Geothermal Alteration of Basaltic Core from the Snake River Plain, Idaho

114 Pages·2016·5.66 MB·English

by  Christopher Joseph Sant

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All Graduate Theses and Dissertations Graduate Studies
5-2012
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Christopher Joseph Sant
Utah State University
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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