Geomechanical Understanding of Fault Zone Mixing and Implications for Fluid Flow Along Faults in Sedimentary Rocks

Brook Runyon, & John H. Shaw

Submitted September 7, 2025, SCEC Contribution #14938, 2025 SCEC Annual Meeting Poster #TBD

Faults can serve as barriers or conduits to fluid flow, significantly impacting fault strength and influencing the nucleation and rupture of both natural and induced earthquakes. Traditional methods for assessing fault fluid flow behavior focus on measuring the clay or shale content entrained along fault planes. While these methods have some empirical basis, they have limited predictive capability due to their inability to accurately model the deformation processes that govern the composition, textures, and other properties of fault zones that affect fluid flow. To address these challenges, we use a physics-based Distinct Element Method (DEM) model, which enhances our understanding of these phenomena. By calibrating the DEM model with laboratory-based sand and clay box models, we examine the effects of grain size contrast and mechanical strength differences between sand and shale horizons on fault zone properties. Our findings indicate that variations in grain size and mechanical strength significantly affect fault zone width and the localization of secondary fracturing. These variations, in turn, have profound implications for shale and clay entrainment, which are considered to control fluid flow behavior within fault zones. Ultimately, we expect that the DEM models will support the development of a more robust approach to understanding and predicting fluid-related fault zone properties that may influence rupture dynamics. This, in turn, can provide valuable insights to help avoid or limit risks associated with fluid leakage and induced seismicity in various energy and environmental applications, such as subsurface energy and carbon storage.

Citation
Runyon, B., & Shaw, J. H. (2025, 09). Geomechanical Understanding of Fault Zone Mixing and Implications for Fluid Flow Along Faults in Sedimentary Rocks. Poster Presentation at 2025 SCEC Annual Meeting.

Related Projects & Working Groups
Fault and Rupture Mechanics (FARM)