Oil and gas leakage risk analysis of underground storage caverns in bedded salt rock using fault tree analysis

Oil and gas leakage is one of the most important types of underground storage cavern accidents in salt rock, which has the features like abruptness and inestimable loss. By taking the underground storage caverns in bedded salt of China as research object, its oil and gas leakage risk in the operation process is analyzed; the mechanism of oil and gas leakage accident is revealed and the corresponding fault tree model is established. By analysis, mostly influence factors and fault patterns are found out; and the occurrence probability formula is deduced, which is applicable to the typical underground storage caverns in bedded salt rock. The results show that there are 28 fault patterns of oil and gas leakage accidents of underground storage caverns in bedded salt and this kind of accidents are likely to happen and difficult to prevent; namely, its occurrence possibility is pretty large; according to the calculation results of the basic events' importance degree, low strength of salt rock, excessive creep of salt rock, fault near the cavern, earthquake, incorrect control of cavern construction parameters, non-uniform ground stress field, human error and so on are the main factors leading to oil and gas leakage accidents. By using Delphi method and fault tree analysis synthetically, it is concluded that the risk probability of oil and gas leakage accidents at five old caverns of Jintan salt mine in recent 10 years is about 0.703%, belonging to incidental accidents.