Development and application of coal rock permeability test system

Permeability is one of the most important reservoir properties in coalbed methane (CBM) production, with the accurate measurement of its value being crucial for improving the efficiency of CBM extraction. For this reason, this paper independently designs and develops a coal rock permeability test system that can select the measurement methods (the steady state method and the pressure pulse decay method). In this paper, in order to fully and accurately evaluate the reliability level of the system, the variable pressure under constant external stress is tested, and the results show that the device has high measurement accuracy and convenient operation. The test results are consistent with the existing results with a classical V-shaped trend being observed, which reflected how permeability varied under gas pressure. In addition, it was found that the system could simulate the effect of differences in boundary conditions relating to seepage under different geological formations, which would provide technical support for understanding the change law concerning permeability in complex geological environments.