[论文解读] PorePy: An Open-Source Simulation Tool for Flow and Transport in Deformable Fractured Rocks

Eirik Keilegavlen, Alessio Fumagalli+3 more|arXiv (Cornell University)|Dec 1, 2017

Hydraulic Fracturing and Reservoir Analysis参考文献 26被引用 36

一句话总结

PorePy 是一个开源的、基于有限元法的模拟框架，用于在具有复杂裂缝网络的三维裂缝性多孔介质中模拟流动、运移和变形。它采用混合维方法，将不同维度的物体（点、线、面）之间的过程耦合起来，能够对裂缝储层中的流动、运移和孔隙弹性变形进行精确且可重复的模拟。

ABSTRACT

Fractures are ubiquitous in the subsurface and strongly affect flow and deformation. The physical shape of the fractures, they are long and thin objects, puts strong limitations on how the effect of this dynamics can be incorporated into standard reservoir simulation tools. This paper reports the development of an open-source software framework, termed PorePy, which is aimed at simulation of flow and transport in three-dimensional fractured reservoirs, as well as deformation of the reservoir due to shearing along fracture and fault planes. Starting from a description of fractures as polygons embedded in a 3D domain, PorePy provides semi-automatic gridding to construct a discrete-fracture-matrix model, which forms the basis for subsequent simulations. PorePy allows for flow and transport in all lower-dimensional objects, including planes (2D) representing fractures, and lines (1D) and points (0D), representing fracture intersections. Interaction between processes in neighboring domains of different dimension is implemented as a sequence of couplings of objects one dimension apart. This readily allows for handling of complex fracture geometries compared to capabilities of existing software. In addition to flow and transport, PorePy provides models for rock mechanics, poro-elasticity and coupling with fracture deformation models. The software is fully open, and can serve as a framework for transparency and reproducibility of simulations. We describe the design principles of PorePy from a user perspective, with focus on possibilities within gridding, covered physical processes and available discretizations. The power of the framework is illustrated with two sets of simulations; involving respectively coupled flow and transport in a fractured porous medium, and low-pressure stimulation of a geothermal reservoir.

研究动机与目标

• 解决标准储层模拟器在处理具有复杂三维几何形状的长而细的裂缝时的局限性。
• 实现对具有真实裂缝网络的裂缝性多孔介质中流动和运移的精确模拟。
• 提供一个透明、可重复的多物理场建模框架，包括孔隙弹性及裂缝变形。
• 支持从多边形裂缝描述中实现裂缝-基质模型的半自动网格划分。
• 促进不同维度域（例如二维裂缝和一维交线）之间过程的耦合。

提出的方法

• 将裂缝表示为嵌入三维域中的二维多边形，实现精确的几何描述。
• 采用混合维方法，其中流动和运移在低维流形（二维裂缝、一维交线、零维点）中求解。
• 采用有限元离散化方法并保证局部质量守恒，从而在维度异质域中实现精确的通量近似。
• 通过mortar方法或弱施加连续性条件的方式实现相邻域之间的耦合。
• 集成孔隙弹性、岩石力学和裂缝变形模型，实现与流动和运移过程的完全耦合。
• 提供复杂裂缝网络的自动网格生成，显著减少人工预处理工作量。

实验结果

研究问题

• RQ1 如何在模拟框架中高效且准确地表示具有不同几何形状的复杂三维裂缝网络？
• RQ2 在不同维度域（例如二维裂缝和一维交线）之间耦合流动、运移和变形对模拟精度有何影响？
• RQ3 开源、透明的框架是否能够支持裂缝储层中多物理场过程的可重复且可扩展的模拟？
• RQ4 与传统的全维模拟相比，混合维方法在计算成本和精度方面表现如何？
• RQ5 该框架在模拟具有低压注入的现实地热储层压裂场景方面具备哪些能力？

主要发现

• PorePy 成功模拟了具有复杂裂缝几何形状的裂缝性多孔介质中的耦合流动与运移，展示了精确的通量和浓度分布。
• 该框架能够模拟地热储层中的低压压裂，显示出裂缝网络中流体传播和压力响应的现实特征。
• 半自动网格划分功能显著减少了预处理时间，并可在无需人工网格划分的情况下支持复杂裂缝网络。
• 混合维公式能够实现不同维度域（如二维裂缝和一维交线）之间过程的稳定且精确的耦合。
• 集成孔隙弹性与裂缝变形模型，可实现对储层压实体和应力依赖性流动行为的真实模拟。
• PorePy 的开源特性确保了透明性、可重复性以及面向未来科研和工业应用的可扩展性。