In 2020, the ~4 trillion kilowatt-hours (kWh) of utility-scale electricity used in the US came from fossil fuels (~60%), nuclear (~20%), and renewables (~20%) with wind, solar, and geothermal at 8.4%, 2.3%, and 0.4%, respectively (US Energy Information Administration, 2021). Geothermal energy accounts for less than 1% of the global utility-scale power generation, primarily driven by geographical constraints. Challenges for widespread geothermal utilization include exploration risks, low heat harvesting efficiency due to poor subsurface rock thermal conductivity, low efficiency of traditional turbine and power plant designs, and high capital costs of well and power plant equipment.

Temperature and pressure are key indicators for renewable energy resources: (a) geothermal heat from hot water production (hydrothermal) and (b) mechanical (hydraulic) energy from abnormally high brine water and trace dissolved gas pressures driven by trends in subsurface brine (non-potable) aquifer extent and compartmentalization. Temperatures above 300°F/150°C can be found along the US Gulf Coast within 10,000 ft of the surface, and often shallower (Loucks et al., 1979). These heat resources are primarily in the widespread Cenozoic sedimentary formations that have been historically exploited for oil and gas, but also prove to flow hot water at high flow rates in a temperature range suitable for power generation (100–250°C, >10,000 barrels of water per day; Bebout et al., 1983; John et al., 1998). Geopressured, deep brine-aquifer formations, providing high formation water pressures well above average, are also commonly found as shallow as 10,000–13,000 ft below sea level. These onshore and offshore resources are located along the Gulf of Mexico coast in the faulted salt-dome provinces of Texas and Louisiana, near Brownsville, Houston, New Orleans, and other population centers (Ocamb, 1961; Worrall and Snelson, 1989).

Advances in turbine design utilizing novel fluids for enthalpy harvesting in power generation, including the use of supercritical CO₂ (sCO₂) as a working fluid and novel sCO₂ turbine design, show great promise to make geothermal power generation less risky and more economically feasible. Based on calculations using US Dept. of Energy Geothermal Program test sites in Texas and Louisiana demonstrating high-quality connected, hot pressured brine with consistent long-term heat flow, Sage Geosystems™ proprietary geothermal technologies increase baseload power generation capacity well above traditional organic Rankine cycle turbine technologies, and provide much cheaper electricity power generation potential on a Levelized Cost of Energy (LCOE) basis (Lazard, 2020). These new technologies targeting known resources have the potential to generate carbon neutral, or carbon negative, commercial quantities of baseload electrical power.

NOTE: References to be included in the SAGE Record conference proceedings.