1. Risk in Well Plugging & Abandonment by Twachtman Snyder & Byrd, Inc
Risk in Well Plugging & Abandonment by Twachtman Snyder & Byrd, Inc. September 2006

2. 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.

3. Robert 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

4. Well Plugging & Abandonment Summary

5. WELL PLUGGING & ABANDONMENT
Rigless Method used predominantly in Gulf of Mexico & North Sea
Rig-based method used primarily on subsea wells 6 7 6

6. Well P&A Objectives Assure isolation of hydrocarbon zones
Protection of fresh water aquifers
Prevention of migration of fluids & gases

7. General 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.

8. Well P&A -
Rig vs.
Rigless
Step 1
Typical Wellbore Schematic

9. Well P&A - Rig vs. Rigless Step 2 Bottom Plugs Set With
Tubing Pulled Out of Hole

10. Well P&A - Rig vs. Rigless Step 3 Balanced Plug on Rigless and
Stopped Plug With the Rig

11. Well P&A - Rig vs. Rigless Step 4 Rigless with Cut Casing
and CIBP; Rig with
Same but with a little more
Casing Out of the Hole

12. Performance Risk Issues in Well P&A
Time lapse between well completion and P&A
Deterioration of hardware
Loss 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

13. Risk Mitigation Factors in Well P&A
Formations generally produced out, therefore pressures not high.
Systems and tools are available to deal with any eventuality.

14. Well P&A Cost Risk Example

15. Offshore Platform Components
Production Equipment
Deck
Drilling Rig
Quarters
Power
Generation
Pipeline
Conductors/Wells
Jacket
Piles
Offshore Platform Components

16. Other Risk Issues in Well P&A

17. Risk 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 Pale in comparison with the uncertainty following a Catastrophic Event (Hurricane).