Maintaining subsurface integrity in subsurface operations is critical to many activities including geothermal power generation, oil and gas production (conventional, unconventional, fractured crystalline, heavy-oil fields), mining, and storage of CO2 and natural gas. Predicting and mitigating out-of-zone fluid migration includes but goes beyond maintaining well integrity ; it relies on technical understanding of top and fault seals, reservoir and overburden deformation, production/injection-induced stress changes, reservoir management, completions design and engineering, hydraulic fracturing/height containment, wastewater disposal, induced seismicity/fracture reactivation, and reservoir monitoring (e.g., geodetic and downhole measurement and interpretation). Subsurface integrity typically excludes surface facilities and spill response but includes regulations regarding subsurface activities and the connections at the wellhead for these ; it promotes safety for both process and people as well as social license-to-operate.
This talk will present a high-level overview of subsurface integrity, focusing on storage of natural gas in underground facilities. Following a set of representative examples of containment loss events in the industry, key principles will be outlined that provide a framework for developing effective subsurface integrity programs. A defense-in-depth containment strategy that is aligned with US State and federal regulations for underground natural gas storage is outlined that can improve the safety of facilities such as Aliso Canyon.
