STOCHASTIC HYDRAULIC SAFETY FACTOR FOR GAS CONTAINMENT IN UNDERGROUND STORAGE CAVERNS

Abstract

Since the previous hydraulic safety factor for gas containment in gas storage caverns did not consider the spatial hydraulic conductivity variation, which directly affects the variation of hydraulic head and gradient, it is insufficient to fulfill the hydraulic safety from gas leakage. Therefore, based on the stochastic simulation considering the heterogeneity of hydraulic conductivity, a method for determining the hydraulic safety factor for gas containment in underground storage cavern is suggested. Instead of a single hydraulic gradient value obtained by using deterministic modeling, a possible range of a hydraulic gradient under a given probability was examined by means of stochastic simulation. The term 'stochastic safety factor' is newly defined as a head value at the water curtains, which is needed to make the critical hydraulic gradient of the cavern larger than a proposed critical gradient. By using this stochastic safety factor, the shortage of hydraulic gradient can be replenished and the risk of gas leakage due to heterogeneity of hydraulic conductivity can be reduced.