Stanford Geothermal WorkshopFebruary 9-11, 2026

Repeated stimulation, circulation, and cleanout operations at Utah FORGE have produced a suite of solid mineral scales and corrosion products recovered from the subsurface and surface infrastructure. This study synthesizes mineralogical and textural observations from these scale and corrosion samples collected between 2019 and 2025. These observations are then related to mineral saturation perturbations due to cyclic temperature and composition changes during circulation activities. In addition, we document effective fluid additives for scale and corrosion mitigation used to date at Utah FORGE, and those proposed for future, longer term circulation testing. Scale and corrosion products were characterized by using X-ray diffraction, a scanning electron microscope equipped with an energy-dispersive spectroscopy, and X-ray fluorescence. Mineral scales consist of calcite, siderite, anhydrite, halite, sylvite, and a Fe- and Si-rich expandable smectite group clay. Corrosion products include magnetite, hematite, lepidocrocite, and goethite, as well as boehmite and an Al-bearing phase with structural similarity with greenalite, reflecting both iron and aluminum infrastructure degradation, respectively. Carbonates and anhydrite are expected to deposit from injection waters on heating in the wellbore and/or within the fracture network in the reservoir rocks. Incorporation of CO2 into the fluids in the reservoir lowers pH and somewhat inhibits carbonate deposition. Rapid equilibration with quartz in the reservoir results in the potential for silica scaling on cooling in the production wellbore and topside equipment. After significant scaling issues were encountered in 2024 during stimulation activities, a scale and corrosion mitigation strategy was employed by dosing the injected fluids with additives that has been effective during subsequent cleanout and circulation activities.

Topic: FORGE