Borehole-to-Surface Electrical Imaging Technology for Dynamic Monitoring of Underground Gas Storage and Case Study

Abstract

Summary To solve the issue of seasonal gas peak shaving, building underground gas storage is an effective solution. Geophysical monitoring technology is necessary for dynamic gas storage management. However, as these technologies are not highly accurate in the lateral direction, new technologies need to be developed. In recent years, borehole-to-surface electrical imaging (BSEI) technology has been widely used in reservoir and fracturing monitoring. In the dynamic monitoring of gas storage, high-power direct current is applied to the borehole through the steel casing, and the potential is measured on the surface. Then, resistivity inversion is performed to analyze the transverse distribution of the injected gas. To prove the feasibility of monitoring injected gas, a 3D forward case is simulated using the finite difference method (FDM). The model-structure-constrained inversion approach is verified. Based on the forward simulation results and the formation pressure period, the gas storage observation scheme is designed. The case study shows that the gas storage inversion results constrained by the upper formation have a high resolution and clearly show the transverse boundary of the target reservoir, which is consistent with the fault boundary determined by seismic prospecting. Therefore, 3D resistivity imaging can clearly show the distribution of gas reservoirs during injection and production. This study shows that BSEI is an effective technique for dynamic monitoring of gas storage and has good application prospects.