The authors conducted the in-situ gas-tightness tests in a fractured rock at the Namikata underground LPG storage construction site in Ehime prefecture, Japan. The test consisted of two independent setups, a gas-tightness test that used boreholes, and a chamber-scale test that used a horizontal drift sealed with a concrete plug. In each test, the gas pressure was increased up to the onset of the measurable gas flow to obtain the maximum containment pressure. This paper discusses the hydraulic conditions for gas leakage initiation and the importance of the pore pressure measurement for monitoring the gas-tightness of the LPG storage cavern based on the test results. The results of preliminary two-phase flow simulation study based on the in-situ test results are also presented.
Gas transport characteristics of fractured rocks is a great concern to variety of engineering applications such as underground storage of LPG, nuclear waste disposal, CCS and gas flooding in the oil field.
Besides absolute permeability, relative perme- ability and capillary pressure as a function of liquid phase saturation have direct influences to the results of two phase flow simulation. However, due to limited number of field tests, the applicability of the conventional two-phase flow functions, such as van Genuchten model or linear model to fractured rocks are not well understood.
The authors conducted the two types of in-situ tests, with different scales, a borehole gas-injection test and a chamber water/gas injection test in fractured granitic rock. The test area was developed at the underground LPG storage cavern construction site (Kato et al., 2007) at Namikata in Ehime prefecture in Japan (Figure 1).