Analysis of leakage risks and prevention measures of underground salt cavern gas storage

Good sealing performance is the fundamental prerequisite for a safe operation of a salt cavern gas storage engineering. However, the complicated geological conditions, the lack of practice in building gas storage, and the incomplete theoretical knowledge will lead to various leakage risks for the gas storage in the salt cavern. According to engineering practices and statistics on accidents worldwide, and combined with the unique engineering geological conditions and operational states of the salt cavern gas storage, three major leakage factors (i.e. geological factors, engineering factors and human activity) and four leakage types were summarized in this paper. The potential leakage types in underground salt cavern gas storage include near-horizontal leakage of gas caused by insufficient interlayer sealing, upward movement of gas through the strata caused by the breakthrough and failure of caprock, natural gas leakage along the wellbore due to its insufficient integrity, the gas flow to the faults owing to the connectivity between the interlayers and faults. Based on their respective leakage characteristics, corresponding preventive measures were proposed to prevent the occurrence of gas leakage accidents and its large-scale spread. In view of the fact that the development of salt cavern gas storage in China is temporarily at a developing period, this research results have certain reference and guiding significance for safety construction of deep salt cavern gas storage.