Containing fluids within their intended zones applies to both conventional and unconventional exploration and production. Effective containment requires a three-fold approach incorporating both the subsurface geology, the wells and the operations teams at the surface. From a technical perspective, both well integrity and subsurface integrity are crucial to subsurface containment. A loss of either can induce a subsurface containment loss.
Containment losses can be classified into one of two broad categories and then further classified by asset, location, volume of loss and many other qualities. Some representative losses are listed here.
|Well Integrity||Offshore||Deepwater Horizon, Macondo Prospect, Gulf of Mexico, 2010||Failures of cement job, blow-out preventer|
|Well Integrity||Heavy Oil||Cold Lake, Alberta, 1997||Poorly cemented wellbore in steam injection well|
|Well Integrity||Natural Gas Storage||Aliso Canyon, CA, 2015||Casing failure of gas injection well in repurposed depleted oil field|
|Subsurface Integrity||Onshore||Baldwin Hills/Inglewood, CA, 1963||Normal faulting and ground subsidence induced by water injection|
|Subsurface Integrity||Heavy Oil||Joslyn Creek, Alberta, 2006||Explosive failure of caprock above steam chamber|
|Subsurface Integrity||Heavy Oil||Primrose, Alberta, 2009, 2013||Leakage of heated bitumen to surface through cracks in overburden|
|Undocumented Wellbores||Unconventional (Shale Gas)||Tioga County, PA, 2012||Methane/water geyser|
The final item on the list above lies at the intersection of both well and subsurface issues. When wells are unknown or improperly sealed, exploration and production activities in the subsurface can cause fluids to migrate unexpectedly and sometimes explosively to the surface.
Images: “Cold Lake, Canada” by Derrick Goode, United States Air Force; “Graphic” by Top Energy Training, adapted from Dr. Richard Shultz