Geothermal Alteration of Basaltic Core from the Snake River Plain, Idaho PDF
Preview Geothermal Alteration of Basaltic Core from the Snake River Plain, Idaho
UUttaahh SSttaattee UUnniivveerrssiittyy DDiiggiittaallCCoommmmoonnss@@UUSSUU All Graduate Theses and Dissertations Graduate Studies 5-2012 GGeeootthheerrmmaall AAlltteerraattiioonn ooff BBaassaallttiicc CCoorree ffrroomm tthhee SSnnaakkee RRiivveerr PPllaaiinn,, IIddaahhoo Christopher Joseph Sant Utah State University Follow this and additional works at: https://digitalcommons.usu.edu/etd Part of the Geology Commons RReeccoommmmeennddeedd CCiittaattiioonn Sant, Christopher Joseph, "Geothermal Alteration of Basaltic Core from the Snake River Plain, Idaho" (2012). All Graduate Theses and Dissertations. 1451. https://digitalcommons.usu.edu/etd/1451 This Thesis is brought to you for free and open access by the Graduate Studies at DigitalCommons@USU. It has been accepted for inclusion in All Graduate Theses and Dissertations by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. GEOTHERMAL ALTERATION OF BASALTIC CORE FROM THE SNAKE RIVER PLAIN, IDAHO by Christopher J. Sant A thesis submitted in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE in Geology Approved: ______________________ ________________________ John W. Shervais Thomas E. Lachmar Major Professor Committee Member ______________________ ________________________ James P. Evans Mark R. McLellan Committee Member Vice President of Research and Dean of the School of Graduate Studies UTAH STATE UNIVERSITY Logan, Utah 2012 Copyright © Christopher Joseph Sant 2012 All Rights Reserved iii ABSTRACT Geothermal Alteration of Basaltic Core from the Snake River Plain, Idaho by Christopher Joseph Sant, Master of Science Utah State University, 2012 Major Professor: Dr. John W. Shervais Department: Geology The Snake River Plain is located in the southern part of the state of Idaho. The eastern plain, on which this study focuses, is a trail of volcanics from the Yellowstone hotspot. Three exploratory geothermal wells were drilled on the Snake River Plain. This project analyzes basaltic core from the first well at Kimama, north of Burley, Idaho. The objectives of this project are to establish zones of geothermal alteration and analyze the potential for geothermal power production using sub-aquifer resources on the axial volcanic zone of the Snake River Plain. Thirty samples from 1,912 m of core were sampled and analyzed for clay content and composition using X-ray diffraction. Observations from core samples and geophysical logs are also used to establish alteration zones. Mineralogical data, geophysical log data and physical characteristics of the core suggest that the base of the Snake River Plain aquifer at the axial zone is located 960 m below the surface, much deeper than previously suspected. Swelling smectite clay clogs pore spaces and reduces porosity and permeability to create a natural base to the aquifer. Increased temperatures favor the formation of smectite clay and other secondary minerals to the bottom of the hole. Below 960 m the core shows signs of alteration including color iv change, formation of clay, and filling of other secondary minerals in vesicles and fractured zones of the core. The smectite clay observed is Fe-rich clay that is authigenic in some places. Geothermal power generation may be feasible using a low temperature hot water geothermal system if thermal fluids can be attained near the bottom of the Kimama well. (113 pages) v PUBLIC ABSTRACT Geothermal Alteration of Basaltic Core from the Snake River Plain, Idaho by Christopher Joseph Sant, Master of Science Utah State University, 2012 Major Professor: Dr. John W. Shervais Department: Geology The Snake River Plain is located in the southern part of the state of Idaho. The eastern plain, which this study focuses on, is a trail of volcanics from the Yellowstone hotspot. Three exploratory geothermal wells were drilled on the Snake River Plain. This project studies basaltic core from the first well at Kimama, north of Burley, Idaho. The objectives of this project are to establish zones of geothermal alteration and analyze the potential for geothermal power production near the center of the Snake River Plain. Thirty samples from 1,912 m of core were sampled and analyzed. Mineral data, temperature data, and physical characteristics of the core suggest that the base of the Snake River Plain aquifer is located 960 m below the surface, much deeper than previously suspected. Swelling clay clogs pore spaces to create a natural base to the aquifer. Below 1,020 m the core shows signs of alteration including color change, formation of clay, and filling of other secondary minerals in vesicles and fractured zones of the core. Geothermal power generation may be a reasonable option using a hot water low temperature geothermal system if the thermal fluids can be accessed below the base of the Snake River Plain aquifer. vi DEDICATION I have many to thank for their support in assisting me through this project. First, I would like to thank my advisor, John Shervais, my thesis committee, and the many professors from Utah State University and other schools that have mentored and helped me get to the point where I am today. Special regards go out to my thesis committee for their concern and guidance toward me as a student, a scientist, and a researcher. They have taught me valuable lessons that will follow me throughout my life. Apart from my thesis committee I would especially like to thank clay mineralogist Jeff Walker from Vassar College. His insight and assistance with analysis, modeling, and interpretation were an integral part of this research. I thank him for all his valuable assistance, and for becoming a great friend. I would also like to thank my fellow student Katie Potter for allowing me to use her samples and unpublished data. Above all, I would like to thank my wonderful family for enduring my schooling years amidst my almost continual absence and for their love and support through this entire process. My thanks and love go out to my beautiful wife, Elizabeth, and three children, Sebastian, Paige, and Luke. Thanks to my friends, family and fellow students that have been a shoulder to lean on and for being willing to listen, and pretend to be interested, to all my science babble. So many have helped me get to this point that it is impossible to thank them all. To all those who have interacted with me through this process, you know who you are, and I thank you for your support. vii ACKNOWLEDGEMENTS Many thanks go to the United States Department of Energy (DOE) and the International Continental Drilling Program (ICDP) for funding this project. I would like to thank the drilling company, DOSECC, for the opportunity to work with them on an active drilling project. I would especially like to thank the principal investigator, John Shervais, and accountant, Nina Glaittli, on the project for their hard work and dedication that often goes unnoticed. I would also like to thank all the students, faculty, and graduates that I was able to work alongside. This project has been a once-in-a-lifetime experience, thank you to all who made it possible. Chris Sant viii CONTENTS Page ABSTRACT ....................................................................................................................... iii PUBLIC ABSTRACT ........................................................................................................ v DEDICATION ................................................................................................................... vi ACKNOWLEDGEMENTS .............................................................................................. vii LIST OF FIGURES ........................................................................................................... xi INTRODUCTION .............................................................................................................. 1 OVERVIEW.................................................................................................................... 1 OBJECTIVES ................................................................................................................. 2 SIGNIFICANCE ............................................................................................................. 2 BACKGROUND ................................................................................................................ 3 SETTING ........................................................................................................................ 3 Basalts of the SRP ....................................................................................................... 5 Eruptive Style.......................................................................................................... 6 Basalt Facies ........................................................................................................... 7 Basaltic Structures .................................................................................................. 8 Sediments on the SRP ............................................................................................... 10 Fluid Flow in SRP Basalts .................................................................................... 11 Fluid Flow Enhancements..................................................................................... 11 Fluid Flow Restrictions ......................................................................................... 13 Sediment Influence on Fluid Flow ........................................................................ 14 SRP Aquifer .......................................................................................................... 14 Previous Work ........................................................................................................... 16 HAWAIIAN GEOTHERMAL STUDIES .................................................................... 20 Temperature Data ...................................................................................................... 20 Alteration ................................................................................................................... 20 ix CLAY MINERALOGY ............................................................................................... 22 X-ray Diffraction Interpretation ................................................................................ 26 Previous Work ........................................................................................................... 28 METHODS ....................................................................................................................... 32 SAMPLE COLLECTION ............................................................................................ 32 SAMPLE PREPARATION .......................................................................................... 33 SAMPLE ANALYSIS ................................................................................................. 34 RESULTS ......................................................................................................................... 38 INTRODUCTION ......................................................................................................... 38 PHYSICAL DESCRIPTION OF KIMAMA CORE .................................................... 38 TEMPERATURE DATA .............................................................................................. 45 MINERALOGICAL DATA ......................................................................................... 48 Whole-Rock Powders ................................................................................................ 48 Clay Separate Samples .............................................................................................. 48 Clay Modeling ........................................................................................................... 68 DISCUSSION ................................................................................................................... 71 BASE OF AQUIFER .................................................................................................... 71 ALTERATION ZONES ................................................................................................ 72 THERMAL ALTERATION ......................................................................................... 73 GEOTHERMAL POWER GENERATION.................................................................. 75 SUMMARY ...................................................................................................................... 77 REFERENCES ................................................................................................................. 79 APPENDIX ...................................................................................................................... 89
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