Investigation on the permeability enhancement of Dahebian syncline coal rock in Liupanshui coalfield

Guizhou Province of Southwest China is abundant in coal mines, including a significant amount of coalbed methane (CBM) resources. However, the development of CBM has not yet achieved major commercial success. The main method of CBM development in Guizhou Province is hydro-fracturing technology, primarily using cluster-well mode. To accurately evaluate the reconstruction effect and permeability enhancement of the typical coal seams of the Dahebian syncline, and to provide a scientific basis for the hydro-fracturing and drainage control of the target coal seams, systematic research was conducted on the Longtan Formation coal seam in Dahebian syncline of Liupanshui coalfield. Firstly, porosity and permeability tests were conducted to analyze the relationship between the permeability of original coal samples and confining pressure. Secondly, uniaxial compressive tests were performed on coal samples with bedding angles of 0° and 90°, respectively, thus to induce splitting cracks or shear cracks in the samples and to simulate the fracturing effect in the coal seam. Thirdly, the permeability of coal after uniaxial compression was measured, and the characteristics of permeability change in fractured/damaged coal samples were analyzed. Finally, the differences in permeability characteristics between original coal samples and those after uniaxial compression were compared. The reconstruction and effects of permeability enhancement of coal were also analyzed by considering the brittleness characteristics of coal seam as well as the distribution of original fissures/cracks/fractures. Furthermore, countermeasures for CBM development that are conducive to on-site fracturing were discussed.