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注热强化煤层气抽采的试验研究及工业应用

Experimental research and industrial application of heat injection-enhanced coalbed methane extraction

  • 摘要: 煤层气作为煤层中主要的清洁能源,其高效抽采和利用,将有利于提高资源利用率和保障煤矿安全生产。然而,甲烷的强吸附性和煤层的低渗透性,导致煤层气的采收率特别低。基于能量守恒方程,完善了注热强化煤层气抽采的理论,在实验室和煤矿井下分别进行了注热强化煤层气抽采的试验,研究了不同条件下甲烷的解吸规律和注热对煤层气抽采的促进作用。室内试验结果表明,注水解吸、自然解吸和注热解吸3种条件下的煤样终态解吸率分别为12%、37%和81%。定量计算结果表明,自然解吸和注水解吸后的注热强化解吸,分别可以增加46%和68%的解吸率,证明了注热具有强化甲烷解吸以及解除水锁效应的作用。阳泉矿区现场试验结果表明,注热方法不仅可以提高煤层气的抽采率,还可以缩短煤层气的抽采时间。注热方法可以将煤层气的浓度和日产气量分别提高10倍和100倍,其中最大煤层气浓度和最大日均产气量分别为98%和123 m3/d。8号注热钻孔的有效注热半径超过5 m,并且注热后的抽采阶段是煤层气高效抽采时间段。研究结果可为注热强化煤层气抽采的现场应用和煤矿井下局部瓦斯的防治提供参考。

     

    Abstract: As the main clean energy in coal seams, the efficient extraction and utilization of coalbed methane (CBM) will help to improve resource utilization and coal mine safety production. However, due to the strong adsorption characteristics of methane and the low permeability characteristics of coal seams, the recovery efficiency of CBM is particularly low. Based on the energy conservation equation, the theory of heat injection-enhanced CBM extraction was improved. The experiments of heat injection-enhanced CBM extraction were carried out in the laboratory and in the coal mine, and the desorption law of methane under different conditions and the promotion effect of heat injection on CBM extraction were studied. The laboratory experiment results show that the final desorption rates of coal samples under the three conditions of water injection desorption, natural desorption and thermal injection desorption are 12%, 37% and 81%, respectively. The quantitative calculation results show that the enhanced desorption by heat injection after natural desorption and water injection desorption can increase the desorption rate by 46% and 68% respectively, which proves that heat injection can enhance the desorption of methane and release the water lock effect. The field test results in Yangquan mining area show that the heat injection method can not only improve the desorption rate of CBM, but also shorten the extraction time of CBM. The heat injection method can increase the concentration of CBM and the daily gas production by 10 times and 100 times respectively, wherein the maximum concentration of CBM and the maximum daily average gas production are 98% and 123 m³/d, respectively. The effective heat injection radius of No.8 heat injection borehole is more than 5 m, and the extraction stage after heat injection is the efficient extraction period of CBM. The research results can provide reference for the field application of heat injection-enhanced CBM extraction and the prevention and control of local gas in coal mines.

     

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