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.