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Underground gas storage (UGS) is a critical component within the natural gas industry's value chain, encompassing production, distribution, storage, and marketing. Hence, it is vital for national energy supply security, economic stability, and people's livelihood. Evaluating UGS' sealing capacity is essential for its safe construction and operational efficiency. This involves evaluating both the static sealing capacity of traps during hydrocarbon accumulation and the dynamic sealing capacity of UGS under intensive gas injection and withdrawal, and alternating loads. This study reviewed the sealing capacity evaluation of 28 UGS projects in China, detailing the methodology developed by Sinopec and its implementation. The approach merges disciplines like geology, geomechanics, and hydrodynamics, employing both dynamic-static and qualitative-quantitative analyses. Sinopec's evaluation methods, grounded in the in situ stress analysis, include mechanistic studies, laboratory tests, geological surveys, stress analysis, and fluid-solid interactions. Through tests on the static and dynamic sealing capacity of UGS, alongside investigations into sealing mechanisms and the geological and geomechanical properties of cap rocks and faults, Sinopec has devised a geomechanics - rock damage - seepage mechanics dynamic coupling model (the fluid-solid coupling model). This model predicts in situ stress variations relative to pore pressure changes during UGS operations, evaluating fault sealing capacity and cap rock integrity, thereby setting the maximum operational pressures. Utilizing this evaluation technique, Sinopec has defined performance metrics and criteria for evaluating the sealing capacity of depleted reservoirs and salt cavern UGS, enabling preliminary sealing capacity evaluations at its UGS sites. These evaluations have significantly informed the design of UGS construction schemes and the evaluation of fault sealing capacity and cap rock integrity during UGS operations.
Zhang et al. (2024) studied this question.