A case study on optimum identification of water curtain hydraulic pressure using three-phase flow numerical simulation

Groundwater-sealed liquid propane storage cavern is usually built in crystalline rock mass. Water curtain system is an indispensable facility to ensure the containment efficiency of the cavern due to the strong heterogeneity of fractured rock mass and the special properties of stored product. In this study, a propane cavern in Yantai, Shandong province is selected as a study case to investigate the reasonable water curtain pressure. Stochastic mathematical method was applied to calculate the permeability coefficient of the study area. A vertical 2D three-phase flow model based on THOUGH2 is established to study the migration characteristics of the stored product under different water curtain pressure and the influence of water curtain pressure on the gas containment of the cavern. It was found that the leakage of stored product can be restrained effectively when the water curtain pressure is greater than or equal to 0.8 MPa. When the water curtain is greater than or equal to 1.2 MPa, part of water in the water curtain is discharged from the simulation area, which will reduce the utilization rate of water resources and increase the operating cost. Therefore, the reasonable range of horizontal water curtain pressure is 0.8~1.1 MPa under this case or similar condition. The geological conditions and the migration characteristics of stored product considered in this paper, and the reasonable range of water curtain pressure obtained as well, can provide a new reference and methodology for the optimum determination of water curtain pressure in groundwater-sealed cavern engineering to increase the efficiency and reduce the cost of the work.