Stanford Geothermal WorkshopFebruary 9-11, 2026

Stimulated geologic hydrogen generated via subsurface serpentinization of fractured ultramafic rocks at temperatures between 150 °C and 400 °C offers a promising low-carbon energy resource. However, the economic viability of stimulated geological hydrogen has not yet been established. During the hydrogen generation, a substantial amount of thermal energy is transported by the co-produced water, but the thermal potential of the fluid has not yet been established. This study explores the feasibility of harnessing thermal energy of the stimulated geological hydrogen co-produced fluid through an Organic Rankine Cycle (ORC) power generation system. The aim is to investigate the overall system efficiency gains that can be derived through such a process. Additionally, utilizing the produced water for heat extraction also reduces the cooling requirements before its reinjection into the subsurface, which may lead to lower operational expenses. This study proposes a self-sustaining circular system that integrates a geothermal binary power plant and a water treatment unit into geologic hydrogen production, using waste heat from the produced fluid to generate power while recycling the co-produced water for reinjection. The methodology begins with field-scale reservoir modeling to simulate subsurface serpentinization, capturing the coupled heat generation and hydrogen production processes to estimate reservoir temperature evolution, production rates and production fluid compositions. This is followed by thermodynamic modeling of a binary power plant to evaluate the heat extraction potential from the produced fluid. Subsequently, a sensitivity analysis is performed on key parameters, such as decline rate, well number and configuration, and restimulation strategies to assess their influence on overall thermal recovery and system performance. Reservoir simulation results indicate that restimulated reservoirs maintain higher hydrogen and water production rates, along with elevated outlet temperatures for extended durations. Correspondingly, thermodynamic modeling of the power plant reveals that the increased fluid temperature significantly enhances ORC performance, resulting in up to 35% higher net power generation compared to initial stimulated cases. Furthermore, repurposing the generated heat for power recovery through the binary system, rather than dissipating it via surface cooling prior to reinjection, conserves substantial energy, lowers overall power demand, and improves operational efficiency. The novelty of this work lies in creating a circular system that effectively manages both heat and excess produced water, achieving self-sustainability by utilizing internally generated power for surface operations. This integrated approach converts the challenges of waste heat and water management into potential valuable economic opportunities.

Topic: General