| With the expansion of the scale of coal mining and the continuous extension of the mining depth, not only most of the mine is high gas coal mine, but the permeability of the coal is reduced and the effect of the gas pre pumping is poor. Through using mature compound technique of perforating in the field of petroleum transplant into coal mine to increase the pore and fracture of coal, for enhancing the coal seam permeability and finally to achieve the fundamental purpose of improving gas drainage effect. It provides a new technology and new ideas for improving the gas drainage rate in the low permeability coal seam.The development of composite perforating technology and its matching device are introduced in this paper. The basic theory of the formation of jet and penetration of the perforating bullet and the mechanism of the formation of the cracking gas are discussed. The feasibility and safety of compound perforation technology in coal mine are analyzed.By using the software ANSYS / LS-DYNA, the jet formation and energy effects of different angles and different thickness of the liner cone angle are analyzed and selecting the appropriate simulate parameters; Through the simulation of the coal body penetrated, the penetrating depth of the coal body were obtained and it provides the basis for the destruction of coal, the fracture coalescence and the improvement of the gas drainage rate.In this paper, the type selection and installation of the perforating gun is determined and the 89 models of super deep perforating gun and 89DP25R10-100 are selected as the test equipment. Taking the 2103 working face of Changcun coal mine as an engineering example, the field test was carried out and the corresponding drilling, sealing technology and construction safety measures were set up. Through the comparison of experiments, the maximum increase of gas drainage is 3.39 times, the effect of pumping and mining is nearly 1.3 times and the extraction radius is more than 1 times higher than that of the original. It is proved that it is feasible to apply the combined perforating technology in coal mine and improve the gas drainage rate of the low permeability coal seam. |
