Experimental study of water curtain performance for gas storage in an underground cavern

An artificial water curtain system is composed of a network of underground galleries and horizontal boreholes drilled from these galleries. Pre-grouting measures are introduced to keep the bedrock saturated all the time. This system is deployed over an artificial or natural underground cavern used for the storage of gas (or some other fluids) to prevent the gas from escaping through leakage paths in the rock mass. An experimental physical modeling system has been constructed to evaluate the performance of artificial water curtain systems under various conditions. These conditions include different spacings of caverns and cavern radii located below the natural groundwater level. The principles of the experiment, devices, design of the physical model, calculation of gas leakage, and evaluation of the critical gas pressure are presented in this paper. Experimental result shows that gas leakage is strongly affected by the spacing of water curtain boreholes, the critical gas pressure, and the number and proximity of storage caverns. The hydraulic connection between boreholes is observed to vary with depth or location, which suggests that the distribution of water-conducting joint sets along the boreholes is also variable. When designing the drainage system for a cavern, drainage holes should be orientated to maximize the frequency at which they encounter major joint sets and permeable intervals studying in order to maintain the seal on the cavern through water pressure. Our experimental results provide a significant contribution to the theoretical controls on water curtains, and they can be used to guide the design and construction of practical storage caverns.