

http://en.wikipedia.org/wiki/Carbonate_mineral

http://en.wikipedia.org/wiki/Limestone

http://en.wikipedia.org/wiki/Calcite

http://en.wikipedia.org/wiki/Dolostone

http://en.wikipedia.org/wiki/Dolomite




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Element 6 – Turbidites and Deep Water Deposition


1 Describe the basic processes of sediment gravity flows (turbidity currents and debris flows).

Describe: Sediment gravity flow is a sediment transport mechanism where sediment is transported in a combination of the forces of gravity and the buoyancy of the fluid.

Turbidity current – Grains are

suspended by fluid turbulence within the flow. Because the behavior of turbidity currents is largely predictable, they exhibit Newtonian behavior.

Debris flow – Grains are supported

by the strength and buoyancy of the matrix. Debris flows have cohesive strength, which makes their behavior difficult to predict using the laws of physics. As such, these flows exhibit non-Newtonian behavior. Because debris flows have cohesive strength, unusually large rocks may be able to literally float on top of the mud.

2 Explain the nature of turbidite systems and the reservoirs contained within them.

Explain: A Turbidite is the geologic deposit of a turbidity current, which is responsible for distributing vast amounts of clastic sediment into the deep ocean. Reservoirs are of a clastic material and usually have a fining upward sedimentology.

3 Define the principal elements of typical turbidite systems.

Define: The normal sequence is a series of fining upwards structures. From top down: - Massive mudstone (may be missing

due to erosion after deposition). - Parallel laminated siltstone - Ripple laminated fine grained

sandstone - Planar laminated fine to medium

grained sandstone - Massive, fine to course grained

sandstone.

http://en.wikipedia.org/wiki/Turbidity_current

http://en.wikipedia.org/wiki/Newtonian_fluid

http://en.wikipedia.org/wiki/Debris_flow

http://en.wikipedia.org/wiki/Non-Newtonian_fluid

http://en.wikipedia.org/wiki/Geologic

http://en.wikipedia.org/wiki/Deposition_(geology)

http://en.wikipedia.org/wiki/Turbidity_current

http://en.wikipedia.org/wiki/Clastic

http://en.wikipedia.org/wiki/Sediment

http://en.wikipedia.org/wiki/Ocean




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Element 7 – Fluviodeltaic and Shallow Marine Clastic Systems and Reservoirs


1 Define basic processes in the paralic environment.

Define: Sediment is carried from the land by rivers to the ocean. The water velocity slows down when it hits the ocean resulting in the sediment dropping out in different areas depending on the grain size. Tides, waves, and ocean current redistribute this sediment. Over time, the path of the river changes creating a delta.

2 List the main depositional environments.

List:

Deltaic – a complex environment at

the mouth of a river

Tidal – a high energy environment

seaward of the shoreline.

Lagoonal – a low energy

environment landward of the shoreline.

Beach – an environment created at

the shoreline which is then subsequently buried.

3 Describe reservoir properties dependent on position within the margin/shelf.

Describe: The reservoir properties will be complex and depend on the position in the ancient shoreline. A high energy environment will deposit large sediment and result in a high porosity, high permeability reservoir. The areas with limited flow or low energy, the porosity and permeability will be lower.

Element 8 – Non-marine Depositional Systems and Reservoirs


1 Define basic processes and deposits in non-marine environments.

Define: Weathered sediment is

carried by wind or water to collection areas on land.

2 List the main depositional environments.

List:

Alluvial – loose sediment pulled by

temporary events such as landslides.

Aeolian – windblown sediment such

as desert or beach sand dunes.

Fluvial – sediment found at the

bottom of moving water in rivers or streams.

Lacustrine – occurring on the bottom

of lakes and other still, fresh water.




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Element 9 - Plate Tectonics and Regional Processes


1 Describe effects of stress, effective stress, strain and rock properties in geomechanics.

Describe: Stress is the amount of force applied to a rock.

Overburden stress is found in all

rocks and is the weight of the rocks above. It is the average density of the rocks multiplied by the force of gravity.

Lateral stresses are caused by

tectonics and may be different in different directions (stress anisotropy). For example, rock at the top of an anticline fold will be in tension while rocks at the top of a sinecline fold will be in compression. Also, rocks near a fault will have lateral forces.

Effective stress is the stress on the

rock after pore pressure is removed. Pore pressure partially supports the rock and helps resist compressional forces.

Strain is the physical deformation of

the rock due to stress. The rock may stretch or break (fracture) depending on the amount of force and the nature of the rock.

Rock properties such as Young’s

modulus and Poisson’s ratio describe how the rock will respond to the forces.

2 Describe how faults and fractures act as barriers, conduits, seals, and filters.

Describe: Fractures are cracks in the rock where the rock has failed due to past stress. Faults are fractures with lateral or vertical movement.

Fractures and faults can be openings, channels, or conduits in the formation allowing fluid to flow through the fracture. Depending on the fracture aperture, the fracture can filter out rock grains or separate fluids based on viscosity.

Faults that cause a vertical shift can result in a porous formation abutting an impermeable rock, forming a seal or barrier. Fractures can also be healed by a cementing process by the formation fluid, becoming a barrier to flow.




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3 Describe fundamental processes and geometries of salt tectonics.

Describe: Salt tectonics is concerned

with the geometries and processes associated with the presence of significant thicknesses of rock salt in a sequence of rocks. Salt has a low density which does not increase with burial and a low strength which means it deforms plastically. The overburden stress above a slat layer will cause the salt to deform into a characteristic series of ridges and depressions. Active tectonics will cause the crust to move and change the overburden pressure, further driving the movement of the salt. Buckling of the overburden layer will allow the salt to rise into the cores of anticlines, which causes salt domes. A significant proportion of the world’s hydrocarbon reserves are found in structures related to salt tectonics.

4 Describe fundamental processes and geometries of extensional tectonics.

Describe: Faults result from the action of plate tectonics. A fault is a planar fracture or discontinuity in a rock, across which there has been significant displacement along the fractures as a result of earth movement. The two sides of a non-vertical fault are known as the hanging wall and footwall. By definition, the hanging wall occurs above the fault plane and the footwall occurs below the fault. A normal, or extensional, fault occurs when the crust is extended due to the earth’s crust being in tension. The hanging wall moves downward, relative to the footwall.

5 Describe fundamental processes and geometries of compressional tectonics.

Describe: Faults result from the action of plate tectonics. A fault is a planar fracture or discontinuity in a rock, across which there has been significant displacement along the fractures as a result of earth movement. The two sides of a non-vertical fault are known as the hanging wall and footwall. By definition, the hanging wall occurs above the fault plane and the footwall occurs below the fault. Reverse and thrust faults are caused by compressive shortening of the

http://en.wikipedia.org/wiki/Rock_salt

http://en.wikipedia.org/wiki/Anticline

http://en.wikipedia.org/wiki/Salt_dome

http://en.wikipedia.org/wiki/Hydrocarbon

http://en.wikipedia.org/wiki/Plate_tectonics

http://en.wikipedia.org/wiki/Fracture










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crust. The hanging wall moves up relative to the footwall. Reverse faults have dip angles greater than 45 degrees while thrust faults have dip angles less than 45 degrees.

6 Describe fundamental processes and geometries of strike slip tectonics.

Describe: Faults result from the action of plate tectonics. A fault is a planar fracture or discontinuity in a rock, across which there has been significant displacement along the fractures as a result of earth movement. In strike-slip faults, the fault surface is usually near vertical and the fault surface moves either left or right laterally with very little vertical motion.








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UNIT 16 – Well Operations This unit is about common well operations, quality control and well design. The employee will be assessed in the elements relevant to the tasks he/she undertakes.

Element 1 – HC Wellsite Operations Mudlogging


1 Define lag time and describe how it is used in mud logging.

Define: Lag time is the time between when a rock cutting is created by the drill bit and when the cutting appears at the surface in the shaker. Due to the lag time, the drill bit is at a deeper depth when the cutting is caught. The mud logger must know the lag time in order to know the depth the drill bit was at when that particular rock cutting was cut.

2 Describe techniques for recognizing mineralogy from cuttings.

Describe: Rock cuttings are caught at the shaker. The mud logger washes them and examines them under a microscope. The mud logger will record (on the mud log) the size of rock grains as well as the material. Many rock types can be determined by the color and texture under the microscope. In addition, the mud logger will run chemical tests of the clean cuttings. For example, calcium carbonate (limestone) will “fizzle” when exposed to acid.

3 Describe techniques to detect the presence of hydrocarbons.

Describe: Formation gas will come out of solution with the drill mud when exposed to surface pressure. This gas can be detected and sampled in a gas trap in the mud system’s flow line. Also, liquid hydrocarbons in the cleaned cuttings will fluoresce or glow under ultraviolet light.

Element 2 – HC Wellsite Operations Drilling


1 Compare and contrast percussion and rotary sidewall coring with conventional coring.

Conventional coring uses a rotating

bit attached to the drill pipe to cut out a cylinder of the rock at the bottom of the hole. A liner is used to hold the core in the core barrel. Cores are




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usually between 3 and 6 inches in diameter and provide a significant volume of rock for study. Conventional coring provides the best rock samples but is expensive in terms of rig time and the cost of handling the core. Percussion sidewall coring uses

cylindrical "bullets" explosively propelled into the wall of a borehole to retrieve a small, short core sample. These tend to be heavily shattered, rendering porosity/ permeability measurements dubious, but are often sufficient for lithological study. Many samples can be attempted in a single run of the tools. The success rate for retrieving the sample is relatively low. Percussion coring is relatively inexpensive but the rock samples are of limited value. Rotary sidewall coring where a

miniaturized rotary drilling tool is applied to the side of the borehole to cut a sample similar in size to a percussion sidewall. These tend to suffer less deformation than percussion cores; however the core-cutting process takes longer. Rotary coring can be an economic solution to taking small samples over large depth intervals. It provides better samples than percussion without the high costs of conventional coring.

Element 3 – Well Design


1 Describe the mechanisms which contribute to abnormal pore pressure.

Describe: Pore pressure is the pressure of the fluid inside the pore spaces. Pore pressure increases with depth due to hydrostatic pressure of the fluid column and, for this reason, is normally presented as a gradient instead of an absolute pressure. Normal values for fresh water are 0.433 psi/ft or 9.81 kPa/m. Abnormal pressure is a pressure greater than hydrostatic pressure. Over pressure is created whenever the volume of a sealed formation is reduced or the temperature is


http://en.wikipedia.org/wiki/Permeability_(earth_sciences)

http://en.wikipedia.org/wiki/Petrography




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increased. If a sealed formation is subsequently buried under more sediment, compaction occurs and the volume reduces, thereby increasing the pressure. Similarly, if a sealed formation is driven deeper than previous, the temperature will likely rise, resulting in increased pressure.

Element 4 – Horizontal Well Design


1 List and describe the various uses for horizontal wells.

List:

- Exposing more of the reservoir to the borehole by drilling through the reservoir at an angle.

- Drilling into the reservoir where vertical access is difficult due to surface (land access) or subsurface constraints.

- Allowing more wellheads to be grouped together on one surface location can make it easier and cheaper to complete and produce the wells. For instance, on an oil platform many wells can be grouped together. The wells will fan out from the platform into the reservoir(s) below. This concept is being applied to land wells, allowing multiple subsurface locations to be reached from one pad, reducing surface costs.

- Drilling along the underside of a reservoir-constraining fault allows multiple productive sands to be completed at the highest stratigraphic points.

- Drilling a "relief well" to relieve the pressure of "blowout".

2 List and describe the considerations that go into a horizontal well design.

List: - The decision to drill a horizontal

well versus a vertical well is an economic decision. If it is less expensive to drill a horizontal well from an offset location due to surface constraints (i.e. buildings or land forms) or surface opportunities (i.e. single offshore platform or ability to tie into gathering facilities), then the operator will drill the well horizontal.

- Also, a horizontal well will typically contact more of the productive

http://en.wikipedia.org/wiki/Wellhead

http://en.wikipedia.org/wiki/Oil_platform

http://en.wikipedia.org/wiki/Oil_platform

http://en.wikipedia.org/wiki/Relief_well

http://en.wikipedia.org/wiki/Blowout_(well_drilling)




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formation than a vertical well; therefore, fewer wells are required to drain the reservoir. If the savings from drilling fewer vertical wells is greater than the added cost of drilling horizontal, the operator will choose horizontal.

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