In order to optimize the layer selection of coal horizontal well drilling and achieve the best fracturing effect,through tensile strength test,triaxial compressive strength test and the determination of coal sample determine the mechanical parameters,and using Moore -Coulomb criterion calculate coal roof and floor mud window,the stability of the wellbore is analyzed by the method mentioned above.The basic method of grey theory is applied to quantitatively analyze the factors affecting the layer selection and fracturing effect,and determine the primary and secondary relation of the factors,creating a gray GM (1,N) model to achieve the reference number of Columns of ash equations and differential equations,and then evaluation of the fracture and compression capacity forecast.The results showed that the mechanical properties of the roof and floor was stable,the drilling fluid density window was 1.09～5.61 g/cm3,and the adjustment range was wider,well drilling in the roof and floor was stable.Overall error and the maximum error of model did not both exceed 10％,the model predicts that the output of coal bed methane was in agreement with the actual production data,and there was clear upward trend.%为了优化煤储层水平井的钻进层位,达到最佳压裂效果.通过抗拉强度测试、三轴抗压强度测试和煤样普氏系数测定等试验对煤样及顶底板进行了主要力学参数测试及摩尔-库仑准则计算的钻井液密度窗口,分析了井壁稳定性;并应用灰色理论的基本方法对影响选层及压裂效果的因素定量分析,确定各影响因素的主次关系,建立灰色GM(1,N)模型得到参考数列的灰分方程和微分方程,进而进行了压裂效果评价和压后产能预测.结果表明:顶底板的力学性质稳定,钻井液密度窗口为1.09 ～ 5.61 g/cm3,调节范围较宽,在顶底板中钻进井壁稳定性较好;GM(1,N)模型的整体误差和最大误差都不超过10％,模型预测压后煤层气的产量与实际生产数据基本相吻合,并有明显的上升趋势.
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