Effective Containment in the Subsurface
Containment of produced or injected fluids within their intended wellbores or geologic zones is critical 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 result in a subsurface containment loss.1Schultz, R.A., Summers, L.E., Lynch, K.W. and Bouchard, A.J., 2014, March. Subsurface containment assurance program-Key element overview and best practice examples. In Offshore technology conference-Asia. OnePetro.
The consequences of containment loss to an operator or partner can be large, including both direct and indirect costs (e.g., clean-up cost, loss of production, and damage to reputation), even for small events. On the other hand, effective containment assurance programs can minimize drilling and operational risk and enhance a company’s reputation as a safe and prudent operator or partner.2Schultz, R.A., Summers, L.E., Lynch, K.W. and Bouchard, A.J., 2014, March. Subsurface containment assurance program-Key element overview and best practice examples. In Offshore technology conference-Asia. OnePetro.
Containment losses can be classified into one of two broad categories:
- well integrity loss
- subsurface integrity loss
Containment losses can then be further classified by type of asset, location, volume of loss, and many other qualities. Some representative losses are listed here.
Risk Factor | Type | Location | Description |
---|---|---|---|
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