Abstract: The key to the operation of underground water-sealed oil storage cavern is to maintain a certain thickness of water seal, which is dependent on the behavior of oil vapor migration under varying water seal depth. To determine a proper water seal depth, we developed a finite element numerical simulation method based on gas-liquid two-phase flow theory to model the evolution process of oil vapor leakage from an underground water-sealed oil storage cavern in China during its operation. Results showed that in construction stage in the absence of water curtain system, a large drainage area at the top of the cavern made oil storage inoperable. However, the construction of a water curtain system enabled the maintenance of a certain thickness of water seal above the coal seam. The range and volume of oil vapor leakage in the surrounding rock displayed positive power function correlation with operation time, with smaller leakage range and volume observed at thicker water seals. However, excessively thick water seals greatly increased engineering costs. Our study suggests an economically and reasonably safe water seal thickness of 30 m, which meets recommended standards and provides a sound basis for water-sealed oil storage cavern design and oil vapor leakage control.

Key words: oil vapor leakage, underground water-sealed oil storage caverns, two-phase flow, water curtain system, numerical simulation, thickness of water seal