| The article mainly studies about hydraulic fracturing for permeability enhanced in Mabu coal mine adopting methods of theoretical analysis, numerical stimulation and field experience. Cracks formation, expansion and stretch would be analyzed by relevant mechanics theories. According to mechanical parameter of coal and rock and actual geology situation in Mabu coal mine, RFPA2D-Flow numerical stimulation software was applied to simulate the process of hydraulic fracture, in fracture zone according to the mechanical parameter of coal and rock and actual geology situation in Mabu coal mine, as well as the way of field experiment. Through hydraulic fracture technique being implemented in 15108 working face of NO.15 coal seam, stress is reduced and permeability of coal seam is significantly enhanced. At last, fracture radius Mabu coal mine fitted is determined in the field application. Article was expounded in detail from three aspects as follows:In the first place, original rock stress, types of crack, principles of crack fracture caused by high pressure water and theories of crack extend and were analyzed. Significantly, relationship between surrounding rock stress and percolation rate variation of borehole before water injection and distribution and variation of stress around the borehole after water injection were analyzed.Subsequently, model was established according to physical mechanics parameter of coal seam and actually geological characteristics, RFPA2D-Flow numerical stimulation software to simulate the process of hydraulic fracture, moreover, shearing stress field, acoustic emission field and distribution law of water press in the rock around the borehole were stimulated, process of coal damage caused by high water pressure and process of crack extension were analyzed as well.Finally, technique of hydraulic fracturing for permeability enhanced is conducted in 15108 working face of Mabu coal mine, comparing gas drainage concentration and flow before technique of hydraulic fracturing with that after hydraulic fracturing. It is found that gas drainage concentration and flow greatly increased and permeability significantly improved. Through comparing water ratio before fracturing with that after fracturing, comparing gas concentration and flow in fracture zone with that in non-fracture zone. It is sufficiently demonstrated effectiveness and feasibility of hydraulic fracturing for permeability enhanced technique, and it is substantial way of enhancing permeability and improving drainage effectiveness. |
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