页岩的矿物组分和微观结构对于水力压裂中裂缝的产生和扩展有重要影响.采用微分等效模量模型的方法建立页岩微观物理模型,基于扩展有限元法,从矿物组分的角度对水力压裂造成的裂缝扩展进行数值模拟分析.模拟结果表明,裂缝最先在遇到石英矿物时开始扩展,裂缝在石英矿物内的宽度和孔隙压力整体上都大于黄铁矿,页岩中的石英矿物更有利于裂缝的扩展.根据模拟结果,在页岩气开发时,应优先选择石英矿物含量较高的页岩层.

The mineral composition and microstructure of shale have an important influence on the generation and expansion in hydraulic fracturing. The shale microphysical model was established with the differential equivalent modulus model. In order to study the influence of shale mineral composition on the crack propagation caused by hydraulic fracturing, the numerical simulation analysis by the extended finite element method was carried out. The results show that the crack begins to expand when it encounters quartz, and the width and pore pressure of the crack in quartz are larger than that of pyrite. It is also concluded that quartz is more conducive to the crack propagation in the shale. In the development of shale gas, the shale layer with high quartz content would be favorable.