Improved Geothermometry Through Multivariate Reaction-path Modeling

1. Improved Geothermometry Through Multivariate Reaction-path Modeling Craig Cooper, Idaho National Laboratory (PI) Geochemistry Team Carl Palmer, Idaho National Laboratory Bob Smith, University of Idaho, CAES Microbiology Team Yoshiko Fujita, Idaho National Laboratory David Reed, Idaho National Laboratory Vicki Thompson, Idaho National Laboratory 18-January, 2012

2. Presentation Overview U.S. Geothermal, Raft River Facility • Statement of need • Project goals and objectives • Brief introduction to geothermometry • What geothermometry is and why it is important • Principles of geothermometry • Scientific challenges in geothermometry • Discuss our project • Conceptual approach • Project tasks • Challenges, advancements, and innovations

3. Statement of Need U.S. DOE, Technology Needs for Geothermal Development • Need to reduce costs of geothermal exploration • Geothermal exploration is expensive and risky • Reduce financial risk via deploymentof improved exploration technologies • Geochemistry needs • Need more accurate predictions from geothermometry • Account for lithology, complex reaction path • New geothermometers and analytical techniques

4. Goals and Objectives • Research Goals • Advance geothermal energy development by developing and deploying geothermometry technologies that reduce the costs, risks, and uncertainties of geothermal exploration • Project Objectives (how the goals will be met) • Develop knowledge required to use geothermometry to predict reservoir temperature to within ±30 °C • Develop associated software technology product that can be commercialized for use in the geothermal industry • Advance the scientific state of the art of geothermometry • Note: Typical state of geothermometry practice in the geothermal industry is to conduct single-equilibria spreadsheet calculations based on older literature.

5. Importance of Geothermometry • What is geothermometry? • Use of chemical and/or isotopic composition of thermal waters to estimate reservoir temperatures • Water samples typically collected from wells, natural springs, or fumaroles • Major tool for geothermal exploration and development • Why is geothermometry important? • Discovery and early stage development of geothermal reservoirs involves significant risk • This risk is a major barrier for geothermal energy development • Accurate temperature prediction can reduce exploration risk and speed development Black Growler Steam Vent, Norris Basin Neal Hot Springs, Oregon

6. Principles of Geothermometry • Basic Principles • Assume that water preserves its chemical composition as it moves from the reservoir to the surface • Calculate temperature, assuming temperature-dependent equilibrium between the water and minerals in the host rock at deep reservoir conditions • Key Assumptions • Equilibrium between water and mineral phases in the reservoir • Valid assumption • Challenge is understanding which minerals control equilibrium • Water chemistry is preserved along the reaction/transport path • Not necessarily true • Water composition can be affected by cooling, phase changes, mixing, and mineralization/dissolution reactions.

7. Geothermometry Challenges Example from Reed & Spycher (Geochim. Cosmochim. Acta, 1984) • Reservoir geochemistry • Which minerals control equilibrium? • Different mineral sets have different temperature relationships • Reaction paths may converge at different temperature points • Need to account for multiple convergences • Reaction path parameterization • What happens to the solution between the reservoir and the sampling point? • Pressure changes, chemical reactions, and mixing with cooler waters can distort the geothermometry signal • Microbial impacts below ~120 °C TEM of silicified bacteria from Icelandic geyser outflow Konhauser et. al., Ambio, 2004

8. Our Conceptual ApproachMultivariate Reaction Path Modeling for Improved Geothermometry • Three stage system • Deep Reservoir • Mineral dissolution • Partial equilibrium between multiple mineral phases • Intermediate flow • Temperature and pressure drop • Mixing, boiling • Some chemistry • Near-surface • Geochemistry (including reactions mediated by microorganisms

9. Software Tool to Capture Conceptual Model • This is a technology development project • Purpose is to developan improved geothermometry software “tool” that can later be deployed into the geothermal market • Software will help improve the accuracy of geothermometric predictions • Translate scientific advancements into standard practice • Project tasks develop conceptual model into a software tool • Modeling Tasks— Develop and demonstrate a geothermometry exploration tool using low-cost commercial modeling software • Laboratory Tasks— Test the robustness of model, and help prioritize future work

10. Task Descriptions • Geochemistry and Modeling • Task 1, Reservoir Temperature Prediction—Develop geothermometry software applications that can help a geothermal developer to estimate reservoir temperature • Task 2, Reaction Path Parameterization—Develop a set of heuristics that use sampling data to define the reaction path and correctly apply the temperature prediction model • Task 3, Abiotic Process Characterization—Conductlaboratory experiments to test how well the software can describe the intermediate flow path, including mixing and abiotic chemical reactions • Geomicrobiology • Task 4, Geomicrobiological Process Characterization—Conductlaboratory experiments to help describe the impacts of microbial metabolism on major element geothermometers, and test the ability of the software to account for microbiological impacts

11. Geochemistry and Modeling (Tasks 1 – 3) • Current state of practice in geothermometry • Typically Excel spreadsheet calculations based on single-mineral equilibria • Does not take advantage of current knowledge and computing capability • Advances and innovations • Facilitate simultaneous consideration of multiple mineral equilibria, including use of both Si and Al in calculations • Help select minerals and/or alteration products to use for a given reservoir Gjögur, Hveravik, Iceland (low T) Reykjanes #8, Iceland (high T) ~290 °C ~75 °C

12. Geomicrobiology (Task 4) • Current state of practice in geothermometry • Microbiology is generally not considered • Yet, geomicrobiological investigations have shown that microorganisms can impact the chemistry of major element geothermometers (e.g. Al, Ca, Mg, Si, Na, Fe) at temperatures of up to 121 °C • Advances and innovations • Introduce geomicrobiology into geothermometry • Conduct tests to determine the extent to which particular microbial metabolic processes impact major element geothermometers • Focus on elucidating the extent to which microbiological processes are catalyzing reactions and accelerating the reaction path • Focus initially on sulfur metabolism • Begin developing techniques to help ascertain and account for microbiological impacts on chemistry of geothermometers

13. Other Project Activities • Field Samples • Collect samples from Raft River, Neal Hot Springs; analyze for a range of geothermometers and other geochemical indicators • Use results to test model predictions and help improve accuracy • Commercialization • Identify potentially interested industrial partners in geothermal industry and amongst providers of geochemical modeling software • Gather input on software functionality and utility as it is developed • Develop commercialization plan and pursue funding to enable commercialization • Team with industrial partner to seek support for commercialization and further product development

14. Concluding Remarks • Exciting opportunity to put geoscientific research to work • Successful product will lower the costs of geothermal development • Cleaner, more secure, more sustainable energy • More options for mitigating climate change • Chance to translate scientific advances into “real-world” products • Chance to advance the state of the art in geothermometry, and lay a solid foundation for a continuing program • Encourage collaboration • Just kicking off, so there is plenty of opportunity to help • Wider input = better product • More contributors = more opportunity

15. Additional Microbiology Slides

16. Extremophilic Microorganisms • Many microorganisms thrive in geothermal waters • Growth up to 121°C, probably higher. • Growth from 0.5 < pH < 12 • Growth in presence of toxic metals, high pressures, etc. • Microorganism metabolisms can alter many of the chemistries present in geothermal waters

17. Na-K-Ca-(Mg) and Silica • Microorganisms responsible for carbonate cycling1 • Metabolism of C and N compounds and reduction of SO4-2 can promote carbonate precipitation • Can (co-)precipitate Ca, Na, Mg, and Fe • Microorganisms can also promote dissolution of carbonate minerals and liberation of Ca2+, Mg2+, and Na+ • Microorganisms can precipitate or mobilize silica2 • Surface OH- and COOH- groups on biomass • Microbial production of acid, alkali and polysaccharides 1Bonatti, 1966; Ehrlich, 1990; Zavarzin, 2002; and Power, 2009 2Renault, 1998; and Ehrlich, 1990

18. Isotopic Ratios and REE • Sulfate reducing bacteria in Lost City hydrothermal field preferentially depleted deuterium1 • A geothermometer using H2O-H2 and CH4-H2 isotopes under predicted the temperature of these vents by 20-60°C • Sulfate reducers preferentially reduce 32S over 34S2 • Archaeoglobus fulgidusenriches 32S in sulfide up to 42‰ • Microorganisms can selectively enrich REEs3 • 106 Enrichment of REEs in hot spring biofilm and mat • Heavy REEs (Tm, Yb, and Lu) selectively enriched at higher temperatures 1Proskurowski, 2006 2Habicht, 2005 3Takahashi, 2007; Takahashi, 2005; and Anderson, 2003

19. Experimental Plan (Year 1) • Batch microcosms for testing different conditions • Artificial porous media and synthetic geothermal water • 80°C and anaerobic • Inoculate with Archaeoglobus (sulfate reducing micro-organism isolated from various geothermal waters) • Test varying Na, K, Ca, Mg, and silica concentrations under sulfate reducing conditions with matching abiotic controls • Measure concentrations over time