Publications
Geotechnical Concerns of Bayou Choctaw Strategic Petroleum Reserve and Explanations
Geotechnical concerns arise due to the close proximity of the some of the caverns to each other (e.g., Caverns 15 and 17) or to the edge of the salt dome (e.g., Cavern 20). There are nine abandoned caverns, one of which collapsed (Cavern 7) in 1954 and another (Cavern 4) which is believed to be in a quasi-stable condition. This report provides explanations for these geotechnical concerns. The structural integrity of the pillar between BC-15 and 17 is examined. No salt fall is expected through 2045. However, the dilatant damaged area increases with time, especially, at the chimney area of BC-17. One drawdown leach for both caverns could be allowed if they are normally operated as a gallery, depressurized simultaneously. The possibility of a loss in integrity of BC-20 is examined in the salt between the dome edge and the cavern. The edge pillar is predicted to have experienced tensile stress since September 1999, but the small tensile stressed area is predicted to disappear in 2018 because BC-20 is filled fully with brine rather than oil since 2/7/2013. Even though BC-20 is no longer used as an SPR cavern, we need to continue monitoring the cavern integrity. BC-4 is also currently filled with brine and will not hold pressure at the wellhead. The cavern extends upward into the caprock and has no effective salt roof The results indicate that any sort of caprock roof collapse for BC-4 is not imminent but salt falls will likely occur from the near-roof portions of the cavern. The uncertainty due to salt falls illustrates the importance of continued monitoring of the area around BC-4 for behavior such as subsidence and tilt which may indicate a change in the cavern's integrity status.