1. Title U.S. Department of the Interior U.S. Geological Survey Probable Production Induced Subsidence, Fault Reactivation, and Wetland Loss in the Gulf Coast Region R. Morton, N. Buster, D. Krohn, and R. Peterson U.S. Geological Survey Center for Coastal and Watershed Studies St. Petersburg, FL 33701 http://coastal.er.usgs.gov/gc-subsidence/

2. SCIENTIFIC OBJECTIVES Investigate timing of subsidence and faulting Compare geological and historical rates of subsidence Evaluate geological and engineering factors that may influence induced subsidence and faulting

3. Objectives continued Examine mechanisms of subsidence and faulting Evaluate methods of regional subsidence detection and monitoring Develop predictive capabilities (subsidence susceptibility)

4. ENVIRONMENTAL APPLICATIONS Evaluate potential contributions to historical wetland losses Incorporate into resource management and coastal restoration plans Evaluate methods of subsidence mitigation

5. EVIDENCE OF INDUCED SUBSIDENCE AND FAULT REACTIVATION Temporal and spatial correlation of surficial changes and hydrocarbon production Large or rapid subsurface pressure decline (regional depressurization)

6. Evidence continued Consistent orientation and displacement of active surface and subsurface faults Historical subsidence rates significantly greater than geological subsidence rates Preservation of marsh sediments beneath open water (historical wetland loss)

7. Overburden stress

8. Fieldwork

9. COCODRIE TIDE GAUGE

10. Coring

11. Texas location map

12. Fields table Port Neches

13. Port Neches field map

14. Port Neches field graph

15. Port Neches diagram

16. Texas location map

17. Bolivar photo

18. Caplen Field map

19. Caplen Field graph

20. Caplen Field diagram

21. Texas location map

22. Clam Lake map

23. Aerial photo

24. Clam Lake graph

25. Wetlands photo

26. Louisiana map

27. Well field map

28. Fields table Valentine

29. Annual Production Valentine

30. BHP Valentine

31. Annual Production Houma

32. Annual production Lirette

33. Annual production Lapeyrouse

34. BHP Exposito

35. Pressure gradient decline

36. Core MB 06

37. Houma tide gauge

38. Loss lines

39. NGS Data 1965 - 1982

40. Benchmarks

41. NGS Data 1966 - 1993

42. Average geological and historical rates of subsidence for the Terrebonne delta plain region near Madison Bay.

43. Annual Production Lapeyrouse

44. DELTA PLAIN WETLAND LOSS

45. Prior studies attributed regional wetland loss to delta plain compaction, canal construction, and biogeochemical processes Subsidence associated with natural compaction should be slow and decrease with geologic time Some delta plain subsidence rates accelerated recently and are greater than geologic subsidence rates CONCLUSIONS

46. Marsh sediments are preserved where accommodation space is created by induced subsidence Prior explanations of regional wetland loss fail to explain the rapid increase and decrease in rates of loss (1950s-1970s) Close temperal and spatial correlations among regional wetland loss, highest historical subsidence rates, maximum rates of fluid extraction and pore- pressure reduction, and locations of potentially reactivated faults Decrease in wetland loss possibly related to decreased subsidence associated with decrease oil & gas production CONCLUSIONS CONTINUED