3-D Elastic Wave Simulation and Microseismic Source Localization in Underground Water-Sealed Oil-Storage Caverns

Underground water-sealed oil storage caverns (UWOC) are among the primary methods for large-scale oil storage worldwide. Undesired geological phenomena can lead to rock fracturing under external loading, posing risks to the structural integrity and operational safety of UWOC. Microseismic monitoring enables real-time tracking of the spatial locations and scales of fractures, providing early warning of rockburst risks and minimizing casualties and damage to the equipment. However, in the process of microseismic monitoring in UWOC, the long-term monitoring requirements lead to instability issues in the microseismic numerical simulation. Furthermore, the distinctive structure of UWOC and geological conditions increases the complexity of the three-dimensional (3D) wavefield, affecting the accuracy of numerical simulation and microseismic monitoring. To address these issues, we propose a long-term 3D elastic wave numerical simulation and 3D space microseismic source localization method in UWOC. This method can address instability issues in long-term microseismic monitoring, laying the foundation for higher accuracy source localization. To further improve 3D source localization accuracy, the difference in reference travel times is used to construct the objective function in a simulated annealing (SA) inversion. Key factors influencing microseismic source localization accuracy were systematically analyzed and discussed. Numerical simulations and field experiments demonstrate that the proposed method achieves long-term stable numerical simulations of 3D elastic wave and enhances source localization accuracy in UWOC, highlighting its potential for practical application in microseismic monitoring within UWOC.