Construction and application of “one core and three wings” gas control technology system in coal-oil-gas symbiotic coal seam of Huangling mining area

Huangling No. 2 Coal Mine, as a representative coal-oil-gas symbiotic coal seam mine in the Huanglong coalfield, has experienced a significant increase in gas emission with the progressive increase in mining depth and production capacity. In particular, the abnormal emission of oil-type gas from the roof and floor has become increasingly prominent, which severely constrains the safe and efficient coal mining operations. Based on a systematic analysis of the gas geological characteristics of the No. 2 coal seam, it is identified that gas occurrence is significantly controlled by geological structures. Specifically, the synclinal core in the central region constitutes a high-gas zone with gas content exceeding 4 m³/t. Meanwhile, four major oil-type gas-bearing strata are developed in the roof and floor, with pressures ranging from 2.98 to 3.17 MPa. Furthermore, the coal seam is characterized by low permeability and rapid borehole attenuation, thereby rendering conventional gas extraction techniques insufficiently effective. To address these challenges, a comprehensive gas governance system is proposed, centered on “regional advanced treatment” and integrating three key components: staged governance in the longwall face, dynamic prevention and control in the heading face, and collaborative prevention and control technology for oil-type gas. This “one core and three wings” framework is further supported by coordinated institutional, equipment, and management mechanisms, thereby enabling an integrated “exploration–extraction–drivage–mining” process. Field-scale industrial tests demonstrate that directional borehole hydraulic fracturing in the target coal seam increases the gas extraction concentration by 1.35–2.57 times. Moreover, the combined application of ultra-high-pressure water jet slotting and nitrogen injection flooding enhances the net gas extraction rate by 53.09%. In addition, controllable shock wave permeability enhancement extends the pressure relief range to 3 m and doubles the extraction concentration of oil-type gas. Field application results indicate that the gas extraction rates of the 215 and 422 working faces reach 81%–84%, while the gas concentration in the heading face is effectively maintained below 0.5%. Consequently, both the efficiency and safety of gas extraction are significantly improved.