Research on controllable shock wave technology for in-situ development of tar-rich coal

The world is rich in tar-rich coal resources, which have broad exploration and development prospects. At present, the academic community has relatively weak research on the impact of shock waves on the permeability of target coal bodies. This article focuses on the development technology of controllable shock waves in tar-rich coal reservoirs. Firstly, a systematic analysis was conducted on the drilling situation and physical parameters of the target coal seam. Secondly, the impact of shock waves on permeability of target coal was systematically analyzed. Thirdly, a systematic summary was conducted on the process parameters and measures of coal seam operations. Research has shown that: (a) The permeability of coal samples after shock wave action is much greater than the permeability of coal samples in their original state. (b) Under the same axial and confining pressure conditions, as the gas pressure increases, the increase in the permeability of coal under the action of shock waves shows a decreasing trend. (c) The shock wave generates a large number of crack structures inside the coal body. These cracks will undergo very obvious closure under external pressure. (d) Under different axial and confining pressures, when the gas pressure is 1 MPa, the maximum increase in permeability of coal samples under shock wave action can reach 90–200 times. When the gas pressure is 2 MPa, the increase in permeability before and after shock wave action is the smallest, reaching 30–90.