Four-Dimensional Geomechanical Model of Gas Storage Reservoir Group Linkage and Its Application

The Nanpu Sag gas storage reservoir complex is a complex faulted depression with complex faulting characteristics, and the sealing performance and ultimate pressure-bearing capacity evaluation of the gas storage reservoir complex face severe challenges. The ultimate pressure-bearing capacity evaluation method for the gas storage reservoir complex has not yet been systematized. This paper introduces a multi-scale geomechanical model to evaluate the integrity of the gas storage reservoir complex’s geological body. By applying Python subroutines to connect the ABAQUS virtual topological surface technology and using wedge-shaped grid element bodies to achieve fluid-solid coupling calculations, and utilizing the rock fatigue test data under the high-speed injection and production cycle alternating load of the gas storage reservoir and the in-situ stress measurement data in the field, a large-scale in-situ stress model for the gas storage reservoir complex was established for the first time. The four-dimensional stress field distribution under different pore pressures was simulated, and the stress changes and stability of faults and cap rocks were analyzed. Based on multi-dimensional and multi-index evaluation of the geological body integrity, a full-system monitoring system was deployed at weak positions. The four-dimensional geomechanical simulation results of single gas storage reservoirs and gas storage reservoir complexes show that the safety factor of the fault zone in the sag is less than 1 according to the injection and production plan, and the faults are in a stable state. The operation safety of the gas storage reservoir under the influence of the dynamic stress field was quantitatively evaluated, achieving the characterization from the single gas storage reservoir to the gas storage reservoir complex scale, and from static to dynamic stress fields. Compared with the operation of a single gas storage reservoir, the stress disturbance caused by the multi-reservoir coordinated operation to the boundary faults was quantitatively evaluated, and a more accurate ultimate pressure-bearing capacity index system was constructed, filling the gap in the research on the distribution of in-situ stress fields under arbitrary dynamic changes in the same injection and production conditions of complex fault-block gas storage reservoir complexes.