The use of a commercially available reservoir simulator as a supporting tool in the simulation and analysis of parameters of underground gas storage in a salt cavern

The paper presents the developed methodology and the obtained results of modeling related to the verification of potential use of specific software packages from Computer Modeling Group Ltd. (commercial reservoir simulation software) as a support tool for simulation and analysis of changes in selected parameters of the underground gas store in a salt cavern. As a part of the task, with use of the Builder package, an attempt was made to build a static model of the salt cavern. Dynamic modeling (IMEX package) was focused on convergence as a parameter having a key impact on the efficiency of underground gas storage in the salt cavern. Due to the large size of the static model created based on original data (thickness and radius of equivalent chamber slices from echometric measurements) and restrictions of the software, it was decided to create a simplified cylindrical model (consisting of a smaller number of cells) characterized by constant values of thickness and radius of selected slices. Further analysis of the simulation possibilities led to the need to separate a calculation model - created on a rectangular grid for which the geomechanical model was created. In total, 24 simulations were made (six depths of the top level of cavern, four variants of the minimum required pressure of the stored gas). The values of walls, top and bottom layers' movements towards the center determined the base to specify the size of the change in the storage volume. The convergence values were calculated for the cylindrical model as the final simulation model. In addition, the optimal cavern foundation depth was determined based on the analyses of convergence changes and the size of the gas cushion.