risk in well plugging & abandonment by twachtman snyder & byrd, inc. september 2006
TRANSCRIPT
Risk in Well Plugging & AbandonmentRisk in Well Plugging & Abandonment
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Twachtman Snyder & Byrd, Inc. Twachtman Snyder & Byrd, Inc.September 2006September 2006
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.
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
WELL PLUGGING & ABANDONMENTWELL PLUGGING & ABANDONMENT
• Rigless Method used predominantly in Gulf of Mexico & North Sea
• Rig-based method used primarily on subsea wells
Well P&A ObjectivesWell P&A Objectives
• Assure isolation of hydrocarbon zones
• Protection of fresh water aquifers
• Prevention of migration of fluids & gases
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.
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
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
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
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
•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
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.
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
Production Equipment
Deck
Drilling Rig
Quarters
PowerGeneration
Pipeline
Conductors/Wells
Jacket
Piles
OffshoreOffshorePlatform Platform ComponentsComponents
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).