scotland north uist exploration well environmental statement

7/31/2019 Scotland North Uist Exploration Well Environmental Statement

1/156

Clair

SchiehallionFoinavenSullom Voe

bp


2/156

Information SheetProject name North Uist Exploration Well

DECC reference number W/4123/2011

Type of project Exploration well

Undertaker name BP Exploration Operating Company Limited (BP)

Undertaker address 1-4 Wellheads Avenue, Dyce, Aberdeen, AB21 7PB

Licences/owners Licence number P.1192BP Exploration Operating Company Limited is thenominated operator

Field interests

BP Exploration Operating Company LimitedNexen Petroleum UK LimitedFaroe Petroleum (U.K.) Limited

Cieco Exploration and Production (UK) LimitedIdemitsu Petroleum U.K. Limited

47.5%35%

6.25%

6.25%5%

Short description The project involves the drilling and subsequentabandonment of an exploration well and possible sidetracksat the location of the North Uist prospect. It is located in UKBlock 213/25c, approximately 125 km north west of theShetland Islands and approximately 30 km southeast of theUK-Faroes median line in a water depth of 1,291 m.

Anticipated date forcommencement of works

January 2012. This may change depending on availability ofthe drillship and other operational matters.

Date and reference of any earlierenvironmental statements

N/A

Significant environmental impactsidentified

None

Statement prepared by Genesis Oil and Gas Consultants Ltd.


3/156

North Uist Exploration WellEnvironmental Statement

This page is intentionally left blank


4/156

Non-Technical Summary North Uist Exploration WellEnvironmental Statement

Non-Technical SummaryIntroductionThis Environmental Statement (ES) presents thefindings of the Environmental Impact Assessment(EIA) conducted by BP for the proposed NorthUist Exploration Well project. The project involvesthe drilling and abandonment of a singleexploration well and possible sidetracks into theNorth Uist reservoir to determine the presence ofhydrocarbons.

The North Uist prospect is located in UK Block213/25c, approximately 125 km north west of theShetland Islands and approximately 30 kmsoutheast of the UK-Faeroes median line(Figure 1) in a water depth of 1,291 m.

Project background and purposeThe North Uist prospect is one of severalhydrocarbon prospects identified west of Shetlandfor which BP is the Operator, on behalf of itselfand its partners in the field licence. Drilling in thewest of Shetland area has been taking place formore than 30 years, in water depths of up to

1,800 m and BP has a successful track record ofdevelopment in this area. BP has pioneered the

production of oil and gas from the Clair,

Schiehallion, Loyal and Foinaven fields over thelast 15 years.

The North Uist prospect is a potential hydrocarbonreservoir that could have significant reserves.The aim of this exploration well is to obtainreservoir properties that enable the prospect to beevaluated for potential future development.

Development concept and scheduleThe development concept is a vertical explorationwell into the prospect using a dynamicallypositioned drillship, the Stena Carron, owned andoperated by Stena Drilling, a highly experienceddrilling company. The choice of the Stena Carronbrings a highly stable drilling vessel withsignificant weather tolerances and avoids theneed for anchor handling vessels andconsequential anchor scars on the seabed.

Drilling of the well is planned to commence inJanuary 2012, however this could changedepending on availability of the drillship and otheroperational matters, and could be any time fromOctober 2011 until August 2012.

Environmental statement remitThis ES has been prepared in accordance with

Figure 1: Location of theproposed project.


5/156


the requirements of the Offshore Petroleum Production and Pipelines (Assessment of

Environmental Effects Regulations 1999 (as amended) which require evaluation of projectslikely to have a significant effect on the offshoreenvironment. As a single exploration well with noinstallation of a pipeline or hydrocarbonproduction, the project does not require astatutory ES. Nevertheless BP has chosen tovoluntarily prepare and submit this ES.

The aim of the EIA is to assess the potentialenvironmental impacts that may arise from theproject and to identify measures that will be put inplace to prevent or minimise these impacts. TheES summarises the EIA process and outcomes.

The scope of the EIA is well established for suchprojects and the proposed project as assessedwithin this ES comprises;

drilling of the well taking measurements to profile the

geology and

well abandonment prior to leaving thesite.

Environmental philosophy

BP and its field partners are committed toconducting activities in compliance with allapplicable legislation and in a manner whichcontributes to BPs stated goals of no accidents,no harm to people and no damage to theenvironment.

The development

Reservoir and fluid characteristicsThe current most likely interpretation of North Uistis a sequence of Jurassic sediments overlyingeither Basement or Devono-Carboniferoussediments. Evidence from the Eribol well 18 km

d h R b k d L h ll

A single well will be drilled in five sections withcemented steel casings, designed to BPs well

design standards and approved in accordancewith the UK Regulations covering well integrity.Downhole equipment will be used to determinekey reservoir properties and additionalgeophysical data will be obtained by acombination of an airgun at the surface and amoving sensor in the well (a Vertical SeismicProfile). Should a significant find of hydrocarbonsbe discovered there is a potential for one or moresidetracks to be drilled to further evaluate theprospect. In any hole section, there is a low riskthat the section may have to be re-drilled shouldthe hole collapse or the drilling assembly becomestuck.

Drilling muds and cuttings handling

Different types of mud are used for different partsof the well for a number of reasons including thecontrol of pressure in the well, lubrication of thedrill bit and circulation of the rock cuttings out ofthe hole.

The 36, 26 and 17 1 / 2sections of the well will bedrilled using water-based mud (WBM), which issuitable for discharge to the sea. Design work isstill ongoing to determine whether WBM or Oil-

based mud (OBM) provides the best mud type forthe 12 1 / 4 section of the well. If OBM is selected,this will be reflected in the PON15B (chemicalpermit) application. OBM will be used for drillingthe 8 1 / 2section and into the reservoir formationitself, since this has superior properties for thoseparticular sections. The OBM will be returned toshore and recovered.

WBM cuttings from the tophole sections will bedischarged to the seabed. Drill cuttingscontaminated with WBM from the middle holesection will be discharged from the drillship intothe sea following mud recovery operations. Thisis normal practice and is not considered to be arisk to the environment. OBM contaminated drill


6/156


Well completion

Since the objective of the well is to determine thepresence of hydrocarbons, and there is nointention to flow the well or preserve the well foruse in the future, the tubing, valve work and otherequipment necessary for production (known aswell completion) will not be installed.

Well abandonment

At the end of the operation, the well will be sealedwith cement plugs, in line with the current DECCguidance and industry good practice. Thewellhead will be severed approximately 3 m belowthe seabed using a mechanical cutter prior toremoving the wellhead and leaving the seabedfree of obstructions.

The environmentThe North Uist project site is located on the floorof the Faroe-Shetland Channel at a depth of1,291 m. The seabed at the project site is gentlyundulating with a very low slope gradient.

The oceanographic regime consists of an upperlayer of warm North Atlantic water flowing towardsthe northeast, overlying a lower layer of coldNorwegian Sea bottom water, flowing towards thesouthwest.

The area is exposed to strong winds from thewest and south west while significant waveheights exceed 2.5 m for 50% of the year and 4 mfor 10% of the year.

Surveys of the floor of the Faroe-ShetlandChannel show it to be made up of relativelyfeatureless mud with some gravel, overlain by athin layer (


7/156


Physical presence

Seabed impactsSeabed impacts are unlikely to be significant andwill be limited to the immediate area around thewell location.

These localised impacts may include the directphysical injury of benthic (seabed) species, thelocalised loss of seabed habitat or indirect impactswhich may be caused by the re-suspension andre-settlement of sediments.

The maximum area that will be directly impactedis extremely small and is expected to recoverquickly.

Discharges to seaPotential discharges to sea during drillingoperations include cuttings, WBM, cement andassociated chemicals.

WBM cuttings generated from drilling the topholesection of the well will be discharged to theseabed in line with current practice. Drill cuttingswith WBM generated from drilling the middlesection(s) of the well will be discharged from thedrillship into the sea following mud recoveryoperations in line with current practice. The risksto the marine environment from these dischargesare assessed as non-significant and will besubject to detailed controls under the UKconsenting process for permitting offshorechemicals.

Existing procedures will be followed to containand ship to shore for disposal the OBM cuttingsgenerated from drilling the lower section(s) of thewell.Cuttings on the seabed will cover a wide area at avery low thickness, and a small area near the wellat thicknesses of a few centimetres. Smotheringor burial will be limited to the thickest areas withinaround 100 m of the well. In other areas, the

well to gain geological information, which is aroutine operation. These have the potential to

disturb marine mammals and the JNCC guidelinesfor seismic surveys (JNCC, 2010) will be followedto minimise any risk.

In order to remove the wellhead at the end of theoperation and keep the seabed clear, it isproposed to use a mechanical cutting tool. Use ofan explosive cutting charge will be a contingencymeasure if mechanical cutting is unsuccessful. If

this method is used, to mitigate any potentialimpact to cetaceans, three levels of mitigation willbe adopted: a charge design which minimises theblast size and radius, marine mammal observersto visually observe mammals and passiveacoustic monitoring to listen for marine mammalsounds. As a result, it is considered that the riskof injury to a marine mammal is negligible andapplication for a licence to disturb such mammals

is not required.

Atmospheric emissionsAtmospheric emissions will occur from fuel use onthe drillship and supporting vessel. These will becommensurate with normal marine activities. Acidgas emissions from fuel consumption arecontrolled under MARPOL Annex VI, and

specifically the drillship will have an InternationalAir Pollution Prevention Certificate demonstratingcompliance with good practice on emissionscontrol.

Accidental eventsThis ES incorporates the latest analysis of oil spillrisks currently available and relevant to the

project. The North Uist project site is a reservoirthat does not contain fluids at high pressure andtemperature.

Oil spills

BPs target is for zero oil spills. Numerous andb i l d il ill


8/156


consequences of a blowout can be significant, BP

implements a wide range of measures to preventa loss of well control incident.

In addition to having in place a number ofcomprehensive prevention measures, BPimplements a range of response/ mitigationmeasures in order to address the small remainingresidual risk of an oil spill. Theseresponse/mitigation measures are detailed in BPs

spill response strategy.Spill response strategy

An Oil Pollution Emergency Plan (OPEP) will besubmitted for this project. The OPEP containsBPs plans for responding to any unplannedrelease of oil.

BP, along with other North Sea operators, have

engaged Oil Spill Response to provide a widerange of spill response equipment and expertise,including aircraft, vessels, dispersants, booms,recovery and surveillance equipment. Theseresources can be mobilised to the project site.

BP maintains an onshore oil spill plan for its westof Shetland operations (the Schiehallion/ Loyal,Foinaven and Clair fields) in addition to the

offshore response. Chemical spills

As with oil spills, BPs target is for zero chemicalspills. The possibility of a chemical spill howevercannot be completely eliminated.

Given the nature of the high energy marineenvironment of the project area, any chemical spill

is expected to rapidly disperse with only anegligible to minor localised impact on plankton orfish egg/larvae, depending on the season. Thelow probability of a chemical spill occurring withany significant associated environmental impactmeans the residual risk of a chemical spill is low.

and will occur over a well-defined period of time.

Standard communication and notificationmeasures will be in place to ensure that allvessels operating in the area are aware of theproject activities occurring. A standby vessel willalso be present throughout. The temporarilyincreased vessel presence in the project area isexpected to have an insignificant impact.

Fishing interaction

The drillship will not leave anchor mounds on theseabed while only a small, thin layer of cuttingswill remain.

Other users of the sea

The project site is outwith any known areas ofrenewable energy or of military activity. Theproposed site is within an area of current oil andgas activity.

Cumulative and transboundary impactsCumulative effects are those that impact on theenvironment and add to existing or reasonablyforeseeable future impacts. Transboundaryeffects are those impacts where the area ofinfluence could reasonably be expected to extendbeyond the UK boundary line into either Faroeseor Norwegian waters.

Other oil and gas fields currently developed in theWest of Shetland area include the Foinaven,Schiehallion and Clair fields. In addition, theLaggan and Tormore fields are currently underdevelopment and drilling by other operators hasrecently taken place, and continues to take place,

for other prospects such as Alligin, Lagavulin,Rosebank, Lochnagar, Cambo, Glenlivet, Tornadoand South Uist.

This assessment indicates that the impacts of thisproject are not expected to have a detrimentalimpact on the local environment either individually


9/156


where no response measures were implemented,indicate that in the very unlikely event of a worst

case spill, oil is likely to move into Norwegianwaters and is ultimately likely to affect theNorwegian coastline. In a minority ofcircumstances, it could affect the northwestShetland coast for this scenario. The assessmentof spill frequency demonstrates the extremely lowprobability of such an event, without a relevantprecedent in the North Sea. For this scenario oilis also predicted to cross over into the Faroesewaters, but the overall conclusion from a variety ofmodelling outputs is that oil is not expected tobeach on the Faroes. Clearly the potential worstcase scenario impacts described above would bereduced by response measures put in place.

In the event of a worst case spill which ispredicted to drift into Norwegian waters theNORBRIT plan will be activated by the UKs

Counter Pollution Branch of the Maritime andCoastguard Agency (MCA). The NORBRIT plan isa joint UK/Norway oil spill contingency planoperating within the framework of the 2006National Contingency Plan. In the event of a majorspill which is predicted to drift into Faroesewaters, the MCA will liaise with the MarineRescue and Co-ordination Centre (MRCC) inTorshavn, Faroe.

ConclusionsOverall it is considered that, following applicationof preventative and mitigation measures identifiedwithin this ES, the planned operation will notcause any significant residual environmentalimpacts. It is recognised that the consequences ofa major oil release, however low the probability ofthat occurring could be significant, and this isreflected in the planning, preventative control andcontingency measures that are put in place. Thepreventative measures control the risk of oil spillto an extremely low level and set in placemeasures to combat any pollution. In line with

d i l i d DECC


10/156

Abbreviations and Glossary North Uist Exploration WellEnvironmental Statement

AbbreviationsAFEN Atlantic Frontier Environmental

Network

AIW Arctic Intermediate Water

API American Petroleum Institute

AQO Air Quality Objectives

BAOAC Bonn Agreement Oil AppearanceCode

BIOFAR BIOlogical investigations of theFARoese

BMT BMT ARGOSS

BODC British Oceanographic Data Centre

BOP Blowout Preventer

CEFAS Centre for Environment, Fisheriesand Aquaculture Science

CFC Chlorofluorocarbon

CHARM Chemical Hazard and RiskManagement

CO Carbon Monoxide

CO 2 Carbon Dioxide

cP Centipoise

CPR Continuous Plankton Recorder

cSAC Candidate Special Area of

Conservation

dB DeciBel

DECC Department of Energy and ClimateChange

DP D i P iti i

EIA Environmental Impact Assessment

EMS Environmental Management System

EPC Offshore Installations (EmergencyPollution Control) Regulations 2002

EPS European Protected Species

ES Environmental Statement

ESE East Southeast

EU European Union

FEPA Food and Environment ProtectionAct

FPSO Floating Production Storage andOffloading (vessel)

GDP Group Defined Practice

FSCBW Faroe-Shetland Channel BottomWater

GEBCO General Bathymetric Chart of theOceans

GHG Greenhouse Gas

GOR Gas to Oil Ratio

HCFC Hydrocarbofluorocarbon

HR Habitat Regulations

HSE Health & Safety Executive

Hz Hertz

IAPP International Air Pollution

ICES International Council for theExploration of the Sea

IMO International Maritime Organisation

ISO I t ti l St d d O i ti


11/156


LMRP Lower marine riser package

m Metre

m3 Cubic Metres

MARPOL International Convention for thePrevention of Pollution from Ships

MCA Maritime and Coastguard Agency

MDBRT Measured Depth Below Rotary Table

mg Milligram

mm Millimetre

MMO Marine Mammal Observer

MNAW Modified North Atlantic Water

MODU Mobile Offshore Drilling UnitMRCC Marine Rescue and Coordination

Centre (located in the FaroeIslands)

m/s Metres per Second

N North

NATO North Atlantic Treaty Organisation

NAW North Atlantic Water

Nm Nautical Mile

NMHC Non Methane hydrocarbons

NNE North Northeast

NNW North Northwest

NOX Nitrogen Oxides

NSAIW Norwegian Sea Arctic IntermediateWater

OPOL Offshore Pollution LiabilityAssociation

OPPC Oil Pollution Prevention and ControlRegulations

OPRC Oil Pollution PreparednessResponse and CooperationRegulations

OSCAR Oil Spill Contingency and Response

OSPAR Oslo and Paris Convention for theProtection of the MarineEnvironment of the North EastAtlantic

OSPRAG Oil Spill Prevention and ResponseAdvisory Group (OSPRAG)

OSR Oil Spill Response Limited

PAH Poly Aromatic Hydrocarbons

PAM Passive Acoustic Monitoring

PEXA Practice and Exercise Area

PLONOR Pose Little Or No Risk to theenvironment

PON Petroleum Operation Notice

ppb Parts per Billion

ppm Parts per Million

psi Pounds per Square Inch

pSAC Possible Special Area ofConservation

PTS Permanent Threshold Shift

ROV Remotely Operated Vehicle

SAC Special Area of Conservation

SAST S bi d S T


12/156


Industrial Research

sm3

/day Standard Cubic Metre per DaySMRU Sea Mammal Research Unit

SNH Scottish Natural Heritage

SOPEP Shipboard Oil Pollution EmergencyPlan

SOSREP Secretary of State Representative

(Energy and Climate Change)

SO x Sulphur Oxides

SPA Special Protection Area

SPU Strategic Performance Unit

SSSI Site of Special Scientific Interest

SVT Sullom Voe Terminal

SW South West

TBT Tributyltin

THC Total Hydrocarbon Concentration

TTS Temporary Threshold Shift

UK United Kingdom

US United States

UKAPP United Kingdom Air PollutionCertificate

UKCS United Kingdom Continental Shelf

UKDEAL UK Digital Energy Atlas and LibraryUKHO United Kingdom Hydrographic Office

UKMMAS United Kingdom Marine Monitoringand Assessment Strategy

UKOOA United Kingdom Offshore Operators


13/156


14/156


Conductor The conductor is the first casingstring which is cemented in the

well. It extends from just abovethe seabed to a depth sufficient tosupport the structured loadsplaced on it during operations.

Conspecific Of or belonging to the samespecies.

Continental shelf Continental shelf or the area atthe edges of a continent from the

shoreline to a depth of 200 m,where the continental slopebegins. The shelf is commonly awide, flat area with a slightseaward slope.

Continental slope This is the seaward border of thecontinental shelf.

Commissioning Preparatory testing work,

servicing etc. usually on newlyinstalled equipment prior tocoming into full production.

Completion Generic term used to describethe assembly of downholetubulars and equipment requiredto enable safe and efficientproduction from an oil or gas well.

Copepod A large family of aquaticbelonging to the class Crustaceaof the phylum Arthropoda, livingin fresh water or sea water. Manyare free living in the plankton or inseabed sediments, whilst othersare parasitic.

Cuttings pile A pile formed on the seabed as aresult of the deposition of drill

cuttings.

Decibel (dB) A unit used in the comparison oftwo power levels relating tosound (one tenth of a Bel).

Decommissioning Shutdown of the developmenth l d

Drill cuttings Chips and small fragments ofrock generated while drilling a

well, which are brought to thesurface by the flow of the drillingmud as it is circulated.

Drilling mud Special clay, water and chemicaladditives, pumped downholethrough the drill pipe and drill bit.The mud cools the rapidlyrotating bit, lubricates the drillpipe as it turns in the well bore,

carries rock cuttings to thesurface, maintains downholepressure and serves as a plasterto prevent the wall of theborehole from collapsing.

Drill string Lengths of steel tubing roughly 10m long screwed together to forma pipe connecting the drill bit tothe drilling rig. It is rotated to drill

the hole and delivers the drillingfluids to the cutting edge of thedrill bit.

Duty of Care The duty to avoid an act oromission which may have as itsreasonable and probableconsequence injury to persons towhom the duty is owed.

Dynamic positioning Use of thrusters (instead ofanchors) to maintain the positionof a vessel.

Echolocation The locating of objects usingreflected sound.

Ecosystem Consists of all the organismsliving, including non-livingphysical components of the

environment, with which theyinteract a biological communityand its physical environment.

Elasmobranch Elasmobranch refers to thesharks, rays and skates -cartilaginous fishes. These


15/156


Epifauna Benthic organisms that inhabit

the surface of the seabed.

Espoo Convention The Espoo (EIA) Convention laysdown the general obligation ofStates to notify and consult eachother on all major projects underconsideration that are likely tohave a significant adverseenvironmental impact acrossboundaries.

Exploration Well A well drilled to test a potentialbut unproven hydrocarbon trap orstructure where good reservoirrock and a seal or closurecombine with a potential sourceof hydrocarbons.

Faults A fracture in rock where there hasbeen an observable amount ofdisplacement.

Fauna This is all of the animal life of anyparticular region or time.

Fetch Oceanographic terminology thatdescribes distance over a body ofwater that wind blows.

Flare A vent for burning of unwantedgases or to burn off hydrocarbonswhich, due to temporarymalfunction or maintenance ofprocess plant, cannot be safelystored or retained in processvessels.

Flowline Pipe laid on the seabed for thetransportation of production orinjection fluids. It is generally aninfield line, linking a subseastructure to another structure orto a production facility. Its lengthranges from a few hundredmeters to several kilometres.

Formation fluids Any fluid that occurs in the poresof a rock. Strata containing

Habitat An area where particular animalor plant species and

assemblages are found, definedby environmental parameters.

Greenhouse gas Gases in the atmosphere thatadsorb and emit radiation withinthe thermal infrared range.Primary greenhouse gasesinclude water vapour, carbondioxide, methane, nitrous oxideand ozone.

Habitats Directive The Habitats Directive (togetherwith the Birds Directive) forms thecornerstone of Europe's natureconservation policy. It is builtaround two pillars: the Natura2000 network of protected sitesand the strict system of speciesprotection. All in all the directiveprotects over 1,000 animal and

plant species and over 200 socalled "habitat types" (e.g. specialtypes of forests, meadows,wetlands, etc.), which are ofEuropean importance.

Hydrocarbons Organic chemical compounds ofcarbon and hydrogen atoms.There are a vast number of thesecompounds and they form the

basis of all petroleum products.They may exist as gases andliquids. Examples includemethane, hexane and asphalt.

Hydrographic The study, description andmapping of waterways, includingseas, lakes, rivers.

Hydrophones Underwater microphones used

for recording subsea noise.

Hydrostatics Is the science of fluids at rest.

ICES rectangles A statistical area of the sea that is0.5North by 1West, defined bythe International Council for the


16/156


Macrofauna Benthic organisms that areretained in a 0.3 mm sieve.

Masking Perception of biologicallyimportant sounds is decreaseddue to interference by soundenergy from other sources(including ambient noise).

Migration Any regular animal journey alongwell-defined routes, particularlythose involving a return to

breeding grounds.

Mitigation Process that would make aconsequence less severe.

Mud This is generally synonymouswith drilling fluid andencompasses most fluids used inhydrocarbon drilling operations,especially fluids that contain

significant amounts of suspendedsolids, emulsified water or oil.Mud includes all types of water-based, oil-based and synthetic-based drilling fluids.

Mysticete Any whale in the taxon Mysticeti;a mysticete is a whale that hasbaleen instead of teeth.Mysticetes are filter feeders,

straining water through theirbaleen to capture prey items.Mysticetes include the largest ofthe whales, the fin and bluewhales.

Natura 2000 An EU wide network of natureprotection areas establishedunder the 1992 HabitatsDirective.

NORBRITAgreement

A joint counter pollution operationbetween Norway and the UK inthe zone extending 50 nauticalmiles either side of the medianline separating the UK andNorway continental shelf.

Plankton Tiny plants and animals that driftin the surface water of seas and

lakes. Of great economic andecological importance as they area major component of marinefood chains.

Plume Term used to describe thedispersion of oil in the watercolumn following an uncontrolledoil release. Turbulence causesthe oil to be broken up at the exit.

As a result the oil spreads out asit rises, mixing with the wateraround it.

Pollution The introduction by man, directlyor indirectly, of substances orenergy to the environmentresulting in deleterious effectssuch as harm to living resources;hazards to human health;

hindrance of marine activitiesincluding fishing, and impairmentof the quality for use of seawaterand reduction of amenities.

Polychaete Bristle worms. A class ofsegmented worms belonging tothe phylum Annelida, generallymarine. Each body segment hasa pair of fleshy protrusions called

parapodia that bear manybristles, called chaetae, which aremade of chitin.

Production well A development well specificallyfor the extraction of reservoirfluids. Production is the full-scaleextraction of oil and gas reserves.

Ramsar site Statutory areas designated by the

UK Government under theRamsar Convention (theConvention on Wetlands ofInternational Importance)especially as waterfowl habitat.

Recruitment Young fish joining the main adultfish population


17/156


Salinity The saltiness or dissolved salt

content of a body of water.

SCI Site of Community Interest

Sedentary Remaining or living in one area,not migratory.

Seismic survey A survey conducted to map thedepths and contours of variousrock strata by timing thereflections of sound waves. 2-D

seismic surveys measure depthsfrom the reflections. 3-D seismictakes simultaneous obliquemeasurements that provide amore accurate picture. 4-Dseismic incorporates time as the4th dimension to a standard 3-Dseismic survey.

Sessile An organism that is attached to

another structure by its base andis unable to move freely.

Shoal Sandbar (or just bar in context),or gravelbar is a somewhat linearlandform within or extending intoa body of water, typicallycomposed of sand, silt or smallpebbles.

Slurry A thick suspension of solids in aliquid.

Side scan sonar A form of sonar used to create animage of areas of the seafloor.Uses include creation of charts,identification of bathymetricalfeatures and detection of objectson the seafloor.

Sidetrack This term is used for drilling adirectional hole to bypass anobstruction in the well that cannotbe removed or damage, such ascollapsed casing that cannot berepaired. Sidetracking is alsodone to deepen a well or to

Source level Defined as the sound intensity, indecibels with reference to specific

level, at a point which is a unitdistance from a source (1 m isoften used).

Spawning Reproductive stage of fish andother marine animals when eggsare released into the watercolumn or deposited on to theseabed or other substrata.

Special Area ofConservation (SAC) Areas considered important forcertain habitats and non-birdspecies of interest in a Europeancontext. One of the mainmechanisms by which the ECHabitats and Species Directive1992 is implemented. In addition,there are four designations belowfull SAC status:

Sites of Community Importance(SCIs) are sites that have beenadopted by the EuropeanCommission but not yet formallydesignated by the government ofeach country;

Candidate SACs (cSACs) aresites that have been submitted tothe European Commission, butnot yet formally adopted;

Possible SACs (pSACs) are sitesthat have been formally advisedto UK Government, but not yetsubmitted to the EuropeanCommission; and

Draft SACs (dSACs) are areasthat have been formally advisedto UK government as suitable forselection as SACs, but have notbeen formally approved bygovernment as sites for publicconsultation.

Special ProtectionArea (SPA)

Sites designated under the EUBirds Directive as a SpecialProtection Area.


18/156


Thermocline Oceanic water layer in whichwater temperature decreases

rapidly with increasing depth.Thruster A propulsive device used by

vessels for station keeping,attitude control, or long durationlow acceleration.

Tier 1 Response Local Response, within thecapability of the operator at theproject site.

Tier 2 Response Regional, beyond the in-housecapability of the operator.

Tier 3 Response Response requiring nationalresources.

Topsides Describes the equipment situatedon a platform including, forexample, the oil production plant,

accommodation block and drillingrig.

Trawling Method of fishing in which a largebag-shaped net is dragged ortrawled. Mouth of the bag is keptopen by a variety of methodsincluding wooden beams (beamtrawl) or a large flat (otter) board(otter trawl).

Umbilical Any of various external electricallines or fluid tubes which connectone portion of a system toanother.

Viscosity The resistance of flow of a liquid.

Well clean up Leaving the well bore clean afterdrilling by displacing mud andcuttings to bring on production.

Well completion The work of preparing a newlydrilled well for production,including cementing and valvework.

Well control We ll control is the technique used

in oil and gas operations toprevent influx of formation fluidsinto the wellbore .

Wellhead A top of casing and the attachedcontrol and flow valves. Thewellhead is where a connection ismade to the well by the blowoutpreventer and drilling riser.

Well testing Testing in an exploration orappraisal well is directed atestimating of reserves incommunication with that well, inaddition to well productivity.Testing in a production well alsomonitors the effects of cumulativeproduction on the formation.

Zooplankton Animals that drift in the plankton,

mostly microscopic.


19/156

Contents North Uist Exploration WellEnvironmental Statement

This page is intentionally left blank


20/156


ContentsInformation Sheet ....................................... i Non-Technical Summary ........................... iii

Introduction ............................................................ iii

The development .................................................. iv

The environment .................................................... v

Assessment of potential impacts ........................... v

Abbreviations ............................................. ix Glossary ................................................... xii

Contents .................................................. xix

1 Introduction ........................................ 1

1.1 Project background and purpose ................ 1

1.2 Regulatory context ...................................... 1

1.3 Key environmental legislation ..................... 2

1.4 BP environmental policy and requirements 2

1.5 Aim of the EIA process and scope of theenvironmental statement ............................. 4

2 The Development .............................. 5

2.1 Fields and reservoirs ................................... 5

2.2 Wells and drilling ......................................... 6

2.3 Decommissioning ........................................ 8

3 The Environment ............................... 9

3.1 Introduction .................................................. 9

3.2 Environmental Legislation ProtectingHabitats and Species ................................ 10

3.3 Hydrology .................................................. 12 3.4 Meteorology ............................................... 14

3.5 Seabed sediments .................................... 15

3.6 Plankton .................................................... 18

4.3 Likelihood .................................................. 39

4.4 Consequence ............................................ 39

4.5 Combining Likelihood and Consequencesto Establish Risk ....................................... 39

4.6 Assessment of impacts ............................. 40

4.7 EIA integration with overall environmentalmanagement ............................................. 40

5 Physical Presence ........................... 41

5.1

Seabed impacts ........................................ 41

5.2 Interaction with other sea users ................ 43

6 Discharges to Sea ........................... 45

6.1 Introduction ............................................... 45

6.2 Regulatory control ..................................... 45

6.3 Drilling discharges .................................... 45

6.4 Management and mitigation ..................... 47 7 Underwater Noise ............................ 49

7.1 Introduction ............................................... 49

7.2 Regulatory control ..................................... 49

7.3 Marine mammals and sound .................... 50

7.4 Noise sources and potential impacts ........ 51

7.5 Noise modelling and potential impact ....... 54 7.6 Management and mitigation measures .... 57

7.7 Residual impacts ...................................... 57

7.8 European protected species (EPS) riskassessment ............................................... 58

8 Atmospheric Emissions ................... 63

8.1 Introduction ............................................... 63 8.2 Regulatory control ..................................... 63

8.3 Environmental impact ............................... 64

8.4 Management and mitigation ..................... 65


21/156


9.8 Cumulative and transboundary risk ......... 102

9.9 Chemical spills ......................................... 103

10 Conclusions ................................... 105 10.1 Potential environmental issues ................ 105

10.2 Key residual issues .................................. 105

10.3 Cumulative and transboundary impacts .. 106

10.4 Protected areas and species ................... 106

10.5 Commitments .......................................... 106

10.6 Final remarks .......................................... 107

11 References ..................................... 109 Appendix A Summary of

Environmental Legislation .............. A-1

Appendix B EIA Matrices .................. B-1


22/156

Introduction North Uist Exploration WellEnvironmental Statement

1 IntroductionThis chapter explains the background and purposeof the proposed project and describes the aim andscope of the environmental impact assessment(EIA) process carried out. The underlyingRegulatory and BP environmental requirementsare also outlined.

This Environmental Statement (ES) presents the

findings of the environmental impact assessment(EIA) conducted by BP for the proposed North UistExploration Well project. The project involves thedrilling and abandonment of a single explorationwell into the North Uist reservoir to determine thepresence of hydrocarbons and to gain geologicalinformation.

The project is located within Quadrant 213 of theUnited Kingdom Continental Shelf Area (UKCS,which includes the UK Exclusive Economic Zone)in a water depth of 1,291 m at the bottom of thecontinental shelf slope in the Faroe-Shetlandchannel (Figure 1-1).

1.1 Project background andpurpose

The main exploration objective of the well is to testthe Pre-Cretaceous North Uist Prospect and to

gather data on reservoir age and characteristics,hydrocarbon presence, hydrocarbon water contactpressures and temperatures. This information willbe used to form decisions on any futuredevelopment and to optimise future drilling plans.

The selected concept for the project was thedrilling of the North Uist prospect using a singlevertical exploration well, using the Stena Carrondrillship. The selected project concept is describedfurther in Chapter 2.

There is also a very low likelihood of encounteringa second shallower hydrocarbon prospect calledthe Cardhu prospect while drilling the North Uistwell. The drilling tools will be closely monitored atthe expected depth for any signs of hydrocarbonpresence. If hydrocarbons were found in Cardhu,apart from some logging and sampling, no furtherevaluation would take place during execution ofthis well. The design of the well accounts for the

possibility of encountering the Cardhu prospect.

1.2 Regulatory context

1.2.1 Requirement for an EIAThe EIA reported in this ES has been carried out inaccordance with the requirements of the Offshore Petroleum Production and Pipelines (Assessment of Environmental Effects) Regulations 1999 (as amended ). These regulations require the


23/156

Introduction North Uist Exploration WellEnvironmental Statement undertaking of an environmental impactassessment and production of an ES for certaintypes of offshore oil and gas project with thepotential to have a significant effect on theenvironment.

For this project, the criteria for a statutory EIA arenot triggered. Nevertheless BP is submitting theES on a voluntary basis. Once submitted, the ESundergoes the same regulatory process includingconsultation and the requirement for consentbefore the project can proceed. The undertakingof the EIA aims to consider all of the potentialimpacts from the project. The project and potentialimpacts have been discussed with externalstakeholders. These included DECC, MarineScotland and JNCC.

1.3 Key environmentallegislation

The project will be subject to the requirements ofUK and EU legislation in addition to otherinternational treaties and agreements such as theOslo and Paris Commission (OSPAR). As thedevelopment lies outwith UK territorial waters (i.e.more than 12 nm from land), the majority of theactivities undertaken will be governed under theapplicable legislation regarding offshore oil and

gas activities, rather than that governing inshorewaters.

The key environmental legislation applicable to theproject is listed below and summarised inAppendix A. Onshore legislation is included in theAppendix in the unlikely event of a blowoutresulting in beaching.

Offshore Petroleum Production and

Pipelines (Assessment of EnvironmentalEffects) Regulations 1999

Offshore Production and Pipelines(Assessment of Environmental Effects)(Amendment) Regulations 2007

Offshore Marine Conservation (NaturalHabitats &c.) Regulations 2007 (asamended)

Merchant Shipping (Prevention of Pollutionby Sewage and Garbage from Ships)Regulations 2008

Oil Pollution Preparedness, Response andCo-operation Convention Regulations1998 (as amended)

Offshore Installations (EmergencyPollution Control) Regulations 2002

In addition, key legislation and guidance relating tothe main environmental issues associated with theproject are presented in Chapters 6 to 9 of the ES.

1.4 BP environmental policyand requirements

BP are committed to conducting activities incompliance with all applicable legislation and in amanner which contributes to BPs stated goals ofno accidents, no harm to people and no damageto the environment. In order to achieve thesegoals, there is a hierarchy of common policies,commitments and expectations that identify policyand regulatory requirements and provide tools toassist in compliance and performanceimprovements.The project is subject to the following BPenvironmental requirements:

BP North Sea Region HSE policy (Figure1-2)

BP Environment and Social Group DefinedPractice (GDP) on Environment

During operations, the project will conform to therequirements of the Environmental ManagementSystem (EMS) established for the BP North SeaSPU, which is certified to ISO 14001.


24/156

Introduction North Uist Exploration WellEnvironmental Statement


25/156

Introduction North Uist Exploration WellEnvironmental Statement 1.5 Aim of the EIA process and

scope of the environmentalstatement

The aim of the EIA process is to assess thepotential environmental impacts that could arisefrom the project and identify measures that will beput in place to prevent or minimise these impacts.

The EIA process is integral to the project,assessing potential impacts and challengingdesign and operational procedures to ensure thatthe residual impacts of the project are minimal.The process also provides for the concerns ofstakeholders to be identified and addressed as faras possible at an early stage, and ensures that theplanned activities comply with environmentallegislative requirements and with BPsenvironmental policy.

The ES is a report summarising the EIA processand outcomes. It also includes details of how theproject decision-making was undertaken and howenvironmental criteria were incorporated into thatprocess. The ES is submitted to DECC to informthe decision on whether or not the project mayproceed, based on the acceptability or otherwise ofthe residual levels of impact, and is subject toformal public consultation.

This ES reports the outcome of the EIA processand includes the following:

A non-technical summary of the whole ES

Justification for the project and the role ofthe EIA

Description of the environment in thevicinity of the project and the keyenvironmental sensitivities

Methods used to identify and evaluate theenvironmental issues associated with theproject and consultation undertaken todate

Detailed assessment of each issue,


26/156

The Development North Uist Exploration WellEnvironmental Statement

2 The DevelopmentThis chapter provides an overview of the proposedproject, which forms the basis of the EIA reportedin Chapters 5 to 9 of this ES.

2.1 Fields and reservoirs

2.1.1 OverviewThe North Uist prospect is located in an areawhere there is significant existing and plannedexploration activity, and where BP successfullyoperates a number of fields, namely Clair,Schiehallion, Loyal and Foinaven. The fields andprospects located west of Shetland are illustratedin Figure 2-1.

2.1.2 Objective of the ProjectThe main exploration objective of the well is to testthe Pre-Cretaceous North Uist Prospect. The mostlikely interpretation of North Uist is a sequence ofJurassic sediments overlying either Basement orDevono-Carboniferous sediments. There ispotentially a secondary prospect in the overlyingCardhu reservoir at approximately 3000 m belowthe seabed that the well may encounter. Ifhydrocarbons were found in the Cardhu reservoir,apart from logging and sampling, no furtherevaluation would take place during execution ofthis well.

There are several data gathering requirements. Itis important to determine the reservoir age andcharacteristics. This information will come from

downhole logging, using specially designed

logging tools and the use of vertical seismicprofiling. This information will be used tocoordinate with previously gathered seismic surveyinformation to estimate hydrocarbon volumes inplace, and to inform future decisions about furtherappraising this prospect and determining if thesurrounding acreage is prospective.

If hydrocarbons are present then fluid samplingand determination of the hydrocarbon-watercontact are key objectives for the calculation of

hydrocarbon volumes in place and developmentplanning. Depending on the outcome of the fluidsampling one or more sidetracks would beconsidered so that further information on thereservoir and the potential size of anyaccumulation of hydrocarbons may be gathered.

Geological information will be recorded along thewell trajectory to help plan any future development

and optimise future drilling.

2.1.3 Reservoir CharacteristicsThe most likely oil type to be encountered in eitherthe Cardhu or North Uist prospects will be similarto the light crudes found in the Rosebank andLochnagar discoveries. These are the nearestwells to North Uist with equivalent reservoir depth,

geology and fluid samples . The Eribol well,although closer to North Uist did find evidence ofhydrocarbons but no fluid samples were retrieved.There is a very low probability that any oilencountered would be as heavy as that found inthe Clair Field, which could potentially have agreater impact on the environment. In order tofully understand the potential environmentalimpacts of the project, worst case scenarios have

been used. In this case it has been assumed the

N h Ui E l i W ll


27/156

The Development North Uist Exploration WellEnvironmental Statement oil type will be similar to Clair.

Maximum reservoir pressures are predicted to be

between 7,582 psi for oil and 8,183 psi for gas.This well is not classified as a high-pressure high-temperature (HPHT) well.

Due to the nature of an oil reservoir, which isessentially oil droplets held within a porous rock, similar to water held in a sponge, the rate that theoil flows up a well drillled into it will depend on howdeep the well is drilled into the porous reservoirrock. The more the open hole or well bore isexposed to the reservoir, the higher the rate of flowpossible. The rate will also depend on the howporous the rock is, the type of oil in the rock(whether it is light or heavy) and the pressure ofthe reservoir that is drilled into. To control themaximum rate of flow possible, the reservoir will bedrilled in stages.

Ongoing analysis will be conducted to ensure thata potential blowout rate is at no time created thatexceeds the rating of the subsea capping system.The maximum blowout rate is therefore limited to75,000 barrels per day. This is discussed furtherin Chapter 9.

2.1.4 Seismic surveySeismic surveys and shallow gas surveys havepreviously been undertaken for this project. Afurther shallow gas survey will be undertaken priorto drilling the well and a vertical seismic profile willbe undertaken after drilling has been completed.

2.2 Wells and drilling

2.2.1 OverviewThe North Uist well will be in a water depth of1,291 m. According to the UKDEAL database,which is the mandatory database for all UK oil andgas wells, 37 wells have been drilled in waterdepth exceeding 1 km to date in UK waters.Several are deeper than the North Uist location

2.2.2 Well programmeDrilling of the well is planned to commence inJanuary 2012 but this may change depending onavailability of the drillship and other operational

matters. The project is expected to last threemonths but may take longer.

2.2.3 Rig selectionA number of rigs have been considered for use inthis location, including;

an anchored drilling rig suitable for thiswater depth, which uses multiple anchorsand chains to control its position, and mayalso use thrusters for additional control;

a dynamically positioned semi-submersibledrilling rig, which uses only thrusters tocontrol its position, which are managed by

hi i i i

0

200

400

600

800

1000

1200

1400

1600

1800

2000

Depthm

Proposed North Uist well

Figure 2-2 UK wells in water deeper than 1,000 m.Source; UKDEAL database and recent environmental statements

North Uist Exploration Well


28/156


balance the higher fuel consumption rate. Duringperiods of adverse weather conditions, fewer riserdisconnections are typically required for DPvessels relative to anchored drilling rigs, henceproducing a lower volume of waste bulk fluids.

Irrespective of the rig type in exceptional cases, forexample rapidly deteriorating and unexpectedlysevere weather or a total failure of the DP system,an emergency disconnect may be required tosafely secure the well. In this rare instance, the

fluid in the riser would be released into the sea. APON1 would be submitted. To date the StenaCarron (drillship) has never had to perform anemergency disconnect.

The drillship chosen for this project is the StenaCarron, a 6 th generation drillship owned andoperated by Stena Drilling (Figure 2-3). This is adynamically-positioned vessel with twin drilling

derricks and is designed and constructed for oiland gas exploration in ultra deep water (up to3,000 m) and harsh environments such as theNorwegian and Barents Seas. It has adisplacement of 97,000 tonnes, an overall length of228 m and breadth of 42 m and it is one of theworld's largest drillships. The drillship is designedto be able to maintain connection with the well inwind speeds up to 27 m/s (10-minute average) and

wave heights up to 6.7 m (significant wave height)(Stena factsheet, 2011), which includes the vastmajority of conditions encountered west ofShetland.

cuttings generated by the drill bit to the surface,lubricating and cooling the drill bit and string, anddeposition of an impermeable cake on the wall ofthe well bore sealing and stabilising theformations being drilled. Drilling fluid requirementsfor a typical well design in this geology fall intothree broad categories:

Simple water based mud (WBM) for thesurface and upper hole (36 and 26")sections

WBM for the middle hole (17") sectionand possibly the lower (12 1 / 4) sections

Description

SURFACE LOCATIONGrid East (m) : 490430 Latitude () : 3 o 10' 43.63"WGrid North (m) : 6 799 615 Longitude () : 61 o 19' 44.60"N

MSL-RT Elevation (Estimated)

Water Depth

18-3/4" HP Wellhead Elevation36" Housing Elevation

Mudline

30" Shoe36" Hole TD

TOC @

20" Shoe LOT = 1.26sg26" Hole TD

TOC @

13-3/8" Shoe17-1/2" Hole TD

LOT = 1.36sg

Well Schematic

Balder Sand

Eocene Fan (Strachan)

Cardhu Secondary Target

Balder

Eocene Fan (Strachan)

Eocene Sands

h l North Uist Exploration Well


29/156


Typically, oil based mud (OBM) for thelower hole (12" and 8") sectionssuitable for drilling into the reservoirformation. Low toxicity mineral oil is usedas the base fluid for these mud systems.OBMs reduce torque and drag as well asmaintaining well bore quality and optimumconditions for high quality fractureidentification, data acquisition andminimum formation damage.

2.2.5 Drill cuttings handlingWBM cuttings from the tophole sections will bedischarged to the seabed. Drill cuttingscontaminated with WBM from the middle holesection will be discharged from the drillship into thesea following mud recovery operations. This isnormal practice and is not considered to be a riskto the environment. OBM contaminated drillcuttings will be recovered and shipped to shore fortreatment and disposal.

A final decision as to whether to use OBM or WBMfor the 12 1 / 4 section is still under technical review.

2.2.6 CementingSteel casings will be installed in the well during the

drilling operation to provide structural strength andto isolate unstable formations and differentformation fluids. Each casing will be cementedinto place to form a seal between the casing andthe formation. Most cement will remain in the wellbore, however some cement will be discharged tothe seabed during the setting of the top sectionand the cement unit is flushed to sea following theoperation. This is normal practice and is not

considered to have a significant impact on theenvironment.

2.3 DecommissioningAt the end of the operation the well will be

a contingency plan to use a precision explosive,cutting charge. This latter option if employedwould be performed with multiple mitigationmeasures to protect marine mammals asdiscussed in Section 7.

Th E i t North Uist Exploration Well


30/156

The Environment pEnvironmental Statement

3 The EnvironmentThis chapter provides data on the keyenvironmental sensitivities in the project area.

3.1 IntroductionThe North Uist project is located within UKCSBlock 213/25c in the Faroe-Shetland Channel, 125

km northwest of Shetland (Figure 3-1). The westof Shetland is an area already developed forhydrocarbon production with drilling commencingover thirty years ago. During this time, a widerange of environmental baseline andenvironmental monitoring surveys have beenundertaken in the region (Figure 3-2). The distanceof these surveys from the North Uist project site isgiven in Table 3-3. This chapter has drawn on thisdata as far as possible.

In addition to reviewing the data obtained from theseabed surveys, information has been taken from

DECCs Strategic Environmental Assessment(SEA4 assessment document and associatedtechnical reports), the Atlantic FrontierEnvironmental Forum (AFEN) and the SERPENT(Scientific and Environmental ROV Partnershipusing Existing industrial Technology) project.

AFEN was a body set up to manage anenvironmental programme for exploration andproduction activities in the sea area to the northand west of Scotland (Atlantic Margin), on behalf of

the oil and gas industry and the governingregulators and advisors.

SERPENT is a global project hosted by theDEEPSEAS group, within Ocean Biogeochemistryand Ecosystems (OBE) at the NationalOceanography Centre, Southampton (NOCS).Remotely Operated Vehicle (ROV) technology anddata made available by the oil and gas industry is

used in the SERPENT project to promote thesharing of scientific knowledge and effectingprogress in deep-sea research.

Th E i North Uist Exploration Well


31/156

The Environment North Uist Exploration WellEnvironmental Statement

3.2 Environmental LegislationProtecting Habitats andSpecies

This section summarises the current environmentallegislation in place to ensure the environmentalimpacts of offshore activities remain within

Europe. Through the establishment of a networkof protected sites these directives provide for theprotection of animal and plant species of Europeanimportance and the habitats that support them.

The Conservation of Habitats and SpeciesRegulations 2010 replace all previous regulationsand amendments and transpose the HabitatsDirective into national law out to 12 nm.

Figure 3-2 Location of surveys carried out in the region of the North Uist Project.

The Environment North Uist Exploration Well


32/156

The Environment Environmental Statement

Site Description

SAC

Sites that have been adopted by theEuropean Commission (EC) andformally designated by thegovernment of each country in whoseterritory that site lies.

CandidateSAC

(cSAC)

Sites that have been submitted to theEC but not yet formally adopted.cSACs are considered in the same

way as if they have already beendesignated. Therefore as with SACs,any activity likely to have a significanteffect on the site of a cSAC must beappropriately assessed.

PossibleSAC

(pSAC)

Sites that have been formally advisedto UK Government, but not yetsubmitted to the EC.

DraftSAC

(dSAC)

Sites that have been formally advisedto UK government but not yetapproved by it.

Sites ofCommunityImportance

(SCI)

Sites that have been adopted by theEC but not yet formally designated bythe government of each country.

Table 3-1 UK SAC/SCI sites summary.The Offshore Marine Conservation (NaturalHabitats, &c) Regulations 2007 and the 2009 &2010 amendments (known as the Offshore MarineRegulations) alongside the Offshore Petroleum(Conservation of Habitats) Regulations 2001 (andamendments 2007) implement the requirement ofthe Habitats Directive. They extend the protection

of marine habitats and species from 12 nm to200 nm from the UK coast. Under theseregulations it is an offence to deliberately disturbany European Protected Species (EPS) while it iswithin its SAC or to capture, injure or kill a EPS atany time. New oil and gas projects/developments

(Section 3.9).

HabitatsOf the habitat types listed in the Habitats Directive(Annex I) requiring protection, four of them occuror potentially occur in the UK offshore area (EC,1999):

sandbanks which are slightly covered byseawater at all times

reefs bedrock reefs; made from continuous

outcroppings of bedrock which may be ofvarious topographical shape (e.g.pinnacles and offshore banks)

stony reefs; aggregations of boulders andcobbles which may have some finersediments in interstitial spaces

biogenic reefs; formed by cold watercorals (e.g. Lophelia pertusa ) and thepolychaete worm Sabellaria spinulosa

submarine structures made by leaking gases submerged or partially submerged sea caves.

Currently in UK Offshore waters there are five sitesthat are designated as cSACs/SCIs, six cSACsand four dSACs. None are in close proximity tothe project site. The closest are the Wyville-

Thomson Ridge and the Darwin mounds, bothcSACs located approximately 225 and 260 kmrespectively southwest of the project site (Figure3-1).

Wyville-Thomson Ridge

The Wyville-Thomson Ridge is a rock ridge at thenorthern end of Rockall Trough rising from over

1000 m at its deepest point to 400 m at thesummit. Along the ridge there are large areas ofstony reef, thought to have been formed by theploughing movement of icebergs through theseabed at the end of the last ice age. Bedrock reefis present on the flanks of the ridge and due to

The Environment North Uist Exploration Well


33/156

The Environment Environmental Statement support many other species such as starfish andsponges.

SpeciesThe designation of fish species that require specialprotection in UK waters is receiving increasingattention with particular attention being paid tolarge slow-growing species such as sharks andrays. At a national level The Wildlife andCountryside Act, 1982, which implements theConvention on the Conservation of European

Wildlife and Natural Habitats, lists seven protectedspecies of marine and estuarine fish (Europeansturgeon, Allis and Twaite shad, basking shark, thewhitefish Coregonus lavaretus , the Giant goby andthe Couchs goby). Under the EC HabitatsDirective there are six fish species (Europeansturgeon, Allis and Twaite Shad, River and Sealamprey, basking sharks and the whitefishCoregonus lavaretus ) that are afforded protection.

In addition, the International Union for theConservation of Nature and Natural Resources(IUCN) has assessed the conservation status of alimited number of fish groups, and haverecommended that two North Atlantic inhabitants;the basking shark ( Cetorhinus maximus ) and thecommon skate ( Leucoraja batis ), be added to thered list of endangered species. The porbeagle (a

species of mackerel shark) is classified asvulnerable on the IUCN Red List. Few of the fishspecies listed above have distributions that extendinto the area of the Faroe-Shetland Channel andare thus not vulnerable to human activity in theareas of Quadrant 213.

Of the species listed, the basking shark (UKBiodiversity Action Plan & IUCN Red List

Endangered), is most likely to occur in the Faroe-Shetland Channel. Although present within theChannel, basking sharks are uncommon andwidely dispersed.

Four species from Annex II of the HabitatsDirective occur in relatively large numbers in UK

(EPS), along with several other marine faunafound in UK waters. As such, developers mustconsider the requirement to apply for thenecessary licences should they consider there tobe a risk of causing any of the potential offences toEPS species.

Of the Annex II species occurring in large numbersin UK waters, the harbour porpoise, bottlenosedolphin and the grey seal have been sighted in thewider region of the project area, althoughobservations of these species at these water

depths would be a rare event.

3.3 Hydrology

Environmental Sensitivity: hydrology, currentregime, waves and salinity are not particularlysensitive to offshore oil and gas activities.However, they are of importance in understanding

the wider ecology of the area and the potentialbehaviour and effects of possible discharges and itis therefore important to understand how they mayaffect the project.

3.3.1 BathymetryThe sea area to the west of Shetland ischaracterised by its complex bathymetry and

oceanography and can be divided into three mainregions:

the West of Shetland Continental Shelf (100 to200 m depth),

the West of Shetland Continental Slope (200 to1,000 m depth) and

the Faroe-Shetland Channel (>1,000 m depth).

The North Uist drill site is on the basin floor of theFaroe-Shetland Channel. The Channel is a narrowdeep-water trough lying between the westShetland shelf and the Faroe Islands platform. Thetrough narrows southward from about 190 km wideat 62 o30 N to 90 km wide at 60 oN. Over the same



34/156

Environmental Statement

acquired at North Uist did not indicate thepresence of any gas seeps.

3.3.2 Current regime

The oceanographic regime (Figure 3-3) of theFaroe-Shetland Channel consists of an upper layerof warm North Atlantic water flowing towards thenortheast, overlying a lower layer of coldNorwegian Sea bottom water, flowing towards thesouthwest (Turrell et al ., 1999).

In detail, five separate water masses arerecognised within the Faroe-Shetland Channel onthe basis of their salinity and temperaturecharacteristics (Turrell et al ., 1999 and referencestherein) (Figure 3-3).

The inflowing current on the Shetland side of theFaroe-Shetland Channel occupies the upperwaters and is dominated by North Atlantic Water(NAW). The remaining surface water is occupiedby the cooler, slightly less saline Modified NorthAtlantic Water (MNAW) which originates to thewest of the Rockall Plateau. A branch of theMNAW flows over the Iceland-Faroe Ridge andcirculates anticyclonically around the Faroe Shelf, entering the channel from the north. Typically thesurface waters occupy the upper 200-400 m of the

water column, being thickest under the core of theNAW closest to the west Shetland shelf edge. The

net flow of these two water masses is to thenortheast (Turrell et al ., 1999).

Below the surface layers, Arctic IntermediateWater (AIW) flows anticlockwise along thesouthern edge of the Norwegian Sea Basin andaround the Faroe-Shetland Channel, typicallybetween 400 and 600 m water depth. Below theAIW, two cold (typically 0 oC) water masses; theNorwegian Sea Arctic Intermediate Water (NSAIW)and the Faroe-Shetland Channel Bottom Water

(FSCBW), flow towards the south. This cold waterflow escapes southward into the Atlantic by way ofthe Faroe Bank Channel.

Currents in the upper water mass are typically 30to 60 cm/s towards the northeast, and in the lowerwater mass 10 to 20 cm/s towards the southwest(Saunders, 1990).

Internal waves may propagate the boundaries ofthe various water masses (Hughes et al ., 2003)along with large scale eddy currents and stormgenerated surges (Grant et al ., 1995). Suchsporadic water movements can have an impact onseabed currents, increasing them by around 0.7m/s for short periods of up to a few hours (BP,2004).

The Environment North Uist Exploration WellEn ironmental Statement


35/156

The Environment Environmental Statement 3.3.3 WavesThe deep waters to the west of Shetland areexposed to strong winds (particularly from the westand southwest) and a large westerly fetch which inturn generates a far more severe wave climatethan that found in the northern North Sea. Theconditions generate an extreme wave regime inthe area with significant wave heights exceeding2.5 m for 50% of the year and 4.0 m for 10% of theyear (DTI, 2003). There has been a steadyincrease in significant wave heights of

approximately 2 3 cm annually in the 30 yearsleading up to 2000 (AFEN, 2001).

3.3.4 Salinity and temperatureMean sea temperatures range between 7.5C inFebruary and 13C in August at the surface butcan be as low as -1.5C at 1300 m water depth. Atwater depths of 500 600 m temperature

variations of several degrees may occur over amatter of hours to days (Ferguson et al. , 1997).The mean salinity in the area varies annually, butis typically between 35.25 and 35.42 (BODC,1998). UKMMAS (2010) report a slight increase insalinity in the northern regional seas, including thatin which the project is located. A comparison oftemperature and salinity for the different watermasses in the Faroe-Shetland Channel are shown

in Table 3-2.Water mass Temperature (C) Salinity

North Atlantic Water >7.5 >35.3

Modified North AtlanticWater

6.0 7.5 35.12 35.18

ArcticIntermediate/North

Icelandic Water

3.0 4.5 34.95 35.00

Norwegian SeaIntermediate Water

0.25 0.75


36/156

Figure 3-4 Annual wind speed and direction atMet Office K7 monitoring buoy.

3.5 Seabed sediments

3.5.1 Sediment and seabed features

Environmental Sensitivity: Potential dischargesarising from the drilling activities could impact onthe sediments causing increased contamination inthe project area.

The character of the local seabed sediments is animportant factor in assessing the potential impactsassociated with offshore operations (e.g. thedischarge of drill cuttings). As well as being animportant factor in determining the type of flora andfauna present, seabed sediment type is alsoimportant in relation to contaminant concentration

e.g. finer sediments and sediments with highorganic content are more likely to support higherconcentrations of metals and hydrocarbons.

A series of major regional surveys (Figure 3-2)were undertaken in the West of Shetland area inthe late 1990s and early 2000s; these include the

The Environment North Uist Exploration WellEnvironmentalStatement


37/156

Environmental Statement

.

Figure 3-5 Regional sediment type.



38/156

Site Distance fromNorth Uist

Depth

(m)

% Fines

(2mm)

Description Reference

AFEN: TR900 TR1300

8-28km N toSE - - Very fine to fine muddy sand Bett (1999)

South Uist(213/25) 12km SE 1,152 50.3 17.6 Medium silt to fine sand Gardline (1998)

AFEN : Z1-Z2 17-19km N - - Sandy muds & mud Bett (1997)

AFEN: X1 15km SE 59.9 2.78Slightly pebbly sand and

muddy sandGardline (1998) &

Bett (1997) AFEN: X2 22km SE 9.7 8.56 AFEN: X3 30km SW 7.27 12.18

AFEN: Y3 26km E - - Muddy & slightly pebblymuddy sands Bett (1997)

Lochside(213/23) 21km W 1,150 29 -

Fine silt to very fine sandswith gravel of different sizes

Chevron (2008) Aberlour

(213/28)37km SW 1,087 33 - Fine silt and clay

AFEN: U1 33km SE - - Slightly pebbly muddy sand Bett (1997)

AFEN: Y4-Y5 33km NE - - Muddy & slightly pebblymuddy sands Bett (1997)

213/27-1z 34km SW 87 - Very fine to fine silt Chevron (2008)

RosebankLochnagar (RB-A)

38km SW 1,200 70.7 0.8 Coarse sand , shell fragments& very fine silt

Chevron (2008)RosebankLochnagar (RB-G)

48km SW 1,200 47.5 14.2 Coarse sand , shell fragments& very fine silt

Table 3-3 Faroe-Shetland Channel sediment characteristics.

AFEN surveys of the floor of the Faroe-ShetlandChannel shows the seabed at these depths to bemade up of relatively featureless mud with somegravel which is overlain by a thin layer (


39/156

3.5.2 Seabed contaminantsDeep-water marine environments generally showrelatively low levels of contamination compared tocoastal waters and industrial estuaries.Concentrations of hydrocarbons and heavy andtrace metals in sediments have been recorded inthe region by surveys conducted by the AFEN(Bett 1997 and 1999) and other Operators(Gardline 1998, Chevron 2008). Data indicatesthat total hydrocarbon concentrations (THCs) arelow, ranging from:

0.3g/g to 1.7g/g at South Uist (Gardline

Uist, Rosebank, Aberlour and Lochside are in linewith those recorded during the AFEN surveys(Chevron, 2008). Slightly elevated levels ofchromium and vanadium were noted at South Uist,but this was thought to be due to naturalconcentrations found in sediments in the region(Gardline, 1998). All concentrations were withinlevels considered to be indicative of

uncontaminated sediments.

3.6 Plankton

Environmental Sensitivity: Plankton are potentiallysensitive to contamination from chemical or oil

Cross section showingno anomalies

Figure 3-6 Seabed features in the immediate vicinity of the proposed well site (Gardline, 2008).



40/156

The survey takes advantage of ships on regularroutes to tow the CPRs at a depth of approximately

10 m. Data collection from the CPRs began in1931 and allows long-term changes, as well asseasonal cycles, in the plankton community to beidentified.

PhytoplanktonPhytoplankton are the primary producers oforganic matter in the marine environment and formthe basis of marine ecosystem food chains.

The composition and abundance of phytoplanktoncommunities varies throughout the year and isinfluenced by several factors, in particular sunlightand vertical mixing in the water column due to windand currents. All these factors are at their optimumin the spring months, leading to a pronouncedperiod of phytoplankton growth, known as thespring bloom. The size and timing of the bloomsmay vary from year to year depending on localweather and oceanographic conditions.

Huthnance (1986) notes that phytoplanktondistributions vary between areas due to effects ofslope topography on the propagation of oceaniceddies and internal waves, differences in shelfedge tidal currents and slope currents, andseasonal and latitudinal variations in the degree of

stratification across the shelf edge. However abroadly similar pattern of phytoplankton bloomingis reported for the Northwest European shelf edgeand adjacent Atlantic from the Rockall Troughthrough the Faroe-Shetland Channel to thenorthern North Sea.

Robinson (1970) observed that, in deeper oceanicwaters north of 60 oN, (which includes the area of

the project), phytoplankton abundance is lower andthe productive season is shorter than that seen inthe central or southern North Sea.

Information on phytoplankton specific to the Faroe-Shetland channel is limited. Howeverh t l kt i h l i th

Phytoplankton

Ceratium fusus

Thalassiosira spp.

Chaetoceros (Hyalochaete ) spp.

Ceratium furca

Chaetoceros (Phaeoceros ) spp.

Rhizosolenia alata alata

Ceratium tripos

Thalassionema nitzscioides

Rhizosolenia styliformis

Nitzschia delicatissima

Table 3-4 Some of the more abundantphytoplankton species found in the North

Atlantic (DTI, 2003).

Zooplankton are dependent upon phytoplankton asa food source and therefore show a similartemporal distribution pattern. Zooplankton are notrestricted to the photic upper layers of the watercolumn and as a rule undergo diurnal verticalmovement, moving towards the surface to feed atnight and sinking during daylight hours.

The zooplankton of the Faroe-Shetland Channel isdominated by the oceanic calanoid copepods e.g.Calanus finmarchicus and C. Helgolandicus (Madden et al ., 1999). Other abundant taxapresent include cyclopoid copepods in particularOithona spp., the euphausiids (or krill) e.g.

Thysanoessa longicaudata and the chaetognaths.C. Finmarchinus overwinters in denseaggregations within the Faroe-Shetland Channelwith overwintering populations being estimated at4.5 x 10 14 individuals (Heath and Jonasdottir,



41/156

the diet (Bjelland and Monstad, 1997). Krill is alsoan important prey item for mackerel, redfish andother pelagic carnivores found in the Faroe-

Shetland Channel. In addition krill are animportant food source for cetaceans in the areassuch as blue-whales and fin-whales as well as forseveral seabirds species e.g. fulmars and Storm-petrels (Debes et al ., 2007).

UKMMAS (2010) report that plankton communitiesare generally not subjected to anthropogenicpressures. This will be a result of a number of

factors including their widespread distribution,However it should be noted that fluctuations inspecies numbers have been recorded as a resultof rising temperatures, which can have knock-oneffects on foodwebs and marine ecosystems.

3.7 Benthic communities

Environmental Sensitivity: Seabed fauna arepotentially sensitive to physical disturbance e.g.damage from anchors and the deposition of drillcuttings and chemical changes such as increasedlevel of hydrocarbons. Each species has its ownresponse and degree of adaptability to changes inthe physical and chemical environmental.

Bacteria, plants and animals living on or within theseabed sediments are collectively referred to asbenthos. Species living on top of the sea floor may

be sessile (e.g. seaweeds) or freely moving (e.g.starfish) and are collectively referred to asepibenthic organisms. Animals living within thesediment are termed infaunal species (e.g. clams,tubeworms and burrowing crabs) while animalsliving on the surface are termed epifaunal (e.g.mussels, crabs, starfish and flounder). Semi-infaunal animals, including sea pens and somebivalves, lie partially buried in the seabed. Asshown in Table 3-5 benthic species may also beclassified in terms of their size.

Bacteria and benthic organisms play a major rolein the decomposition of organic material thatoriginates from primary production byphytoplankton in surface water and settles on theseabed (North Sea Task Force, 1993). Forexample bacteria degrade hydrocarbons through

their utilisation as a food source (Clark, 1996).

Size Categories Examples of RepresentativeGroups Feeding Notes

Macrobenthos(>1 mm) Polychaeta (annelid worms)

Plankton, organic material, seaweeds. There are some specialisedcarnivores.

Crustacea (e.g. crabs) Carnivores, scavengers. Some, such as barnacles, filter plankton &bacteria.

Echinodermata (e.g. sea urchins,starfish & brittlestars)

Starfish & brittlestars are usually carnivorous. Sea urchins graze onalgae.

Bivalvia (e.g. mussels) Bivalves may filter phytoplankton or feed on organic matter in thesediment.

Gastropoda (e.g. limpets) Gastropods graze using a radula. May be herbivorous orcarnivorous.



42/156

Benthic animals display a wide variety of feedingmethods. Suspension and filter feeders captureparticles which are suspended in the water column(e.g. sea pens) or transported by the current (e.g.mussels). Deposit feeders (e.g. sea cucumbers)ingest sediment and digest the organic materialcontained within it. Other benthic species can beherbivorous (e.g. sea urchins), carnivorous (e.g.crabs) or omnivorous (e.g. nematodes).

Sessile infaunal species are particularly vulnerableto external influences that may alter the physical,chemical or biological community of the sedimentas they are unable to avoid unfavourableconditions. Each species has its own responseand degree of adaptability to changes in thephysical and chemical environment. Consequentlythe species composition and relative abundance ina particular location provides a reflection of theimmediate environment, both current and historic(Clark, 1996).

In most deep water environments, faunal diversityand biomass decrease with depth as a result offood limitation. In the Faroe-Shetland Channel, thistrend is evident in terms of biomass such that itdoes decline with depth. However the relationshipbetween macrobenthic diversity and depth is notso evident. The presence of cold arctic waters inthe deeper areas of the Faroe-Shetland Channelarea appears to exert a marked influence(decrease) on the diversity of the deep-seamacrofauna of the region, most clearly seen whencompared with the diversity of the benthos fromthe adjacent Rockall Trough which does notexperience these arctic conditions (Betts, 2003,Campbell et al ., 2010).

Latitudinal trends in benthic communitycomposition in the Faroe-Shetland Channel arerelatively weak (Bett, 2003), indicating that localcommunities in the vicinity of the proposed welllocation will be comparable to those sampledregionally at locations in similar water depths

Lochside and Aberlour with 42% of species beingannelids, 34% crusteaceans, 10% mollusca and

2% echinoderms (Chevron, 2008).

Plate 3-2 Crossaster sp. Photographed at 1,050min Faroe-Shetland Channel (Jones & Gates, 2010).



43/156

The dominant species in the region are typicallypolychaetes such as Myriochele oculata , M.fragilis ,Clymaldane, Pseudeurythoe hemuli andNotomastus sp, Paramphinome jeffreysii,Notoproctus oculatus and Chaetozone setosa.The sipunculid worm Golfingia margaritcea is alsopresent as are the amphipods Harpinia mucronata and Haroinia abyssi and the cumacean Eudorella sp (Gardline, 1998; Chevron, 2008). Photographstaken within the Greater Rosebank Area show

epifauna such as: cold water fish (Arctic rockling,Arctic skate and various eelpout species); seaspiders ( Boreonymphon abyssorum ); amphipodcrustaceans; sunstar ( Solaster squamatus ) brittlestars ( Ophiopleura borealis ); burrowing seaanemones and fan worms (Chevron, 2008).

The AFEN surveys found no evidence of largereefs or colonies of cold water corals in the Faroe-Shetland Channel (Bett, 1997 and 1999). Theprotected coldwater coral Lophelia pertusa doesoccur to the west of Shetland and in the AtlanticOcean but typically does not tolerate temperaturesbelow 4 Celsius, whereas the temperature at thebottom of the Faroes-Shetland Channel is typicallyaround zero Celsius.

No evidence of species or habitats of conservationimportance were identified (under the UKsOffshore Petroleum Activities (Conservation ofHabitats) Regulations 2001) in the region(Gardline, 2007).

Plate 3-5 Atlantopandalus propinqvus iscommon in Faroe-Shetland Channel (Jones &Gates 2010).

Plate 3-6 Cerianthus vogti in the Faroe-Sh tl d Ch l (J & G t 2010)



44/156

3.8 Fish

Environmental Sensitivity: Juvenile and adult fishspecies present in the area around the project arepotentially sensitive to chemical and oil discharges.Demersal laid fish eggs are particularly sensitive toseabed disturbance during spawning seasons.

Fish communities consist of species that havecomplex interactions with one another and thenatural environment. They consume a wide range

of benthic invertebrates and/or act as predators athigher trophic levels, while themselves being asource of prey for larger animals. Forconvenience, fish can be split into finfish andshellfish, with the former being broadly split intopelagic and demersal species. Pelagic species(e.g. herring, mackerel, blue whiting and sprat) arefound in mid-water and typically make extensiveseasonal movements or migrations. Demersalspecies (e.g. skates and rays, red mullet, andmonkfish) live on or near the seabed and similar topelagic species, many are known to passivelymove (e.g. drifting eggs and larvae) and/or activelymigrate (e.g. juveniles and adults) between areasduring their lifecycle.

Fish occupying areas in close proximity to offshoreoil and gas activities could be exposed to aqueousdischarges and may accumulate hydrocarbons andother contaminating chemicals in their bodytissues. The most vulnerable stages of the lifecycle of fish to general disturbances (such asdisruption to sediments) and oil pollutio

scotland north uist exploration well environmental statement

Documents