钻孔瓦斯压力恢复法求解煤层透气性系数

煤层透气性系数可以准确评估煤层瓦斯的可抽采性能，指导煤层增透改造工艺。借鉴油气试井中的压力恢复曲线相关方法求解煤层透气性系数，建立适应于煤矿井下钻孔瓦斯流动的理论模型。采用半对数直线段分析方法，利用双对数、半对数压力恢复特征曲线，合理确定压力恢复曲线中期直线段起始点位置，准确计算中期直线段的斜率大小，继而计算煤层透气性系数。通过现场实例验证，并和径向流量法计算结果对比，其相对误差为13%~36.6%，平均误差为24.62%，验证了压力恢复曲线求解煤层透气性系数方法的可行性。 

Borehole gas pressure build-up to evaluate the permeability of coal seam

The permeability of coalbed benefits the right evaluation of gas drainage capability, which could be used to select the suitable technique to increase the permeability and drainage effect. The permeability of coalbed is evaluated referring to the theory and experience of gas pressure build-up in the well testing. The gas flow model appropriate to the underground coal mine has been set up. The starting point of radial flow in the pressure build-up curve could be designated rationally using the double and half logarithmic pressure build-up curves with the analytic method of half logarithmic straight line. Therefore the slope of the interim radial flow section and the permeability of the coalbed could be determined accurately. After the verification and comparison with the result of in-situ examples by the radial flow method, the relative error of the five examples was between 13% and 36.6% and the average was lower than 24.62%. So the permeability of coalbed by the borehole gas pressure build-up curve is practical.