CO2-Based Geothermal Energy at the St. Johns Dome--A Status Report

Abstract

In September of 2010, GreenFire Energy received a US Department of Energy grant to attempt a real-world trial of CO2-based geothermal energy (CO2G) at a site on the St. Johns-Springerville CO2 Dome near the Arizona-New Mexico border. Though CO2G was proposed in 1998, and there has been a significant amount of computer modeling, there has never until now been an attempt to test the idea in the field. The chosen site is uniquely suited for testing CO2G, as it incorporates the St .Johns CO2 reservoir, from which approximately 450 MM tons of CO2 is recoverable from relatively shallow deposits. The CO2-bearing formations overlie a moderate-temperature geothermal area. Thus the plan is to produce CO2 from the shallow formations, compress as necessary to obtain supercritical CO2, which will then be injected into the hot basement granite/schist formation containing the geothermal heat. This paper will describe the work to date, including a summary of the pertinent literature, early results from passive seismic monitoring, and the types of data that the project will generate as steps toward further development, and as improved input into mathematical models. Plans for further exploitation of this resource will also be discussed.