| With the increasing intensity of coal mining in China,the amount of gas escaping from the mining space of the mine has increased significantly.Even in low-gas mines,the problem of gas"burst"has appeared.However,the existing underground ventilation and conventional gas drainage measures have also encountered dilemmas such as insufficient governance capacity and affecting mining replacement in solving the problem of gas overrun in working face.Gas well extraction technology in the mining area makes full use of the mining pressure relief effect during coal mining,and a large amount of gas is extracted to reduce the overrun of the gas in the mining face.The extracted gas can also be used as energy Therefore,surface well extraction technology is a research hotspot of major domestic universities and coal enterprises.However,how to carry out large-scale and regional continuous extraction to form a low-cost and long-term control of gas emission from the recovery space is still an important problem.Therefore,relying on the 13th Five-Year National Science and Technology Major Task"Key Technology of Gas Surface Well Group Extraction in Active Mining Areas"(2016ZX05045-001-1)and"Technology of Coalbed Methane Development and Utilization in Xinjiang Large Inclined Multi-Coal Group Coal Mines"(2016ZX05043005),This paper studies the key problems that affect the extraction effect of the well group such as the optimization of the layout and the evaluation of the extraction effect faced by the extraction of surface well groups in the mining area.The main research results are as follows:(1)The distribution law of mining overburden crack field is analyzed,and the coal and rock bodies in the rectangular area behind the working face are considered as non-uniform porous media,and the porosity and permeability in the overburden crack field within the range are regionalized.Assign a value and establish a mathematical model of gas seepage in the mining fracture field to provide a theoretical basis for studying the influence law of coalbed methane surface well group extraction on the gas flow field in the mining area.(2)Establish an evaluation system for the extraction effect of coalbed methane surface well groups in the mining area.Considering the two aspects of resource output and gas concentration control effect of the working face,the indicators to determine the extraction effect of the well group are mainly the gas concentration reduction rate of the working face,the gas production and extraction rate of the surface well,and the surface well extraction rate calculation method.(3)The results of numerical simulation analysis using COMSOL Multiphysics show that:under certain conditions of numerical simulation,the effective extraction range of a single well in the mining area is 40m,and 240m in engineering applications.The single-pumped pure gas drainage has the characteristic of"single peak and long tail".The average pure gas drainage flow rate is 8.25m~3/min.The average gas drainage of the wells in No.1,2,and 3 surface wells The pure flows are 7.33 m~3/min,5.98 m~3/min,5.33 m~3/min,and the daily gas production of surface wells is close to 20,000 m~3.(4)Evaluate the extraction effect of the ground well group in the mining area of the first wing of the north wing of Yuecheng Coal Mine of Shanxi Jinmei Coal Group Qinshui Coal Industry Co.,Ltd.,and verify the correctness of the numerical simulation analysis results.The main conclusions are:the extraction rate of surface wells is higher than that of upper layers when the working face is recovered and the lower stratification,the extraction rate of surface wells whose shaft structure is damaged or fails to operate normally is extremely low;The gas duration is long,and the extracted gas volume is continuous and stable,which has very good economic benefits.When the local face well is about 100m away from the working face,the gas concentration in the working face and the return airway decreases to the minimum. |
