Chemical Impact of Elevated CO2 on Geothermal Energy Production Geothermal Lab Call Project

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Last modified on July 22, 2011.

Project Title Chemical Impact of Elevated CO2 on Geothermal Energy Production
Project Type / Topic 1 Laboratory Call for Submission of Applications for Research, Development and Analysis of Geothermal Technologies
Project Type / Topic 2 Supercritical Carbon Dioxide / Reservoir Rock Chemical Interactions
Project Description Numerical simulations have shown that the use of supercritical CO2 instead of water as a heat transfer fluid yields significantly greater heat extraction rates for geothermal energy. If this technology is implemented successfully, it could increase geothermal energy production and offset atmospheric emissions of greenhouse gases. However, the impact of geochemical reactions between acidic waters in equilibrium with supercritical CO2 and the reservoir rock have not been evaluated. At issue are enhanced rock-water interactions that may reduce reservoir porosity and permeability and may exacerbate downstream scaling. Reactive transport simulations for CO2 sequestration in saline sandstone aquifers suggest that geochemistry plays a negligible role on reservoir integrity and storage capacity. Simulations show that mineral reactions are minimal, have negligible impact on permeability and porosity, and that a very small amount of CO2 is trapped as carbonate minerals. If dawsonite (sodium-aluminum-carbonate mineral) precipitates, as is predicted, experiments suggest that it will dissolve when the CO2 fluid is flushed out with CO2-poor water. Although the carbon sequestration literature suggests that geochemical reactions in geothermal reservoirs might also be minimal, temperatures in geothermal fluids are significantly higher (200 to 300°C) than deep saline reservoirs (below 100°C). Higher temperatures and more acid waters yield much higher mineral dissolution rates and could impact reservoir integrity and downstream operations. Unfortunately it is not possible to predict the impact of CO2 within geothermal systems, because kinetic data at elevated temperatures is limited and simulations made with laboratory data alone will likely underestimate the geochemical impact on production of geothermal energy, because mineral precipitation from geothermal waters is much higher than it is in laboratory studies.
State California
Objectives Assess the geochemical impact of CO2 on geothermal energy production by analyzing the geochemistry of existing geothermal fields with elevated natural CO2, measuring realistic rock-water rates for geothermal systems using laboratory and field-based experiments, and developing reactive transport models using the filed-based rates to simulate production scale impacts.
Awardees (Company / Institution) Lawrence Livermore National Laboratory

Funding Opportunity Announcement DE-PS36-09GO99017
DOE Funding Level (total award amount) $1,025,000.00
Total Project Cost $1,025,000.00

Principal Investigator(s) Susan Carroll

Targets / Milestones - Determine impact of CO2 on geochemistry of existing geothermal fields.

- Laboratory experiments to determine rock-water interactions in geothermal reservoirs for supercritical CO2 fluids.
- Field experiments to further determine rock-water interactions for supercritical CO2 fluids.
- Reactive-transport simulations to test that the use of supercritical CO2 will not be compromised by mineral dissolution and precipitation reactions.

Location of Project Livermore, CA

Funding Source American Recovery and Reinvestment Act of 2009
References EERE Geothermal Technologies Programs[1]


  1. EERE Geothermal Technologies Programs