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Environmental Considerations in Offshore Decommissioning
and Removal
Presented by Joe Ferris, PhD
6 June 2014
BMT Cordah Limited
Aberdeen
Scotland
Presentation Content
• Introduction
• Supporting Studies
• Selection of Preferred Option through a Comparative Assessment
• Impact Assessment Process
• Identifying Risk
• Principal Decommissioning Impacts
• Conclusions
BMT Cordah Decommissioning Services
• Environmental advisor support / secondment to decommissioning projects
• Tailored decommissioning programme(s)
• Comparative assessments or Best Practical Environmental Option (BPOE) assessment
• Environmental impact assessment
• Environmental risk identification workshops
• Marine and coastal habitat assessment
• Energy use and gaseous emissions
• Marine growth assessment
• Subsea acoustic modelling
• Waste management strategy and planning
• Management of cutting piles
BMT Cordah
supported CNRI with the
decommissioning of their
188 m high Murchison Platform
Supporting Studies • Scoping study • Environmental Surveys – pre and post decommissioning
oHydrocarbons
oHeavy metals
oOther Contaminants
o Biota
oDrill cuttings
• Pipeline survey
• Fisheries socio-economic study
• Energy use and emissions
• Marine growth assessment
Comparative Assessment of Options
Risk of major project failure
Economics
Fisheries
Amenities
Communities
Marine Impacts
Energy/resource consumption
Other consequences
Risk to personnel Risk to other users of the sea Risk to those on land
Safety Environ-ment
Technical Feasibility & Cost
Societal
Impacts from Decommissioning
Operations End-points
Short-term
Localised
Obvious
Long-term
Possibly extensive
Not immediately obvious
Possible legacy issues
May be cumulative
Environmental Impact Assessment Process
• Assessment of seabed condition
• Assessment of potential impacts to marine environment
• Assessment of atmospheric & terrestrial impacts
• Waste management
• Energy use associated with re-use and
recycling
• Potential impacts to future users of
the sea
• Determination of significance
Significance of Impacts As Determined Through Risk Assessment Methods
Principal Environmental Issues I. Waste Management
II. Marine Growth
III. Cuttings and Seabed Debris
IV. Socioeconomic Concerns
V. Hazardous Substances
VI. Direct Impacts to Marine Ecosystem
I. Waste Management
Eliminate
Reduce
Reuse
Recycle / Recover
Disposal
• Waste management should align with
the Waste Hierarchy
• Operator ensures obligations met
• Set targets for reuse / recycling of
materials
• Initial segregation of waste is important
• Transboundary considerations
• Duty of Care
Waste Hierarchy
Most Favourable Option
Least Favourable Option
Waste Management Planning
II. Marine Growth
• Weight of marine growth on jackets & supports
• Occurrence of protected species
• Transfer of non-native species
• Onshore odour and disposal issues
Weights of Marine Growth
• Estimated wet weights (in air) in relation to
jacket/support structural weight were:
o Miller: 10%
o Heather Alpha: 9%
o NW Hutton: 6%
• Weights of marine growth received by the
decommissioning contractors:
Estimated
Wet Weight
Actual Weight Received
(Dry Weight in Tonnes) (Tonnes)
1,000 200 (80% reduction)
40-50 7 (82-95% reduction)
Management of Marine Growth • Current marine growth management is company- and location- specific
• Opportunities exist for more effective technologies
• Landfill is a common disposal end point
• Composting and landspreading are alternatives to landfill
• Bulk removal of marine growth at sea
• Natural drying
III. Drill Cuttings and Seabed Debris
• Drill cuttings and muds
o medium sized discharges (5,000 to 20,000 tonnes)
o larger discharges (>20,000 tonnes)
• Contaminants in cuttings piles:
o hydrocarbons
o heavy metals
o other chemicals from drilling mud additives
• Potential ecotoxicological affects
• Debris that may impact fishermen
Example of a Large Cuttings Pile
• volume of 22,545m3
• footprint area of 6,840m2
• elevated levels of total hydrocarbons and PAHs
• oil loss to water column predicted at 6 tonnes/year
IV. Socioeconomics Concerns • Commercial and Recreational Fisheries • Impacts to onshore resources • Waste disposal and chemical contaminants
• Shipping and transit • Obstructions left on the seabed • Stakeholders, regulators & public
Impact of Pipelines and Subsea Structures
V. Hazardous Substances
• Radioactive Materials (NORM)
• Tank Contents (chemical soup)
• Hydrogen sulphide gas
• Topside materials, e.g.
asbestos, PCBs, lead paint
VI. Direct Impacts to Marine Ecosystem Disturbance to Seabed
Noise Impacts
Sensitive Species & Habitats
Beneficial Outcomes from Decommissioning
• Increased access to fishing grounds • Removal of obstructions to commercial shipping • Removal of source of potential environmental
contaminants • Re-establishment of marine habitat • Economic benefits to suppliers and service providers • Use of jackets and platforms for habitat enhancement
(often referred to as rigs-to-reefs)
Use of Platforms for Habitat Enhancement • Proposed as replacement for or enhancement of declining natural
reef ecosystems
• Potential benefits
o enhance biological productivity
o improve population connectivity
o prevent trawl damage / protect deep water reefs
• Potential drawbacks / concerns
o physical habitat damage
o spread of invasive species
o change marine food webs
o release of contaminants over time
Methods for Creating Reefs from Platforms • Tow and place platform at designated location / area
o The rig is submerged and converted into artificial reef
o Primary costs in towing and cutting
o Divers cutting the jacket legs below the mud line
o Can be expensive, labour intensive
• Topple in place
o The remaining portion of the platform is completely submerged and converted into artificial reef
o Primary cost is in cutting
o Lower costs and time savings.
• Partial removal of platform
o Remove a certain portion of the platform
o Remaining part of the platform is completely submerged and left at the drilling site
o Primary cost is also cutting
o Reduces the removal costs and risks for divers
Using Rigs-to-Reefs as Disposal? • Concern that placement of rigs for reefs used to legitimise the “dumping” of
waste or other materials
• UNCLOS (1982) calls for the adoption of regional rules, standards and recommended practices and procedures to prevent, reduce and control pollution of the marine environment from dumping and from seabed activities subject to national jurisdiction
• Intent of National and International Guidance to:
o prevent pollution or degradation of the marine environment;
o ensure that placement of artificial reefs is not used as a mechanism to circumvent the provisions of the London Convention on the “dumping” of waste;
o promote artificial reef development that has environmental benefits
• Current concepts: increase biomass; create conservation hotspots; re-establish biological community; ecotourism; or compensation for habitat loss
• Clear domestic laws and institutional organization are needed
A Few Conclusions • Environmental risk and impacts should be identified early in
decommissioning planning
• Both localized, short term and wider, long-term impacts need to be considered
• Beneficial outcomes should be highlighted and negative risks mitigated
• Reuse and recycling is a reasonable expectation
• Artificial reefs for ecological and fisheries enhancement or the protection of endangered species are legitimate under international law
• Goals of a rigs-to-reef program must be clearly defined
