Theory and technology of enhanced coal seam gas production by integrated drilling, hydraulic punching and fracturing in coal mine: Part 2 technology

Abstract To enhance the efficiency and cost-effectiveness of coal seam gas extraction in coal mines, this study introduces an integrated approach combining drilling, hydraulic punching, and fracturing technologies. This method optimizes drilling media tailored to specific coal seams and fine-tunes technical parameters during drilling and permeability improvement processes. Furthermore, it clarifies the relationships among the coal breaking rate, discharge of drill cuttings, jet velocity, rotation speed, and displacement. This ensures precise and effective permeability improvement in both soft and hard coal formations. To implement this technology, a set of high-performance drilling tool with a large inner diameter, high pressure resistance, and superior sealing capabilities has been developed. Consisting of a water braid, drill pipe and hydraulic ejector, this tool meets the requirements of substantial displacement and high pump pressure. Field test results demonstrate remarkable enhancements in borehole formation, coal breaking and slagging efficiency. Specifically, the operation time is reduced by 60%–80%, the coal output is increased by 1–1.5 times, the pure coal seam gas extraction yield is increased by 1–2 times, and the extraction radius expands by more than 100%. These results highlight significant advancements in operational efficiency and permeability improvement effects, paving the way for efficient and economical coal seam gas extraction practices.