The U.S. Strategic Petroleum Reserve stores crude oil in 62 caverns located at four sites in Texas and Louisiana and currently contains over 700 million barrels. Most of the caverns were solution mined by the Department of Energy. Oil leaks have been found in two wellbores taken from caverns located at the Big Hill Strategic Petroleum Reserve in Texas. According to the multi-arm caliper survey performed by DM Petroleum Operations in 2009 and 2010, two instances of casing damage occurred at the depth of the interface between the caprock bottom and salt top. To help analyze the failures, Sandia researchers used high-performance computing resources to model the geomechanics of the wellbores. A three-dimensional mesh that allowed each cavern to be configured individually was created to investigate wellbore damage at the interbed between the caprock bottom and the salt top as shown in the companion image. The mesh consists of 1,050,760 nodes and 1,012,932 elements with 37 element blocks, 5 node sets, and 28 side sets. Sandia-developed three-dimensional solid mechanics code, Adagio, was used in the analyses. The simulation was carried out on Sandia’s Red Sky, using 512 nodes (4,096 cores) and 51 hours of computer

running time. The analysis results indicated wellbore failures resulted from shear stress that exceeded the wellbore shear strength from the horizontal movement of the salt top relative to the caprock. Another wellbore failed from tensile stress created by the downward movement of the salt top from the caprock within the cavern. Computation images were constructed to enable comparisons of predictions to actual casing failures. These simulations matched the survey images well.


Overview of the finite element mesh of the stratigraphy and cavern field at Big Hill.