Study On Gas Drainage By Combining Surface Well Drilling Fracturing With Underground Horizontal Drilling

With the rapid popularization of comprehensive mechanical coal mineproduction and the increasing of the depth of coal mining in recent years,disaster related coal mining problems are increasingly serious. Especially gasdisaster which symbiosis with coal mine, seriously threaten the safety of mineproduction. Tunliu mining area belongs to low permeability, high gas coal mine.It is difficult to make the coal seam gas content decrease in a short period oftime by using underground coal seam gas drainage in the past. It is not onlyhindered the speed of mining on working face, but also impacted on the safetyof mine personnel.In this paper, regarding the N2105working face in Tunliu mining area asthe test area, it is used to carry out the ground coal mine shaft of hydraulicfracturing in coal seam before gas drainage underground. By comprehensive useof experimental research, theoretical analysis, engineering practice, and othermeans, it is a comparative study of crack extension characteristics in the processof coal seam fracturing and underground gas pre-drainage effect. The main workand research results are as follows:On analysis of coal (rock) layer basic mechanical properties andpermeability characteristics of coal layer, theoretical analysis of shaft wallcharacteristics, crack mechanism of hydraulic fracturing, the characteristics andtypes of crack propagation in the process of hydraulic fracturing, it is concludedthe minimum water pressure of coal seam crack. Study on the formulation of the hydraulic fracturing technology scheme,the relevant parameters of hydraulic fracturing process was determined. Analysisof the vertical crack space extension theory at the theoretical level, it isestablished the mathematical model of the coal seam three-dimensionalhydraulic fracturing crack extension, to predict the fracture geometry parametersin fracturing process. On analysis of the fracturing well injection pump andpump displacement about construction process.The layout plan of underground drilling bedding and the extraction methodof gas monitoring system, combined with the parameters of gas fieldconstruction acquisition, it is used to analysis the actual effect of hydraulicfracturing field. It is guided and optimized the liquid injection pressureparameters, reasonable fracturing well spacing and underground drilling beddingconstruction spacing in the construction process of fracturing. The coal seamhydraulic fracturing test results show that: the method of gas drainage bycombining surface well drilling fracturing with horizontal drilling undergroundis a kind of active gas drainage technology. It can reduce the content of gaseffectively.