中硬煤层长钻孔"射孔-压裂"复合增透区域瓦斯治理技术OA

To address technical problems such as high fracture initiation pressure and uncontrollable fracture propagation when conventional hydraulic fracturing is used for gas control in medium-hard coal seams,a regional gas control technology based on directional long-borehole perforation-fracturing composite permeability enhancement was systematically investigated against the engineering background of regional gas control at Shaanxi Huangling No.2 Coal Mine Co.,Ltd.through theoretical analysis,numerical simulation,and field tests,and a complete technical system covering parameter optimization,staged fracturing operations,and performance verification was established.The core of this technology was to use high-pressure water-jet perforation to form directional guide slots,thereby reducing the initiation pressure of subsequent hydraulic fracturing by approximately 30％and inducing stable fracture propagation along the perforation direction.Numerical simulations and field tests determined the matching perforation and fracturing parameters as a nozzle diameter of 3.0 mm and a jet pressure of 5 MPa.Field hydraulic fracturing operations were completed in four boreholes using a fracturing-stage spacing of 30-50 m and a fluid injection volume of at least 80 m3 per stage.The application results showed that after the perforation-fracturing composite permeability enhancement technology was applied,the coal-seam fracture initiation pressure was effectively controlled at 11.5-13.7 MPa,lower overall than the conventional fracturing initiation pressure.The radial fracture propagation distance reached 50 m;the average pure gas drainage rate per 100 m of borehole reached 0.226 m3/(min.hm),2.9 and 3.8 times those of slotted boreholes and ordinary boreholes,respectively.The gas drainage volume fraction remained above 67％over the long term.