恩村井田煤体结构与煤层气垂直井产能关系

Relations Between Productivity of CBM Vertical Wells and Coal Structure in Encun Mine Field

煤储层原始渗透率、压裂改造后渗透率及围岩的渗透率共同影响着煤层气垂直井排采过程中压力传播轨迹,并最终影响着煤层气垂直井的产能。以焦作矿区恩村井田勘探开发原始资料为基础,根据测井响应曲线,结合钻井取心,把煤体结构划分为原生结构煤(I类)、碎裂煤(Ⅱ类)和构造煤(Ⅲ类和Ⅳ类)3类4种。根据岩石弹性力学理论结合不同煤体结构天然裂隙发育状况,建立了天然裂缝方位与地应力方向关系模型,分析出不同煤体结构主裂缝方位的主控因素。根据裂缝延伸方位结合煤层气井排采过程压力传播轨迹,得出不同煤体结构与产能关系。排采试验表明:以目前的水力压裂工艺进行储层改造,碎裂煤对产能的贡献最大,原生结构煤次之,构造煤几乎不可被改造。

The original permeability,fracturing and reconstructing permeability,surrounding permeability affect the pressure spread contrail in the production process of the CBM vertical wells,and then control the productivity of CBM vertical wells.Based on the raw data of exploration and development of CMB in the Encun mine field,we classified the coal structure into the primary structure coal（Ⅰ）,fragmentation coal（Ⅱ） and tectonic coal（Ⅲ and Ⅳ）,in combination of curve of logging response and drilling core.According to elasticity theory of rock and state of natural fracture in different coal structures,we set up a model about the azimuth of natural fracture and the direction of the stress,and discussed the main controlling factors about main fractures in different coal structures.Based on azimuth of extended fracture and pressure spread contrail in the production process of CBM vertical wells,we got the relations between the productivity of CBM vertical wells and different coal structures.The production tests showed that under current hydraulic fracturing crafts the fragmentation coal would be the best coal reservoir,then primary structure coal,and the tectonic coal was hardly modified to improve production capacity of CBM vertical wells.