Analysis of Hydraulic Permeability Enhancement Effect Based on an Experimental System of Highly Pressurized Water Invasion and Gas Seepage

To study the influence of various factors on coal permeability in the process of coal seam water injection and the relationship between water injection parameters, an experimental system of highly pressurized water invasion and gas seepage is developed. The system consists of four parts: an overburden pressure loading unit, a micro water injection control unit, a gas injection, and vacuum pumping unit, data acquisition and real-time monitoring unit. It can not only be used for coal seam water injection radial seepage experiments. It can also be used as a set of experimental systems to simulate the geothermal exploitation of deep coal seams and explore the heat transfer law of geothermal exploitation. To verify its applicability, a coal seam water injection seepage experiment is carried out based on the experimental system. The results show that the coal permeability increases by 7–31% before and after water injection; at the same time, under different stress conditions, the internal and external pressure difference of the coal sample before and after water injection has a decrease of 0.01–0.05 MPa. The conclusion is consistent with previous studies, which shows that the experimental system is accurate and reliable.