煤岩毫米级尺度裂隙网络重构及渗透率预测

Millimeter sized crack network reconstruction and permeability prediction of coal and rock

为了表征煤中毫米级裂隙的连通性,并得出其渗透性对整个煤的渗透性的影响,通过大量煤样显微镜下观察统计,应用蒙特卡罗方法对毫米级裂隙网络进行重构。采用赋零法并结合Matlab软件得出有效连通裂隙网络;应用二维渗流方程,得出了毫米级裂隙网络有效渗透率。与实测渗透率对比结果表明:煤岩中有效连通的毫米级裂隙网络是渗透率的主要贡献者;其他参数一定的情况下,随着毫米级裂隙密度、宽度的增加,渗透率呈指数型增加。毫米级裂隙长度增加到一定程度后,渗透率几乎不再增加。储层改造中形成新的裂隙或增加裂隙宽度是增加其导流能力的关键。重构的毫米级尺度裂隙网络能够更清晰地显示裂隙的连通性,为煤层气在裂隙网络运移路径选择及流动方式研究奠定了基础。

In order to characterize the connectivity of the millimeter sized cracks in the coal and obtain the contribution of the permeability to whole coal＇s permeability,with observation and statistic of a lot of coal samples under microscope,the Monte Carlo method was applied to the reconstruction of the millimeter sized crack network. In combination with the Matlab software,the effective connective crack network could be obtained with the zero given method. The effective permeability of the millimeter sized crack network was obtained with 2D seepage equation. In comparison with the site measured permeability,the results showed that the effective connective millimeter sized crack network in the coal and rock would be a major contributor of permeability. Under the condition that the other parameters were constant,with the density and width of the millimeter sized cracks increased,the permeability would be increased in an index type. When the length of the millimeter sized cracks increased to a certain degree,permeability would not increase. The new cracks and increased crack length occurred in the reservoir reconstruction would be the key to increase the flow capacity. The reconstructed millimeter sized crack network could clearly show the connectivity of the cracks and would set up the base to select the migration access of the coalbed methane crack network and to study the flow mode.