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At least 19 recordsLinked to original sources
USGS1991

Chemical, isotopic, and dissolved gas compositions of the hydrothermal system in Twin Falls and Jerome counties, Idaho

The chemical, isotopic, and gas compositions of the hydrothermal system in Twin Falls and Jerome counties, Idaho, change systematically as the water moves northward from the Idaho-Nevada boundary toward the Snake River. Sodium, chloride, fluoride, alkalinity, dissolved helium, and carbon-13 increase as calcium and carbon-14 decrease. Water-rock reactions may result in dissolution of plagioclase or volcanic glass and calcite, followed by precipitation of zeolites and clays. On the basis of carbon-14 age dating, apparent water ages range from 2,000 to more than 26,000 years; most apparent ages range from about 4,000 to 10,000 years. The older waters, north of the Snake River, are isotopically depleted in deuterium and are enriched in chloride relative to waters to the south. Thermal waters flowing northward beneath the Snake River may join a westward flow of older thermal water slightly north of the river. The direction of flow in the hydrothermal system seems to parallel the surface drainage.

Geothermal Resources Council Transactions↗
USGS1999

Compilation of gas geochemistry and isotopic analyses from The Geysers geothermal field: 1978-1991

We present 45 chemical and isotopic analyses from well discharges at The Geysers geothermal field and summarize the most notable geochemical trends. H 2 and H 2 S concentrations are highest in the Southeast Geysers, where steam samples have δD and δ 18 O values that reflect replenishment by meteoric water. In the Northwest Geysers, samples are enriched in gas/steam, CO 2 , CH 4 , and N 2 /Ar relative to the rest of the field, and contain steam that is elevated in δD and δ18O, most likely due to substantial contributions from Franciscan-derived fluids. The δ13C of CO 2 , trends in CH 4 vs. N 2 , and abundance of NH 3 indicate that the bulk of the non-condensable gases are derived from thermal breakdown of organic materials in Franciscan meta-sediments.

Geothermal Resources Council Transactions↗
USGS1999

Geochemistry of waters from springs, wells, and snowpack on and adjacent to Medicine Lake volcano, northern California

Chemical analyses of waters from cold springs and wells of the Medicine Lake volcano and surrounding region indicate small chloride anomalies that may be due to water-rock interaction or limited mixing with high-temperature geothermal fluids. The Fall River Springs (FRS) with a combined discharge of approximately 37 m3/s, show a negative correlation between chloride (Cl) and temperature, implying that the Cl is not derived from a high-temperature geothermal fluid. The high discharge from the FRS indicates recharge over a large geographic region. Chemical and isotopic variations in the FRS show that they contain a mixture of three distinct waters. The isotopic composition of recharge on and adjacent to the volcano are estimated from the isotopic composition of snow and precipitation amounts adjusted for evapotranspiration. Enough recharge of the required isotopic composition (-100 parts per thousand ??D) is available from a combination of the Medicine Lake caldera, the Fall River basin and the Long Bell basin to support the slightly warmer components of the FRS (32 m3/s). The cold-dilute part of the FRS (approximately 5 m3/s) may recharge in the Bear Creek basin or at lower elevations in the Fall River basin.

Geothermal Resources Council Transactions↗
USGS1999

Thermal regime of the Great Basin and its implications for enhanced geothermal systems and off-grid power

The Basin and Range Province of the Western United States covers most of Nevada and parts of adjoining states. It was formed by east-west tectonic extension that occurred mostly between 50 and 10 Ma, but which still is active in some areas. The northern Basin and Range, also known as the Great Basin, is higher in elevation, has higher regional heat flow and is more tectonically active than the southern Basin and Range which encompasses the Mojave and Sonoran Deserts. The Great Basin terrane contains the largest number of geothermal power plants in the United States, although most electrical production is at The Geysers and in the Salton Trough. Installed capacities of electrical power plants in the Great Basin vary from 1 to 260 MWe. Productivity is limited largely by permeability, relatively small productive reservoir volumes, available water, market conditions and the availability of transmission lines. Accessible, in-place heat is not a limiting condition for geothermal systems in the Great Basin. In many areas, economic temperatures (>120°C) can be found at economically drillable depths making it an appropriate region for implementation of the concept of "Enhanced Geothermal Systems" (EGS). An incremental approach to EGS would involve increasing the productivity and longevity of existing hydrothermal systems. Those geothermal projects that have an existing power plant and transmission facilities are the most attractive EGS candidates. Sites that were not developed owing to marginal size, lack of intrinsic permeability, and distance to existing electrical grid lines are also worthy of consideration for off-grid power production in geographically isolated markets such as ranches, farms, mines, and smelters.

Geothermal Resources Council Transactions↗
USGS2012

Hotspot: the Snake River Geothermal Drilling Project--initial report

The Snake River volcanic province (SRP) overlies a thermal anomaly that extends deep into the mantle; it represents one of the highest heat flow provinces in North America. The primary goal of this project is to evaluate geothermal potential in three distinct settings: (1) Kimama site: inferred high sub-aquifer geothermal gradient associated with the intrusion of mafic magmas, (2) Kimberly site: a valley-margin setting where surface heat flow may be driven by the up-flow of hot fluids along buried caldera ringfault complexes, and (3) Mountain Home site: a more traditional fault-bounded basin with thick sedimentary cover. The Kimama hole, on the axial volcanic zone, penetrated 1912 m of basalt with minor intercalated sediment; no rhyolite basement was encountered. Temperatures are isothermal through the aquifer (to 960 m), then rise steeply on a super-conductive gradient to an estimated bottom hole temperature of ~98°C. The Kimberly hole is on the inferred margin of a buried rhyolite eruptive center, penetrated rhyolite with intercalated basalt and sediment to a TD of 1958 m. Temperatures are isothermal at 55-60°C below 400 m, suggesting an immense passive geothermal resource. The Mountain Home hole is located above the margin of a buried gravity high in the western SRP. It penetrates a thick section of basalt and lacustrine sediment overlying altered basalt flows, hyaloclastites, and volcanic sediments, with a TD of 1821 m. Artesian flow of geothermal water from 1745 m depth documents a power-grade resource that is now being explored in more detail. In-depth studies continue at all three sites, complemented by high-resolution gravity, magnetic, and seismic surveys, and by downhole geophysical logging.

Snake River↗
USGS2012

The ICDP Snake River Geothermal Drilling Project: preliminary overview of borehole geophysics

Hotspot: The Snake River Geothermal Drilling Project was undertaken to better understand the geothermal systems in three locations across the Snake River Plain with varying geological and hydrological structure. An extensive series of standard and specialized geophysical logs were obtained in each of the wells. Hydrogen-index neutron and γ-γ density logs employing active sources were deployed through the drill string, and although not fully calibrated for such a situation do provide semi-quantitative information related to the ‘stratigraphy’ of the basalt flows and on the existence of alteration minerals. Electrical resistivity logs highlight the existence of some fracture and mineralized zones. Magnetic susceptibility together with the vector magnetic field measurements display substantial variations that, in combination with laboratory measurements, may provide a tool for tracking magnetic field reversals along the borehole. Full waveform sonic logs highlight the variations in compressional and shear velocity along the borehole. These, together with the high resolution borehole seismic measurements display changes with depth that are not yet understood. The borehole seismic measurements indicate that seismic arrivals are obtained at depth in the formations and that strong seismic reflections are produced at lithological contacts seen in the corresponding core logging. Finally, oriented ultrasonic borehole televiewer images were obtained over most of the wells and these correlate well with the nearly 6 km of core obtained. This good image log to core correlations, particularly with regards to drilling induced breakouts and tensile borehole and core fractures will allow for confident estimates of stress directions and or placing constraints on stress magnitudes. Such correlations will be used to orient in core orientation giving information useful in hydrological assessments, paleomagnetic dating, and structural volcanology.

Snake River↗
USGS2012

Mapping temperature and radiant geothermal heat flux anomalies in the Yellowstone geothermal system using ASTER thermal infrared data

The purpose of this work was to use satellite-based thermal infrared (TIR) remote sensing data to measure, map, and monitor geothermal activity within the Yellowstone geothermal area to help meet the missions of both the U.S. Geological Survey Yellowstone Volcano Observatory and the Yellowstone National Park Geology Program. Specifically, the goals were to: 1) address the challenges of remotely characterizing the spatially and temporally dynamic thermal features in Yellowstone by using nighttime TIR data from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) and 2) estimate the temperature, geothermal radiant emittance, and radiant geothermal heat flux (GHF) for Yellowstone’s thermal areas (both Park wide and for individual thermal areas). ASTER TIR data (90-m pixels) acquired at night during January and February, 2010, were used to estimate surface temperature, radiant emittance, and radiant GHF from all of Yellowstone’s thermal features, produce thermal anomaly maps, and update field-based maps of thermal areas. A background subtraction technique was used to isolate the geothermal component of TIR radiance from thermal radiance due to insolation. A lower limit for the Yellowstone’s total radiant GHF was established at ~2.0 GW, which is ~30-45% of the heat flux estimated through geochemical (Cl-flux) methods. Additionally, about 5 km 2 was added to the geodatabase of mapped thermal areas. This work provides a framework for future satellite-based thermal monitoring at Yellowstone as well as exploration of other volcanic / geothermal systems on a global scale.

Wyoming↗
USGS2012

Using hydrogeologic data to evaluate geothermal potential in the eastern Great Basin

In support of a larger study to evaluate geothermal resource development of high-permeability stratigraphic units in sedimentary basins, this paper integrates groundwater and thermal data to evaluate heat and fluid flow within the eastern Great Basin. Previously published information from a hydrogeologic framework, a potentiometric-surface map, and groundwater budgets was compared to a surficial heat-flow map. Comparisons between regional groundwater flow patterns and surficial heat flow indicate a strong spatial relation between regional groundwater movement and surficial heat distribution. Combining aquifer geometry and heat-flow maps, a selected group of subareas within the eastern Great Basin are identified that have high surficial heat flow and are underlain by a sequence of thick basin-fill deposits and permeable carbonate aquifers. These regions may have potential for future geothermal resources development.

Nevada, Utah↗
USGS1990

Monitoring the hydrologic system for potential effects of geothermal and ground-water development in the Long Valley caldera, Mono County, California, U.S.A.

In the early 1980's, renewed interest in the geothermal potential of the Long Valley caldera, California, highlighted the need to balance the benefits of energy development with the established recreational activities of the area. The Long Valley Hydrologic Advisory Committee, formed in 1987, instituted a monitoring program to collect data during the early stages of resource utilization to evaluate potential effects on the hydrologic system. Early data show declines in streamflow, spring flow, and ground-water levels caused by 6 years of below-average precipitation. Springs in the Hot Creek State Fish Hatchery area discharge water that is a mixture of nonthermal and hydrothermal components. Possible sources of nonthermal water have been identified by comparing deuterium concentrations in streams and springs. The equivalent amount of undiluted thermal water discharged from the springs was calculated on the basis of boron and chloride concentrations. Quantifying the thermal and nonthermal fractions of the total flow may allow researchers to assess changes in flow volume or temperature of the springs caused by groundwater or geothermal development.

California↗
USGS1985

Monitoring the hydrothermal system in Long Valley caldera, California

An ongoing program to monitor the hydrothermal system in Long Valley for changes caused by volcanic or tectonic processes has produced considerable data on the water chemistry and discharge of springs and fluid temperatures and pressures in wells. Chemical and isotopic data collected under this program have greatly expanded the knowledge of chemical variability both in space and time. Although no chemical or isotopic changes in hot spring waters can be attributed directly to volcanic or tectonic processes, changes in hot spring chemistry that have been recorded probably relate to interactions between and variations in the quantity of liquid and gas discharged. Stable carbon isotope data are consistent with a carbon source either perform the mantle or from metamorphosed carbonate rocks. Continuous and periodic measurements of hot spring discharge at several sites show significant co seismic and a seismic changes since 1980.

California↗
USGS2018

Which geologic factors control permeability development in geothermal systems? The geologic structure of Dixie Valley

Geothermal systems occur where subsurface permeability and temperature are sufficiently high to drive fluid circulation. In the Great Basin region of the United States, which hosts ~20% of domestic geothermal electricity generation capacity and much of the projected undeveloped and undiscovered resource, crustal heat flow is relatively high, so permeability is the dominant factor controlling the occurrence or absence of a geothermal system. In the most general sense, fracture permeability along faults and/or networks of interconnected faults and fractures serves as a pathway for fluids upwelling from depth. Within the Great Basin, Dixie Valley hosts an anomalously high number of geothermal systems. It is unclear whether this relatively dense collection of systems is associated with regional strain or structural patterns, local structural or geological characteristics, basin hydrogeology, or some other factors. The relatively rich data-set available for Dixie Valley, and the well-studied nature of the area affords the opportunity to characterize the geologic and lithologic factors that control permeability development at the local scale. There are at least eleven distinct geothermal systems in Dixie Valley, NV. We utilize a wealth of existing data, which have been collected over several decades, to assess the geologic controls on geothermal fluid upwelling in these systems.

Geothermal Resources Council Transactions↗
USGS2018

New data yield new geologic insights at the Fallon FORGE site, Carson Sink Region, Nevada

The geologic structure beneath the Fallon Frontier Observatory for Research in Geothermal Energy (FORGE) site represents a record of the Mesozoic through Cenozoic tectonism, volcanism, and sedimentation that has affected the Carson Sink local to Fallon, NV. A robust dataset confirms that the lithologic sequence consists of Quaternary through Miocene sedimentary and volcanic rocks resting non-conformably on Mesozoic crystalline basement. The basement consists of four lithologic units; 1) Triassic-Jurassic low-to-medium grade meta-rhyolites, 2) Jurassic low-to-medium grade quartzites and other metamorphosed marine sedimentary rocks, and 3) Jurassic low-to-medium grade meta-basalt and -basaltic-andesite lavas, all intruded by 4) Jurassic-Cretaceous quartz monzonite. The geologic section dips ~20-25° west, tilting that was accommodated by a predominant system of north-to-north-northeast striking, east and west moderately-to-steeply dipping normal faults. The above, relatively broad-scale characteristics of the geologic framework of the Fallon site have been developed throughout the ~3 year duration of the project. With the collection of new data and re-analysis of existing data in Phase 2B of the Fallon FORGE project, our detailed understanding of the relatively finer-scale aspects of the geologic framework, including aspects of the stratigraphic sequence and the locations and attitudes of individual faults have evolved and an updated 3D geologic map has been developed. Here, we compare the Phase 1 3D geologic map to the Phase 2B 3D geologic map and demonstrate the evolution of our understanding of the geologic framework of the Fallon site and the value of the new data that was collected in Phase 2B in developing this updated framework.

Geothermal Resources Council Transactions↗
USGS2018

2D and 3D potential field mapping and modelling at the Fallon FORGE site, Nevada, USA

Accurate geological characterization of Fallon FORGE is important for preparing the site as an EGS laboratory. As part of this effort, a 3D geologic map was constructed previously from well logs, surface geologic mapping, 2D seismic profiles, interpreted gravity & magnetic maps, and a gravity-inferred basement surface. In this study, we have conducted both 2D and 3D modelling of high-resolution gravity and magnetic data (pre-existing and new) in an effort to further refine and test this 3D geologic map at Fallon. This effort enabled a direct comparison of the 2D and 3D model results. Potential field modelling was guided by rock-property measurements of samples from drill-core and outcrop from the Fallon area. In total, five 2D potential field model profiles, up to 30 km in length, were constructed that extend across the Fallon area. The 3D gravity model volume was 8 km (N-S) x 8 km (E-W) x 4 km (thick). The majority of the 3D gravity model volume had 100 m cubic cells; but cells near the land surface were 1 m thick to adequately capture topography. Overall, the 2D & 3D geophysical modelling largely confirmed the previously constructed 3D geologic map at Fallon for three reasons: 1) lithologic boundaries in the 2D & 3D density models mostly agree with those in the 3D geologic map, 2) the rock properties used in the models lie within the range of independent measurements made on representative rock samples from the region, and 3) the match between the observed and calculated anomalies are largely within the measurement error of the observed fields. In places where the geophysical and geologic models differ, geophysical model results have revealed subsurface structural features that have helped refine geologic interpretations which, in turn, lead to adjustments to the 3D geologic map. In this paper, we present the 2D & 3D geophysical model results and discuss how they were utilized to confirm and refine our 3D geologic understanding of the Fallon FORGE site.

Geothermal Resources Council Transactions↗
USGS2018

Discovery of a blind geothermal system in Southern Gabbs Valley, western Nevada, through application of the play fairway analysis at multiple scales

The Great Basin region is capable of generating much greater amounts of geothermal energy than currently produced. Most geothermal resources in this region are blind, and thus favorable characteristics for geothermal activity must be synthesized and methodologies developed to discover new commercial-grade systems. The geothermal play fairway concept involves integration of multiple parameters indicative of geothermal activity to identify promising areas for new development. In the Nevada play fairway project, geologic, geochemical, and geophysical parameters were initially synthesized to produce a new geothermal potential map of 96,000 km2. Southern Gabbs Valley in western Nevada is a particularly promising site selected for detailed study. It contains favorable structural settings, including Quaternary fault intersections and a displacement transfer zone. Geologic, geophysical, and geochemical techniques were employed to define the most likely sites for high permeability and select targets for temperature-gradient holes. Permeability models were revised to reflect results of detailed analyses and generate new detailed play fairway maps. The most promising site lies in an area of multiple fault intersections in a broader displacement transfer zone directly north of the Petrified Springs dextral fault, as revealed by gravity, magnetic, and MT data. A 2-m temperature anomaly and warm temperature gradient wells (~120oC at ~150 m depth) confirm the presence of a geothermal system and provide initial validation of the play fairway methodology. The system is blind, with no surface hot springs, fumaroles, or paleo-geothermal deposits. Lessons learned in the detailed studies include: 1) initially identified sites commonly include multiple favorable settings at a finer scale; 2) promising sites in Cenozoic basins cannot be recognized without detailed geophysical surveys; and 3) play fairway analysis is critical at multiple scales.

Geothermal Resources Council Transactions↗
USGS2019

Can geologic factors be predictive for distinguishing between productive and non-productive geothermal wells?

Geologic data are examined to evaluate whether certain geologic characteristics occur in higher abundance or higher magnitude along production geothermal wells relative to non-productive wells. We perform 3D geologic mapping, 3D stress modeling, and fault-slip modeling to estimate fourteen different geologic factors that are hypothesized to control or correlate with well productivity. The geologic factors are; heat, fault-damage zone thickness, distance from active faults, fault intersection/termination density, fault curvature, slip tendency of faults, dilation tendency of faults, dilation resulting from modeled fault slip, normal stress reduction resulting from modeled fault slip, Coulomb shear stress increase resulting from modeled fault slip, the summed thickness of ‘favorable’ lithologies within a borehole, the summed thickness of fault damage zones in favorable lithologies within a borehole, the distance along the borehole to the nearest geologic contact, and the thickness of individual stratigraphic units. These geologic factors are quantified along fifty wells at Brady geothermal system, including twelve production wells and thirty-one non-productive wells. Results indicate that geologic factors such as stress changes associated with faulting, nearness to and thickness of fault zones, distance from geologic contacts, and heat occur in higher magnitude or higher abundance along production wells relative to non-productive wells. These geologic factors may play an important role in controlling the locations and distribution of fluid circulation in geothermal fields.

Geothermal Resources Council Transactions↗
USGS2006

Heat flow in Railroad Valley, Nevada and implications for geothermal resources in the south-central Great Basin

The Great Basin is a province of high average heat flow (approximately 90 mW m -2 ), with higher values characteristic of some areas and relatively low heat flow (<60 mW m -2 ) characteristic of an area in south-central Nevada known as the Eureka Low. There is hydrologic and thermal evidence that the Eureka Low results from a relatively shallow, hydrologically controlled heat sink associated with interbasin water flow in the Paleozoic carbonate aquifers. Evaluating this hypothesis and investigating the thermal state of the Eureka Low at depth is a high priority for the US Geological Survey as it prepares a new national geothermal resource assessment. Part of this investigation is focused on Railroad Valley, the site of the largest petroleum reservoirs in Nevada and one of the few locations within the Eureka Low with a known geothermal system. Temperature and thermal conductivity data have been acquired from wells in Railroad Valley in order to determine heat flow in the basin. The results reveal a complex interaction of cooling due to shallow ground-water flow, relatively low (49 to 76 mW m -2 ) conductive heat flow at depth in most of the basin, and high (up to 234 mW m -2 ) heat flow associated with the 125°C geothermal system that encompasses the Bacon Flat and Grant Canyon oil fields. The presence of the Railroad Valley geothermal resource within the Eureka Low may be reflect the absence of deep ground-water flow sweeping heat out of the basin. If true, this suggests that other areas in the carbonate aquifer province may contain deep geothermal resources that are masked by ground-water flow.

Nevada↗
USGS2003

Searching for an electrical-grade geothermal resource in Northern Arizona to help geopower the west

The U.S Department of Energy s "Geopowering the West" initiative seeks to double the number of states (currently 4) that generate geothermal electric power over the next few years. Some states, like New Mexico and Oregon, have plentiful and conspicuous geothermal manifestations, and are thus likely to further DOE's goal relatively easily. Other states, including Arizona, demonstrate less geothermal potential, but nevertheless have sites worthy of additional investigation. The Arizona site with greatest potential is near Sunset Crater, a basaltic volcano less than 1,000 years old several kilometers northeast of Flagstaff. Several silicic volcanoes nearby are young enough to have still-hot intrusive roots. Moreover, there is geophysical evidence for magma or hot rock in middle to lower crust beneath the area. A high level of interest in this area by the geothermal industry during the 1970s waned because surface thermal indicators, such as high heat flow, hot springs, and fumaroles are absent. The absence of these features is probably the result of a well-documented deep and pervasive regional aquifer, which likely creates a thermal barrier to the rise of hydrothermal activity from depth, Surface based geological and geophysical studies are under way to evaluate further the geothermal potential of the area and to locate a site for a drill hole to explore for a hydrothermal system beneath the ground-water barrier.

California, Nevada↗
USGS2008

Establishing major permeability controls in the Mak-Ban geothermal field, Philippines

Recent updating of the conceptual model of the Mak-Ban (Bulalo) geothermal field verified both structural and stratigraphic controls on permeability and connectivity in the reservoir. Two silicic units within the predominantly andesitic production zone were identified from borehole logs, core and drill cuttings. Whole rock chemical data and petrographic analysis confirmed two rhyolite units that consist of partially welded ash-flow tuffs and lava with primary devitrification and vapor-phase alteration textures typical of subaerial rhyolites. U/Pb dating of zircons from the units showed two distinct episodes of silicic volcanism at 352 ± 16 ka and 501 ± 12 ka, respectively. A recent drilling campaign allowed the running of more gamma ray (GR) in tandem with PTS logs. The logs validated the presence of two units with high GR response generally coinciding with permeable zones just below the interpreted top of the reservoir. Naphthalene disulfonate tracer testing defined a predominantly fault-controlled flow path of fluids from the edges of the field into the central production area. Fifteen to 25% of injected tracers were recovered in production wells over a five-year monitoring period. Peak arrival of tracer returns indicated average speeds between 0.1 to 1.3 m/hr, allowing for sufficient time for the fluids to heat up prior to re-emergence in production wells. Although faults are known to be important pathways in most geothermal reservoirs, the identification of specific structures with high connectivities in Mak-Ban provide an important insight on fluid migration from peripheral areas. This information is critical in preparing a reservoir management strategy for addressing the entry of cool marginal recharge into the center of the field.

Mak-Ban geothermal field↗