alma field development

285 Pages·2011·7.99 MB·English

EnQuest Heather Limited
Alma Field Development
Environmental Statement
DECC Document Ref: D/4110/2011
Intertek METOC Document Ref: P1459BA_RN2525_Rev0
EnQuest Heather Limited Document Ref: ENQ-KN501-HS-001-ENS-0001
ISSUED: 21 JULy 2011
WHERE ENGINEERING MEETS THE ENVIRONMENT
ENQUEST HEATHER LIMITED
ALMA FIELD DEVELOPMENT
STANDARD INFORMATION SHEET
Project Name Alma Field Development
DECC Reference
D/4110/2011
Number
Type of Project Small oil field development
Undertaker Name EnQuest Heather Limited
Undertaker Address 5 Floor Consort House, Stell Road, Aberdeen, AB11 5QF, United Kingdom
Licencees / Owners EnQuest Heather Limited (100%)
EnQuest Heather Limited wishes to redevelop the Ardmore field in the UK Central North Sea (CNS). The
field, to be renamed Alma, will be developed through two drill centres tied-back via new oil production
and water injection flowlines to the Uisge Gorm floating production, offloading and storage facility
(FPSO). The development will consist of six production wells and two water injection wells (which will be
used to drive production due to low reservoir pressures).
Wells will be drilled using a combination of water and oil based muds. Cuttings and water based muds
will be discharged to sea both at the seabed and from the drilling rig approximately 10m below the sea
surface. Oil based mud and cuttings will not be discharged and will be skipped and shipped back to
shore for disposal.
Due to the relatively short expected field life of the Alma development (ten years), the Uisge Gorm FPSO
will be used instead of installing a platform. Produced crude will be collect by shuttle tanker once every
Short Description two weeks. The majority of the produced gas will be used for power generation, however there may be a
short period early part of field life where excess gas is produced that cannot be burned, this will be flared.
All produced water will be re-injected.
Production flowlines will be surface laid and protected. The water injection flowline will be trenched and
buried, but where trenching is not possible it will be surface laid and protected. Concrete mattresses and
rock material will be used for protection.
Current estimates are that based on a 10 year field life the base case recovery from the Alma field will be
20.7 million barrels (2.8 million tonnes) and a high recovery case of 32.5 million barrels (4.4 million
tonnes). Peak production in the first year will be in the region of 4.5 million barrels (0.61 million tonnes) for
the base case and 7.8 million barrels (1.06 million tonnes) for the high recovery case.
Construction is scheduled to start in January 2012 with the drilling of the first producer wells. First oil is
anticipated in August 2013.
Anticipated Start of
January 2012
Works
Previous / Other
Statements Related to N/A
this Project
EnQuest is aiming to limit environmental effects to low impact through project design, mitigation
measures and operational controls. No impacts associated with the development have been categorised
as Major or Critical, meaning that the majority of the impacts were assessed as having no or minor
residual impact (i.e., impacts can be managed through effective standard operating procedures). A few
impacts were assessed as Moderate (i.e., the residual impact has been subject to feasible and cost
effective mitigation and no further measures are practicable).
Significant
During construction and production it is considered that the following activities may have an impact: on
Environmental
the environment; atmospheric emissions from power generation; anchoring ; discharge of chemicals and
Impacts Identified
drill cuttings; positioning of structures, rock material and concrete mattressing on the seabed; and the
accidental spill of hydrocarbons and/or chemicals. However in all instances the severity of the impact is
limited by the nature and composition of the environment and by the fact that these activities are short-
term and affect a localised area.
With mitigation measures in place, the Alma field development will have a minor impact on the
environment.
Statement Prepared
Intertek METOC and EnQuest Heather Limited
By
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ENQUEST HEATHER LIMITED
ALMA FIELD DEVELOPMENT
NON-TECHNICAL SUMMARY
INTRODUCTION
EnQuest Heather Limited wishes to redevelop the Ardmore field in the UK Central North Sea
(CNS). The field, to be renamed Alma, will be developed through two drill centres tied-back
via new oil production and water injection flowlines to a floating production, offloading and
storage facility (FPSO). Export will be through the use of a shuttle tanker from the FPSO.
The proposed Alma development will be located in United Kingdom continental shelf (UKCS)
Blocks 30/24 and 30/25, approximately 274km east of the nearest landfall on the
Northumberland coastline and approximately 18.5km from the Norway/UK international
boundary (median line).
In compliance with regulatory requirements, and to responsibly manage any impacts from the
development, EnQuest has carried out an Environmental Impact Assessment (EIA) of the
proposed development.
The EIA process establishes the environmental baseline in the area of the proposed
development and identifies environmental sensitivities, particularly with relevance to the
concerns of stakeholders and regulatory bodies. It also evaluates relevant environmental
impacts and their significance, and finally proposes mitigation measures which the operator
will implement to minimise these impacts.
This document reports on the EIA process, its findings and conclusions.
GOVERNING LEGISLATION
Offshore oil and gas developments are governed by a collection of international, European
Community (EU) and UK laws, policies and guidelines. These dictate the management goals
and objectives which an environmental assessment may aim to achieve. The main UK
regulations that apply to the project are:
Petroleum Act 1998 – Requires all offshore oil and gas development to apply for
consent to undertake the project.
Offshore Petroleum Production and Pipelines (Assessment of Environmental Effects)
(Amendment) Regulations 2007 – These regulations implement the EC EIA and Public
Participation Directive, and require an ES to be submitted for offshore oil and gas
projects and public participation in the consent process.
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Offshore Marine Conservation (Natural Habitats, &c.) Regulations 2007 (as amended
in 2009 and 2010) – These regulations implement in the UK the EC Habitats Directive
(92/43/EC) and the EC Birds Directive (79/409/EC) and aim to protect marine species
and wild birds from environmentally damaging activities. It is now an offence under the
Regulations to deliberately disturb wild animals of a European Protected Species.
Offshore Petroleum Activities (Conservation of Habitats) Regulations 2001 (amended
in 2007) – The regulations apply the EC Habitats and EC Birds Directives in relation to
oil and gas projects on the UKCS.
PROJECT JUSTIFICATION
Oil is the UK’s second largest source of primary energy, supplying over 30% of the country’s
total energy needs (OGUK 2009). In 2008, the UKCS oil production was enough to satisfy
97% of domestic consumption, produced mainly from fields in the Central North Sea (CNS)
basin, with some production in the NNS and Southern North Sea (SNS). In 2000, the UK
Government identified the need to stimulate oil and gas investment and activity to ensure
that indigenous production of oil and gas remained at significant levels into the future. The
Promote UK campaign is designed to attract new entrants onto the UKCS, and focused on:
Independent oil companies with the resources to drill wildcat exploration wells and
exploit the full value chain from exploration to development; and
Niche ‘developers’, particularly those with the skills to develop previously undeveloped
discoveries by using technically innovative and best cost solutions (DECC 2011a).
As a result of these initiatives, EnQuest has been active on the UKCS since 2010. It
specialises in predominantly mature areas of the NNS and CNS, aiming to maximise the
potential from existing fields and future developments in the UKCS. The longer term strategy
is to become a prominent exploration and development operator.
The Alma Field development is part of this strategy and fits many of the UK energy policy
objectives:
It would bring on-stream a marginal field that it is now feasible to develop with the
prevailing oil price and the small field allowance applicable to this size of field
It is a national resource that will help contribute towards energy security
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ALMA FIELD DEVELOPMENT
Current estimates predict that P501 recovery over field life will be 20.7 million barrels of oil
(2.8 million tonnes). P102 recovery is estimated to be 32.5 million barrels (4.4 million
tonnes).
PROJECT ALTERNATIVES
EnQuest have considered a number of development options for the Alma field. Given the
compact nature of the field and relatively short field life, the decommissioning strategy has
played an important role in option selection. Options considered included the choice of
surface facilities (FPSO, floating production facility (FPF), platform or subsea tie-back), the
choice of drilling rig (semi submersible or heavy duty jack-up) and the installation philosophy
of the flowlines (trenched and buried or surface laid and protected).
After considerable deliberation, the FPSO, semi submersible and a combination of trenching
and surface lay options were selected, based on combination of technical, environmental
economic considerations. Table 3-3 details all the pros and cons of each option.
FPSO
A number of FPSOs are available for deployment
Provides an integrated storage and offloading system
Modifications required are more economic that other available options e.g. new
platform
FPSOs fit for expected field life
Using an existing FPSO is cheaper than a new build
FPSOs considered have proven track record in the UKCS
Minimal seabed disturbance from installation
Can be easily redeployed at end of field life
Semi Submersible
Less weather dependant during positioning on site
More scope for moving rig but maintaining same anchor pattern – less seabed
disturbance. For example, moving to allow subsea infrastructure to be installed,
moving rig if subsurface philosophy changes

1 50% confidence level of this volume of oil being produced
2 10% confidence level of this volume of oil being produced
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ALMA FIELD DEVELOPMENT
Ability to drill six wells on same anchor pattern – less seabed disturbance
Easier to run horizontal xmas trees
Better selection options- at least two rigs are known to be available
Current drilling team has extensive knowledge of semi submersible drilling operations
Flowlines
Buried
Greater protection for flowlines – no additional protection such as rock would be
required except for mattressing and grouting at trench transition areas
Conventional / proven solution
Option to surface protect spans which cannot be buried due to existing subsurface
obstructions
Surface Laid
Ease of installation - range of installation vessels available
Benefit as compact field layout with possible drilling rig on site during installation
Lower mobilisation costs for installation
Potential of re-use / decommissioning easier
Conventional / proven solution
Minimal seabed disturbance
Lower risk of subsurface obstructions because no trenching
Additional protection such as rock material will be required for certain spans
Technically preferred option for production flowlines due to temperature issues
PROJECT DESCRIPTION
SCHEDULE
Construction is scheduled to start in January 2012 with the drilling of the first production well.
Construction activities will continue through to May 2013 with first oil expected in third quarter
2013. A total of six production wells and two water injector wells will be batch drilled and are
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expected to take approximately three months each to drill and complete. Field life is
anticipated to be ten years.
CONSTRUCTION
The development will consist of:
The drilling of six producers and two water injectors
The Uisge Gorm FPSO
Two 10-inch production flowlines, one 10-inch water-injection flowline, two control
umbilicals and one power cable
Production wells will target a total of three reservoirs within the Alma Development area:
Devonian, Zechstein and Rotliegend. Three production wells will be drilled in five sections
using a combination of water based mud (WBM) and oil based mud (OBM), with each
section cement cased. The remaining three production wells and the two water injection
wells will be drilled in four sections also using a combination of WBM and OBM, with each
section cement cased. Cuttings and WBM will either be discharged at the seabed or to sea
approximately 10m below sea surface from the drilling rig. All OBM and cuttings will be
skipped and shipped to shore for disposal.
The water injection flowline will be trenched and backfilled. In the event of any undulations in
the trench (and subsequently the flowline) a contingency will be in place for the provision of
approximately 5,000 tonnes of rock for deposition for protection. The rock will be deployed to
mitigate any upheaval buckling (less of a problem with flexible flowlines) or pipeline out of
straightness events experienced during the trenching and pipe-lay activities. This may be
required for pipeline protection, depth of cover anomalies or dropped object protection. The
requirement for rock deposition will be identified during post lay survey and if required the
rock will be placed accurately utilising a dynamically positioned fall pipe rock installation
vessel. The vessel will be equipped with a fall pipe to deploy rock accurately in the spot
location. Where trenching is not possible the water injection flowline will be surface laid and
protected where required with concrete mattress to eliminate any pipe-spans or seabed
obstructions. The production flowlines will be surface laid and protected. They cannot be
trenched as the arrival temperature of the production fluids at the FPSO would be too high.
After tie-in, the flowlines will be hydrotested and leak tested before being dewatered and then
commissioned. Concrete mattresses and rock material will be used for dropped object
protection and stability. The water-injection flowlines will terminate directly in the FPSO. The
production flowlines will terminate at a bolted straight “T” piece from which flexible risers will
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ALMA FIELD DEVELOPMENT
take produced fluids to the FPSO. All flexible risers will be secured by either vertical piled or
gravity base anchors and horizontal clump weight anchors.
The Uisge Gorm FPSO will be held permanently on station without any aid from thrusters or
other external sources by nine anchors. Modifications and upgrades will be carried out on
the FPSO turret to accommodate the new flowline/umbilical riser systems required to receive
and process the Alma hydrocarbons and to export injected water. The upgrades will be
finished before the FPSO is mobilised to the field.

Note: Image is for illustrative purposes only and does not necessarily reflect exact layout of flowlines and
associated infrastructure
PRODUCTION
Produced crude oil and associated gas will be produced back to the FPSO and oil then
offloaded onto shuttle tankers for export.
First oil is currently expected in third quarter 2013. Current estimates are that based on a 10
year field life the base case recovery from the Alma field will be 20.7 million barrels (2.8
million tonnes) of crude oil and a high recovery case of 32.5 million barrels (4.4 million
tonnes). Peak production in the first year will be in the region of 4.5 million barrels (0.61
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ALMA FIELD DEVELOPMENT
million tonnes) for the base case and 7.8 million barrels (1.06 million tonnes) for the high
recovery case. The reservoir pressure at Alma is such that produced water re-injection is
required to ensure that satisfactory quantities of crude oil are produced. Sufficient quantities
of gas are expected to be produced with the crude to be used for power generation onboard
the FPSO.
Produced water will be passed through a bank of hydrocyclones which will take oil in water
(OIW) concentrations from approximately 1000mgl-1 to below 30mgl-1. It will then be routed
through a degasser and settling vessel. The produced water then passes through the pumps
past an overboard discharge point and into four injection pumps that push the produced
water down the water injection flowline to be re-injected. Should any produced water be
discharged (due to temporary failure, or routine maintenance of the produced water re-
injection system) then OIW concentrations will be below 30mgl-1.
Early in the field life there will be the need to flare gas. This would be due to either
insufficient gas production to power the generators on the FPSO or because of an excess of
gas produced, over that demanded for fuel.
DECOMMISSIONING
Field life is expected to be ten years. Before the end of field life, arrangements for
decommissioning will be developed in accordance with the prevailing UK government and
international legislation. The development plan is based on the assumption that similar
requirements to current legislation will be applicable. These requirements have been
considered in the design of the facilities and during project planning. The impacts of
decommissioning activities on the environment have not been assessed under the scope of
this document as they will be the subject of a separate EIA.
ENVIRONMENTAL IMPACT AND MITIGATION
Mitigation is an integral part of the Alma development. All of the potential interactions
between project activities and environmental receptors are subject to either standard
recognised best practice mitigation measures or to impact specific, feasible and cost
effective mitigation. In general, the mitigation proposed will be sufficient to reduce the effects
of activities to below levels which will cause a significant residual impact. For those where
mitigation isn’t enough, the residual impacts are detailed below with a discussion of the
mitigation that will help to reduce the impact to the acceptable levels identified.
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ALMA FIELD DEVELOPMENT
The following table summarises the findings of the detailed EIA process undertaken in
relation to the Alma development and outlines details of the impacts that were considered to
have a residual impact on the environment.
Receptor & Type Baseline & Impact Assessment Significance Mitigation
of Impact of Residual
Impact
Construction
Seabed The Alma development area comprises a <1m Minor The footprint of the development will
Conditions: thickness of very loose to loose silty shelly sands be minimised.
Disaggregation of (with a varying degree of gravel and shells) over
surface sediments firm to very stiff sandy gravelly clay. A number of
Change in seabed activities have the potential to affect seabed
topography conditions e.g., anchoring and the deposition of drill
cuttings. When retrieved, the anchors are expected
to leave a small area of residual disturbance on the
seabed. Seabed currents (0.42ms-1) will ensure
that all cuttings piles will disperse quickly, although
there is the possibility that they may persist for a
number of years
Seabed Site surveys of the Alma field indicate that there is Minor Daily recording of chemical use to
Conditions: a level of sediment contamination as a result of the allow more refined and efficient use.
Sediment historic use of the area for previous oil and gas Where possible chemicals will be
contamination developments. It is unlikely that further drilling at recycled, skipped and shipped or re-
the site will increase this contamination as injected and not discharged.
chemicals discharged at the seabed are typically
Selections of chemicals will be made
environmentally benign. No OBM will be
in accordance with the CEFAS
discharged.
ranked list, where chemicals ranked
Benthic The benthic community is typical of a sandy Minor as lower potential hazards are
Communities: biotope with moderate diversity. No rare or preferentially chosen.
Potential toxic protected species were identified in the baseline
Only chemicals permitted through the
effects survey. All seabed chemical discharges will be risk
relevant Offshore Chemicals
assessed and will be within permitted levels.
Regulations chemical permit (i.e.
PON15B or PON15C) and that have
been subject to a risk assessment
will be discharged.
Benthic The benthic community is typical of a sandy Minor The development footprint will be
Communities: biotope with moderate diversity. No rare or minimised where operationally
Physical damage to protected species were identified in the baseline possible.
individuals or survey.
habitats and
A total of 8 anchors will be deployed within a
smothering
1,000m (3,281ft) radius of the rig at each drill site.
(Anchoring)
The total area of seabed impacted by all anchors
and chains has been estimated at 4,800m2.
Communities are expected to recover within two
years following cessation of disturbance.
Cuttings discharged at the seabed will have a
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