InterPore2025

Identification of Hydraulic Backbones in Discrete Fracture Networks with Genetic Algorithms and Localized Graph Contraction

21 May 2025, 15:05

1h 30m

Poster Presentation (MS03) Flow, transport and mechanics in fractured porous media Poster

Speaker

Ryan "Emmy" Shaver (Desert Research Institute)

Description

Discrete fracture networks (DFNs) offer high-fidelity simulations of flow and transport in fractured media, but the complex networks they represent are often computationally prohibitive at field scales. Identification of network backbones, relatively small subgraphs that capture major network processes, can significantly reduce computations and expose important topological structures. We introduce a novel method for identifying hydraulic backbones in DFNs using genetic algorithms and localized graph contractions. In contrast to previous work identifying backbones where major transport processes occur, our work provides network simplification further upstream in the DFN methodology, identifying major hydraulic processes and potentially reducing downstream computations. To ensure backbone connectivity, we use a path-based search space. Otherwise prohibitively vast, we introduce an on-the-fly search space reduction technique based on localized graph contractions that utilize fracture networks' fractal-like structure. Unlike prior machine learning-based identification methods that may require extensive offline training, we use a genetic algorithm for backbone identification that requires no training, at the cost of longer prediction times. Our methodology is tested on 27 synthetically generated DFNs of varying heterogeneities, and one DFN imaged from actual fractured rock. We quantitatively measure backbone validity with the size reduction gained by the subgraph, along with how well it mimics the original network's conductivity tensor and flow velocity distribution. Qualitative inspection of identified backbone and non-backbone regions reveals hydraulic structures vital to downstream flow and transport simulations, as well as less hydraulically important structures that may be simplified or omitted altogether.