Aiming at the gas flow problem in fractured coal–rock assemblage during L-shaped horizontal well hydraulic fracturing and gas extraction in coalbed methane development, permeability–stress test of single fractured coal–rock assemblages was carried out. The influence of gas pressure, effective stress and individual permeability of fractured coal–rock mass on the combination permeability were analyzed. With increase in effective stress, the permeability and its stress sensitivity of the single fractured coal–rock assemblage decreased gradually. Due to the existence of slippage effect, the permeability of coal–rock assemblage decreased gradually with increase in gas pressure within the range of study gas pressures. The gas adsorption of the coal caused the fracture aperture to decrease and led to the uneven deformation of coal–rock assemblage because the adsorption deformation of rock mass can be neglected. Comparison of the permeability variation of single fractured rock and coal sample with the increase of gas pressure further verified that the coal adsorption reduced the permeability of coal–rock assemblage. Finally, the permeability calculation model of single fractured coal–rock combination is presented in this paper. This model can well match the laboratory measured data, and it can clarify the contribution of each permeability part to the overall permeability. The permeability model indicated that the permeability of coal–rock assemblage depended on the smaller part of permeability. The contribution of the high permeability part to the overall permeability can only be increased a little on the basis of the low permeability part.

针对煤层气开发L型水平井水力压裂抽采过程中裂隙煤岩组合的气流问题，开展了单个裂隙煤岩组合的渗透率-应力试验。分析了瓦斯压力、有效应力和裂隙煤岩体个体渗透率对组合渗透率的影响。随着有效应力的增加，单个裂隙煤岩组合的渗透率及其应力敏感性逐渐降低。由于滑移效应的存在，在研究瓦斯压力范围内，煤岩组合的渗透率随着瓦斯压力的增加而逐渐降低。由于岩体的吸附变形可以忽略不计，煤对瓦斯的吸附导致裂缝孔径减小，导致煤岩组合变形不均匀。比较单个裂隙岩和煤样随气压升高的渗透率变化，进一步证实煤吸附降低了煤岩组合的渗透率。最后，本文提出了单一裂缝煤岩组合的渗透率计算模型。该模型与实验室实测数据吻合较好，可以明确各渗透率部分对整体渗透率的贡献。渗透率模型表明煤岩组合的渗透率取决于渗透率的较小部分。