Assessing Potential Risk of Loss in Integrity of the Sidewall of a Cavern Located Near the Edge of the Salt Dome

The U.S. Strategic Petroleum Reserve (SPR) stores crude oil in 60 caverns located at four sites located along the Gulf Coast. The reserve contains approximately 695 MMbbls (110 Mm³) of crude oil. Most of the caverns were solution mined by the U.S. Department of Energy (DOE). Bayou Choctaw Cavern 20 (BC-20) is located near the edge of the salt dome (Figure 1). Its proximity close to the edge of the dome raises concerns about potential tensile failure in the surrounding rock near BC-20 induced by the cavern volume closure due to salt creep. The location of BC-20 in the salt dome is similar to the cavern involved in the Bayou Corne Sinkhole shown in Figure 2 admonishing us that a risk of loss integrity of the sidewall of BC-20 should be investigated. Due to the Bayou Corne cavern collapse, 150 homes had been evacuated for nine months since August 2012. This paper evaluates the structural instability in the salt between the dome edge and the cavern (call 'edge pillar', indicated by yellow ovals in Figures 1) through a geomechanical analysis using a newly developed numerical model.

Figure 1. Location of Cavern 20 with respect to the edge of the salt dome

Figure 2. Conceptual diagram of failure/collapse of sidewall of brine-mined Oxy Geismar 3 salt cavern in the Napoleonville Salt Dome (left) and other caverns in vicinity of Oxy 3 (right). Formation of the Bayou Corne sinkhole occurred in August 2012.