Achieving Carbon Sequestration and Geothermal Energy Production: A Win-Win!
Source: Barry Freifeld, Dan Hawkes
Recently, carbon capture and storage (CCS), which involves capturing the CO2 generated from burning fossil fuels and storing it underground, has been proposed as a way to mitigate climate change. Studies conducted over the past few years have shown the potential for combining CCS with geothermal energy extraction, using supercritical CO2 (ScCO2) as the fluid performing the extraction (i.e., working fluid) and producing electricity as a byproduct.
An international team of scientists including ESD’s Barry Freifeld is pursuing this “win-win” strategy—using CO2 sequestration to simultaneously produce geothermal energy—in an important upcoming project. The team has recently been awarded $5 million dollars from DOE to develop new ways to produce electricity from superheated and pressurized carbon dioxide in deep geothermal formations. Their particular project involves creation of new ScCO2 turbomachinery to extract energy from CO2 circulated in deep sedimentary formations. This new cycle is different from other proposed low-temperature systems in its use of a turbine fed directly with geothermally heated ScCO2—eliminating the capital costs, maintenance, and load imposed by a binary cycle system. The cycle will be first tested under laboratory conditions in preparation for final pilot-scale deployment at the Southeast Regional Carbon Sequestration Partnership (SECARB) Cranfield Phase III Tuscaloosa Formation CO2 Storage Project, in Cranfield, Mississippi.
Proposed combined CO2 storage pilot/geothermal energy production at the SECARB Cranfield DAS demonstration site
The program will have two stages. During the first stage, the team will demonstrate the potential resource availability, design the innovative heat extraction cycle, and assess the potential environmental risks. Then, in the second stage, the team will use what it learns from the first stage to design in detail, fabricate, and test the turbomachinery. This machinery will eventually be deployed at the SECARB Cranfield site, the location of a high-rate CO2 injection program that has been operational since 2009. What the team learns from this project will be used to evaluate coupled reservoir/power plant models, as well as predict the potential (and potential limitations) of such enhanced systems at other locations.
Given its importance, and the potential gain from such a project, it is no surprise that a formidable global assembly of expertise is involved. The team includes not only LBNL but the University of Texas at Austin, Echogen Power Systems, Inc. (Akron, Ohio), the Texas Bureau of Economic Geology (BEG), Denbury Resources, Inc. (Plano, Texas), and the Australian Commonwealth Scientific Industrial Research Organization (CSIRO).
Freifeld and LBNL will lead the storage reservoir modeling effort and will perform a robust analysis of the evolution of the proposed reservoir throughout its operating lifetime, particularly looking at the reservoir’s thermal evolution. BEG has expertise in evaluating water needs for power generation facilities, environmental compliance and siting investigations, is the technical lead on the SECARB CCS partnership, and, jointly with LBNL, has collaborated on numerous pilot projects and field demonstrations, including the Frio Brine Pilot, Otway Project, SECARB Cranfield, and others. Echogen Power Systems, Inc., a small business developing high efficiency heat engine cycles using supercritical CO2 as a working fluid, currently holds one patent on their high efficiency CO2 cycle and has filed a number of additional patent applications on cycle innovations and engine controls. Denbury Resources, Inc., is owner and operator of the largest CO2 reserves for tertiary oil recovery east of the Mississippi River and has significant holdings in the Rockies, Permian Basin, Mid-Continent, and Gulf Coast. They have deep expertise in the transportation and processing of CO2 gas streams in industrial quantities, and they are the lease holders and operator of the brine formation proposed for the project’s pilot test, located off the flank of their SECARB Cranfield Field.
Contributing international expertise and perspective is CSIRO, Australia’s national research institution, with experience at the Otway and other CCS test sites, and a new direct use geothermal energy cooling demo under development in Perth for supercomputing facilities. CSIRO will contribute subsurface expertise in hydrodynamics, compartmentalization, monitoring, and risk analysis.
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