Thermoelastic unclamping and pressure-driven fluid loss during multiyear circulation in enhanced geothermal systems

Matthew Weingarten, & David Dempsey

Submitted August 30, 2026, SCEC Contribution #15487, 2026 SCEC Annual Meeting Poster #036

Large-scale enhanced geothermal system (EGS) energy production is rapidly advancing through the use of multi-stage stimulation of horizontal wells. We analyze the first two years of continuous circulation at EGS Project Red, Nevada, drawing on publicly reported operational data, a rare record constraining the coupled evolution of stress, fluid budget, and temperature during sustained energy extraction.

Circulation produced a combination of unique observations over the two-year period: injectivity rose by more than 20% and kept rising, roughly 30% of injected water was permanently lost at a near-steady rate, and produced temperature barely declined. Preliminary calculations show the lost water is highly unlikely to be stored in the stimulated rock volume; storage would produce a loss rate that declines with time, and the observed loss does not.

We present a coupled thermo-hydro-mechanical model of a representative stimulated reservoir that reproduces all three observations. Two distinct processes emerge: (1) thermoelastic unclamping of cooled fractures is consistent with the injectivity rise, and (2) pressure-driven drainage through deeper structure is consistent with the magnitude and steadiness of the loss. The associated stress changes are large, accumulate over years of circulation, and are expressed mostly as aseismic opening rather than seismic slip.

Citation
Weingarten, M., & Dempsey, D. (2026, 08). Thermoelastic unclamping and pressure-driven fluid loss during multiyear circulation in enhanced geothermal systems. Poster Presentation at 2026 SCEC Annual Meeting.

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