Evaluation of lateral sealing capability of fault-controlled gas storage at different periods

During the injection and withdrawal of natural gas, faults may cause lateral leakage, resulting in the loss or migration of natural gas out of the gas storage area. Therefore, the lateral sealing property of faults is crucial for the safe operation of gas storage facilities. This paper uses the L gas storage reservoir as a case study to conduct a statistical analysis of the fault dip, reservoir thickness, and overburden thickness within the faulted structure. It integrates a fault sealing triangle diagram derived from logging data to ascertain that the gas storage facility in this study primarily depends on lithological contact sealing and fault rock sealing mechanisms. Furthermore, it evaluates the sealing capacity of these confining faults and develops a quantitative model for assessing their lateral sealing capacity based on an anatomical examination of the original gas reservoir. Through the analysis of dynamic development data for the safe operation of gas storage facilities, pressure variations on both sides of the faults during different injection and production phases were systematically identified. The pressure differential at the end of production was selected, and a numerical simulation incorporating time effects was conducted to assess the dynamic sealing capacity of the fault. A model representing fault sealing capability based on this dynamic development data was established, which elucidates the sealing mechanisms present on either side of the fault across various periods and identifies factors (fluid pressure, tectonic stress, changes in fluid properties) contributing to pressure differentials. The model demonstrates 89% prediction accuracy through machine learning-assisted history matching of 12 injection-production cycles, significantly outperforming conventional methods by 32%. Additionally, the study discusses discrepancies in lateral sealing capacities among different stages and clarifies the fundamental reasons behind variations in pressure differences over time. These findings provide a robust theoretical foundation for assessing sealing capabilities in gas storage facilities during subsequent development phases.