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基于完全流-固耦合的弹塑性理论给出了水力压裂数值计算的弥散裂缝模型,其中材料的弹性部分采用线弹性本构关系,塑性部分采用摩尔-库仑破坏准则及强化准则。依据当前的有效应力状态修正渗透系数来模拟压裂液在裂缝中的流动。渗透系数的修改使用双曲正切函数,并采用平均有效应力作为水力裂缝的起裂判据。在ABAQUS软件中通过用户自定义程序添加了该模型。根据岩石的切面照片建立了含有硬包裹体分布的非均质岩石的有限元计算模型,模拟了中心点注水条件下的水力压裂传播过程,讨论了在常应力状态下非均质岩石中开裂区域、典型位置的应力路径变化和裂缝传播范围随时间变化的特点。进行了多种条件下含有硬包裹体分布的岩石材料的数值试验,得出了基岩材料的弹性模量、凝聚力和渗透系数以及注水速率对峰值注水压力、平均注水压力和裂缝开度的影响规律。
Based on the complete fluid - solid coupling theory of elasto - plasticity, the numerical model for the hydraulic fracturing is given, in which the elastic constitutive relation of the material is adopted and that of the plastic part is the Mohr - Coulomb failure criterion and the strengthening criterion. According to the current state of effective stress correction permeability coefficient to simulate the flow of fracturing fluid in the fracture. The modification of permeability coefficient uses the hyperbolic tangent function and uses the average effective stress as the initiation criterion for hydraulic fractures. The model was added in the ABAQUS software through a user-defined program. A finite element model of heterogeneous rock with hard inclusions distribution is established based on the photos of rock slices. The hydraulic fracturing propagation process under the condition of water injection at the center is simulated. The cracking of inhomogeneous rocks under normal stress is discussed Region, the typical location of the stress path changes and crack propagation characteristics with time changes. Numerical tests on rock materials with hard inclusions under various conditions were carried out. The effects of elastic modulus, cohesion and permeability coefficient of bedrock material and water injection rate on peak water injection pressure, average water injection pressure and crack opening were obtained law.