Assessing rare earth element concentrations in geothermal and oil and gas produced waters: A potential domestic source of strategic mineral commodities Final Report to U.S. Department of Energy, Geothermal Technologies Office Reporting Period Start Date: July 1, 2016 Reporting Period End Date: June 30, 2018 Authors: Scott Quillinan, Charles Nye, Mark Engle, Timothy Bartos, Ghanashyam Neupane, Jonathan Brant, Davin Bagdonas, Travis McLing, J. Fred McLaughlin Contributors: Erin Phillips, Laura Hallberg, Mahdi Shahabadi, Matthew Johnson Date Report was issued: July 2018 DOE Award Number: DE-EE0007603 Carbon Management Institute University of Wyoming 1020 E. Lewis Street Laramie, WY 82072 Idaho National Laboratory 1955 N. Fremont Ave. Idaho Falls, ID 83415 USGS Eastern Energy Resources Science Center 12201 Sunrise Valley Drive 956 National Center Reston, VA 20192 USGS Wyoming-Montana Water Science Center 521 Progress Circle Suite 6 Cheyenne, WY 82007 1 ACKNOWLEDGEMENT This material is based upon work supported by the U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy (EERE) under the Geothermal Technologies Office Award Number DE-EE0007603. DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, makes any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. 2 EXECUTIVE SUMMARY The project team collected and analyzed 224 water samples and 101 matching rock samples. INL’s improved method of measuring aqueous REEs allows study of samples previously thought too volume limited to measure. The study found that aqueous REEs occur at trace levels in all analyzed samples, and sometimes exceed ocean REE concentrations by a factor of 1,000. No significant predictive relationship to lithology, reservoir temperature, nor salinity was discovered, but aqueous REE concentration appears spatially controlled. Future work is needed to find the spatially–dependent variable that controls aqueous REE concentration. ABSTRACT This study, funded by U.S. Department of Energy Geothermal Technology Laboratory award DE-EE0007603, sought to discover the concentration of aqueous Rare Earth Elements (REEs) in geothermal produced waters. The project team collected 224 samples of geothermal produced water from wells and libraries, as well as 101 rock samples from outcrop and core libraries. These samples were studied with a variety of rock/fluid analyses, a neural network, and human expertise. This project resulted in a characterization of aqueous REEs in United States geothermal resources which will allow future work to: (1) measure aqueous REEs in volumes of water as small as 30mL, (2) extrapolate characteristics and constituents which indicate a prospective REE resource, (3) intelligently predict the most promising areas of the United States for further study and development, and (4) evaluate technologies for extracting extra value from water produced for geothermal energy to off-set costs. To obtain a characterization of dissolved REEs in geothermal produced waters, it was necessary to determine REE concentrations in small volume samples, which form the majority of sample libraries in the United States. To that end, researchers at Idaho National Laboratory improved the methods of McLing 2014 to allow a 33-fold reduction in sample size. This improvement resulted in the addition of samples from the USGS water sample library which expanded the project to national scope. The samples collected showed that a given basin had fairly consistent REE behavior. The basin a sample came from was a better predictor of REE concentration than salinity, temperature, or host rock lithology. The mechanism or variable by which this basin-by-basin control operates is unknown, and is among our top suggestions for future work. The results of the nation-wide REE database were input to an Emergent Self Organizing Map (ESOM). The ESOM output a network of compositional “closeness” of each sample to the others, seen in Chapter 6. By using this network the researchers were able to estimate unmeasured parameters, such as the REE content of the samples in the USGS National Produced Waters Geochemical Database v2.3. The results of this method support the above finding that REE content follows the basin-by-basin trend seen in the measured samples. The set of water samples was compared with a matching sample set of rocks that represented the reservoir the waters were hosted in. The researchers expected a rock type to match high REE waters, however, rock-type associations were less significant than the basin-to- basin trend. 3 The researchers also investigated possible technologies to concentrate and extract REEs. Their conclusion was that methods which can process large volumes are most favorable, even if the increase in concentration is incremental. The concept of treatment-trains allows such incremental increases in concentration to be summed and an ultimately favorable output to be achieved with near-optimal economic efficiency. The ESOM’s predicted REE concentrations are the first attempt to map-out REE concentrations in geothermal produced waters. By doing so researchers can better inform future studies seeking to understand REE concentration in geothermal produced waters. If future work measures the REEs in one of the areas covered by the database, the ESOM could be refined with the new information, and produce improved estimates. The present predictions should not be used for business decisions, but future estimates might be suitable. This project has assessed the REE resources in geothermal produced waters, suggested explanations for the observed behavior, and recommended future research to answer remaining questions. 4 Acknowledgements The authors and project team would like to thank and acknowledge the following groups and individuals. Their assistance during this project made work progress smoothly, facilitated research, made data available, improved the project’s design, and polished the project’s delivered products. Many others, too numerous to list, contributed to this work in other ways and the project team is indebted to them for their support, and guidance. The Geothermal Technologies Office Holly Thomas Josh Mengers The Technical Monitoring Team Thomas Moore Madalyn Blondes Tanya Gallegos Elisabeth Rowan Colin Doolan Mathew Varonka Debbie Lacroix Savannah Bachman Kipp Codington Sitian Xiong Mackensie Swift 5 TABLE OF CONTENTS Executive Summary and Abstract 3 Table of Contents 6 Chapter 1: Project Objectives and Motivation 8 Past Work and Remaining Questions Milestones and Deliverables Conclusion Chapter 2: Sample Collection and Library Selection (Task 1) 16 Existing Samples in Team Member Libraries New Samples Collected for this Project Analogous Rock Sample Collection Conclusion Chapter 3: Rare earth element hydrogeology/groundwater-quality sections for individual lithostratigraphic/hydrogeologic units within specific Wyoming hydrocarbon production fields 24 Greater Green River Basin Powder River Basin Wind River Basin Conclusion Chapter 4: Aqueous Sample Analysis (Task 2) 47 Methods for Aqueous REE and Geochemical Analysis Results of REE and Geochemical Analysis New Options for Aqueous REE Normalization Conclusion Chapter 5: Rock Sample Analysis (Task 3) 66 Introduction Data Collection Rock Sample Results and Discussion Conclusion Chapter 6: Predicting Rare Earth Element Potential in Produced and Geothermal waters of the United States: Application of Emergent Self-Organizing Maps (Task 5) 75 Introduction Methods and Data 6 Results Summary Chapter 7: Technology screening (Task 6) 106 Review of Processes for Recovering Rare Earth Elements (REEs) from Geothermal Brines Review of Separation Processes for REEs in Mixed Brines Conclusion Chapter 8: Conclusions and Future Work 114 Conclusions of this Study Opportunities for Future Work Conclusion Appendices: 119 A0: Uploads – ESOM, Membrane Recovery Cost Tool, Rock Data A1: Sample List A2: Aqueous Geochemistry A3: Aqueous Rare Earth Element Concentration 7 DE-EE0007603 Final Report to Department of Energy, Geothermal Technologies Office Chapter 1: Project Objectives and Motivation Charles Nye, Scott Quillinan, Jonathan Brant, Travis McLing Scott Quillinan, Director of Research and Communications, University of Wyoming, 1000 E. University Ave., Laramie, WY 82072 [email protected] Keywords: Rare Earth Elements, REE, Project Management, Review, Critical Minerals ABSTRACT In the years after the discovery of Rare Earth Elements (REEs) they were considered insoluble except in acidic solutions. Some studies that were ahead of their time, like (Goldschmit, 1937), showed that REEs occurred in neutral aqueous systems like the ocean, but reports of REEs as inert tracers for physical processes gained more attention (Bhatia and Crook, 1986). REE solubility at