Shale gas reservoirs have an extremely low permeability and porosity; hence, it is necessary to perform hydraulic fracturing to improve production. To design effective stimulation measures, it is necessary to fully understand the propagation of hydraulic fractures and their interactions with natural fractures. In this study, a two-dimensional fully coupled mixed-mode model based on the extended finite-element method (XFEM) is established, which includes rock deformation, fracturing fluid flow and leak-off and mixed-mode fracture propagation. We focused on different factors (Young’s modulus, Poisson’s ratio, in situ stress and fracturing fluid rate) to investigate hydraulic fracture initiation, propagation and interaction with two kinds of natural fractures. The results reveal that all the factors have great influences on the fracture geometry, among which in situ stress has the greatest influence. A smaller frictional coefficient of the natural fracture surface enables the hydraulic fracture to divert into the natural fracture. A smaller interaction angle and lower natural cemented fracture strength allow hydraulic fracture propagation along the cemented natural fracture. In the field, hydraulic fracturing parameters should be adapted to the specific conditions to achieve the desired fracturing effect and better economic exploitation.

中文翻译：

---

页岩气藏混合模式水力压裂扩展及与不同类型天然裂缝相互作用的数值模拟

页岩气储层的渗透率和孔隙度极低。因此，必须进行水力压裂以提高产量。要设计有效的增产措施，必须充分了解水力压裂裂缝的扩展及其与天然裂缝的相互作用。本研究建立了基于扩展有限元方法（XFEM）的二维全耦合混合模式模型，该模型包括岩石变形，压裂液流动和渗漏以及混合模式裂缝扩展。我们集中于不同的因素（杨氏模量，泊松比，原地应力和压裂流体速率）来研究水力压裂的萌生，扩展以及与两种天然裂缝的相互作用。结果表明，所有因素对断裂几何形状都有很大影响，其中，原地应力影响最大。自然裂缝表面的较小的摩擦系数使得水力裂缝能够转移到自然裂缝中。较小的相互作用角和较低的天然固结断裂强度允许水力压裂沿着固结天然裂缝传播。在现场，水力压裂参数应适合于特定条件，以实现所需的压裂效果和更好的经济利用。