A Novel Hydraulic Mode to Promote Gas Extraction: Pressure Relief Technologies for Tectonic Regions and Fracturing Technologies for Nontectonic Regions

Extraction of gas (coalbed methane) produces clean energy and can ensure that coal mines maintain high-efficiency production. The currently available coal seam permeability enhancing technologies and modes have certain application restrictions. Therefore, a novel mode is proposed to promote gas extraction. This mode divides complex coal seams into tectonic regions and nontectonic regions based on geological structures. Then, the characteristics of different regions are matched with the advantages of different hydraulic technologies; thus, pressure relief technologies are proposed for tectonic regions, and fracturing technologies are proposed for nontectonic regions. The permeability of coal seams will be sharply increased without leaving unfractured areas. This mode will promote the effectiveness of gas extraction, shorten the extraction time, and ensure safe and efficient production in coal mines. A field application shows that this mode has a better effect than slotted directional hydraulic fracturing technology (SDHFT). The gas concentration and pure gas flow were increased by 47.1% (up to 24.94%) and 44.6% (up to 6.13 m3/min), respectively, compared to SDHFT over 9 months. The extraction time was reduced by 4 months. This mode reduced the number of times that gas concentration exceeded government standards during coal roadway excavation, and the coal roadway excavation speed was increased by 16% (up to 158 m/month).