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Application of Hydrothermal Alteration Mineral Analysis to Geothermal Reservoir Characterization for Three Geothermal Fields in the Western United States /

Record Type:	Electronic resources : Monograph/item
Title/Author:	Application of Hydrothermal Alteration Mineral Analysis to Geothermal Reservoir Characterization for Three Geothermal Fields in the Western United States // Kurt O Kraal.
Author:	Kraal, Kurt O.,
Description:	1 electronic resource (246 pages)
Notes:	Source: Dissertations Abstracts International, Volume: 85-01, Section: B.
Contained By:	Dissertations Abstracts International85-01B.
Subject:	Geology. -
Online resource:	https://pqdd.sinica.edu.tw/twdaoapp/servlet/advanced?query=30522548
ISBN:	9798379769581

Application of Hydrothermal Alteration Mineral Analysis to Geothermal Reservoir Characterization for Three Geothermal Fields in the Western United States /
Kraal, Kurt O.,

Application of Hydrothermal Alteration Mineral Analysis to Geothermal Reservoir Characterization for Three Geothermal Fields in the Western United States /Kurt O Kraal. - 1 electronic resource (246 pages)

Source: Dissertations Abstracts International, Volume: 85-01, Section: B.

Geothermal energy is a renewable electricity resource that has the potential to reduce greenhouse gas emissions through continued development of new resources and management of currently produced reservoirs. In order to expand geothermal energy production, it is important to increase our understanding of these resources. One technique for characterizing geothermal resources is through analysis of hydrothermal alteration minerals. In this dissertation, I present detailed hydrothermal alteration analysis of three geothermal fields in the western Unites States: 1) a proposed Enhanced Geothermal System (EGS) site in the Basin and Range province (the Fallon FORGE EGS site), 2) an amagmatic convective fault-controlled intermediate-temperature geothermal resource in the Basin and Range province (Tungsten Mountain geothermal field, operated by Ormat Technologies.), and 3) a high-temperature magmatic-heat-sourced vapor- dominated geothermal system in northern California (The Geysers, operated by Calpine Corp). These three fields represent three distinct endmembers in terms of resource type, distinguished by variability in temperature, permeability, and geologic setting.Hydrothermal alteration minerals and lithologic characteristics of surface rock samples, drill core, and drill cuttings from geothermal wells are analyzed using the following techniques: sample inspection, petrographic microscopy, infrared spectroscopy in the Short Wave (1000-2500 nm) and Long Wave (2.5-25 μm) infrared wavelength ranges, bulk X-Ray Diffraction, and Scanning Electron Microscopy equipped with an energy dispersive X-ray spectroscopy (EDS) system. The hydrothermal alteration data generated in this study are compared with multidisciplinary datasets including geologic maps, downhole geophysical logs, temperature data, and fluid geochemistry in order to understand how the type and distribution of hydrothermal alteration minerals relate to the resource conceptual models of these sites.At the Fallon FORGE EGS site, the analyses supports previous interpretations that the site hosted a high temperature (>250 °C) convective hydrothermal system in the past that is no longer active. This conclusion is based on the zonation of several hydrothermal alteration minerals, with the deepest relict illite-chlorite-epidote zoneiiioverprinted with low-temperature smectite minerals that are likely stable with the current thermal regime. In addition, several discrete zones of high phyllosilicate abundance may indicate localized zones of past fluid-flow that can be targeted or avoided in future EGS experiments at the site.At The Geysers geothermal field, I utilize several infrared spectroscopy techniques that have not been previously applied to geothermal wells at this location. I identified a zonation in mineralogy that changes from illite + chlorite ± kaolinite ± smectite ± calcite at shallow depths, to illite + chlorite ± calcite at intermediate depths, to actinolite + phlogopite + chlorite ± tourmaline at greatest depths, with the boundaries of these zones loosely co-located with the capping rocks, the convective steam reservoir, and the transition to a high-temperature conduction-dominated reservoir inferred to be proximal to a Holocene intrusion. This work supports and provides new detail to previous studies of hydrothermal alteration at the Geysers that utilized more time-intensive analytical techniques for mineral analysis.At Tungsten Mountain, surface hydrothermal mineral mapping and analyses of samples from geothermal wells indicate several phases of hydrothermal activity at the site: (1) illite/sericite + chlorite alteration of Mesozoic siltstone following the intrusion of a diorite pluton in the Cretaceous, (2) kaolinite + montmorillonite + silica alteration associated with extensional faulting along the Clan Alpine fault zone since the Miocene, (3) a phase of high-temperature (220 °C or higher) alkali-chloride fluids producing the macro-zonation of phyllosilicate and calc-silicate minerals in the subsurface (montmorillonite ± chlorite to montmorillonite + illite ± chlorite, to illite + chlorite ± epidote, along with quartz, silica polymorphs, zeolites, and anhydrite), and, (4) hydrothermal minerals (smectite, zeolites, kaolinite, carbonates) associated with the current system (~141 °C) characterized by bicarbonate fluids. Interpretation of the type and spatial location of hydrothermal alteration minerals provides insights into the hydrology of the field, such as structures that host hydrothermal upwelling (characterized by abundant quartz, calcite, and anhydrite veining), structures associated with acidic peripheral water influx (inferred by kaolin group minerals), and potential low- permeability zones (associated with abundant laumontite). This study supports thehypothesis that many extensional fault-controlled systems, although long lived, evolve through time episodically with pulses of higher-temperature fluids followed by longer- lived intermediate-temperature hydrothermal activity.Overall, these three studies found that analysis of hydrothermal alteration mineral can be useful for understanding the history of hydrothermal activity at a site in a variety of geothermal resource settings, and provide information regarding geothermal reservoir architecture, including structures controlling flow. This information can then be incorporated into resource conceptual models that are more accurate, and therefore can better support resource exploration and reservoir management.

English

ISBN: 9798379769581Subjects--Topical Terms:

516570
Geology.
Subjects--Index Terms:

Alteration

Application of Hydrothermal Alteration Mineral Analysis to Geothermal Reservoir Characterization for Three Geothermal Fields in the Western United States /
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502 $b Ph.D. $c University of Nevada, Reno $d 2023.
520 $a Geothermal energy is a renewable electricity resource that has the potential to reduce greenhouse gas emissions through continued development of new resources and management of currently produced reservoirs. In order to expand geothermal energy production, it is important to increase our understanding of these resources. One technique for characterizing geothermal resources is through analysis of hydrothermal alteration minerals. In this dissertation, I present detailed hydrothermal alteration analysis of three geothermal fields in the western Unites States: 1) a proposed Enhanced Geothermal System (EGS) site in the Basin and Range province (the Fallon FORGE EGS site), 2) an amagmatic convective fault-controlled intermediate-temperature geothermal resource in the Basin and Range province (Tungsten Mountain geothermal field, operated by Ormat Technologies.), and 3) a high-temperature magmatic-heat-sourced vapor- dominated geothermal system in northern California (The Geysers, operated by Calpine Corp). These three fields represent three distinct endmembers in terms of resource type, distinguished by variability in temperature, permeability, and geologic setting.Hydrothermal alteration minerals and lithologic characteristics of surface rock samples, drill core, and drill cuttings from geothermal wells are analyzed using the following techniques: sample inspection, petrographic microscopy, infrared spectroscopy in the Short Wave (1000-2500 nm) and Long Wave (2.5-25 μm) infrared wavelength ranges, bulk X-Ray Diffraction, and Scanning Electron Microscopy equipped with an energy dispersive X-ray spectroscopy (EDS) system. The hydrothermal alteration data generated in this study are compared with multidisciplinary datasets including geologic maps, downhole geophysical logs, temperature data, and fluid geochemistry in order to understand how the type and distribution of hydrothermal alteration minerals relate to the resource conceptual models of these sites.At the Fallon FORGE EGS site, the analyses supports previous interpretations that the site hosted a high temperature (>250 °C) convective hydrothermal system in the past that is no longer active. This conclusion is based on the zonation of several hydrothermal alteration minerals, with the deepest relict illite-chlorite-epidote zoneiiioverprinted with low-temperature smectite minerals that are likely stable with the current thermal regime. In addition, several discrete zones of high phyllosilicate abundance may indicate localized zones of past fluid-flow that can be targeted or avoided in future EGS experiments at the site.At The Geysers geothermal field, I utilize several infrared spectroscopy techniques that have not been previously applied to geothermal wells at this location. I identified a zonation in mineralogy that changes from illite + chlorite ± kaolinite ± smectite ± calcite at shallow depths, to illite + chlorite ± calcite at intermediate depths, to actinolite + phlogopite + chlorite ± tourmaline at greatest depths, with the boundaries of these zones loosely co-located with the capping rocks, the convective steam reservoir, and the transition to a high-temperature conduction-dominated reservoir inferred to be proximal to a Holocene intrusion. This work supports and provides new detail to previous studies of hydrothermal alteration at the Geysers that utilized more time-intensive analytical techniques for mineral analysis.At Tungsten Mountain, surface hydrothermal mineral mapping and analyses of samples from geothermal wells indicate several phases of hydrothermal activity at the site: (1) illite/sericite + chlorite alteration of Mesozoic siltstone following the intrusion of a diorite pluton in the Cretaceous, (2) kaolinite + montmorillonite + silica alteration associated with extensional faulting along the Clan Alpine fault zone since the Miocene, (3) a phase of high-temperature (220 °C or higher) alkali-chloride fluids producing the macro-zonation of phyllosilicate and calc-silicate minerals in the subsurface (montmorillonite ± chlorite to montmorillonite + illite ± chlorite, to illite + chlorite ± epidote, along with quartz, silica polymorphs, zeolites, and anhydrite), and, (4) hydrothermal minerals (smectite, zeolites, kaolinite, carbonates) associated with the current system (~141 °C) characterized by bicarbonate fluids. Interpretation of the type and spatial location of hydrothermal alteration minerals provides insights into the hydrology of the field, such as structures that host hydrothermal upwelling (characterized by abundant quartz, calcite, and anhydrite veining), structures associated with acidic peripheral water influx (inferred by kaolin group minerals), and potential low- permeability zones (associated with abundant laumontite). This study supports thehypothesis that many extensional fault-controlled systems, although long lived, evolve through time episodically with pulses of higher-temperature fluids followed by longer- lived intermediate-temperature hydrothermal activity.Overall, these three studies found that analysis of hydrothermal alteration mineral can be useful for understanding the history of hydrothermal activity at a site in a variety of geothermal resource settings, and provide information regarding geothermal reservoir architecture, including structures controlling flow. This information can then be incorporated into resource conceptual models that are more accurate, and therefore can better support resource exploration and reservoir management.
546 $a English
590 $a School code: 0139
650 4 $a Geology. $3 516570
650 4 $a Energy. $3 876794
650 4 $a Alternative energy. $3 3436775
653 $a Alteration
653 $a Geothermal system
653 $a Hydrothermal alteration minerals
653 $a Renewable energy
653 $a Mineralogy
690 $a 0372
690 $a 0363
690 $a 0791
710 2 $a University of Nevada, Reno. $b Geology. $e degree granting institution. $3 3814477
720 1 $a Ayling, Bridget F. $e degree supervisor.
773 0 $t Dissertations Abstracts International $g 85-01B.
790 $a 0139
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