GeoDFN - A Flexible, Open-Source Software for Generating Geologically Consistent Discrete Fracture Networks

GeoDFN is an open-source software that provides comprehensive control over fracture properties and allows us to explore how a broad range of geological uncertainties impact the geometry and connectivity of fracture networks. GeoDFN employs a hybrid approach, combining the advantages of mechanical and statistical methods in generating DFNs, which ensures geological consistency in fracture placement while maintaining computational efficiency. At the core of this hybrid approach is the consideration of stress shadow, as buffer zone around fractures, which impose a minimum spacing between fractures and prevent them from being placed in geologically unrealistic locations. Considering stress shadow also imposes a natural limit on the maximum fracture intensity of the network, reflecting the network saturation observed in real geological formations. Various models for calculating fracture apertures are provided in GeoDFN, including models that account for external stress conditions, such as the Barton-Bandis model. This capability enables detailed analysis of how fracture apertures influence fluid flow and network permeability under different geological conditions.<br>GeoDFN can be linked to any flow simulator capable of modeling fluid flow in fractured geological formations, providing a versatile tool for subsurface flow analysis. Here, we demonstrate its integration with the MATLAB Reservoir Simulation Toolbox (MRST), an open-source simulator widely used for modeling flow and transport processes. The integration with MRST enables users to easily import generated DFNs and conduct a variety of simulations, including single-phase and multiphase flow, heat transfer, and solute transport. By utilizing MRST’s Embedded Discrete Fracture Model (EDFM) approach, the complex interactions between fractures and the surrounding rock matrix are accurately represented. This connection facilitates the evaluation of how different uncertainties in fracture properties affect subsurface flow behavior, making it a powerful tool for uncertainty quantification and sensitivity analysis in diverse geological settings.<br>GeoDFN是一款开源软件，可对裂缝属性实现全面管控，支持研究者探究各类地质不确定性因素对裂缝网络（Discrete Fracture Network，DFN）几何形态与连通性的影响。GeoDFN采用混合建模思路，融合力学方法与统计方法在生成裂缝网络时的优势，既保障了裂缝布设的地质合理性，又兼顾了计算效率。该混合方法的核心是考量应力阴影（stress shadow）——将其作为裂缝周边的缓冲带，为裂缝设定最小间距，避免将其布设在不符合地质实际的位置。同时，考虑应力阴影可为裂缝网络的最大裂缝密度设定自然上限，这一特性契合真实地质构造中观测到的网络饱和现象。GeoDFN内置多种裂缝开度计算模型，其中包含可考虑外部应力条件的巴顿-班迪斯（Barton-Bandis）模型，该功能支持研究者开展精细化分析，探究不同地质条件下裂缝开度如何影响流体流动与网络渗透率。<br>GeoDFN可与任意可模拟裂缝性地质构造内流体流动的流动模拟器相连接，为地下流动分析提供通用化工具。本研究展示了其与MATLAB油藏模拟工具箱（MATLAB Reservoir Simulation Toolbox，MRST）的集成方案——该开源模拟器广泛应用于流动与输运过程的模拟建模。通过与MRST的集成，用户可便捷导入生成的裂缝网络，并开展各类模拟工作，涵盖单相流、多相流、传热以及溶质输运等场景。借助MRST的嵌入式离散裂缝模型（Embedded Discrete Fracture Model，EDFM）方法，可精准刻画裂缝与周边岩石基质之间的复杂相互作用。该集成方案可支持研究者评估裂缝属性的各类不确定性对地下流动行为的影响，使其成为不同地质场景下开展不确定性量化与敏感性分析的高效工具。