基于PHF-LSM-MT法岩石材料细观边界建模与水力裂缝扩展研究

Study on Mesostructure Boundary Modeling and Hydraulic Fracture Propagation for Rock Material Based on the PHF-LSM-MT Method

天然非均质岩石具有复杂的细观结构和分布特征,本文结合柏林噪声建立考虑非规则边界的颗粒几何模型,实现考虑任意粒径、长短半轴、倾角和平面填充率的非规则颗粒填充.基于完全流-固耦合弹塑性理论,在已有的PHF-LSM(permeability-based hydraulic fracture level set method)模型基础上,通过引入MT(Mori-Tanaka)均匀化方法考虑积分点有效范围内细观尺度的材料分布特征,进而建立了PHF-LSM-MT非均质岩石材料细观特征建模及其水力压裂过程模拟方法.结合误差分析验证了该方法的可行性,在此基础上对非均质岩石材料进行了水力压裂过程模拟,得到了等效开裂区域.模拟结果表明:注水点水压力呈先升高后降低的趋势,起裂压力随包裹体体积分数增加而降低.

Natural heterogeneous rock material has complex mesostructure and distribution characteristics.An approach to model inclusions with irregular boundary by using the Perlin noise,and considering features,e.g.,specific radius,semi-axial ratio,orientation angle and plane filling rate,is introduced.In order to include the mesostructure characteristics of rock material at integration point,the permeability-based hydraulic fracture level set method(PHF-LSM)is improved by introducing the Mori-Tanaka(MT)homogenization method based on a coupled fluid-solid elastoplastic theory.The proposed PHF-LSM-MT method is verified by error analysis.Finally,the propagation features of equivalent fracture zone in heterogeneous rock material were simulated by using the proposed method.The results indicate that the water pressure at injection point first increases and rapidly decreases,and the breakdown pressure decreases while the inclusion fraction increases.