Lithological Controls on the Permeability of Geologic Faults: Surrogate Modeling and Sensitivity Analysis

Fuente: arXiv
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Auteurs principaux: Lu, Hannah, Salo-Salgado, Lluıs, Juanes, Ruben
Format: Preprint
Publié: 2025
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author Lu, Hannah
Salo-Salgado, Lluıs
Juanes, Ruben
author_facet Lu, Hannah
Salo-Salgado, Lluıs
Juanes, Ruben
contents Fault zones exhibit complex and heterogeneous permeability structures influenced by stratigraphic, compositional, and structural factors, making them critical yet uncertain components in subsurface flow modeling. In this study, we investigate how lithological controls influence fault permeability using the PREDICT framework: a probabilistic workflow that couples stochastic fault geometry generation, physically constrained material placement, and flow-based upscaling. The flow-based upscaling step, however, is a very computationally expensive component of the workflow and presents a major bottleneck that makes global sensitivity analysis (GSA) intractable, as it requires millions of model evaluations. To overcome this challenge, we develop a neural network surrogate to emulate the flow-based upscaling step. This surrogate model dramatically reduces the computational cost while maintaining high accuracy, thereby making GSA feasible. The surrogate-model-enabled GSA reveals new insights into the effects of lithological controls on fault permeability. In addition to identifying dominant parameters and negligible ones, the analysis uncovers significant nonlinear interactions between parameters that cannot be captured by traditional local sensitivity methods.
format Preprint
id arxiv_https___arxiv_org_abs_2511_09674
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Lithological Controls on the Permeability of Geologic Faults: Surrogate Modeling and Sensitivity Analysis
Lu, Hannah
Salo-Salgado, Lluıs
Juanes, Ruben
Geophysics
Machine Learning
Data Analysis, Statistics and Probability
Fault zones exhibit complex and heterogeneous permeability structures influenced by stratigraphic, compositional, and structural factors, making them critical yet uncertain components in subsurface flow modeling. In this study, we investigate how lithological controls influence fault permeability using the PREDICT framework: a probabilistic workflow that couples stochastic fault geometry generation, physically constrained material placement, and flow-based upscaling. The flow-based upscaling step, however, is a very computationally expensive component of the workflow and presents a major bottleneck that makes global sensitivity analysis (GSA) intractable, as it requires millions of model evaluations. To overcome this challenge, we develop a neural network surrogate to emulate the flow-based upscaling step. This surrogate model dramatically reduces the computational cost while maintaining high accuracy, thereby making GSA feasible. The surrogate-model-enabled GSA reveals new insights into the effects of lithological controls on fault permeability. In addition to identifying dominant parameters and negligible ones, the analysis uncovers significant nonlinear interactions between parameters that cannot be captured by traditional local sensitivity methods.
title Lithological Controls on the Permeability of Geologic Faults: Surrogate Modeling and Sensitivity Analysis
topic Geophysics
Machine Learning
Data Analysis, Statistics and Probability
url https://arxiv.org/abs/2511.09674