Enhanced Geothermal System

Sage pairs drilling techniques from the oil & gas industry with their patented technologies to target hot dry rock formations for geothermal, which are far more common than traditional geothermal resources. They fracture the rock layers, creating underground reservoirs. Water is pumped into these reservoirs where it becomes both heated and pressurized. It is then released back to the surface, where the heat and pressure are used to generate electricity. Sage completed a feasibility study for Ellington Field JRB in September 2022 with the University of Texas to identify the depth to reach 200°C temperatures and characteristics of the targeted formations and completed geothermal system-level modeling, which estimated the electric power that could be generated from this geothermal resource. Sage also field-tested its patented technologies in their Starr County well in April 2022 and again in March 2023. Modeling showed 4MWe (electric) net power total from two wells, with each well having four fractures that are 3,000 feet by 490 feet. Modeling and design work will be further refined after Sage tests their sCO2 turbine at Southwest Research Institute in San Antonio, Texas in January 2024. A preliminary power plant design was presented; however Sage has advanced their technology development since the feasibility study and will have a slightly different approach for the EGS power plant to yield the highest energy generation capacity. The proposed TACFI funding will enable Sage to generate electricity with their geothermal EGS technologies at their Starr County, Texas well which will be the first ever test of new generation geothermal that produces electrons thus enabling a future full-scale geothermal power plant at Ellington Field Joint Reserve Base and beyond. The subsurface temperature gradients and lithologies of geothermal EGS target formations in Starr County, Texas have important similarities to geothermal targets across the Texas Gulf coast. This includes the Ellington Field Joint Reserve Base which is part of the Cenozoic Texas Gulf coast geothermal fairway system, with only minor formation variances from Starr County, Texas (i.e., the targeted formation in Starr County is the Vicksburg versus the Wilcox formation in the Ellington Field Joint Reserve Base area). All of these areas feature very low permeability/porosity mudstones and estimates of accessing 200°C formation temperatures at approximately 16,000 to 18,000 feet, true vertical depth (with Starr County having slightly shallower depth to 200°C).