Identification of the characteristic shape of two-phase saturation functions for fractured rock through compressed air energy storage field test and 3D numerical analyses

Identification of such hydraulic properties as absolute permeability, porosity, relative permeability, and capillary pressure has been conducted in this study with measurement data acquired in a hydraulic confining system of the compressed air energy storage (CAES) which was excavated in fractured rock mass. Capillary pressure curve and relative permeability curves as the function of water saturation were composed of the combination of two equations by van Genuchten, Brooks and Corey, Mualem, and Burdine. The results indicate us that the shape of the gas relative permeability which could reproduce measurement data of gas leakage amount from the cavern is convex upward. Since the shape of relative permeability curves for sedimentary rocks are generally convex downward, this shape might be characteristic for fractured rock which could have small porosity and therefore have relatively larger permeability than sedimentary rock. (author)