Experimental Study Of Improving The Test Depth Of Initial Velocity From Borehole Gas Emission And Its Application

In this paper, the initial velocity of gas emission as coal and gas outburst prediction index can not accurately predict the situation of coal and gas outburst, a deep borehole prediction technique is proposed. By changing the existing initial velocity of gas emission measurement equipment to improve the depth of drilling, the accuracy of prediction of coal and gas outburst is greatly improved by the initial velocity of gas emission. On the basis of collecting, sorting and analyzing the existing data, the corresponding theoretical analysis, laboratory experiment, equipment improvement and field test were carried out, obtaining the following results:(1)A balance differential equation of gas pressure was established for q value measuring chamber. An analytical expression of such pressure was deduced. Gas chamber pressure-time curves were drawn. On the basis of this analysis, the feasibility of deep borehole prediction is analyzed.(2) A set of similar simulation device for coal seam drilling is made, in the laboratory. The device can real-time observe the state of coal accumulation after drilling hole sealing device and real-time measure the resistance of the hole sealing device. According to the experimental results, 15 degree-20 hole packer is more favorable to advance in the simulation of drilling hole.(3) Based on the experimental results and the analysis of the drilling depth limited reason, the new drilling gas emission initial velocity measurement equipment was improved. The initial velocity of the improved gas emission was obviously shortened by the equipment and reduces the resistance of the hole sealing device in the process of feeding and effectively improve the measuring depth.(4) The field test of deep hole prediction of coal and gas outburst was carried out, Prediction of drilling depth reaching to 12-16 m. The determine depth of the borehole is more deep the time of initial velocity of borehole gas emission is more late.(5) In the prediction of deep hole, gas emission initial speed and drilling gas flow attenuation coefficient is more reliable than⊿h2. Compared with the initial velocity of gas emission from the traditional borehole, the new drilling speed of the new borehole gas emission is more reliable. However, the initial velocity of borehole gas emission is combined with the borehole gas flow attenuation coefficient.