一场 “页岩革命” 已在世界范围内展开. 我国已探明页岩气储量居世界首位, 但由于我国页岩储藏极深, 孔隙率极低等特点, 开采中需要在页岩储层内构建大规模裂纹网络. 而水力裂纹转向是构建裂纹网络的基本问题之一. 其耦合了固体裂纹转向和流体动边界问题, 并受到射孔方向、压裂液黏度和注入速率、地应力及其各向异性、以及储层物性参数的影响. 为此, 本文从水力裂纹转向建模和地质材料评估两个方面进行研究.

建立了描述水力裂纹扩展的弹性-水动力学模型, 应用位移不连续方法和有限差分法进行数值计算. 得到了控制裂纹转向的无量纲压裂液数和无量纲地应力数. 分析了裂纹转向过程中岩石内静水应力场和切应力场变化. 厘清了射孔角度对水力裂纹转向的影响. 将压裂液黏度和注入速率对裂纹转向的影响分为三个阶段, 获得了施工中控制裂纹转向的两个最佳点. 分析了缝宽振荡现象和黏性耗散的耦合作用. 定量衡量了地应力及其各向异性对裂纹转向的影响.

首次将 Ashby 图应用于地质材料的评估之中. 建立了应用 Ashby 图进行地质评估的理论框架, 实现了学科间研究方法的转移. 首次将水力压裂施工曲线与储层岩石脆性关联, 并将储层脆性用 Ashby 图进行表征. 得到了岩石节理和接触面的断裂能, 用 Ashby 图评估了整岩, 岩石节理及岩石间接触面的稳定性. 得到了控制滑坡中岩石稳定性, 煤层顶板和煤壁稳定性, 以及岩石传递地震波能力的效能因子, 绘制了相应的 Ashby 图.

本论文系统考量了水力裂纹转向和扩展过程中自然因素和人为因素的影响, 为实际施工中控制水力裂纹转向提供参考, 为地质材料评估提供新思路.

The “shale revolution” has been all around the world. The shale gas reserve in China is proven the highest in the world. However, the large-scale fracture network needs to be formed in the development of shale gas due to the extreme depth and the low porosity of the shale in China. The deflection of hydraulic fractures is one of the key problems in the formation of fracture network. It combines the deflection of cracks in solid and the moving boundary of liquid. It is affected by the perforating direction, the viscosity and injecting rate of fracturing fluid, the magnitude and anisotropy of in-situ stress, as well as the physical properties of reservoir rocks. In this thesis, the problem is studied from two aspects: the modeling of hydraulic fracture deflection and the evaluation of geomaterials.

An elasto-hydrodynamics model is established to study the deflection of hydraulic fracture. The displacement-discontinuity method and the finite difference method are used in the numerical simulation. The dimensionless fracturing fluid number and the dimensionless in-situ stress number that control the deflection process are derived. The stress field in rock during the deflection process is calculated and the effect of perforating direction is classified. The effect of the viscosity and injecting rate of fracturing fluid is divided into three stages and the points to control the deflection are derived. The combined effect of the width oscillation and the viscous dissipation is analyzed and the effect of in-situ stress is measured quantitively.

For the first time the Ashby plots are applied to the evaluation of geomaterials. The theoretical frame of the application in geomaterial evaluation is established. For the first time the brittleness of reservoir rock is associated with the fracturing curve and expressed by the Ashby plots. The fracture energy of rock joints and rock interfaces is derived and plotted in the Ashby plots. The performance indices describing the stability of rocks in landslides, coal-gas outbursts and instability of coal roofs are derived. The related Ashby plots are plotted.

In this thesis, the effects of natural and manual conditions are systematically evaluated in the deflection and the propagation of hydraulic fractures. This provides theoretical basis for the hydraulic fracturing operation. New scheme is provided for the evaluation of geomaterials.