Method of evaluating the permeability of rock mass by the combination of packer test and flowing fluid electrical conductivity log

It is necessary to obtain accurate and reliable permeability parameters of the rock mass in the analysis and evaluation of the water-sealed conditions of the underground water-sealed cavern, while the commonly used hydrogeological test methods for obtaining the rock mass permeability coefficient exist obvious deficiencies. In order to keep accuracy of the data, relying on a certain groundwater sealing reservoir project in Yantai, the paper took the propane cavern traffic tunnel drilling as an example, carried out the water pressure test and used the theory of unsteady flow of GRF model to optimize the analytical test data based on the generalized radial flow theory. The water-conducting fracture location was confirmed by the flowing fluid electrical conductivity logging test and the permeability coefficient within the fracture range is obtained. The test results show that the analytical results of GRF model is 1-2 times larger than that of steady flow model. The reason is that when the fractured rock mass is subjected to sectional water pressure, the water flow dimensions of each section are different. The traditional steady flow theory assumes that the water flow dimension has only two-dimensional flow, while the GRF model fits all the data of the pressurized n-dimensional fracture flow with the pressure water process. The time period is calculated under the corresponding dimension. Therefore, the calculated permeability coefficient K is closer to the true value of the test section, which is more compatibility and practicality. The use of flowing fluid electrical conductivity logging test will further refine the average permeability coefficient obtained from the GRF model analysis, and provide a more scientific and reliable data base for the evaluation of the effect of the water-sealed cavern.