Geothermal Reservoir Deformation and Stress Evolution at Brawley Constrained from Well Operation History, 4D InSAR Observations, and Poroelastic Modeling

Ganiyat Shodunke, Junle Jiang, & Segun Bodunde

In Preparation September 6, 2026, SCEC Contribution #15668

Linking geothermal operations to surface deformation and subsurface processes requires detailed analysis and integration of geophysical data and physical modeling. At the Brawley Geothermal Field (BGF) in Southern California, which has been active since 2009, satellite geodetic observations have revealed subtle and persistent surface deformation linked to regional tectonics and industrial activity. However, the underlying mechanisms driving the anthropogenic deformation patterns remain uncertain. Here, we analyze monthly injection and production volumes from 57 wells between 2009 and 2024 and incorporate these data into a poroelastic reservoir model with layered hydromechanical properties. The model simulates the time evolution of stress and deformation in response to spatially variable fluid management, enabling us to quantify how operational practices influence surface displacement and to validate these models with multitemporal interferometric synthetic aperture radar (InSAR) observations. Net production volumes were initially high but declined after 2013, while net injection volumes increased; the total injected mass remained below $2\times10^{6}$ kg/year. These trends produce heterogeneous deformation across the field. According to our model outputs and geodetic observations, the surface displacement field contains a localized feature bounded by a fault zone that acts as a hydrological barrier, potentially limiting cross-fault fluid migration and inducing stress redistribution. We quantify the sensitivity of key parameters and the temporal sampling to producing modeled deformation patterns consistent with InSAR observations. The simulated fluid pressure and stress changes are further compared with the decadal seismicity characteristics since the 2012 M5+ Brawley earthquake swarms. Our results demonstrate that integrating subsurface and satellite datasets with physical modeling provides a valuable framework for understanding hydromechanical behavior in geothermal systems. This approach can inform reservoir management strategies and improve predictions of reservoir response to subsurface operations.

Citation
Shodunke, G., Jiang, J., & Bodunde, S. (2026). Geothermal Reservoir Deformation and Stress Evolution at Brawley Constrained from Well Operation History, 4D InSAR Observations, and Poroelastic Modeling. Journal of Geophysical Research: Solid Earth, (in preparation).