Abstract: To address issues such as insufficient quantitative risk assessment in leakage accidents of in-service crude oil storage tanks, this paper introduces a mathematical method combining the Poisson process with a continuous physical model. First, it is assumed that the number of leakage events follows a Poisson distribution. Taking the annual expected oil spill volume as the core risk indicator, the orifice outflow equation is employed to quantitatively model the leakage consequences under different leakage scenarios, and a sensitivity analysis of key parameters is conducted. The study shows that although small-hole leakages occur with higher frequency, their individual consequences are limited, and their risk contribution is mainly reflected as a long-term cumulative effect. In contrast, although rupture leakages have a lower probability of occurrence, the resulting oil spill volume per event is extremely large, making them the key factor dominating the overall risk level and uncertainty. The sensitivity analysis indicates that the annual occurrence rate of rupture leakages and the leakage duration have a significant amplifying effect on the risk level.

Key words: crude oil storage tank, leakage risk assessment, Poisson process, expected annual oil spill volume, control strategy