Case Study of the Impact of Prior Cavern Abandonment on Long-Term Oil Storage at a Strategic Petroleum Reserve Site

摘要

This paper presents a case study of the effect of an abandoned cavern of large diameter on the long-term stability of an oil storage facility in domal salt. The U.S. Strategic Petroleum Reserve stores crude oil in solution-mined caverns in the Bryan Mound salt dome, located near Freeport, Texas. An additional 400-m diameter cavern, Cavern 3, was constructed for brine production and storage in the 1940s and plugged and abandoned in 1980. Surface subsidence measurements show an unexpectedly larger subsidence rate over Cavern 3 than the rest of the site, possibly indicating that this cavern may be losing pressure, which would affect boreholes for nearby storage caverns. This paper evaluates the current status of Cavern 3 using subsidence data from site-wide surveys and GPS and tiltmeters installed over the cavern, and large-scale computational analyses including realistic cavern geometries and the effects of heterogeneous salt creep properties. Next, it describes a surface subsidence evaluation plan to analyze current surface subsidence data,in addition to possibly obtaining other available information such as InSAR data, to monitor future subsidence on a continuous basis. Finally, the paper will use the case study to discuss the formation of a strategy for abandoning decommissioned caverns in a long-term storage facility built in domal salt.