Abstract: Underground water-sealed oil storage caverns represent an effective oil storage technology that typically employs an artificial water curtain system to maintain a stable groundwater level and prevent product leakage. The pressure of oil and gas within the cavern can influence the groundwater seepage field, creating an oil and gas leakage zone around the cavern, thereby affecting water inflow and leakage rates. The proper control of oil and gas pressure is crucial for ensuring the functionality of the water-sealing system and the long-term stability of the storage facility. Using finite element numerical simulation, this study investigates the evolution of oil and gas leakage and water inflow during the storage operation phase under varying oil and gas pressures, based on a specific underground water-sealed oil storage project. The results indicate that oil and gas pressure impacts the seepage field, with increased pressure expanding the leakage zone. Elevating the groundwater level can reduce water inflow and lower operational costs; however, as oil and gas pressure increases, the leakage zone expands, and leakage volume rises. When oil and gas pressure exceeds 0.2 MPa, rapid leakage occurs, spreading to the water curtain boreholes and eventually to the surface, causing significant environmental pollution due to the accumulation of oil and gas near the surface and its entry into the atmosphere. For the studied case, maintaining an oil and gas pressure at 0.2 MPa ensures no leakage and achieves the most economically reasonable control of water inflow.