risk in well plugging & abandonment by twachtman snyder & byrd, inc. september 2006
DESCRIPTION
Risk in Well Plugging & Abandonment by Twachtman Snyder & Byrd, Inc. September 2006. Twachtman Snyder & Byrd, Inc. Houston, Texas, based company founded in 1987. Provides project management, well P&A and contracting services to the oil and gas industry. - PowerPoint PPT PresentationTRANSCRIPT
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Risk in Well Plugging & AbandonmentRisk in Well Plugging & Abandonment
byby
Twachtman Snyder & Byrd, Inc. Twachtman Snyder & Byrd, Inc.September 2006September 2006
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Twachtman Snyder & Byrd, Inc.Twachtman Snyder & Byrd, Inc.
• Houston, Texas, based company founded in 1987.
• Provides project management, well P&A and contracting services to the oil and gas industry.
• Specialized in decommissioning of offshore facilities.
• Consulting services for decommissioning planning and liability assessment.
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Robert C. ByrdRobert C. Byrd
Over 30 Years in the Offshore Industry• Joined TSB in 1993• Responsible for Risk and Liability Consulting
Services• Educational Background:
– B.Sc. Marine Engineering, US Coast Guard Academy– M.Sc. Ocean Engineering, Unv. of Alaska, Fairbanks– M.Sc. Structural Engineering, Unv. of California, Berkeley– Ph.D. Engineering, Unv. of California, Berkeley
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Well Plugging & AbandonmentWell Plugging & AbandonmentSummarySummary
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WELL PLUGGING & ABANDONMENTWELL PLUGGING & ABANDONMENT
• Rigless Method used predominantly in Gulf of Mexico & North Sea
• Rig-based method used primarily on subsea wells
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Well P&A ObjectivesWell P&A Objectives
• Assure isolation of hydrocarbon zones
• Protection of fresh water aquifers
• Prevention of migration of fluids & gases
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General Well P&A ProcedureGeneral Well P&A Procedure
• Cement plug is placed below and across the lowest production zone, tagged and tested.
• Cement plugs across all production zones
• All open annuli are plugged.
• Tubing cut approximately -100 m below the mud line (BML) and the tree is removed.
• Production casing removed to -100 m BML.
• Surface cement plug is pumped into the casing with top at -32 m BML.
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Well P&A - Well P&A - Rig vs. Rig vs. RiglessRigless Step 1Step 1
Typical Wellbore Schematic
26" @ 804'
18-5/8" @ 1607'
13-3/8" @4344'
9-5/8" @ 9945'
4-1/2" Liner top@ 9549'
4-1/2" @10,545'
Perforations
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Well P&A - Well P&A - Rig vs. Rig vs. RiglessRigless
Step 2Step 2
Bottom Plugs Set With Tubing Pulled Out of Hole
26" @ 804'
18-5/8" @ 1607'
13-3/8" @4344'
9-5/8" @ 9945'
4-1/2" Liner top@ 9549'
4-1/2" @10,545'
26" @ 804'
18-5/8" @ 1607'
13-3/8" @4344'
9-5/8" @ 9945'
4-1/2" Liner top@ 9549'
4-1/2" @10,545'
RIGLESS RIG
BOTTOM SQUEEZE
PERFORATIONS
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Well P&A - Well P&A - Rig vs. Rig vs. RiglessRigless Step 3Step 3
Balanced Plug on Rigless and Stopped Plug With the Rig
18-5/8" @ 1607'
13-3/8" @4344'
9-5/8" @ 9945'
4-1/2" Liner top@ 9549'
4-1/2" @10,545'
26" @ 804'
18-5/8" @ 1607'
13-3/8" @4344'
9-5/8" @ 9945'
4-1/2" Liner top@ 9549'
4-1/2" @10,545'
RIGLESS RIG
300' INTERMEDIATECEMENT PLUG
BOTTOM SQUEEZE
PERFORATIONS
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Well P&A - Well P&A - Rig vs. Rig vs. RiglessRigless Step 4Step 4
Rigless with Cut Casing and CIBP; Rig with Same but with a little more Casing Out of the Hole
18-5/8" @ 1607'
13-3/8" @4344'
9-5/8" @ 9945'
4-1/2" Liner top@ 9549'
4-1/2" @10,545'
26" @ 804'
18-5/8" @ 1607'
13-3/8" @4344'
9-5/8" @ 9945'
4-1/2" Liner top@ 9549'
4-1/2" @10,545'
RIGLESS RIG
300' INTERMEDIATECEMENT PLUG
200' SURFACECEMENT PLUG
W/ CIBP
BOTTOM SQUEEZE
PERFORATIONS
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•Time lapse between well completion and P&A
Deterioration of hardwareLoss of, incomplete or inaccurate records
•Often performed long after platforms shut-in
•P&A personnel often know little about the wells
•Cost pressure: Not income generating
Performance Risk Issues in Well P&APerformance Risk Issues in Well P&A
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Risk Mitigation Factors in Well P&ARisk Mitigation Factors in Well P&A
•Formations generally produced out, therefore pressures not high.
•Systems and tools are available to deal with any eventuality.
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InvGauss(0.89492, 1.86797) Shift=+0.49924X <= 0.765
5.0%X <= 2.600
95.0%
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0.5 1 1.5 2 2.5 3 3.5
Data CharacteristicsMean: 1.394Mode: 0.998Median: 1.234
Actual Cost/Estimated Cost
PDF of Well P&A Experience
Well P&A Cost Risk ExampleWell P&A Cost Risk Example
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Production Equipment
Deck
Drilling Rig
Quarters
PowerGeneration
Pipeline
Conductors/Wells
Jacket
Piles
OffshoreOffshorePlatform Platform ComponentsComponents
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Other Risk Issues in Well P&AOther Risk Issues in Well P&A
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Risk in Well P&ARisk in Well P&A
Conclusions
•The performance risk in well P&A is primarily economic: It is very difficult to estimate the cost accurately for a single well.
•We can estimate the cost of multiple wells probabilistically.
•These Risks PaleRisks Pale in comparison with the uncertainty following a Catastrophic EventCatastrophic Event (Hurricane).