Study on the Key Factors Controlling Natural Gas Loss at the Boundary Fault of the X1 Gas Storage Facility

Natural gas loss directly threatens the safety and economic viability of underground gas storage (UGS) facilities. The short-term, high-rate cyclic injection and withdrawal processes may cause fault reactivation, resulting in gas loss. Current assessment techniques are mostly concerned with overall storage performance, with few studies focusing on fault-related leakage. This study looks at a UGS facility developed from a difficult fault-block sandstone dry gas resource in China. Focusing on one of its border faults, we develop geological and numerical models to systematically examine the impacts of well-to-fault distance, gas injection rate, and gas withdrawal rate on fault leakage. The results show that numerical simulations can accurately estimate this gas loss. The well-to-fault distance, injection rate, and withdrawal rate are highlighted as critical regulating variables. There is an ideal range for the well-to-fault distance, and altering the injection/withdrawal rates of wells within this range is an effective loss mitigation approach. The crucial distance between injection–production wells and the fault in the X1 gas storage facility is 900 m. Notably, improving the gas withdrawal rate of wells close to the fault considerably minimizes leakage. Reducing the gas injection rate from 11 × 104 m3/d to 7 × 104 m3/d reduces natural gas loss by 353 × 104 m3. Increasing the gas production rate from 9 × 104 m3/d to 29 × 104 m3/d reduces natural gas loss by 975 × 104 m3. The findings provide a scientific basis for assessing and managing natural gas loss at boundary faults in similar UGS plants.