Research On Numerical Simulation And Application Of Hydraulic Fracturing In Crossing Borehole Of Tectonic Coal In Yuxi

Aiming at the problems of low coal seam permeability and gas extraction rate existed in Yuxi mining area, an effective technology was urgently needed to change the status quo. Hydraulic fracture which was primarily used to improve permeability in coal mine recently. Althrough a good effect had been obtained, there were still many key issues needed further study. Therefore,the mechanism of hydraulic fracturing and the regularity of the crack initiation and expansion in coal bed had been systematically studied in this dissertation by using the brittle fracture mechanics theory, numerical analysis and mathematical statistics methods, and the main innovative results are showed in the following aspects.(1) The general law of coal and rock drilling initiation direction was got: when k<1, fracture initiation occurred in X direction, when k=1, fracture initiation would disorient, when k<1, fracture initiation occurred in Y direction.(2) In the non-uniform stress field, the fracture pressure changed with the change of maximum principal stress, minimum principal stress and stress difference; Cracks always extended along the direction of the maximum principal stress, and its geometry was wide and short.(3) Based on the numerical simulation results of hydraulic fracturing, the parameters of hydraulic fracturing process were optimized in the study area: the azimuth of pressure hole was parallel to the maximum principal stress' direction,the dip was consistent with the seam dip, and the spacing of borehole was 100 m in the depth of 500 m, the borehole initial injection pressure was 10 MPa,the single borehole injection time was over 2 hours.(4) Influenced by fracturing, the water rate of coal increased by 2~3 times, the gas permeability coefficient of coal seam was increased by 60 ~ 150 times, the gas extraction concentraction was increased by 50%~200% as well as the extraction flow rate increased by 60%~300%, the recovery attenuation cycle was prolonged to more than 3 months.In short, the anti-reflection technology of hydraulic fracturing had a good pressure relief anti-reflection effect in Yuxi mining area, and it can be widely applied in the similar mine gas geological conditions.