Development of models and dedicated numerical methods for dynamics in fractured rocks is an active research field, with research moving towards increasingly advanced process couplings and complex fracture networks. The inclusion of coupled processes in simulation models is challenged by the high aspect ratio of the fractures, the complex geometry of fracture networks, and the crucial impact of processes that completely change characteristics on the fracture-rock interface. This paper provides a general discussion of design principles for introducing fractures in simulators, and defines a framework for integrated modeling, discretization, and computer implementation. The framework is implemented in the open-source simulation software PorePy, which can serve as a flexible prototyping tool for multiphysics problems in fractured rocks. Based on a representation of the fractures and their intersections as lower-dimensional objects, we discuss data structures for mixed-dimensional grids, formulation of multiphysics problems, and discretizations that utilize existing software. We further present a Python implementation of these concepts in the PorePy open-source software tool, which is aimed at coupled simulation of flow and transport in three-dimensional fractured reservoirs as well as deformation of fractures and the reservoir in general. We present validation by benchmarks for flow, poroelasticity, and fracture deformation in porous media. The flexibility of the framework is then illustrated by simulations of non-linearly coupled flow and transport and of injection-driven deformation of fractures. All results can be reproduced by openly available simulation scripts.

裂缝岩石动力学模型和专用数值方法的开发是一个活跃的研究领域，研究朝着越来越先进的过程耦合和复杂的裂缝网络发展。在模拟模型中包含耦合过程受到以下挑战：高纵横比的裂缝，复杂的裂缝网络几何形状以及完全改变特征的过程对岩石-岩石界面的关键影响。本文对在模拟器中引入裂缝的设计原理进行了一般性讨论，并定义了用于集成建模，离散化和计算机实现的框架。该框架是在开源仿真软件PorePy中实现的，该软件可以用作解决裂隙岩石中多物理场问题的灵活原型工具。基于裂缝及其相交作为低维对象的表示，我们讨论了混合维网格的数据结构，多物理场问题的表达以及利用现有软件的离散化。我们进一步提出一个这些概念的Python实现在PorePy开源软件工具中进行，该工具的目的是耦合模拟三维裂缝性储层中的流动和输运以及裂缝和总体储层的变形。我们通过基准测试验证了多孔介质中的流动性，孔隙弹性和裂缝变形。然后，通过非线性耦合的流动和传输以及注入驱动的裂缝变形的模拟来说明框架的灵活性。所有结果都可以通过公开可用的仿真脚本进行复制。