Sage Geosystems, Next-Gen Geothermal Source Driven By Earth's Pressure

Forbes

26-07-2025

Sage drilling activity Sage
Cindy Taff is CEO and co-founder of Sage Geosystems. The company was founded in 2020 and is developing energy storage and geothermal baseload technologies deep in the earth and above temperatures of 170℃ degrees.
The Sage Geosystems team has over 200 combined years in the oil and gas industry, with experience delivering major projects including Deepwater, Arctic, and Unconventional shales. The company is headquartered in Houston, Texas. For more information, visit www.sagegeosystems.com. News reports are available, as well as videos. The following is an interview with Cindy Taff.
1. Sage calls their next-generation geothermal technology 'pressure geothermal.' Can you explain what this means and how it differs from other next-generation geothermal technologies?
Pressure geothermal leverages both the Earth's heat and pressure to generate more power. By using the natural elasticity of the rock, we can bring hot water to the surface without pumps. Unlike traditional approaches, we maintain pressure in the system rather than venting it at the surface, and we hold open fractures with pressure instead of adding bridging materials like sand or proppant. These innovations reduce friction and energy losses, boosting net power output by 25-50% compared to other next-generation geothermal technologies.
2. The Sage pressure geothermal concept is a huff-and-puff in two synchronized wells. How does this work?
Sage's proprietary cycle-based heat recovery approach, adapted from the 'huff-and-puff' method in oil and gas, is designed for efficient energy extraction. Each well has its own set of fractures (i.e., wells are not connected in the subsurface like EGS) and operates in a repeating cycle. In one well, water is injected for 12 hours, expanding the fracture network to ensure full contact with the hot rock and maximum heat absorption. After a brief soaking period, the process reverses: the natural pressure and elasticity of the rock push the heated water back to the surface, without the need for pumps. The hot water flows through a heat exchanger to heat a refrigerant, or low-boiling-point working fluid, which drives a turbine to generate electricity. By alternating between wells, Sage enables near-continuous power generation.
3. The operation depends on creating a fracture network in the hot dry rock, which is then inflated with a 'pad' of water, and 10-20% of this pad is cycled to harvest the Earth's heat. How are the fractures created and how is the water cycled?
Sage uses their proprietary downward gravity fracturing to create the subsurface fracture network. This technique uses a high-density fluid, weighted with heavy minerals like barite or hematite, to initiate and propagate fractures using gravity rather than high-pressure pumping. Because the fluid is heavier, it creates fractures at lower surface pressure, making the process more efficient and controlled. This approach is similar to methods used for disposing of nuclear waste. Once the fracture network is established, the high-density fluid is circulated out and replaced with water, which is then cycled to extract heat, as described above.
4. What reservoir characteristics does the Sage method need to be viable, such as depth, temperature, overpressure, natural fracture permeability? How extensive are these potential locations in the USA? For comparison, hot, dry rock permeabilities in Los Alamos and Project Forge have extremely low permeabilities.
Conventional geothermal requires a rare combination of three things: hot subsurface temperatures, naturally occurring water (an aquifer), and enough natural permeability to allow the water to flow. These conditions typically only exist near volcanic zones, such as those along the Ring of Fire. Sage's pressure geothermal approach removes two of those constraints. We don't rely on natural permeability or existing water – we create our own artificial reservoir and cycle water through it to extract heat. We specifically target low-permeability rock (< 50 millidarcies), temperatures of 170°C, and avoid natural faults and fractures. As a result, our method opens up vast new areas for geothermal development. In the U.S. Lower 48 alone, conservative estimates are 13 terawatts of geothermal potential down to 6 km (20,000 feet).
Depths to reach 180C Anderson, Parker, et al.
5. A two-well pair provides almost continuous electricity for 24 hours. Can the supply of a few MW be made fully dispatchable for days or weeks at a time?
Yes. Geothermal power generation is available regardless of weather conditions. Like all geothermal systems, Sage's technology experiences gradual thermal decline, about 10% over 5 years, as heat is extracted from the rock. What makes Sage different is our ability to refracture the same well into untouched hot rock every five years, restoring heat flow without having to drill a new well(s).
6. The fracture network is always operated between frac opening and frac extension pressure, and in each well, the fracture network is inflated for 12 hours before flow is reversed into the other well. You quote water loss is less than 2%. Is this loss per cycle?
Yes, the < 2% water loss is per cycle as measured in the field and is primarily due to evaporation and leak-off into the formation. For geothermal power generation, we expect water losses to be even lower because the system operates as a closed-loop cycle with minimal evaporation. This is a major advantage over traditional EGS systems, where water losses are reported between 10-30%.
Cindy Taff, CEO and co-founder of Sage. Sage
7. How does your cost per MWh compare with other next-generation geothermal methods, and with solar PV plus grid battery storage (BESS)? How does your mechanical energy storage cost per MWh compare with grid battery storage (BESS)?
Pressure geothermal is expected to deliver significantly lower costs per MWh than other next-generation geothermal approaches. Closed-loop systems face higher drilling costs due to complex directional drilling and longer wellbores. EGS technologies lose efficiency from high parasitic pumping loads, venting pressure at surface, and 10-30% water losses.
When paired with solar, Sage's energy storage delivers a blended LCOE of $60-70/MWh for 24/7 generation, comparable with solar plus batteries without tax credits. Sage's mechanical storage is not intended to compete with lithium-ion for < 5-hour durations, but will outperform batteries for durations > 5 hours.
8. What advantages does the Sage method have over other methods such as twin-well EGS (Enhanced Geothermal Systems) or closed-loop systems?
Compared to EGS, Sage's approach avoids the need for sophisticated high-temperature directional drilling technologies as the wellbore alignment and spacing are not critical, and it doesn't require connecting two wells with a fracture network. It also minimizes water loss (< 2% per cycle) and delivers 25-50% more net power output, resulting in a lower cost per MWh. Compared to closed-loop systems, Sage can access a large heat transfer area in less than a day through fracturing, versus months of precision drilling required to construct long well loops. This reduces both drilling risk and cost.
9. What is the commercial stage/position of Sage's various technologies?
Sage's energy storage technology has reached Technology Readiness Level (TRL-8), with a 3MW commercial facility built, tested, and ready to start operations in Q4 2025 after the grid interconnection is complete. Sage's geothermal power generation is at a TRL-7, with its first commercial plant planned for 2026/2027 as part of Phase I for a Meta data center east of the Rockies.
10. Do you foresee Sage applications of individual well-pairs (a few MW) providing a bridge to other massive energy supplies? And what is the potential, and cost, of many well-pairs scaled to the needs of data centers or electrical grids (hundreds of MW)?
Sage's geothermal technology is scalable by drilling multiple wells from a single pad, much like unconventional oil and gas. For projects > 100 MW, such as Meta, we anticipate costs between $60-100/MWh, depending on the location and therefore the geothermal resource depth. Sage's unique subsurface approach, which relies on fractures connected to a single wellbore, will increase our access to superhot geothermal resources as compared to EGS and Closed Loop, as wellbore alignment and spacing are not critical, eliminating the need for sophisticated high-temperature directional drilling equipment. Deeper and hotter geothermal can deliver a 10-fold increase in net power generation, which enables further cost reductions
11. I've heard that Sage can buy electricity when production is plentiful, convert it to pressure similar to conventional pumped storage hydropower and later sell it back to the grid when needed. Is this system operational, and will it be cheaper than grid-scale batteries whose cost is falling?
Sage has completed its first commercial 3MW energy storage system at the San Miguel Electric Cooperative in Christine, Texas, with operations starting in Q4 2025 once grid interconnection is complete. While it's not intended to compete with lithium-ion batteries for short durations (< 5 hours), it outperforms them for longer durations, where battery costs and performance decline.
12. I understand Sage has built a proprietary sCO2 turbine, intended to be an alternative to ORC turbines used widely today in geothermal applications. Can you explain the advantage, when the technology will be available, and the cost?
Sage has successfully designed, built, and load-tested a 3MW prototype supercritical CO2 (sCO2) turbine. Compared to conventional Organic Rankine Cycle (ORC) systems, sCO2 turbines are smaller, more cost-effective to build, and deliver up to 50% more net power due to higher efficiency: 15-20% versus 8-12% for ORC. We plan to deploy this technology in the field in 2027-2028 as part of Meta Phase II.