Nick J Gill

Devex Conference 2016

Aberdeen, UK

ConocoPhillips UK Decommissioning:

June 16, 2016

The Challenge and the Process

Decommissioning at ConocoPhillips

June 16, 20162

Group formed in May 2013:

• 28 Southern North Sea wells Plugged and Abandoned

• Redundant equipment removed at Theddlethorpe Gas Terminal

• MacCulloch FPSO decommissioned and removed from station

• Viking satellites transfer to cold suspension currently in progress

1. Plug & Abandon Wells (P&A)

2. Final Clean & Disconnect

3. Dismantle & Dispose

4. Surveillance & Monitoring

STAGES OF DECOMMISSIONING:

Viking Complex

0

200

400

600

800

Cu

mu

lati

ve T

ime

(d

ays)

Well Plug and Abandonment example: Viking Area

June 16, 20163

VIKING AREA P&A:

• Wells dating back to 1969

• Campaign commenced June 2014

• Ensco 92 jack-up rig satellite campaign

• 28 wells completed to date

RIG PERFORMANCE CURVE:

PLANNED

ACTUAL

Learning Curve takes effect

KEY LESSONS LEARNED

• Offshore: “multi-skill”, retain same team, build on the learning curve

• Offshore: Always have a Plan B (and Plan C)

• Onshore: Ensure a diverse engineering team

• Cost reduction: Look for best value, not necessarily cheapest price

Final Clean and Disconnect example: MacCulloch FPSO

June 16, 20164

105km of pipelines &umbilicals to clean <30ppm

115 subsea disconnects,

+90% to complete by

divers

FPSO on station since

1998

+20 topsides systems to flush and

de-gas

• Final production from the facility in May 2015

• 4 month programme of final clean and disconnect prior to FPSO removal

• Collaborative effort between 2 owners, 3 major sub contractors and downstream operator

Final Clean and Disconnect example: MacCulloch FPSO

June 16, 20165

PIPELINE CLEANING METHODOLOGIES:

Cleaning programme designed to remove hydrocarbon in stages:

1. Gas removal

2. Liquid removal

3. Solids/ immobile hydrocarbon removal

No well disposal – gas lift system used as ‘loop’

Both foam and hard-bodied pigs utilised

Solvents used in oil export system to dissolve wax

Gel pigs used in non-piggable flowlines

KEY LESSONS LEARNED:

Thorough engineering process/ procedure review

Overdesign reduces risk of operational delay (e.g. staged cleaning)

Physical barrier vs turbulent flow

Pig-trials (test and in-situ)

Knowledge of systems

Chemicals and permitting

Agree and document sampling regime

Removal & Disposal

June 16, 20166

INFRASTRUCTURE REMOVED TO DATE:

MacCulloch Field:

• 4km of flexible risers (steel and composite plastics)

• 2 x 100Te mid-water arch structures

Theddlethorpe Gas Terminal:

• 2 x 30Te redundant methanol stills

• 1 x 50Te redundant heat exchanger

KEY LESSONS LEARNED

• Ensure robust philosophy for handling removed material; the “Disposal Hopper”

• Use of photographic survey software (e.g. R2S) will reduce need for offshore surveys

• Ensure all activities are permitted with the appropriate regulatory body

• Contract structure – ensure maximum flexibility but minimise risk (separate or combined removal and disposal contracts?)

• Trial cuts onshore where possible

Summary

June 16, 20167

Final Clean and

Disconnect

Well Plug & Abandon

Remove and

Dispose

Post Removal

Ensure diverse engineering team

Focus on value over price in engineering/ materials

Maintain consistency of offshore crews

Over-engineering reduces risk of operational delay

Multiple checks and procedural reviews

Know the details of the systems

Flexibility in contract structure

Detailed surveys ahead of operations

Disposal philosophy agreed to minimise waste

Stakeholder engagement is crucial

Monitoring regime

8

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