User:Twong/Sandbox CheckActivities2

From Open Energy Information

Coso Geothermal Area 132

 ExplorationTechniqueExpActivityDateExpActivityDateEndExplorationOutcomeExplorationBasisNotesReference material
2-M Probe Survey At Coso Geothermal Area (1977)2-M Probe Survey1977usefulCompare directly shallow temperature results with standard geothermal exploration techniques.Shallow soil temperature data (2m) were collected at 102 sites at Coso. Close geometrical similarity between the shallow soil temperature has been observed with the 30-m contour data for Coso using computer program.Rapid reconnaissance of geothermal prospects using shallow temperature surveys. Semi-annual technical report
2-M Probe Survey At Coso Geothermal Area (1979)2-M Probe Survey1979usefulCorrect previously analyzed 2-m probe dataCorrected 2-m temperature anomaly at Coso was compared with a low altitude aeromagnetic anomaly and an anomaly outlined by electrical resistivity methods obtained independently. Preliminary tests were made with a simple thermal conductivity probe demonstrating the feasibility of measuring soil thermal diffusivity at the time the 2-m temperatures are recorded.Rapid reconnaissance of geothermal prospects using shallow temperature surveys. Second technical report
2-M Probe Survey At Coso Geothermal Area (2007)2-M Probe Survey2007useful regional reconnaissanceAnalyze if coupling remote sensing and field data is effective for determining geothermal areas using 1-M probeThe field data include subsurface temperature measured with temperature probes at depths down to 1 m, surface temperatures recorded with a hand-held infrared camera and an infrared thermometer, reflectance of contrasting surfaces measured with a hand-held spectroradiometer for the purpose of estimating the albedo effect, and radiosonde atmospheric profiles of temperature, water vapor, and pressure in order to apply atmospheric corrections to the images.IN SEARCH FOR THERMAL ANOMALIES IN THE COSO GEOTHERMAL FIELD (CALIFORNIA) USING REMOTE SENSING AND FIELD DATA
Acoustic Logs At Coso Geothermal Area (1977)Acoustic Logs1977not indicatedAcoustic logs indicate fractured rock and potentially permeable zones.Geological and geophysical analysis of Coso Geothermal Exploration Hole No. 1 (CGEH-1), Coso Hot Springs KGRA, California
Static downhole characteristics of well CGEH-1 at Coso Hot Springs, China Lake, California
Acoustic Logs At Coso Geothermal Area (2005)Acoustic Logs2005not indicatedWell bore fracture analysisElectrical and acoustic image logs have been collected from well 58A-10 in crystalline rock on the eastern margin. Electrical image logs appear to be sensitive to variations in mineralogy, porosity, and fluid content that highlight both natural fractures and rock fabrics. These fabric elements account for about 50% of the total population of planar structures seen in the electrical image log, but locally approach 100%. Acoustic image logs reveal a similar natural fracture population, but generally image slightly fewer fractures, and do not reveal rock fabric. Both logs also record textural properties of deformed materials within fractures..COMPARISON OF ACOUSTIC AND ELECTRICAL IMAGE LOGS FROM THE COSO GEOTHERMAL FIELD, CA
Aerial Photography At Coso Geothermal Area (1968-1971)Aerial Photography19681971usefulFumarolic and hot springs activityColor photography has the greatest utility in locating areas of presently active thermal fluid leakage and in facilitating geologic interpretationRemote sensing survey of the Coso geothermal area, Inyo county, California. Technical publication 1968--1971
Aeromagnetic Survey At Coso Geothermal Area (1977)Aeromagnetic Survey1977useful regional reconnaissanceA detailed low-altitude aeromagnetic survey of 576 line-mi (927 line-km) was completed over a portion of the Coso Hot Springs KGRA. This survey defined a pronounced magnetic low that could help delineate the geothermal system that has an areal extent of approximately 10 sq mi (26 sq km) partially due to magnetite destruction by hydrothermal solutions associated with the geothermal system. The anomoly coincides with two other geophysical anomalies: 1) a bedrock electrical resistivity low and 2) an area of relatively high near-surface temperatures.Low-altitude aeromagnetic survey of a portion of the Coso Hot Springs KGRA, Inyo County, California
Aeromagnetic Survey At Coso Geothermal Area (1980)Aeromagnetic Survey1980not indicatedDense, magnetic rocks associated with a complex mafic pluton 9 km in diameter form a relatively impermeable north border of the Pleistocene volcanic field. A heat flow high nearly coincides with the west half of a 6-km-diameter magnetic low. A 2-km-diameter outcrop of a pre-Cenozoic silicic pluton, which has low magnetization compared to the surrounding metamorphic rocks, presumably typifies the rocks that underlie the magnetic low and heat flow high. Hydrothermal fluids may have destroyed some magnetite in the more magnetic wall rock, further reducing the magnetic intensity.Aeromagnetic and gravity surveys in the Coso Range, California
Analytical Modeling At Coso Geothermal Area (1980)Analytical Modeling1980not indicated1) Characterize a magma source. 2) To conduct reservoir modeling of a steam reservoir.1) Closed-form analytical solutions for the conduction heat transfer from various idealized magma geometries (dikes, sills, and spheres) are obtained using either the Schwarz-Christoffel transformation theorem (dikes and sills) or the ‘method of images’ with superposition (spheres). Comparison of these analytically determined heat flux distributions with field data from active geothermal areas at Yellowstone, Avachinsky volcano, Kilauea Iki, and the Coso geothermal area indicates that these fields may be conduction dominant over certain depths. 2) Modeling was undertaken to test the hypothesis that a steam-filled fracture geothermal reservoir exists at Coso Hot Springs. The reservoir proposed in this study was modeled at a cylindrical disk of radius 12,500 ft., height 5000 ft., depth 5000 ft., and steam-filled porosity of 5%.Thermal techniques for characterizing magma body geometries
Exploration model for possible geothermal reservoir, Coso Hot Springs KGRA, Inyo Co. , California
Audio-Magnetotellurics At Coso Geothermal Area (1977)Audio-Magnetotellurics1977not indicatedTo investigate electrical properties of rocks associated with thermal phenomena of the Devil's Kitchen-Coso Hot Springs areaAudio-magnetotelluric geophysical surveys determined that the secondary low in the geothermal area, best defined by the 7.5-Hz AMT map and dc soundings, is caused by a shallow conductive zone (5--30 ohm m) interpreted to be hydrothermally altered Sierra Nevada basement rocks containing saline water of a hot water geothermal system. This zone of lowest apparent resistivities over the basement rocks lies within a closed contour of a heat flow anomaly where all values are greater than 10 heat flow units.Schlumberger soundings, audio-magnetotelluric soundings and telluric mapping in and around the Coso Range, California
Reconnaissance electrical surveys in the Coso Range, California
Compound and Elemental Analysis At Coso Geothermal Area (1991)Compound and Elemental Analysis1991usefulDetermine the fluid origin by looking at variations in dissolved gas compositions of reservoir fluidsGas concentrations and ratios in 110 analyses of geothermal fluids from 47 wells in the Coso geothermal system illustrate the complexity of this two-phase reservoir in its natural state. Two geographically distinct regions of single-phase (liquid) reservoir are present and possess distinctive gas and liquid compositions. Steam sampled from wells in the central and southwestern Coso reservoir is unusually enriched in both H2S and H2. Such a large enrichment in both a soluble and insoluble gas cannot be produced by boiling of any liquid yet observed in single-phase portions of the field. In agreement with an upflow-lateral mixing model for the Coso field, at least three end-member thermal fluids having distinct gas and liquid compositions appear to have interacted (through mixing, boiling and steam migration) to produce the observed natural state of the reservoir.Variations in dissolved gas compositions of reservoir fluids from the Coso geothermal field
Compound and Elemental Analysis At Coso Geothermal Area (2004)Compound and Elemental Analysis2004usefulIn order to test FIS for geothermal exploration, drill chips from Coso well 83-16 were analyzed, which were selected at 1000 ft intervals by Joseph Moore. Sequential crushes done by the CFS (crushfast-scan) method (Norman 1996) show that chips have a high density of homogeneous fluid inclusions. Analyses were averaged and plotted verses depth (Fig. 4), and interpreted. Fluid inclusion gas analyses done on vein minerals from drill hole 68-6 that were earlier analyzed (Adams 2000) were plotted for comparison in order to confirm that similar analyses are obtained from chips and vein minerals.Gas Analysis Of Geothermal Fluid Inclusions- A New Technology For Geothermal Exploration
Conceptual Model At Coso Geothermal Area (1980)Conceptual Model1980not indicated1) Estimate thermal regime and thermal potential of the system. 2) Use field mapping to develop a model of the reservoir system.1) The seismograms of 44 events recorded by the telemetered array and nine events by the Centipede array were analyzed using the reduced spectral ratio technique to determine the differential attenuation factor delta t* for the events recorded with the highest signal-to-noise ratio. 2) Arcuate faults in the Coso Range are interpreted to have been produced by the regional stress field rather than to have been of volcanogenic origin. Focal mechanisms of small-magnitude earthquakes support the stress directions indicated by local fault patterns. Fumeroles in the area are primarily associated with oblique slip faults rather than with arcuate or ring faults. The geothermal reservoir is therefore much different from that of a caldera or subsidence bowl, and the overall geothermal potential is probably less than earlier estimates.Three-dimensional Q (super -1) model of the Coso Hot Springs known geothermal resource area (in Coso geothermal area)
Structure, tectonics and stress field of the Coso Range, Inyo County, California
Conceptual Model At Coso Geothermal Area (1990)Conceptual Model1990usefulTo develop an understanding of the fracture hydrology of the Coso Mountains crystalline terrain and its hydrologic connection to regional groundwater and thermal sourceAn interpreted, conceptually balanced regional cross section that extends from the Sierra Nevada through the geothermal reservoir to the Panamint Mountains is presented. The cross section is constrained by new reflection and refraction seismic data, gravity and magnetic modeling, drilling data from the geothermal reservoir, and published regional geologic mapping. The interpretation presented in the cross section and the geochemistry of the reservoir fluids is used to argue that the geothermal system is a thermal bulge on an otherwise normal fracture-controlled regional groundwater flow.Tectonic setting of the Coso geothermal reservoir
Conceptual Model At Coso Geothermal Area (2005)Conceptual Model2005not indicatedDevelop a conceptual model of the Coso areaInvestigation of the Coso Range using seismicity, gravity, and geochemistry of rocks and fluids, supports the interpretation that the structure hosting the geothermal resource is a nascent metamorphic core complex. The structural setting is a releasing bend in a dextral strike-slip system that extends from the Indian Wells Valley northward into the Owens Valley. This tectonic setting results in NW-directed transtension, which is accommodated by normal and strike-slip faulting of the brittle upper 4–6 km of the crust, and shearing and ductile stretching below this depth, accompanied by shallow igneous intrusions.The Coso geothermal field: A nascent metamorphic core complex
Conceptual Model At Coso Geothermal Area (2005-2007)Conceptual Model20052007usefulDetermine most productive areas of geothermal field using stress and faulting analysis to develop a geomechanical modelNew geologic mapping and measurements of stress orientations and magnitudes from wells 34-9RD2 and 58A-10 were integrated with existing data sets to refine a geomechanical model for the Coso geothermal field. Vertically averaged stress orientations across the field are fairly uniform and are consistent with focal mechanism inversions of earthquake clusters for stress and incremental strain. Active faults trending NNW-SSE to NNE-SSW are well oriented for normal slip in the current stress field, where the mean Shmin orientation is 108V0± 240 in a transitional strike-slip to normal faulting stress regime. These results together with stress magnitudes measured in the East Flank of the field suggest that the most productive portions are in stress environments conducive to normal faulting.Controls on Fault-Hosted Fluid Flow: Preliminary Results from the Coso Geothermal Field, CA
STRESS AND FAULTING IN THE COSO GEOTHERMAL FIELD: UPDATE AND RECENT RESULTS FROM THE EAST FLANK AND COSO WASH
Stress and fault rock controls on fault zone hydrology, Coso geothermal field, CA
Conceptual Model At Coso Geothermal Area (2006)Conceptual Model2006usefulDetermine boiling zones and their relation to production zones by developing a fluid modelA fluid model for the Coso geothermal reservoir is developed from Fluid Inclusion Stratigraphy (FIS) analyses. Fluid inclusion gas chemistry in well cuttings collected at 20 ft intervals is analyzed and plotted on well log diagrams. Models are created using cross-sections and fence diagrams.FLUID STRATIGRAPHY OF THE COSO GEOTHERMAL RESERVOIR
Core Analysis At Coso Geothermal Area (1979)Core Analysis1979usefulCompare microcracks between Coso and Raft River geothermal areasMicrocracks were observed in core samples from Coso. Both permeability and electrical conductivity were measured for a suite of samples with a range of microcracks characteristics. A partial set of samples were collected to study migration of radioactive elements.Microcrack technology. Progress report, 1 October 1978--31 March 1979
Core Analysis At Coso Geothermal Area (1980)Core Analysis1980not indicatedDetermine the heat transfer mechanismIn an investigation of the thermal regime of this Basin and Range geothermal area, temperature measurements were made in 25 shallow and 1 intermediate depth borehole. Thermal conductivity measurements were made on 312 samples from cores and drill cuttings. The actual process by which heat is transferred is rather complex; however, the heat flow determinations can be divided into two groups. The first group, less than 4.0 HFU, are indicative of regions with primarily conductive regimes, although deep-seated mass transfer is implied. The second group, greater than 4.0 HFU, are characteristics of regions with considerable convective heat transfer in the shallow subsurface.Heat flow in the Coso geothermal area, Inyo County, California
Cuttings Analysis At Coso Geothermal Area (1977)Cuttings Analysis1977not indicatedChip samples were collected at ten foot intervals.Geological and geophysical analysis of Coso Geothermal Exploration Hole No. 1 (CGEH-1), Coso Hot Springs KGRA, California
Static downhole characteristics of well CGEH-1 at Coso Hot Springs, China Lake, California
Cuttings Analysis At Coso Geothermal Area (1980)Cuttings Analysis1980not indicatedDetermine the heat transfer mechanismIn an investigation of the thermal regime of this Basin and Range geothermal area, temperature measurements were made in 25 shallow and 1 intermediate depth borehole. Thermal conductivity measurements were made on 312 samples from cores and drill cuttings. The actual process by which heat is transferred is rather complex; however, the heat flow determinations can be divided into two groups. The first group, less than 4.0 HFU, are indicative of regions with primarily conductive regimes, although deep-seated mass transfer is implied. The second group, greater than 4.0 HFU, are characteristics of regions with considerable convective heat transfer in the shallow subsurface.Heat flow in the Coso geothermal area, Inyo County, California
Cuttings Analysis At Coso Geothermal Area (1985-1987)Cuttings Analysis19851987usefulAnalyze an indicator of high permeability zones within a geothermal fieldPetrographic and geochemical analyses of cuttings from six wells in the Coso Hot Springs geothermal field show a systematic variation in the occurrence, texture, and composition of sericite that can be correlated with high permeability production zones and temperature. The wells studied intersect rhyolitic dikes and sills in the fractured granitic and dioritic basement rocks which serve as the reservoir for the geothermal system. Low-permeability non-productive zones in the wells contain coarse-grained compositionally homogeneous primary muscovite. High-permeability production zones are characterized by abundant fine-grained hydrothermal sericite that exhibits a systematic increase in K and Al and decrease in Si with increasing temperature. These calculations suggest that hydrothermal sericites are in local equilibrium with the geothermal fluid, but primary muscovites in low permeability zones are metastable.Correlation of hydrothermal sericite composition with permeability and temperature, Coso Hot Springs geothermal field, Inyo County, California
Variation in sericite composition from fracture zones within the Coso Hot Sprints geothermal system
Cuttings Analysis At Coso Geothermal Area (2003)Cuttings Analysis2003not indicated1) Fracture/stress analysis 2) Determine the EGS potential of Coso Geothermal Region1) Petrologic analyses of cuttings from several wells are used to construct a vein-mineral paragenesis of the Coso east flank. 2) Cuttings collected during the drilling of each of the four east-flank study wells are used to determine the lithologies of the hydrothermally altered zones, the characteristics of the vein fillings, and the extent of large-scale faulting.The Coso EGS Project, recent developments (in International collaboration for geothermal energy in the Americas)
IN SITU STRESS, FRACTURE AND FLUID FLOW ANALYSIS-EAST FLANK OF THE COSO GEOTHERMAL FIELD
Cuttings Analysis At Coso Geothermal Area (2005)Cuttings Analysis2005not indicatedEGS well analysis for fractures to determine the geologic framework of the east flank of the fieldThis paper summarizes petrologic and geologic investigations on two East Flank wells, 34A-9 and 34-9RD2 conducted as part of a continuing effort to better understand how the rocks will behave during hydraulic and thermal stimulation. Well 34A-9 is the hottest well at depth in the East Flank, reaching nearly 350 0C. The reservoir on the East Flank is dominated by diorite and granodiorite.GEOLOGIC FRAMEWORK OF THE EAST FLANK, COSO GEOTHERMAL FIELD: IMPLICATIONS FOR EGS DEVELOPMENT
Cuttings Analysis At Coso Geothermal Area (2006)Cuttings Analysis2006not indicatedTo determine the geology of Injection Well 46A-19RDWell 46A-19RD, located in the southwestern portion of this field is currently the focus of a DOE-funded Enhanced Geothermal Systems (EGS) project. Petrologic and petrographic investigations of the well show that quartz diorite and granodiorite are dominant lithologies. Dikes of granophyre, containing phenocrysts of plagioclase, potassium feldspar, and quartz were encountered at approximately 1438-1457 m and 3459.5-3505.2 m.Geology of Injection Well 46A-19RD in the Coso Enhanced Geothermal Systems Experiment
DC Resistivity Survey (Dipole-Dipole Array) At Coso Geothermal Area (1977)DC Resistivity Survey (Dipole-Dipole Array)1977useful regional reconnaissanceDetailed electrical resistivity survey for a 54 line-km. This survey has defined a bedrock resistivity low at least 4 sq mi (10 sq km) in extent; survey data indicate that a 10 to 20 ohm-meter zone extends from near surface to a depth greater than 750 meters.Dipole-dipole resistivity survey of a portion of the Coso Hot Springs KGRA, Inyo County, California
DC Resistivity Survey (Schlumberger Array) At Coso Geothermal Area (1977)DC Resistivity Survey (Schlumberger Array)1977not indicatedTo investigate electrical properties of rocks associated with thermal phenomena of the Devil's Kitchen-Coso Hot Springs area18 USGS Schlumberger soundings and 6 Schlumberger soundings by Furgerson (1973) were plotted and automatically processed and interpretedSchlumberger soundings, audio-magnetotelluric soundings and telluric mapping in and around the Coso Range, California
Data Acquisition-Manipulation At Coso Geothermal Area (1979)Data Acquisition-Manipulation1979not indicatedDetermine the potential electrical power in the areaThe analysis was concentrated on identifying the major sources of surface and ground water, potential limitations on the usage of this water, and the resulting constraints on potentially developable electrical power in each geothermal resource area.Regional Systems Development for Geothermal Energy Resources Pacific Region (California and Hawaii). Task 3: water resources evaluation. Topical report
Data Acquisition-Manipulation At Coso Geothermal Area (1980)Data Acquisition-Manipulation1980usefulFault mapping in geothermal area to determine the seismicity of the Coso RangeThe rhyolite field has a significantly higher b value of 1.26 +- 0.16; if only the shallow events (depth <5 km) are used in the calculation, the b value for this area becomes even higher, 1.34 +- 0.24. The higher b values were interpreted as reflecting the existence of short average fault lengths (<5 km) within the rhyolite field. The seismic data and other data suggest that the fault system lying between the rhyolite field and the adjacent Coso Basin is an important tectonic boundary. Present information is insufficient to determine the geothermal production capability of this fault system, but this does suggest that the system is a good target for further exploration.Seismicity of the Coso Range, California
Data Acquisition-Manipulation At Coso Geothermal Area (1982)Data Acquisition-Manipulation1982usefulDevelop parameters to identify geothermal regionStatistical methods are outlined to separate spatially, temporally, and magnitude-dependent portions of both the random and non-random components of the seismicity. The methodology employed compares the seismicity distributions with a generalized Poisson distribution. Temporally related events are identified by the distribution of the interoccurrence times. From the temporal characteristics of the seismicity associated with these regions, a general discriminant was constructed that combines several physical parameters for identifying the presence of a geothermal system.Statistical study of seismicity associated with geothermal reservoirs in California
Development Wells At Coso Geothermal Area (1985)Development Wells1985not indicatedThree wells have been drilled by the Los Angeles Department of Water and Power at the Coso Hot Springs KGRA.Long-Term Testing of Geothermal Wells in the Coso Hot Springs KGRA
Direct-Current Resistivity Survey At Coso Geothermal Area (1977)Direct-Current Resistivity Survey1977useful regional reconnaissanceTo investigate electrical properties of rocks associated with thermal phenomena of the Devil's Kitchen-Coso Hot Springs areaDC resistivity geophysical surveys determined that the secondary low in the geothermal area, best defined by the 7.5-Hz AMT map and dc soundings, is caused by a shallow conductive zone (5--30 ohm m) interpreted to be hydrothermally altered Sierra Nevada basement rocks containing saline water of a hot water geothermal system. This zone of lowest apparent resistivities over the basement rocks lies within a closed contour of a heat flow anomaly where all values are greater than 10 heat flow units.Schlumberger soundings, audio-magnetotelluric soundings and telluric mapping in and around the Coso Range, California
Reconnaissance electrical surveys in the Coso Range, California
Electric Micro Imager Log At Coso Geothermal Area (2003)Single-Well and Cross-Well Resistivity2003not indicatedFracture/stress analysisA preliminary fracture/stress analysis was conducted for the recently drilled well 38C-9 as part of a continuing effort to characterize the stress state within the east flank of the Coso geothermal field. Electric Micro Imager (EMI) data were analyzed over the logged interval of 5,881-9,408 ft. Naturally occurring fractures were analyzed in order to determine both fracture dip and azimuth. Drilling induced tensile fractures were used to determine that the orientation of the maximum horizontal stress is 140 + or -160. However, this is approximate as the data have to be corrected for well-bore deviation.The Coso EGS Project, recent developments (in International collaboration for geothermal energy in the Americas)
Electrical Resistivity At Coso Geothermal Area (1972)Direct-Current Resistivity Survey1972usefulIdentify drilling sites for explorationElectrical resistivity studies outline areas of anomalously conductive ground that may be associated with geothermal activity and assist in locating drilling sites to test the geothermal potential.Progress report on electrical resistivity studies, COSO Geothermal Area, Inyo County, California
Exploratory Well At Coso Geothermal Area (1967)Exploratory Well1967usefulHot springs activity in the regionCoso Hot Springs well No. 1 drilled to 114.3 m.Chemical analyses and preliminary interpretation of waters collected from the CGEH No. 1 geothermal well at Coso, California
Exploratory Well At Coso Geothermal Area (1977-1978)Exploratory Well19771978useful1477-m Coso Geothermal Exploration Hole (CGEH) No. 1 well drilled .The objective of well and future well testing is to determine the well productivity and geothermal reservoir parameters.Operations plan Coso geothermal exploratory hole No. 1 (CGEH-1)
Testing operations plan: Coso Geothermal Exploratory Hole No. 1 (CGEH-1)
COSO Geothermal Exploratory Hole No. 1, CGEH No. 1. Completion report. (Coso Hot Springs KGRA)
Fault Mapping At Coso Geothermal Area (1980)Fault Mapping1980usefulTo determine the Late Cenozoic volcanism, geochronology, and structure of the Coso RangeThis system apparently is heated by a reservoir of silicic magma at greater than or equal to 8-km depth, itself produced and sustained through partial melting of crustal rocks by thermal energy contained in mantle-derived basaltic magma that intrudes the crust in repsonse to lithospheric extension.Late Cenozoic volcanism, geochronology, and structure of the Coso Range, Inyo County, California
Field Mapping At Coso Geothermal Area (1968-1971)Field Mapping19681971usefulFumarolic and hot springs activitySnowmelt patterns has the greatest utility in locating areas of presently active thermal fluid leakageRemote sensing survey of the Coso geothermal area, Inyo county, California. Technical publication 1968--1971
Field Mapping At Coso Geothermal Area (1977-1978)Field Mapping19771978not indicatedHydrogeologic investigation of Coso hot springs was conducted by field examination of geologic rock units and springs and other features of hydrologic significance and sampling of waters for chemical analysis; determination of the local Coso Hot Springs and regional groundwater hydrology, including consideration of recharge, discharge, movement, and water quality; determination of the possible impact of large-scale geothermal development on Coso Hot Springs.Hydrogeologic investigation of Coso Hot Springs, Inyo County, California. Final report October 1977--January 1978
Field Mapping At Coso Geothermal Area (1978)Field Mapping1978not indicatedGeology and alteration mapping analyzed exposed rocks in geothermal region. Neither geologic mapping nor deep drilling have revealed potential deep primary aquifers. Surface alteration at Coso is of three main types: (1) clay-opal-alunite alteration, (2) weak argillic alteration, and (3) stockwork calcite veins and veinlets, which are locally associated with calcareous sinter.Geology and alteration of the Coso Geothermal Area, Inyo County, California
Field Mapping At Coso Geothermal Area (1980)Field Mapping1980not indicatedDetermine the areal extent of the magma reservoirThe distribution of quaternary rhyolite dome of the Coso Range was analyzed. Thirty-eight separate domes and flows of phenocryst-poor, high-silica rhyolite of similar major element chemical composition were erupted over the past 1 m.y. from vents arranged in a crudely S-shaped array atop a granitic horst in the Coso Range, California. The immediate source of heat for the surficial geothermal phenomena is probably a silicic magma reservoir that may still contain molten or partially molten material at a depth of around 8 km beneath the central part of the rhyolite field. Outlying rhyolite extrusions probably reflect the presence of feeder dikes emanating from the reservoir beneath the central region. Azimuths of dikes appear to be parallel to the regional tectonic axis of maximum horizontal compression, analogous to some dike-fed flank eruptions on basaltic shields and andesitic strato-volcanoes.Distribution of quaternary rhyolite dome of the Coso Range, California: Implications for extent of the geothermal anomaly
Field Mapping At Coso Geothermal Area (1999)Field Mapping1999not indicatedDevelop an understanding of the sedimentology and stratigraphy of well-exposed Cenozoic sedimentary strataA detailed sedimentation and tectonics study of the Coso Formation was undertaken to provide a more complete picture of the development of the Basin and Range province in this area. Detailed mapping and depositional analysis distinguishes separate northern and southern depocenters, each with its own accommodation and depositional history.Geologic Study of the Coso Formation
Field Mapping At Coso Geothermal Area (2001-2003)Field Mapping20012003not indicatedDetermine structural control on permeability and fluid productionNew multifold seismic reflection data from the Coso geothermal field in the central Coso Range, eastern California, image brittle faults and other structures in a zone of localized crustal extension between two major strike-slip faults. Production in the Coso field primarily occurs in the hanging walls of the listric faults.NEW SEISMIC IMAGING OF THE COSO GEOTHERMAL FIELD, EASTERN CALIFORNIA
Upper crustal faulting in an obliquely extending orogen, structural control on permeability and production in the Coso Geothermal Field, eastern California
Upper crustal structure of an obliquely extending orogen, central Coso Range, eastern California
Field Mapping At Coso Geothermal Area (2006)Field Mapping2006not indicatedDetermine impact of brittle faulting and seismogenic deformation on permeability in geothermal reservoirNew mapping documents a series of late Quaternary NNE-striking normal faults in the central Coso Range that dip northwest, toward and into the main production area of the Coso geothermal field. The faults exhibit geomorphic features characteristic of Holocene activity, and locally are associated with fumaroles and hydothermal alteration. The active faults sole into or terminate against the brittle-ductile transition zone (BDT) at a depth of about 4 to 5 km.Active Faulting in the Coso Geothermal Field, Eastern California
Field Mapping At Coso Geothermal Area (2010)Field Mapping2010not indicatedTo determine if there is geothermal potential in the South RangesIt has been believed that the South Ranges at China Lake may host geothermal resources for several decades. Recent Garlock Fault mapping, associated thermochronology work and a well documented but geologically unresolved steaming well to the west suggests that the South Ranges should be investigated for geothermal potential. In 2009, GPO awarded a contract to the University of Kansas to follow through on detailed mapping, trenching, dating and thermochronoloy in the Lava Mountains and the southern Slate Range region of the South Ranges to see if a geothermal resource might exist. A TGH drilling campaign may be initiated in the South Ranges in 2011.Navy’s Geothermal Program Office: Overview of Recovery Act (ARRA) Funded Exploration in CA and NV and other Exploration Projects
Flow Test At Coso Geothermal Area (1978)Flow Test1978not indicatedFlow tests of well CGEH No. 1 were conducted. LBL performed eight temperature surveys after completion of the well to estimate equilibrium reservoir temperatures. Downhole fluid samples were obtained by the U.S. Geological Survey (USGS) and Lawrence Berkeley Laboratory (LBL), and a static pressure profile was obtained. The first test began September 5, 1978 using nitrogen stimulation to initiate flow; this procedure resulted in small flow and subsequent filling of the bottom hole with drill cuttings. The second test, on November 2, 1978, utilized a nitrogen-foam-water mixture to clean residual particles from bottom hole, following which nitrogen was again used to stimulate the well. The well remained dry after stimulation. Water influx was calculated at 4-5 gal/min as the well filled after unloading of the wellbore.Evaluation of Coso Geothermal Exploratory Hole No. 1 (CGEH-1) Coso Hot Springs: KGRA, China Lake, CA
Flow Test At Coso Geothermal Area (1985-1986)Flow Test19851986not indicatedUnderstand the connectivity of the production and injection wells.A long-term flow test was conducted involving one producing well (well 43-7), one injector (well 88-1), and two observation wells (well 66-6 and California Energy Co’s well 71A-7). The flow test included a well production metering system and a water injection metering system.Long-Term Testing of Geothermal Wells in the Coso Hot Springs KGRA
Fluid Inclusion Analysis At Coso Geothermal Area (1990)Fluid Inclusion Analysis1990not indicatedA system for analysis of inclusion gas contents based upon quadrupole mass spectrometry has been designed, assembled and tested during the first seven months of funding. The system is currently being tested and calibrated using inclusions with known gas contents from active geothermal systems.Volatiles in hydrothermal fluids- A mass spectrometric study of fluid inclusions from active geothermal systems
Fluid Inclusion Analysis At Coso Geothermal Area (1996)Fluid Inclusion Analysis1996not indicatedFluid inclusion homogenization temperatures and salinities demonstrate that cool, low salinity ground waters were present when the thermal plume was emplaced. Dilution of the thermal waters occurred above and below the plume producing strong gradients in their compositions. Comparison of mineral and fluid inclusion based temperatures demonstrates that cooling has occurred along the margins of the thermal system but that the interior of the system is still undergoing heating.Integrated mineralogical and fluid inclusion study of the Coso geothermal systems, California
Fluid Inclusion Analysis At Coso Geothermal Area (1999)Fluid Inclusion Analysis1999not indicatedWell and steam sample comparisonVein and alteration assemblages from eight Coso wells have been collected and their fluid-inclusion gases analyzed by quadrupole mass spectrometry. Four major types of alteration were sampled: 1) young calcite-hematite-pyrite veins; 2) wairakite or epidote veins and alteration that are spatially associated with deep reservoirs in the main field and eastern wells; 3) older sericite and pyrite wallrock alteration; and 4) stilbite-calcite veins that are common in cooler or marginal portions of the geothermal area. The gas compositions of the fluid inclusions display systematic differences among the secondary assemblages. This signature is similar to the present-day gas analyses from steam samples taken from both the Devil’s Kitchen fumarole area and from Coso production wells.TRACING FLUID SOURCES IN THE COSO GEOTHERMAL SYSTEM USING FLUID-INCLUSION GAS CHEMISTRY
Fluid Inclusion Analysis At Coso Geothermal Area (2002)Fluid Inclusion Analysis2002usefulAnalyses were averaged and plotted verses depth (Figure 4). Fluid inclusion gas analyses done on vein minerals from drill hole 68-6 that we earlier analyzed (Adams 2000) were plotted for comparison in order to confirm that similar analyses are obtained from chips and vein minerals. This comparison is far from ideal. The drill holes are better than a kilometer apart, samples analyzed in the two bore holes are not from the same depths, and the chip analyses were performed on the new dual quadrupole system that yields improved H2,He, and organic compound analyses.New Applications Of Geothermal Gas Analysis To Exploration
Fluid Inclusion Analysis At Coso Geothermal Area (2003)Fluid Inclusion Analysis2003not indicated1) Fracture/stress analysis. 2)To determine the driver of the relationship between hydrogen and organic species.1) Fluid inclusion analyses of cuttings from well 83-16 were used to determine the temperatures of vein mineralization. 2) Measurement of organic compounds in fluid inclusions shows that there are strong relationships between H2 concentrations and alkane/alkene ratios and benzene concentrations. Inclusion analyses that indicate H2 concentrations > 0.001 mol % typically have ethane > ethylene, propane > propylene, and butane > butylene. There are three end member fluid compositions that were identified: type one fluids in which alkane compounds predominate, type two fluids that have ethane and propylene and no ethylene and propane, and type three fluids that have propylene and butylene and no propane or butane. The change in alkane/alkene ratios downhole would be reversed if the reactions were temperature driven. Calculations explain why benzene is a common constituent of geothermal fluids.The Coso EGS Project, recent developments (in International collaboration for geothermal energy in the Americas)
ORGANIC SPECIES IN GEOTHERMAL WATERS IN LIGHT OF FLUID INCLUSION GAS ANALYSES
Fluid Inclusion Analysis At Coso Geothermal Area (2004)Fluid Inclusion Analysis2004not indicated1) To determine if analyses of fluid propene and propane species in fluid inclusions can be used to interpret fluid type, history, or process. 2) To evaluate the geology and thermal history of the East Flank, in order to better understand how the rocks will behave during hydro-fracturing.1) Analyses were performed on drill cuttings at 20ft intervals from four Coso geothermal wells. Two wells are good producers, one has cold-water entrants in the production zone, and the fourth is a non-producer. The ratios show distinct differences between producing and the non-producing wells. Propane dominate fluids are associated with cool water entrants. 2) Fluid inclusion studies were implemented to separate different thermal events. Fluid inclusions were studied from three wells: 83-16, 38B-9, and core hole 64-16. Inclusions from calcite, quartz, feldspar, and epidote were studied. Quartz- and calcite-hosted inclusions from the upper 256m in 64-16 are characterized by salinities usually less than approximately 2 weight % NaCl equivalent and homogenization temperatures that differ by less than ~15 0C from the down hole measurements.GEOTHERMAL FLUID PROPENE AND PROPANE: INDICATORS OF FLUID
GEOLOGY AND MINERAL PARAGENESIS STUDY WITHIN THE COSO-EGS PROJECT
Fluid Inclusion Analysis At Coso Geothermal Area (2004-2005)Fluid Inclusion Analysis20042005usefulDetermine if fluid inclusion stratigraphy is applicable to geothermalFluid Inclusion Stratigraphy (FIS) is a new technique developed for the oil industry in order to map borehole fluids.Fluid inclusion gas geochemistry is analyzed and plotted on well log diagrams. The working hypothesis is that select gaseous species and species ratios indicate areas of groundwater and reservoir fluid flow and reservoir seals. Analyses from multiple boreholes should show the stratigraphy of subsurface fluids. Approximately 1,700 samples from three producing and one non-producing well have been analyzed. Preliminary results show megascopic trends and much fine scale detail when the logs are analyzed in detail.FLUID INCLUSION STRATIGRAPHY: NEW METHOD FOR GEOTHERMAL RESERVOIR ASSESSMENT PRELIMINARY RESULTS
IDENTIFYING FRACTURES AND FLUID TYPES USING FLUID INCLUSION STRATIGRAPHY
DISPLAYING AND INTERPRETING FLUID INCLUSION STRATIGRAPHY ANALYSES ON MUDLOG GRAPHS
Fluid Inclusion Analysis At Coso Geothermal Area (2005-2006)Fluid Inclusion Analysis20052006not indicatedInclude more wells from previous analysisThis paper focuses on the interpretation of the additional wells (4 bore holes) and comparison to the previous wells. Preliminary correlation between wells is also presented. Analyses from multiple boreholes show fluid stratigraphy that correlates from well to well. The wells include large producers, small to moderate producers, problem producers, injectors, and non producersFluid Inclusion Stratigraphy: Interpretation of New Wells in the Coso Geothermal Field
Fluid Stratigraphy and Permeable Zones of the Coso Geothermal Reservoir
Fluid Inclusion Analysis At Coso Geothermal Area (Norman & Moore, 2004)Fluid Inclusion Analysis2004usefulTo determine effectiveness of FIS for geothermal explorationIn order to test FIS for geothermal exploration, drill chips were analyzed from Coso well 83-16, which were selected at 1000 ft intervals by Joseph Moore. Sequential crushes done by our CFS (crushfast-scan) method (Norman 1996) show that chips have a high density of homogeneous fluid inclusions. Analyses were averaged and plotted verses depth, and interpreted. Fluid inclusion gas analyses done on vein minerals from drill hole 68-6 that were analyzed earlier (Adams 2000) were plotted for comparison in order to confirm that similar analyses are obtained from chips and vein minerals. It is apparent that fluid inclusion analysis detects a change in gas K466 chemistry at about 5500 ft, which is the top of the Coso production zone.Gas Analysis Of Geothermal Fluid Inclusions- A New Technology For Geothermal Exploration
Gamma Log At Coso Geothermal Area (1977)Gamma Log1977not indicatedextensive geophysical logging surveys were conducted: natural gamma and neutron porosity logs indicate gross rock typeGeological and geophysical analysis of Coso Geothermal Exploration Hole No. 1 (CGEH-1), Coso Hot Springs KGRA, California
Static downhole characteristics of well CGEH-1 at Coso Hot Springs, China Lake, California
Geothermal Literature Review At Coso Geothermal Area (1984)Geothermal Literature Review1984not indicatedTo characterize the magma beneath melt zonesThe melt zones of volcanic clusters were analyzed with recent geological and geophysical data for five magma-hydrothermal systems. These were studied for the purpose of developing estimates for the depth, volume and location of magma beneath each area.Melt zones beneath five volcanic complexes in California: an assessment of shallow magma occurrences
Geothermal Literature Review At Coso Geothermal Area (1985)Geothermal Literature Review1985not indicatedNeed to develop a reservoir model for CosoAnalysis of complex geothermal system was done by looking at the available data on the Coso Geothermal FieldCoso: example of a complex geothermal reservoir. Final report, 1984-1985
Geothermal Literature Review At Coso Geothermal Area (1987)Geothermal Literature Review1987not indicatedCompare multiple theories of the structural control of the geothermal systemThe geothermal system appears to be associated with at least one dominant north-south-trending feature which extends several miles through the east-central portion of the Coso volcanic field. The identified producing fractures occur in zones which range from 10 - 100s of feet in extent, separated by regions of essentially unfractured rock of similar composition. Wells in the Devil's Kitchen area have encountered fluids in excess of 4500F and flow rates of 1 million lb/hr at depths less than 4000 ft.Structural interpretation of Coso Geothermal field, Inyo County, California
Structural interpretation of the Coso geothermal field. Summary report, October 1986-August 1987
Geothermometry At Coso Geothermal Area (1978)Geothermometry1978usefulDetermine fluid origin in two exploratory wellsCollected water from original coso hot springs well (1967) and CGEH No. 1. and completed chemical analysis to determine fluid origin. The surface expression of fumarole and acid sulfate pools and shallow steam wells gives a false indication of an extensive vapor dominated system because upward convecting, boiling alkaline-chloride waters do not reach the surface.Chemical analyses and preliminary interpretation of waters collected from the CGEH No. 1 geothermal well at Coso, California
Geothermometry At Coso Geothermal Area (1980)Geothermometry1980usefulFluid temperature of feed waterCation and sulfate isotope geothermometers indicate that the reservoir feeding water to the Coso Hot Spring well has a temperature of about 240 -250 C, and the reservoir feeding the CGEH well has a temperature of about 205 C. The variation in the chemical composition of water from the two wells suggests a model in which water-rock chemical equilibrium is maintained as a convecting solution cools from about 245-205 C by conductive heat loss.Interpretation of chemical analyses of waters collected from two geothermal wells at Coso, California
Ground Gravity Survey At Coso Geothermal Area (1980)Ground Gravity Survey1980not indicatedThe effect of an underlying magma reservoir cannot be identified within the complex gravity pattern in the Coso Range, California. Rather, linear gravity contours, which suggest a regional tectonic origin, enclose the location of most of the volcanic activity of the Coso Range.Aeromagnetic and gravity surveys in the Coso Range, California
Ground Gravity Survey At Coso Geothermal Area (1990)Ground Gravity Survey1990not indicatedTo identify features related to the heat source and to seek possible evidence for an underlying magma chamber2D and 3D gravity modeling was done using gridded Bouguer gravity data covering a 45 by 45 km region over the Coso geothermal area. Isostatic and terrain corrected Bouguer gravity data for about 1300 gravity stations were obtained from the US Geological Survey. After the data were checked, the gravity values were gridded at 1 km centers for the area of interest centered on the Coso volcanic field. A 3D iterative approach was used to find the thicknesses of both units.A gravity model for the Coso geothermal area, California
Ground Magnetics At Coso Geothermal Area (1984)Ground Magnetics1984usefulThe magnetic intensity contours match general geologic patterns in varying rock types. Hydrothermally altered rocks along intersecting fault zones show up as strong magnetic lows that form a triangular-shaped area. This area is centered in an area of highest heat flow and is a site of concentrated fumarolic activity. In the Coso volcanic field the combination of high heat flow, fumarolic activity, magnetic lows, and hydrothermal alteration along faults suggests that hot fluid filled fractures with high permeability.Ground magnetic survey in the Coso Range, California
Image Logs At Coso Geothermal Area (2004)Image Logs2004not indicatedEGS potential of Coso Geothermal RegionDuring the second year of this project, wellbore logs and stress data were acquired in a new production well drilled in the Coso Geothermal Field, 38C-9. The image analysis results include the discrimination of natural from drilling induced fractures in wellbore image data, natural fracture characterization, and wellbore failure analysisIN SITU STRESS, FRACTURE, AND FLUID FLOW ANALYSIS IN WELL 38C-9:AN ENHANCED GEOTHERMAL SYSTEM IN THE COSO GEOTHERMAL FIELD
Image Logs At Coso Geothermal Area (2011)Image Logs2011usefulDetermine crustul stress heterogeneityBorehole induced structures in image logs of wells from the Coso Geothermal Field (CGF) record variation in the azimuth of principal stress. Image logs of these structures from five wells were analyzed to quantify the stress heterogeneity for three geologically distinct locations: two wells within the CGF (one in an actively produced volume), two on the margin of the CGF and outside the production area, and a control well several tens of km south of the CGF.CRUSTAL STRESS HETEROGENEITY IN THE VICINITY OF COSO GEOTHERMAL FIELD, CA
InSAR At Coso Geothermal Area (2000)InSAR2000usefulTo determine ground subsidence using satellite radar interferometryInterferometric synthetic aperture radar (InSAR) data collected in the Coso geothermal area, eastern California, during 1993-1999 indicate ground subsidence over a approximately 50 km 2 region that approximately coincides with the production area of the Coso geothermal plant. The maximum subsidence rate in the peak of the anomaly is approximately 3.5 cm yr -1 , and the average volumetric rate of subsidence is of the order of 10 6 m 3 yr -1 . The radar interferograms reveal a complex deformation pattern, with at least two irregular subsidence peaks in the northern part of the anomaly and a region of relative uplift on the south.Deformation and seismicity in the Coso geothermal area, Inyo County, California, observations and modeling using satellite radar interferometry
Steady state deformation of the Coso Range, east central California, inferred from satellite radar interferometry
Isotopic Analysis Fluid At Coso Geothermal Area (1997)Isotopic Analysis- Fluid1997not indicatedIdentify the source of chlorineThe 36Cl/Cl values for several geothermal water samples and reservoir host rock samples have been measured. The results suggest that the thermal waters could be connate waters derived from sedimentary formations, presumably underlying and adjacent top the granitic rocks, which have recently migrated into the host rocks. Alternatively, most of the chlorine but not the water, may have recently input into the system from magmatic sources.36Cl/Cl ratios in geothermal systems- preliminary measurements from the Coso Field
Isotopic Analysis- Fluid At Coso Geothermal Area (1982)Isotopic Analysis- Fluid1982not indicatedDetermine recharge for the systemThirty-nine water samples were collected from the Coso geothermal system and vicinity and were analyzed for major chemical constituents and deltaD and delta18O. Non-thermal ground waters from the Coso Range were found to be isotopically heavier than non-thermal ground waters from the Sierra Nevada to the west. The deltaD value for the deep thermal water at Coso is similar to that of the Sierra water, suggesting that the major recharge for the hydrothermal system comes from the Sierra Nevada rather than from local precipitation on the Coso Range.An isotopic study of the Coso, California, geothermal area
Isotopic Analysis- Fluid At Coso Geothermal Area (1990)Isotopic Analysis- Fluid1990not indicatedDetermine the recharge of the areaHydrogen and oxygen isotope data on waters of Coso thermal and nonthermal waters were studied. Hydrogen and oxygen isotopes do not uniquely define the recharge area for the Coso geothermal system but strongly suggest Sierran recharge with perhaps some local recharge.Water geochemistry study of Indian Wells Valley, Inyo and Kern Counties, California. Supplement. Isotope geochemistry and Appendix H. Final report
Isotopic Analysis- Fluid At Coso Geothermal Area (2007)Isotopic Analysis- Fluid2007not indicatedDetermine the location of the heat sourceFluids have been sampled from 9 wells and 2 fumaroles from the East Flank of the Coso hydrothermal system with a view to identifying, if possible, the location and characteristics of the heat source inflows into this portion of the geothermal field. Preliminary results show that there has been extensive vapor loss in the system, most probably in response to production. Wells 38A-9, 51-16 and 83A-16 showthe highest CO2-CO-CH4-H2 chemical equilibration temperatures, ranging between 300-340 C, and apart from 38A-9, the values are generally in accordance with the measured temperatures in the wells. Calculated temperatures for the fractionation of 13C between CO2 and CH4 are in excess of 400oC in fluids from wells 38A-9, 64-16-RD2 and 51A-16,obviously pointing to equilibrium conditions from deeper portions of the reservoir.Chemical and isotopic characteristics of the coso east flank hydrothermal fluids: implications for the location and nature of the heat source
Isotopic Analysis- Rock At Coso Geothermal Area (1984)Isotopic Analysis- Rock1984not indicatedTo analyze evidence for crustal interaction and compositional zonation in the source regions of Pleistocene basaltic and rhyolitic magmas of the Coso volcanic fieldThe isotopic compositions of Pb and Sr in Pleistocene basalt, high-silica rhyolite, and andesitic inclusions in rhyolite of the Coso volcanic field indicate that these rocks were derived from different levels of compositionally zoned magmatic systems. The two earliest rhyolites probably were tapped from short-lived silicic reservoirs, in contrast to the other 36 rhyolite domes and lava flows which the isotopic data suggest may have been leaked from the top of a single, long-lived magmatic system. Most Coso basalts show isotopic, geochemical, and mineralogic evidence of interaction with crustal rocks, but one analyzed flow has isotopic ratios that may represent mantle values.Lead and strontium isotopic evidence for crustal interaction and compositional zonation in the source regions of Pleistocene basaltic and rhyolitic magmas of the Coso volcanic field, California
Isotopic Analysis- Rock At Coso Geothermal Area (1997)Isotopic Analysis- Rock1997usefulDetermine a major lithospheric boundarySr and Nd isotope ratios of Miocene-Recent basalts in eastern California, when screened for crustal contamination, vary dramatically and indicate the presence of a major lithospheric boundary that is not obvious from surface geology. Isotope ratios from the Coso field form a bull's-eye pattern with very low 87Sr/86Sr (0.7033) centered just south of the geothermal area. The boundary between enriched (high 87Sr/86Sr) and depleted (low 87Sr/86Sr) domains is sharply defined in the Coso Range and coincides with the northeastern boundary of recent seismic activity.A major lithospheric boundary in eastern California defined by isotope ratios in Cenozoic basalts from the Coso Range and surrounding areas
Long-Wave Infrared At Coso Geothermal Area (1968-1971)Long-Wave Infrared19681971usefulFumarolic and hot springs activity8- to 14-micrometer IR imagery has value in delineating the typical arcuate structural patternsRemote sensing survey of the Coso geothermal area, Inyo county, California. Technical publication 1968--1971
Magnetotellurics At Coso Geothermal Area (2004)Magnetotellurics2004not indicatedEGS potential of Coso Geothermal RegionA dense grid of magnetotelluric (MT) stations plus contiguous bipole array profiling centered over the east flank of the Coso geothermal system is being acquired. Acquiring good quality MT data in producing geothermal systems is a challenge due to production related electromagnetic (EM) noise and, in the case of Coso, due to proximity of a regional DC intertie power transmission line. To achieve good results, a remote reference completely outside the influence of the dominant source of EM noise must be established. The MT times series has been successfully unwrapped and applied using results from the permanent observatory at Parkfield, CA, and these permanent observations appear adequate to suppress the interference of the artificial EM noise from the DC intertie.MAGNETOTELLURIC SURVEYING AND MONITORING AT THE COSO GEOTHERMAL AREA, CALIFORNIA, IN SUPPORT OF THE ENHANCED GEOTHERMAL SYSTEMS CONCEPT: SURVEY PARAMETERS AND INITIAL RESULTS
Further Analysis of 3D Magnetotelluric Measurements Over the Coso Geothermal Field
3D Magnetotelluic characterization of the Coso Geothermal Field
Three-dimensional magnetotelluric characterization of the Coso geothermal field
Magnetotellurics At Coso Geothermal Area (2006)Magnetotellurics2006usefulUse magnetotelluric data to model the reservoir.Magnetotelluric (MT) data from 101 tensor stations over the East Flank of the Coso geothermal field, southeastern California, were inverted on a PC using a 3-D Gauss-Newton regularization algorithm based on a staggered-grid, finite difference forward problem and jacobians. Static shifts at each MT site can be included as additional parameters and solved for simultaneously. Recent modifications to the algorithm developed here include the addition of an LU solver to calculate the model parameter update, to reduce storage. The inversion for the Coso data set was started from a 22 ohm-m half-space and results qualitatively resemble models from 2-D transverse magnetic (TM) inversions, and from massively parallel 3-D inversion by other workers. In particular, a steeply west-dipping conductor was resolved under the western East Flank tentatively correlated with a zone of high-temperature ionic fluids. Implementation on desktop serial PC's is an attempt to widen the potential user base. Run times for the Coso data set on a 3.4 GHz desktop are 2-3 days, with the greatest amount of run-time taken up in computing the Jacobian matrix explicitly using reciprocity. Continuing efforts are being made in storage efficiencies, in speeding the Jacobian computations, and improved parameter weighting.Three-Dimensional Inversion of Magnetotelluric Data on a PC, Methodology and Applications to the Coso Geothermal Field
Micro-Earthquake At Coso Geothermal Area (1974)Micro-Earthquake1974usefulTo determine the background level of seismicity before any drilling related to production takes place.Two different arrays of portable high-gain seismographs were installed- measurements taken over thirty three days; completed 9 calibration blasts. The microearthquake activity changed considerably including days which had only a few events while others had as many as 100 or more distinct local events; more than two thousand events with S-P times of less than three seconds were detected; observed low value for Poisson's ratio which indicated that the Coso geothermal system is a vapor-dominated system rather than a hot-water system.Heat flow and microearthquake studies, Coso Geothermal Area, China Lake, California. Final report
Micro-Earthquake At Coso Geothermal Area (1987)Micro-Earthquake1987not indicatedAnalysis was done to link the zones of decreased P velocity to contemporary magmatic activityInversion of 4036 P wave travel time residuals from 429 local earthquakes using a tomographic scheme provides information about 3D upper crustal velocity variations in the Indian Wells Valley-Coso region of southeastern CA. The residuals are calculated relative to a Coso-specific velocity model, corrected for station elevation, weighted, and back-projected along their ray paths through models defined with layers of blocks.P wave velocity variations in the Coso region, California, derived from local earthquake travel times
Micro-Earthquake At Coso Geothermal Area (1992-1997)Micro-Earthquake19921997usefulCharacterize subsurface fracture patterns in the Coso geothermal reservoir by analyzing shear-wave splitting of microearthquake seismorgramsA large number of microearthquake seismograms have been recorded by a downhole, three-component seismic network. Shear-wave splitting induced by the alignment of cracks in the reservoir has been widely observed in the recordings. Over 100 events with body wave magnitude greater than 1.0 from microearthquakes recorded since March, 1992 were processed. From the delay time of split shear waves, it was estimated that the crack density in the most active geothermal reservoir area (above 3 km depth) ranges between 0.030 and 0.055.Characterization of subsurface fracture patterns in the Coso geothermal reservoir by analyzing shear-wave splitting of microearthquake seismorgrams
Characterization of geothermal reservoir crack patterns using shear-wave splitting
Micro-Earthquake At Coso Geothermal Area (1993-1994)Micro-Earthquake19931994usefulMultiplet analysisInstances of microseismicity in seismic doublets which are co-located hypocenters that appear to have nearly identical waveforms were searched for. Using 1085 high-quality events from 1993 to 1994, they identified numerous doublets, some occurring within minutes of each other. The hypocentral data was subdivided into spatial clusters to reduce the computational burden and evaluated multiple cross-correlation pairs, assigning scores to each pair. The multiplets do not appear to be true repeating events; rather, they are clusters of small, nearly identically oriented ruptures, perhaps representing swarms of fractures activated by fluid-pressure fluctuations. Using the small volumes encompassing each multiplet, the fracture densities are estimated to measure between 0.02 and 0.4 m−1 and are largest near the injection wells.Microseismicity, stress, and fracture in the Coso geothermal field, California
Micro-Earthquake At Coso Geothermal Area (1996)Micro-Earthquake1996usefulDetermine the attenuation structurePulse width data are used to invert for attenuation structure. The dataset consists of pulse width measurements of 838 microseismic events recorded on a seismic array of 16 downhole stations between August 1993 and March 1994. A broad region of low Q (≈ 30 to 37) is located at 0.5 to 1.2 km in depth below Devil's Kitchen, Nicol Prospects, and Coso Hot Springs. A vertical, low Q (≈ 36 in contrast with surrounding rock of 80) region is interpreted as a channel through which hydrothermal energy is transported from depth to the surface. The location of the channel is between stations S1 and S4, and its dimension is about 1 km.Attenuation structure of Coso geothermal area, California, from wave pulse widths
Micro-Earthquake At Coso Geothermal Area (2000)Micro-Earthquake2000not indicatedCompare results of dense arrays with less densely spaced instrumentsResults from a dense array of passive seismometers are presented. Data collected during the 18-month deployment of 16 dense mini-arrays in the region of the China Lake geothermal field near Ridgecrest, CA was used. The crustal structure within the geothermal field, its relationship to regional tectonic features, and search for an indication of mantle influence on volcanism was imaged. The mini-arrays consist of mostly short period instruments arranged in orthogonal line arrays with 1/2-km station spacing. The average distance between each array is approximately 5 km. It was calculate that there are 375 good quality mini-array beamed receiver functions for teleseismic events.Imaging the Coso geothermal area crustal structure with an array of high-density mini-arrays
Micro-Earthquake At Coso Geothermal Area (2002-2005)Micro-Earthquake20022005not indicatedTo improve understanding of the subsurface fracture systemA shear-wave splitting technique was applied on a set of high quality, locally recorded microearthquake (MEQ) data. Four major fracture directions have been identified from the seismograms recorded by the permanent 16-station down-hole array: N10- 20W, NS, N20E, and N40-45E, of which the first and the third are the most prominent. All orientations are consistent with the known strike of local sets of faults and fractures at depth and at the surface, as well as with previous analyses of seismic anisotropy in the region. Significant changes in shear-wave time delays, which are governed by crack density, have been detected from data recorded during five consecutive years between 1996 and 2000.TEMPORAL VARIATIONS OF FRACTURE DIRECTIONS AND FRACTURE DENSITIES IN THE COSO GEOTHERMAL FIELD FROM ANALYSES OF SHEAR-WAVE SPLITTING
Shear-wave splitting and reservoir crack characterization: the Coso geothermal field
Shear-wave splitting as a tool for the characterization of geothermal fractured reservoirs: lessons learned
Micro-Earthquake At Coso Geothermal Area (2005)Micro-Earthquake2005usefulCharacterization of 3D Fracture Patterns at The Geysers and Coso Geothermal Reservoirs by Shear-wave Splitting, Rial, Elkibbi, Yang and Pereyra. The raw data for the project consists of seismographic recordings of microearthquakes (MEQ) detected over many years by arrays of sensors at both The Geysers and Coso.Federal Geothermal Research Program Update - Fiscal Year 2004
Micro-Earthquake At Coso Geothermal Area (2007)Micro-Earthquake2007not indicatedDevelop and test a tool to better analyze microearthquake dataA GUI-based interface was developed to use inversion software that greatly increases its ease of use and makes feasible analyzing larger numbers of earthquakes than previously was practical. Examples are shown from an injection experiment conducted in well 34-9RD2, on the East Flank. This tight well was re-drilled February – March 2005. Pervasive porosity and fractures were encountered at about 2660 m depth. These mud losses induced a 50-minute swarm of 44 microearthquakes, with magnitudes in the range -0.3 to 2.6. Most of the largest microearthquakes occurred in the first 2 min. Several additional software packages are being developed to enhance the utility of microearthquake data in geothermal operations and EGS experiments.Microearthquake moment tensors from the Coso Geothermal area
IMPROVED METHODS FOR MAPPING PERMEABILITY AND HEAT SOURCES IN GEOTHERMAL AREAS USING MICROEARTHQUAKE DATA
Micro-Earthquake At Coso Geothermal Area (2011)Micro-Earthquake2011not indicatedTo analyze temporal velocity variationsMicroseismic data recorded between 1996 and 2008 was used to determine the temporally varying seismic velocity of the Coso geothermal field. In this study, the double difference tomography method was applied to simultaneously locate a suite of microseismic events and determine the compressional and shear wave velocity as well as their ratio.Temporal Velocity Variations beneath the Coso Geothermal Field Observed using Seismic Double Difference Tomography of Compressional and Shear Wave Arrival Times
Modeling-Computer Simulations At Coso Geothermal Area (1980)Modeling-Computer Simulations1980usefulEstimate thermal regime and potential of the systemA three-dimensional generalized linear inversion of the delta t* observations was performed using a three-layer model. A shallow zone of high attenuation exists within the upper 5 km in a region bounded by Coso Hot Springs, Devils Kitchen, and Sugarloaf Mountain probably corresponding to a shallow vapor liquid mixture or "lossy" near surface lithology.Three-dimensional Q (super -1) model of the Coso Hot Springs known geothermal resource area (in Coso geothermal area)
Modeling-Computer Simulations At Coso Geothermal Area (1999)Modeling-Computer Simulations1999not indicatedTo analyze attenuation and source propertiesA multiple-empirical Green's function method was used to determine source properties of small (M −0.4 to 1.3) earthquakes and P-wave and S-wave attenuation at the Coso Geothermal Field. Source properties of a previously identified set of clustered events from the Coso geothermal region are first analyzed using an empirical Green's function (EGF) method. Stress-drop values of at least 0.5-1 MPa are inferred for all of the events. The inferred attenuation variability corresponds to the heat-flow variations within the geothermal region. A central low-Q region corresponds well with the central high-heat flow region. Also an additional detailed structure was also suggested.Attenuation and source properties at the Coso Geothermal Area, California
Modeling-Computer Simulations At Coso Geothermal Area (2000)Modeling-Computer Simulations2000not indicatedModel ground subsidence using observations of satellite radar interferometryThe InSAR displacement data was inverted for the positions, geometry, and relative strengths of the deformation sources at depth using a nonlinear least squares minimization algorithm. Elastic solutions were used for a prolate uniformly pressurized spheroidal cavity in a semi-infinite body as basis functions for our inversions. Source depths inferred from our simulations range from 1 to 3 km, which corresponds to the production depths of the Coso geothermal plant. Underpressures in the geothermal reservoir inferred from the inversion are of the order of 0.1-1 MPa (except a few abnormally high underpressures that are apparently biased toward the small source dimensions).Deformation and seismicity in the Coso geothermal area, Inyo County, California, observations and modeling using satellite radar interferometry
Steady state deformation of the Coso Range, east central California, inferred from satellite radar interferometry
Multispectral Imaging At Coso Geothermal Area (1990)Multispectral Imaging1990not indicatedTo understand the complex geology seen on the surface and to try to improve the method of locating geothermal wells.Remote sensing studies have been made in and adjacent to the Coso geothermal field using TM FCC satellite imagery, 1:100,000 scale, US Geological Survey orthophotos, 1:24,000 scale, and proprietary black-and-white photography by California Energy Company, Inc., at various scales including black-and-white positive film transparencies at a scale of 1:6,000.Structural investigations at the Coso geothermal area using remote sensing information, Inyo County, California
Neutron Log At Coso Geothermal Area (1977)Neutron Log1977not indicatedextensive geophysical logging surveys were conducted: natural gamma and neutron porosity logs indicate gross rock typeGeological and geophysical analysis of Coso Geothermal Exploration Hole No. 1 (CGEH-1), Coso Hot Springs KGRA, California
Static downhole characteristics of well CGEH-1 at Coso Hot Springs, China Lake, California
Numerical Modeling At Coso Geothermal Area (1995)Numerical Modeling1995usefulLocate an active fault zone by analyzing seismic guided waves from microearthquake dataAn active fault zone was located in the Coso geothermal field, California, by identifying and analyzing a fault-zone trapped Rayleigh-type guided wave from microearthquake data. The wavelet transform is employed to characterize guided-wave's velocity-frequency dispersion, and numerical methods are used to simulate the guided-wave propagation. The modeling calculation suggests that the fault zone is approximately 200m wide, and has a P wave velocity of 4.80 km/s and a S wave velocity of 3.00 km/sLocating an active fault zone in Coso geothermal field by analyzing seismic guided waves from microearthquake data
Numerical Modeling At Coso Geothermal Area (1997)Numerical Modeling1997usefulDevelop tool to identify low velocity zones by modeling fault-zone guided waves of microearthquakesA numerical method has been employed to simulate the guided-wave propagation from microearthquakes through the fault zone. By comparing observed and synthetic waveforms the fault-zone width and its P-wave and S-wave velocity structure have been estimated. It is suggested that the identification and modeling of guided waves is an effective tool to locate fracture-induced, low-velocity fault-zone structures in geothermal fields.Modeling fault-zone guided waves of microearthquakes in a geothermal reservoir
Numerical Modeling At Coso Geothermal Area (1999)Numerical Modeling1999not indicatedTo determine three-dimensional P and S waves velocity structuresHigh precision P and S wave travel times for 2104 microearthquakes with focus <6 km are used in a non-linear inversion to derive high-resolution 3-D compressional and shear velocity structures at the Coso Geothermal Area. Block size for the inversion is 0.2 km horizontally and 0.5 km vertically and inversions are investigated in the upper 5 km of the geothermal area. Spatial resolution, calculated by synthetic modeling of a cross model at critical locations, is estimated to be 0.35 km for Vp and 0.5 km for V s . In the 2 km southwest Sugarloaf region, we found low V p and high V s at geothermal production depths from 1 to 2.5 km. Combined with attenuation results, this may represent a hot, fluid-depleted center of magmatic activity.Three-dimensional P and S waves velocity structures of the Coso geothermal area, California, from microseismic travel time data
P wave anisotropy, stress, and crack distribution at Coso geothermal field, California
Numerical Modeling At Coso Geothermal Area (2000)Numerical Modeling2000not indicatedDetermine areas with fault patterns for geothermal development using Poisson's ratio and porosityHigh-resolution, three-dimensional, compressional and shear wave velocity models, derived from microearthquake travel times, are used to map the distribution of Poisson's ratio and porosity at Coso Geothermal Area. Spatial resolution of the three-dimensional Poisson's ratio and porosity distributions is estimated to be 0.5 km horizontally and 0.8 km vertically. Model uncertainties, + or -1% in the interior and + or -2.3% around the edge of the model, are estimated by a jackknife method. Perturbations of r = Vp/Vs ratio and Psi = Vpdot Vs product were used to derive distributions of Poisson's ratio, sigma , and porosity, which are then used to constrain and delineate possible zones of intense heat, fracture accumulation and fluid saturation. Poisson's ratio at Coso ranges from 0.15 to 0.35 with an average of 0.224, lower than the crustal average of 0.25.Poisson's ratio and porosity at Coso geothermal area, California
Numerical Modeling At Coso Geothermal Area (2006)Numerical Modeling2006usefulDetermine areas of high permeability using isotope transport and exchange analysisFinite element models of single-phase, variable-density fluid flow, conductive- convective heat transfer, fluid-rock isotope exchange, and groundwater residence times were developed. Using detailed seismic reflection data and geologic mapping, a regional cross-sectional model was constructed that extends laterally from the Sierra Nevada to Wildhorse Mesa, west of the Argus Range. The findings suggest that active faults and seismogenic zones in and around the Coso geothermal area have much higher permeability and reactive surface areas than far field crustal rocks such as those in the Sierra Nevada.Isotope Transport and Exchange within the Coso Geothermal System
Numerical Modeling At Coso Geothermal Area (2007)Numerical Modeling2007not indicatedTo determine the importance of fracture networks for fluid migration in tectonically active regions such as the Coso Range.A finite element analysis is used to establish the 3D state of stress within the tectonic setting of the Coso Range. The mean and differential stress distributions are used to infer fluid flow vectors and second order fracture likelihood and orientation. The results show that the Coso Range and adjacent areas are regions of increased likelihood of second order fracture generation.Stress and Fluid-Flow Interaction for the Coso Geothermal Field Derived from 3D Numerical Models
Numerical Modeling At Coso Geothermal Area (2010)Numerical Modeling2010usefulTo determine conditions when fractures nucleateA numerical model was developed using Poly3D to simulate the distribution and magnitude of stress concentration in the vicinity of the borehole floor, and determine the conditions under which petal-centerline fractures nucleate. As a whole, the simulations have demonstrated that a borehole under the stress boundary conditions present at the Coso 58A-10 borehole is able to amplify the stress concentration to produce tension below the borehole floor consistent with the occurrence of petal-centerline fractures in image logs. In vertical boreholes, the maximum magnitude of _1 below the borehole floor reaches tension within only a very small fraction of the frictionally permissible stress states, corresponding to low mean stress. However, deviation towards SHmax in the stress state relevant to Coso increases the potential for tension below the borehole floor, whereas deviation towards SHmin leads to enhanced compression. These results prove that the occurrence of petal-centerline fractures can be used to constrain principal stress magnitudes and determine faulting regime.Numerical Modeling of the Nucleation Conditions of Petal-Centerline Fractures below a Borehole Floor, A Sensitivity Study and Application to the Coso Geothermal Field
Paleomagnetic Measurements At Coso Geothermal Area (2006)Paleomagnetic Measurements2006not indicatedAnalyze fault block kinematics at a releasing stepover of the Eastern California shear zone to determine the partitioning of rotation styleRotations paleomagnetically relative to two different reference frames were measured. At two localities, the secular variation were averaged through sedimentary sections to reveal rotation or its absence relative to paleogeographic north. Where sediments are lacking, a really-extensive lava flows from individual cooling units or short eruptive episodes were used to measure the relative rotation of localities by comparing their paleomagnetic remanence directions to one another.Fault block kinematics at a releasing stepover of the Eastern California shear zone: Partitioning of rotation style in and around the Coso geothermal area and nascent metamorphic core complex
Reflection Survey At Coso Geothermal Area (1989)Reflection Survey1989usefulDetermine the crustul structure of the Coso geothermal systemIn mid-1989 the authors designed and collected four seismic reflection/refraction profiles that addressed the crustal structure of the Coso geothermal field. The two main east-west and north-south profiles crossed at the southeastern most base of Sugar Loaf Mountain. Both in-line and cross-line Vibroseis and explosion data were recorded on each of these approximately 12-mi lines. This was accomplished with the simultaneous operation of two 1024-channel sign bit recording systems while four medium-weight P-wave vibrators traversed each line and 16 drilled charges were set off. A single recording system was used on each of the other profiles, one of which was a 4-mi-long, 700-channel P-wave profile connecting the Sierran front to the center of Rose Valley, and the other of which was a 2-mi-long, 240-channel SH-wave line runnings slightly southeastward from the junction of the main lines. Rough CMP stacks of the data that included depth varying velocities at 2-mi lateral intervals were completed in the field.Coincident P and Sh reflections from basement rocks at Coso geothermal field
Reflection Survey At Coso Geothermal Area (2001)Reflection Survey2001not indicatedLook for features that are characteristic of the geothermal producing region not originally seen by imaging the Coso Field using seismicDuring December of 1999, approximately 32 miles of seismic data were acquired as part of a detailed seismic investigation undertaken by the US Navy Geothermal Program Office. Data acquisition was designed to make effective use of advanced data processing methods, which include Optim's proprietary nonlinear velocity optimization technique and pre-stack Kirchhoff migration. The velocity models from the 2-D lines were combined to construct a 2.5D velocity model of the Coso geothermal field. Analyses of the 2.5D volume were used to tie together velocity signatures seen along individual 2D lines.USE OF ADVANCED DATA PROCESSING TECHNIQUES IN THE IMAGING OF THE COSO GEOTHERMAL FIELD
Reflection Survey At Coso Geothermal Area (2008)Reflection Survey2008not indicatedA reflection survey was done to analyze the brittle upper plate structure revealed by reflection seismic dataThe relationships between upper crustal faults, the brittle-ductile transition zone, and underlying magmatic features imaged by multifold seismic reflection data are consistent with the hypothesis that the Coso geothermal field, which lies within an extensional step-over between dextral faults, is a young, actively developing metamorphic core complex. The reflection images were processed using a non-linear simulated annealing approach to invert P-wave first arrivals in the seismic data for 2-D velocity structure. The combination of magmatic heat and active normal faulting in the regional transtensional setting establishes the conditions for hydrothermal convection in the Coso geothermal field.The nascent Coso metamorphic core complex, east-central California, brittle upper plate structure revealed by reflection seismic data
Refraction Survey At Coso Geothermal Area (1989)Refraction Survey1989usefulDetermine the crustul structure of the Coso geothermal systemIn mid-1989 the authors designed and collected four seismic reflection/refraction profiles that addressed the crustal structure of the Coso geothermal field. The two main east-west and north-south profiles crossed at the southeastern most base of Sugar Loaf Mountain. Both in-line and cross-line Vibroseis and explosion data were recorded on each of these approximately 12-mi lines. This was accomplished with the simultaneous operation of two 1024-channel sign bit recording systems while four medium-weight P-wave vibrators traversed each line and 16 drilled charges were set off. A single recording system was used on each of the other profiles, one of which was a 4-mi-long, 700-channel P-wave profile connecting the Sierran front to the center of Rose Valley, and the other of which was a 2-mi-long, 240-channel SH-wave line runnings slightly southeastward from the junction of the main lines. Rough CMP stacks of the data that included depth varying velocities at 2-mi lateral intervals were completed in the field.Coincident P and Sh reflections from basement rocks at Coso geothermal field
Rock Sampling At Coso Geothermal Area (1995)Rock Sampling1995not indicatedGeologic controls on the geometry of the upwelling plume were investigated using petrographic and analytical analyses of reservoir rock and vein material.Lithology and alteration mineralogy of reservoir rocks at Coso Geothermal Area, California
Self Potential At Coso Geothermal Area (2006)Self Potential2006not usefulSP gradient and MT over portions of the field. SP gradient data ambiguous. Probably not a good candidateHistorical Exploration And Drilling Data From Geothermal Prospects And Power Generation Projects In The Western United States
Static Temperature Survey At Coso Geothermal Area (1977)Static Temperature Survey1977not indicatedTemperature logs were taken during and after drilling: Results: Convective heat flow and temperatures greater than 350 F appear to occur only along an open fracture system encountered between depths of 1850 and 2775 feet. Temperature logs indicate a negative thermal gradient below 3000 feet. Water chemistry indicates that this geothermal resource is a hot-water rather than a vapor-dominated system.Geological and geophysical analysis of Coso Geothermal Exploration Hole No. 1 (CGEH-1), Coso Hot Springs KGRA, California
Static downhole characteristics of well CGEH-1 at Coso Hot Springs, China Lake, California
Stepout-Deepening Wells At Coso Geothermal Area (1986)Step-out Well1986not indicatedA step-out exploration/production well drilled in 1986 to a depth of 6553 ft located several miles south of the Devil's Kitchen region along the identified north-south feature produced fluids with a temperature greater than 640 F.Structural interpretation of Coso Geothermal field, Inyo County, California
Stress Test At Coso Geothermal Area (2004)Stress Test2004not indicatedEGS potential of Coso Geothermal RegionA hydraulic fracturing stress test at 3,703 feet TVD was used to constrain a normal faulting and strike-slip faulting stress tensor for this reservoir. The shear and normal stresses resolved on the fracture and fault planes were calculated and used to identify the subset of critically stressed planes that act to maintain permeability within the Coso Geothermal Field.IN SITU STRESS, FRACTURE, AND FLUID FLOW ANALYSIS IN WELL 38C-9:AN ENHANCED GEOTHERMAL SYSTEM IN THE COSO GEOTHERMAL FIELD
Teleseismic-Seismic Monitoring At Coso Geothermal Area (1975-1976)Teleseismic-Seismic Monitoring19751976not indicatedEstimate thermal regime and potential of the systemThree-dimensional Q -1 model of the Coso Hot Springs known geothermal resource area was conducted. To complete the model a regional telemetered network of sixteen stations was operated by the U.S. Geological Survey; deployed a portable Centipede array of 26 three-component stations near the center of the anomaly.Three-dimensional Q (super -1) model of the Coso Hot Springs known geothermal resource area (in Coso geothermal area)
Teleseismic-Seismic Monitoring At Coso Geothermal Area (1980)Teleseismic-Seismic Monitoring1980usefulDetermine extent of low velocity bodyAn area showing approximately 0.2-s excess travel time that migrates with changing source azimuth, suggesting that the area is the 'delay shadow' produced by a deep, low-velocity body. Inversion of the relative residual data for three-dimensional velocity structure determines the lateral variations in velocity to a depth of 22.5 km beneath the array. An intense low-velocity body, which coincides with the surface expressions of late Pleistocene rhyolitic volcanism, high heat flow, and hydrothermal activity, is resolved between 5- and 20-km depth. It has a maximum velocity contrast of over 8% between 10 and 17.5 km. The shallowest part of this body is centered below the region of highest heat flow and at depth it is elongate in approximately the N-S direction.Teleseismic evidence for a low-velocity body under the Coso geothermal area
Teleseismic-Seismic Monitoring At Coso Geothermal Area (1983-1985)Teleseismic-Seismic Monitoring19831985not indicatedTo study anomalous shear wave attenuation in the shallow crustV s and V p wave amplitudes were measured from vertical component seismograms of earthquakes that occurred in the Coso-southern Sierra Nevada region from July 1983 to 1985. Seismograms of 16 small earthquakes show SV amplitudes which are greatly diminished at some azimuths and takeoff angles, indicating strong lateral variations in S wave attenuation in the area. Three-dimensional images of the relative S wave attenuation structure are obtained from forward modeling and a back projection inversion of the amplitude data. The results indicate regions within a 20 by 30 by 10 km volume of the shallow crust (one shallower than 5 km) that severely attenuate SV waves passing through them.Anomalous shear wave attenuation in the shallow crust beneath the Coso volcanic region, California
Teleseismic-Seismic Monitoring At Coso Geothermal Area (1988)Teleseismic-Seismic Monitoring1988usefulTo analyze three-dimensional Vp/Vs variationA tomographic inversion for the 3D variations of the Vp/V s, the ratio of compressional to shear velocity, was performed. Iterative back projection of 2966 shear and compressional wave travel time residuals from local earthquakes recorded on vertical instruments reveals that Vp/Vs is generally high at the surface and decreases systematically to 10 km depth. Near Devil's Kitchen in the Coso Geothermal Area, Vp/Vs values are very low near the surface, consistent with measured values for steam-dominated geothermal systems. Abnormally high values of Vp/Vs are observed in portions of Indian Wells Valley and also below the Cactus Peak rhyolite dome from 2 to 5 km in depth. In Indian Wells Valley the co-occurrence of low P velocities, low S velocities, high Vp/Vs, and anomalous SV attenuation are indicative of subsurface partial melt.Three-dimensional V p /V s variations for the Coso region, California
Teleseismic-Seismic Monitoring At Coso Geothermal Area (1996-2004)Teleseismic-Seismic Monitoring19962004usefulTo look at time dependent seismic tomographyLocal-earthquake tomographic images were calculated for each of the years 1996 - 2004 using arrival times from the U.S. Navy’s permanent seismometer network. The results show irregular strengthening with time of the wave-speed ratio V p/V s at shallow depths. The period from 1996 through 2006 was studied, and the results to date using the traditional method show, for a 2-km horizontal grid spacing, an irregular strengthening with time of a negative V p/V s anomaly in the upper ~ 2 km of the reservoir.Time-dependent seismic tomography of the Coso geothermal area, 1996-2004
Time-dependent seismic tomography and its application to the Coso geothermal area, 1996-2006
Teleseismic-Seismic Monitoring At Coso Geothermal Area (1998-2002)Teleseismic-Seismic Monitoring19982002not indicatedTwo recent earthquake sequences near the Coso geothermal field show clear evidence of faulting along conjugate planes. Results from analyzing an earthquake sequence occurring in 1998 are presented and compared with a similar sequence that occurred in 1996. The two sequences followed mainshocks that occurred on 27 November, 1996 and 6 March, 1998. Both mainshocks ruptured approximately colocated regions of the same fault system. Following a comparison with the background seismicity of the Coso region, evidence was detected of stress loading within the geothermal field that appears to be in response to the 1998 earthquakes. From an estimate of the tectonic stressing rate on the fault that produced the 1998 sequence, a repeat cycle can be inferred of 135 years for an earthquake of comparable magnitude at the Coso region.Recent earthquake sequences at Coso: Evidence for conjugate faulting and stress loading near a geothermal field
Seismicity and seismic stress in the Coso Range, Coso geothermal field, and Indian Wells Valley region, Southeast-Central California
Three-dimensional anatomy of a geothermal field, Coso, Southeast-Central California
Teleseismic-Seismic Monitoring At Coso Geothermal Area (2004)Teleseismic-Seismic Monitoring2004not indicatedAnalyze seismic data to develop reservoir models that characterize the geothermal systemLarge-amplitude, secondary arrivals are modeled as scattering anomalies. Polarization and ray tracing methods determine the orientation and location of the scattering body. Two models are proposed for the scatterer: (1) a point scatterer located anywhere in a one-dimensional (1-D), layered velocity model; and (2) a dipping interface between two homogeneous half spaces. Each model is derived by non-linear, grid search inversion for the optimal solution which best predicts observed travel times. In each case the models predict a nearly vertical scatterer southwest of stations S4 and Y4, each southeast of Sugarloaf Mountain, a large rhyolite dome. The large amplitude, vertical impedance contrast interface coincides with steep gradients of heat flow measured near the surface and with structural boundaries observed in surface geology. The reflector is most probably the sharp boundary between the northern part of the field where there is significant fluid flow and the southern part where hydrothermal fluids are absent.Scattering from a fault interface in the Coso geothermal field
Teleseismic-Seismic Monitoring At Coso Geothermal Area (2005)Teleseismic-Seismic Monitoring2005not indicatedMore detailed analysis of microearthquakes over a longer period of timeThe permanent 18-station network of three-component digital seismometers at the seismically active Coso geothermal area, California, provides high-quality microearthquake (MEQ) data that are well suited to investigating temporal variations in structure related to processes within the geothermal reservoir. A preliminary study (Julian, et al. 2003; Julian et al. 2004) comparing data from 1996 and 2003 found significant variations in the ratio of the seismic wave-speeds, V p/V s , at shallow depths over this time interval. This report describes results of a more detailed study of each year from 1996 through 2004.Time-Dependent Seismic Tomography of the Coso Geothermal Area, 1996-2004
Teleseismic-Seismic Monitoring At Coso Geothermal Area (2006)Teleseismic-Seismic Monitoring2006usefulTo assess the benefits of surface seismic surveysDifferent migration procedures were applied to image a synthetic reservoir model and seismic data. After carefully preprocessing seismic data, the 2-D and 2.5-D pre-stack depth migration of line 109 in the Coso Geothermal Field shows a well defined reflector at about 16,000 ft depth. Compared to the 2-D pre-stack migrated image, the 2.5-D pre-stack migrated image resolves the deep reflector betterSEISMIC ATTRIBUTES IN GEOTHERMAL FIELDS
Teleseismic-Seismic Monitoring At Coso Geothermal Area (2011-2012)Teleseismic-Seismic Monitoring20112012not indicatedMap hydraulic structure within the field from seismic data2011: 16 years of seismicity were analyzed to improve hypocentral locations and simultaneously invert for the seismic velocity structure within the Coso Geothermal Field (CGF). The CGF has been continuously operated since the 1980's. 2012: 14 years of seismicity in the Coso Geothermal Field were relocated using differential travel times and simultaneously invert for seismic velocities to improve our knowledge of the subsurface geologic and hydrologic structure. Over 60,000 micro-seismic events were utilized using waveform cross-correlation to augment the expansive catalog of Pand S-wave differential arrival times recorded at Coso. Rigorous uncertainty estimation was carried out and found that the results are precise to within 10s of meters of relative location error.MICRO-SEISMICITY, FAULT STRUCTURE AND HYDRAULIC COMPARTMENTALIZATION WITHIN THE COSO GETHERMAL FIELD, CALIFORNIA
USING MICRO-SEISMICITY AND SEISMIC VELOCITIES TO MAP SUBSURFACE GEOLOGIC AND HYDROLOGIC STRUCTURE WITHIN THE COSO GEOTHERMAL FIELD, CALIFORNIA
Telluric Survey At Coso Geothermal Area (1977)Telluric Survey1977not indicatedTo investigate electrical properties of rocks associated with thermal phenomena of the Devil's Kitchen-Coso Hot Springs areaTelluric current mapping outlined major resistivity lows associated with conductive valley fill of the Rose Valley basin, the Coso Basin, and the northern extension of the Coso Basin east of Coso Hot Springs. A secondary resistivity low with a north-south trend runs through the Coso Hot Springs--Devil's Kitchen geothermal area.Schlumberger soundings, audio-magnetotelluric soundings and telluric mapping in and around the Coso Range, California
Reconnaissance electrical surveys in the Coso Range, California
Thermal And-Or Near Infrared At Coso Geothermal Area (1968-1971)Thermal And-Or Near Infrared19681971not indicatedFumarolic and hot springs activityColor IR photographyRemote sensing survey of the Coso geothermal area, Inyo county, California. Technical publication 1968--1971
Thermal And-Or Near Infrared At Coso Geothermal Area (2007)Thermal And-Or Near Infrared2007not indicatedAnalyze if coupling remote sensing and field data is effective for determining geothermal areasThermal infrared (TIR) data from the spaceborne ASTER instrument was used to detect surface temperature anomalies in the Coso geothermal field in eastern California. The identification of such anomalies in a known geothermal area serves as an incentive to apply similar markers and techniques to areas of unknown geothermal potential. Field measurements were carried out concurrently with the collection of ASTER images. The field data included reflectance, subsurface and surface temperatures, and radiosonde atmospheric profiles. Techniques were applied that specifically target to correct for thermal artifacts caused by topography, albedo, and thermal inertia. This approach has the potential to reduce data noise and to reveal thermal anomalies which are not distinguishable in the uncorrected imagery. The combination of remote sensing and field data can be used to evaluate the performance of TIR remote sensing as a cost-effective geothermal exploration tool.Detection of Surface Temperature Anomalies in the Coso Geothermal Field Using Thermal Infrared Remote Sensing
IN SEARCH FOR THERMAL ANOMALIES IN THE COSO GEOTHERMAL FIELD (CALIFORNIA) USING REMOTE SENSING AND FIELD DATA
Thermal And-Or Near Infrared At Coso Geothermal Area (2009)Thermal And-Or Near Infrared2009usefulDetermine the importance of elevation and temperature inversions using thermal infrared satellite imagesExamples of nighttime temperature inversions are shown in thermal infrared satellite images collected over the Coso geothermal field in eastern California. Temperature-elevation plots show the normal trend of temperature decrease with elevation, on which temperature inversions appear superimposed as opposite trends.Importance of Elevation and Temperature Inversions for the Interpretation of Thermal Infrared Satellite Images Used in Geothermal Exploration
Thermal Gradient Holes At Coso Geothermal Area (1974)Thermal Gradient Holes1974usefulUse heat flow studies for the first time at Coso to indicate the presence or absence of abnormal heatLocated 10 sites for heat flow boreholes using available seismic ground noise and electrical resistivity data; data collected from 9 of 10; thermal conductivity measurements were completed using both the needle probe technique and the divided bar apparatus with a cell arrangement. In the upper few hundred meters of the subsurface heat is being transferred by a conductive heat transfer mechanism with a value of ~ 15 µcal/cm2sec; the background heat flow is ~ 3.5 HFU.Heat flow and microearthquake studies, Coso Geothermal Area, China Lake, California. Final report
Heat flow studies, Coso Geothermal Area, China Lake, California. Technical report
Thermal Gradient Holes At Coso Geothermal Area (1976)Thermal Gradient Holes1976usefulTemperatures have been obtained to depths up to 133 m in 22 boreholes with measurements being made at least four times in each borehole. Geothermal gradients ranged from 240C/km to 450 0C/km.Heat flow determinations and implied thermal regime of the Coso geothermal area, California
Thermochronometry At Coso Geothermal Area (2003)Thermochronometry2003not indicatedDetermine the age of the geothermal system and the granitic host rock using the 40Ar/39Ar thermal historyA downhole 40Ar/39Ar thermochronology study of granitic host-rock K-feldspar is presently being undertaken at the New Mexico Geochronology Research Laboratory. The technique couples the measurement of argon loss from K-feldspar and knowledge of the diffusion parameters of transport in K-feldspar to estimate the longevity of the system at present day temperature and also to obtain an estimate of the host rock age. The study centers around a vertical distribution of samples obtained from Coso well 73-19 that reaches temperatures of 3250C at a depth of 1550m and thus represents one of the hottest producing wells in the Coso system. Four samples from Coso well 73-19, from depths 550m (downhole temperature 1500C), 700m (2000C), 1085m (2750C), and 1850m (3250C), were isolated from the granitic host rock chip samples.40AR/39AR THERMAL HISTORY OF THE COSO GEOTHERMAL FIELD
Thermochronometry At Coso Geothermal Area (2010)Thermochronometry2010not indicatedTo determine if there is geothermal potential in the South RangesIt has been believed that the South Ranges at China Lake may host geothermal resources for several decades. Recent Garlock Fault mapping, associated thermochronology work and a well documented but geologically unresolved steaming well to the west suggests that the South Ranges should be investigated for geothermal potential. In 2009, GPO awarded a contract to the University of Kansas to follow through on detailed mapping, trenching, dating and thermochronoloy in the Lava Mountains and the southern Slate Range region of the South Ranges to see if a geothermal resource might exist. A TGH drilling campaign may be initiated in the South Ranges in 2011.Navy’s Geothermal Program Office: Overview of Recovery Act (ARRA) Funded Exploration in CA and NV and other Exploration Projects
Tracer Testing At Coso Geothermal Area (1993)Tracer Testing1993usefulTo determine the steam and water mass flow rateThe method involves precisely metered injection of liquid and vapor phase tracers into the two-phase production pipeline and concurrent sampling of each phase downstream of the injection point. Subsequent chemical analysis of the steam and water samples for tracer content enables the calculation of mass flowrate for each phase given the known mass injection rates of tracer.Enthalpy and mass flowrate measurements for two-phase geothermal production by Tracer dilution techniques
Tracer Testing At Coso Geothermal Area (2004)Tracer Testing2004not indicatedTo determine the EGS potential of the Coso Geothermal FieldA dramatic decrease in the ratio of chloride to boron was observed in the liquid discharge of a well proposed for EGS development. The decrease appears to be related to the transformation of some feed zones in the well from liquid-dominated to vapor-dominated. High concentrations of boron are transported to the wellbore in the steam, where it fractionates to the liquid phase flowing in from liquid-dominated feed zones. The high-boron steam is created when the reservoir liquid in some of the feed zones boils with a steam fraction greater than 90%. Combination of boron from both phases into the liquid phase results in the Cl/B ratio dropping from 40 to as low as 20.USE OF NATURALLY-OCCURRING TRACERS TO MONITOR TWO-PHASE CONDITIONS IN THE COSO EGS PROJECT
Tracer Testing At Coso Geothermal Area (2006)Tracer Testing2006usefulTo characterize the flow patterns of fluid injected into well 68-20RD.A conservative liquid phase tracer, 2-naphthalene sulfonate, and a two-phase tracer, ethanol, were injected into well 68-20RD. Surrounding production wells were sampled over the subsequent 125 days and analyzed for the two tracers. The results demonstrate the efficacy of the simultaneous use of liquid-phase and two-phase tracers in fluid-depleted geothermal fields.A Tracer Test Using Ethanol as a Two-Phase Tracer and 2-Naphthalene Sulfonate as a Liquid-Phase Tracer at the Coso Geothermal Field
Water Sampling At Coso Geothermal Area (1977-1978)Water Sampling19771978not indicatedHydrogeologic investigation of Coso hot springs was conducted by field examination of geologic rock units and springs and other features of hydrologic significance and sampling of waters for chemical analysis; determination of the local Coso Hot Springs and regional groundwater hydrology, including consideration of recharge, discharge, movement, and water quality; determination of the possible impact of large-scale geothermal development on Coso Hot Springs.Hydrogeologic investigation of Coso Hot Springs, Inyo County, California. Final report October 1977--January 1978
Well Log Techniques At Coso Geothermal Area (1985)Well Log Techniques1985not indicatedImpact of long term testing on the well pressureThe downhole pressure monitoring equipment for each well included a stainless steel pressure chamber attached to a 0.25 inch stainless steel capillary tubing. The surface end of the capillary tubing was connected to a Paroscientific quartz pressure trandsducer.Long-Term Testing of Geothermal Wells in the Coso Hot Springs KGRA


Raft River Geothermal Area 77

 ExplorationTechniqueExpActivityDateExpActivityDateEndExplorationOutcomeExplorationBasisNotesReference material
Acoustic Logs At Raft River Geothermal Area (1979)Acoustic Logs1979usefulTo permit the lateral and vertical extrapolation of core and test data and bridged the gap between surface geophysical data and core analyses.Televiewer logs permitted the location and orientation of numerous fractures and several features that may be faults.Role of borehole geophysics in defining the physical characteristics of the Raft River geothermal reservoir, Idaho
Aeromagnetic Survey At Raft River Geothermal Area (1978)Aeromagnetic Survey1978not indicatedTo infer the structure and the general lithology underlying the valleyThe aeromagnetic data indicate the extent of the major Cenozoic volcanic units.Reconnaissance geophysical studies of the geothermal system in southern Raft River Valley, Idaho
Aeromagnetic Survey At Raft River Geothermal Area (1981)Aeromagnetic Survey1981not indicatedAn aeromagnetic survey was undertaken at the Raft River geothermal area by the USGS.Total field aeromagnetic map of the Raft River known Geothermal Resource Area, Idaho by the US Geological Survey
Airborne Electromagnetic Survey At Raft River Geothermal Area (1979)Airborne Electromagnetic Survey1979not indicatedTo show that AEM methods can be useful in exploration for and defining geothermal systemsExtensive audio-magnetotelluric (AMT) work by the USGS in KGRA's showed that many geothermal systems do have a near-surface electrical signature which should be detectable by an AEM system.Airborne electromagnetic surveys as a reconnaissance technique for geothermal exploration
Audio-Magnetotellurics At Raft River Geothermal Area (1978)Audio-Magnetotellurics1978not indicatedTo infer the structure and the general lithology underlying the valleyAn area of low apparent resistivity values defined by the audiomagnetotelluric (AMT) survey appears to outline the extent of the geothermal reservoir even though the reservoir is deeper than the penetration of the survey. Self-potential anomalies relate to near surface hydrology. Upward leakage from the reservoir produces shallower effects that were measured by the AMT survey.Reconnaissance geophysical studies of the geothermal system in southern Raft River Valley, Idaho
Chemical Logging At Raft River Geothermal Area (1979)Chemical Logging1979usefulTo use new methods to assist geothermal well drilling.Chemical logging resulted in the development of a technique to assist in geothermal well drilling and resource development. Calcium-alkalinity ratios plotted versus drill depth assisted in defining warm and hot water aquifers. Correlations between the calcium-alkalinity log and lithologic logs were used to determine aquifer types and detection of hot water zones 15 to 120 m before drill penetration.Chemical logging- a geothermal technique
Compound and Elemental Analysis At Raft River Geothermal Area (1981)Compound and Elemental Analysis1981not indicatedDetermine the validity of data from multiple sources to develop a better conceptual modelFive analytical laboratories have conducted analyses on waters from the KGRA. Charge-balance error calculations conducted on the data produced from these laboratories indicated that data from three laboratories were reliable while two were not. A method of equating all data was established by using linear regression analyses on sets of paired data from various laboratories. The chemical data collected from the deep geothermal wells indicates that a two reservoir system exists within the Raft River KGRA. Each reservoir is associated with a major structural feature. These features are known as the Bridge Fault System and the Narrows Structure.Hydrochemistry of selected parameters at the Raft River KGRA, Cassia County, Idaho
Conceptual Model At Raft River Geothermal Area (1976)Conceptual Model1976not indicatedDetermine productive zones in the reservoirBorehole geophysics techniques were used in evaluating the Raft River geothermal reservoir to establish a viable model for the system. The assumed model for the hot water 1450C reservoir was a zone of higher conductivity, increased porosity, decreased density, and lower sonic velocity.Borehole geophysics evaluation of the Raft River geothermal reservoir
Conceptual Model At Raft River Geothermal Area (1977)Conceptual Model1977not indicatedDetermine time to cool the geothermal field with reinjectionIf reinjection and production wells intersect connected fractures, it is expected that reinjected fluid would cool the production well much sooner than would be predicted from calculations of flow in a porous medium. A method for calculating how much sooner that cooling will occur was developed.Application of thermal depletion model to geothermal reservoirs with fracture and pore permeability
Conceptual Model At Raft River Geothermal Area (1979)Conceptual Model1979not indicatedRecommendations are made concerning field expansion and additional work needed to refine the overall reservoir model.Models described in this report show the source of various minerals in the geothermal water. There appears to be a regional heat source that gives rise to uniform conductive heat flow in the region, but convective flow is concentrated near the upwelling in the Crook well vicinity.Geochemical modeling of the Raft River geothermal field
Geothermal Modeling of the Raft River Geothermal Field
Conceptual Model At Raft River Geothermal Area (1980)Conceptual Model1980not indicatedDetermine the relevant data necessary to assess a geothermal reservoir in similar rock types and use cross plots to potentially define the producing zones.A conceptual model was developed that uses all geophysical data that has been collected on the area to determine the rock types and reasonable values of the parameters of interest. Emphasis has been on developing a simple interpretation scheme from a minimum of data sets. However, the cross plotting of various parameters has allowed a determination of rock types and an analysis of the degree of alteration and the density of fractures.Geophysical logging case history of the Raft River geothermal system, Idaho
Conceptual Model At Raft River Geothermal Area (1981)Conceptual Model1981not indicatedUse geoscience data to develop a conceptual model of the reservoir.The geoscience data gathered in the drilling and testing of seven geothermal wells suggest that the thermal reservoir is: (a) produced from fractures found at the contact metamorphic zone, apparently the base of detached normal faulting from the Bridge and Horse Well Fault zones of the Jim Sage Mountains; (b) anisotropic, with the major axis of hydraulic conductivity coincident to the Bridge Fault Zone; (c) hydraulically connected to the shallow thermal fluid of the Crook and BLM wells based upon both geochemistry and pressure response; (d) controlled by a mixture of diluted meteoric water recharging from the northwest and a saline sodium chloride water entering from the southwest.Raft River geoscience case study
Raft River geoscience case study- appendixes
Geoscience interpretations of the Raft River Resource
Conceptual Model At Raft River Geothermal Area (1983)Conceptual Model1983not indicatedTo create a conceptual model that helps determine the geology and alterationGeology and alteration of the Raft River geothermal system, Idaho
Conceptual Model At Raft River Geothermal Area (1987)Conceptual Model1987not indicatedTo model the kinematics of compressional and extensional ductile shearing deformationAnalysis of shear criteria enables the kinematics of two main ductile-shearing events (D1 and D2) to be established in the Raft River, Grouse Creek and Albion ‘metamorphic core complex’. The first event (D1) is a NNE-thrusting and corresponds to Mesozoic shortening. A well developed non-coaxial ductile deformation (D2), of Cenozoic age, is marked by the occurrence of opposing eastward (in Raft River) and westward shear criteria (in Albion-Grouse Creek). These characterize an arch structure where the shear strain increases outwards. In the axial zone of the complex, D2 seems coaxial.Kinematics of compressional and extensional ductile shearing deformation in a metamorphic core complex of the northeastern basin and range
Kinematic model for postorogenic Basin and Range extension
Conceptual Model At Raft River Geothermal Area (1988)Conceptual Model1988not indicatedUse geophysical logs to determine the reservoir transmissivitySeven fracture orientation sets are recognized in the sedimentary and metamorphic rock units. Although the conventional geophysical logs showed good lithological correlations among the five deep geothermal wells, individual fractures observed using the borehole televiewer logs can be not be traced from well to well. Interpretation of temperature logs, drilling rates and fracture intensity and characteristics indicates that most of the geothermal inflow occurs from three producing zones in each deep geothermal production well. The producing zones are associated mainly with steeply dipping fractures. Single-well pumping tests performed in the site indicate that plots of drawdown per log cycle of time versus discharge rate are nonlinear for each well. This suggests that the calculated values of transmissivity using the single-well pump test data may not represent the actual transmissivity of the reservoir. The multiple-well pumping tests indicate that the geothermal reservoir is anisotropic with transmissivity ranging from 11,200 gpd/ft to 23,900 gpd/ft.Fracture characteristics and their relationships to producing zones in deep wells, Raft River geothermal area
Conceptual Model At Raft River Geothermal Area (1990)Conceptual Model1990not indicatedDevelop a conceptual model to explain the exposed rocks.Although commonly obscured by simple shear, pure shear fabrics occur locally within many metamorphic core complexes. The cover rocks of the Raft River metamorphic core complex exposed within the Black Pine Mountains display an early coaxial strain history which developed prior to the formation of low-angle fault-bounded allochthons. At higher structural levels this is documented by pressure shadows with straight sutures, and oppositely-rotated antitaxial calcite veins.An early history of pure shear in the upper plate of the raft river metamorphic core complex- black pine mountains, southern Idaho
Conceptual Model At Raft River Geothermal Area (2011)Conceptual Model2011not indicatedExplore for development of an EGS demonstration projectThe reservoir is developed in fractured Proterozoic schist and quartzite, and Archean quartz monzonite cut by younger diabase intrusions. The basement complex was deformed during the mid Tertiary and covered by approximately 5000 ft of late Tertiary sedimentary and volcanic deposits. Listric normal faults of Cenozoic age disrupt the Tertiary deposits but do not offset the basement rocks. RRG-9, the target well, was drilled southwest of the main well field to a measured depth (MD) of 6089 ft. The well is deviated to the west and cased to a depth of 2316 ft MD. It penetrated the Proterozoic reservoir rocks at a depth of 5286 ft MD and encountered a maximum temperature of 1390 C. Bottomhole temperatures in other deep wells range from 133 to 149 0C.GEOLOGY AND HYDROTHERMAL ALTERATION OF THE RAFT RIVER GEOTHERMAL SYSTEM, IDAHO
Core Analysis At Raft River Geothermal Area (1976)Core Analysis1976not indicatedFracture analysis to determine if sealing or open fractures existCore samples show diagenesis superimposed on episodic fracturing and fracture sealing. The minerals that fill fractures show significant temporal variations. Fracture sealing and low fracture porosity imply that only the most recently formed fractures are open to fluids.Microfractures in rocks from two geothermal areas
Core Analysis At Raft River Geothermal Area (1979)Core Analysis1979not indicatedPermitted the lateral and vertical extrapolation of core and test data and bridged the gap between surface geophysical data and core analyses.1) Microcracks were observed in core samples. A set of observable characteristics of microcracks were discovered in racks from geothermal regions that appears to be unique and to have considerable potential for exploration for geothermal regions. Both permeability and electrical conductivity were measured for a suite of samples with a range of microcracks characteristics. A partial set of samples were collected to study migration of radioactive elements. 2) Laboratory analyses of cores from the intermediate depth holes were used to provide a qualitative and quantitative basis for a detailed interpretation of logs from the shallow part of the reservoir. A less detailed interpretation of logs from the deeper part of the reservoir is based on much less corroborative evidence. Extensive use was made of computer plotting techniques to arrive at some interpretations.Both the stratigraphic correlation utilizing a full suite of logs and the attitude of bedding calculated from acoustic televiewer logs indicate gentle dips throughout most of the reservoir with some local fractures.Microcrack technology. Progress report, 1 October 1978--31 March 1979
Role of borehole geophysics in defining the physical characteristics of the Raft River geothermal reservoir, Idaho
Core Analysis At Raft River Geothermal Area (1981)Core Analysis1981not indicatedDetermine fault and joint geometryCore taken from less than 200 m above the decollement contains two sets of normal faults. The major set of faults dips between 500 and 70 0. These faults occur as conjugate pairs that are bisected by vertical extension fractures. The second set of faults dips 100 to 200 and may parallel part of the basal decollement or reflect the presence of listric normal faults in the upper plate.Fault and joint geometry at Raft River geothermal area, Idaho
Core Analysis At Raft River Geothermal Area (2011)Core Analysis2011not indicatedExplore for development of an EGS demonstration projectCore was obtained from RRG-3C. The sample is a brecciated and altered siltstone from the base of the Tertiary sequence and is similar to rocks at the base of the Tertiary deposits in RRG-9. The results of thermal and quasi-static mechanical property measurements that were conducted on the core sample are presented.GEOLOGY AND HYDROTHERMAL ALTERATION OF THE RAFT RIVER GEOTHERMAL SYSTEM, IDAHO
Cuttings Analysis At Raft River Geothermal Area (1976)Cuttings Analysis1976not indicatedDetermine the geologic environment of the geothermal areaThe geologic environment of the particular areas of interest are described, including rock types, geologic structure, and other important parameters that help describe the reservoir and overlying cap rock.Geotechnical studies of geothermal reservoirs
DC Resistivity Survey (Schlumberger Array) At Raft River Geothermal Area (1974-1975)DC Resistivity Survey (Schlumberger Array)19741975not indicatedHydrogeologic study of the areaIn 1975, the U.S. Geological Survey made 70 Schlumberger resistivity soundings in the Upper Raft River Valley and in parts of the Raft River Valley. These soundings complement the 79 soundings made previously in the Raft River Valley and bring the total number of soundings to 149. This work was done as part of a hydrogeologic study of the area. The location, number, and azimuth of all 149 Schlumberger sounding stations are presented.Schlumberger soundings in the Upper Raft River and Raft River Valleys, Idaho and Utah
Development Wells At Raft River Geothermal Area (2004)Development Wells2004not indicatedGeothermal Resource Exploration and Definition Projects Raft River (GRED II): Re-assessment and testing of previously abandoned production wells. The objective of the U.S. Geothermal effort is to re-access the available wellbores, assess their condition, perform extensive testing of the reservoir to determine its productive capacity, and perform a resource utilization assessment. At the time of this paper, all five wells had been successfully re-entered and were undergoing testing. A LEAMS unit was modified for Raft River and is working extremely well during this flow-test phaseGeothermal Resource Exploration and Definition Projects
Direct-Current Resistivity Survey At Raft River Geothermal Area (1975)Direct-Current Resistivity Survey1975not indicatedDC resistivity surveys were undertaken at the Raft River geothermal area.Exploring the Raft River geothermal area, Idaho, with the dc resistivity method (Abstract)
Direct-Current Resistivity Survey At Raft River Geothermal Area (1983)Direct-Current Resistivity Survey1983not indicatedThe objectives of the resistivity measurements were to determine if measureable changes could be observed and whether they could be used to infer the direction of fluid flow. Most of the apparent resistivity changes observed after the injection phase of Test 5 are smaller than the estimated standard deviation of the measurements. However, the contour map of the changes suggest an anomalous trend to the northeast which is similar to the trend in the self-potential data.Resistivity measurements before and after injection Test 5 at Raft River KGRA, Idaho. Final report
Earth Tidal Analysis At Raft River Geothermal Area (1980)Earth Tidal Analysis1980not indicatedDetermine the reservoir response to tidal and barometric effectsPorosity-total compressibility product evaluation based on tidal strain response compares favorably with results based on conventional pumping techniques. Analysis of reservoir response to barometric loading using Auto Regressive Integrated Moving Average (ARIMA) stochastic modeling appears also to have potential use for the evaluation of reservoir parameters.Reservoir response to tidal and barometric effects
Earth Tidal Analysis At Raft River Geothermal Area (1982)Earth Tidal Analysis1982not indicatedTo estimate subsurface fracture orientation based on an analysis of solid earth tidal strains.A new practical method has been developed. The tidal strain fracture orientation technique is a passive method which has no depth limitation. The orientation of either natural or hydraulically stimulated fractures can be measured using either new or old static observation wells. Estimates for total compressibility and areal interconnected porosity can also be developed for reservoirs with matrix permeability using a combination of tidal and barometric strain analysis. The tidal method has been successfully demonstrated at the naturally fractured Raft River geothermal field.Fracture orientation analysis by the solid earth tidal strain method
Evaluation of subsurface fracture geometry using fluid pressure response to solid earth tidal strain
Earth Tidal Analysis At Raft River Geothermal Area (1984)Earth Tidal Analysis1984usefulDetermine porosity of the reservoirThe response of a confined, areally infinite aquifer to external loads imposed by earth tides is examined. Because the gravitational influence of celestial objects occurs over large areas of the earth, the confined aquifer is assumed to respond in an undrained fashion. Since undrained response is controlled by water compressibility, earth tide response can be directly used only to evaluate porous medium compressibility if porosity is known. In the present work, change in external stress is estimated from dilatation by assuming a reasonable value for bulk modulus. Earth tide response of geothermal aquifers were analyzed, and the ratio of S3 to porosity was estimated. Comparison of these estimates with independent pumping tests show reasonable agreement.Interpretation of earth tide response of three deep, confined aquifers
Electromagnetic Soundings At Raft River Geothermal Area (1977)Electromagnetic Sounding Techniques1977not indicatedThe purpose of the survey was: (1) to field test U.S. Geological Survey extra-low-frequency (ELF) equipment using a grounded wire source and receiver loop configuration (which is designed to measure the vertical magnetic field (Hz) at the loop center for various frequencies); (2) to present an example of the EM sounding data and interpretations using a previously developed inversion program; and (3) to compare graphically the EM results with previously reported DC Schlumberger results for a geothermal environment.Five ELF frequency soundings were made using a grounded wire source with a minimum length of 1480 meters and a maximum length of 3057 meters. The maximum frequency range for each sounding was from 1 hertz to 2000 hertz.Interpretation of electromagnetic soundings in the Raft River geothermal area, Idaho
Exploratory Well At Raft River Geothermal Area (1950)Exploratory Well1950not indicatedAgricultural WellsThe geothermal resource at Raft River was discovered sometime prior to 1950 when two shallow agricultural wells, the Bridge and Crank wells, encountered boiling water.BOREHOLE PRECONDITIONING OF GEOTHERMAL WELLS FOR ENHANCED GEOTHERMAL SYSTEM RESERVOIR DEVELOPMENT
Exploratory Well At Raft River Geothermal Area (1975)Exploratory Well1975not indicatedFirst exploratory wellRaft River Geothermal Exploratory Hole No. 1 (RRGE-1) is drilled.Raft River Geothermal Exploratory Hole No. 1 (RRGE-1). Completion report
Geothermal R and D project report, October 1, 1976--March 31, 1977
Deep drilling data Raft River geothermal area, Idaho
Exploratory Well At Raft River Geothermal Area (1976)Exploratory Well1976not indicatedSecond and third exploratory wells drilledRaft River Geothermal Exploratory Hole No. 2, RRGE-2 drilled. During this period, a third well, RRGE-3 was also drilled and well production was tested. Down-hole data was obtained from RRGE-3.Raft River Geothermal Exploratory Hole No. 2, RRGE-2. Completion report
Geothermal R and D Project report for period April 1, 1976 to June 30, 1976
Geothermal R and D project report, October 1, 1976--March 31, 1977
Raft River Geothermal Exploratory Hole No. 3
Deep drilling data Raft River geothermal area, Idaho
Exploratory Well At Raft River Geothermal Area (1977)Exploratory Well1977not indicatedRaft River Geothermal Exploratory Hole No. 4, RRGE-4 drilled. During this time Raft River geothermal exploration well sidetrack-C also completed.Update on the Raft River Geothermal Reservoir
Deep drilling data, Raft River geothermal area, Idaho-Raft River geothermal exploration well sidetrack-C
Fault Mapping At Raft River Geothermal Area (1993)Fault Mapping1993usefulGeologic mapping, strain and kinematic analysisThe mountains expose a detachment fault that separates a hanging wall of Paleozoic rocks from Proterozoic and Archean rocks of the footwall. Beneath the detachment lies a 100 to 300m-thick top-to-the-east extensional shear zone. Geologic mapping, strain and kinematic analysis, and 40Ar/39Ar thermochronology suggest that the shear zone and detachment fault had an initial low-angle regional dip(<200). Along a 27 km, E-W transect across the south flank of the range, the base of the shear zone everywhere lies 20 to 60 m beneath the Archean/Proterozoic unconformity, despite an eastward-increasing lateral strain gradient. Strain analyses of mylonite coupled with the regional relationship between the unconformity and the shear zone boundary indicates that the unconformity and overlying Proterozoic metasediments were not rotated into parallelism with the shear zone boundary, but were initially subparallel (0--20).Geologic and thermochronologic constraints on the initial orientation of the Raft River detachment and footwall shear zone
Rheological control on the initial geometry of the Raft River detachment fault and shear zone, western United States
Field Mapping At Raft River Geothermal Area (1977)Field Mapping1977usefulTo estimate the permeability and storage parameters of the geothermal reservoir, and the possible existence of barrier boundaries.Production and interference tests were conducted on the geothermal wells RRGE 1 and RRGE 2 during September--November, 1975. In all, three tests were conducted, two of them being short-duration production tests and one, a long duration interference test. The data collected during the tests also indicated that the reservoir pressure varies systematically in response to the changes in the Earth's gravitational field caused by the passage of the sun and the moon. Overall, the results of the tests indicate that the geothermal reservoir in southern Raft River valley is fairly extensive and significantly permeable and merits further exploration.Reservoir evaluation tests on RRGE 1 and RRGE 2, Raft River Geothermal Project, Idaho
Field Mapping At Raft River Geothermal Area (1980)Field Mapping1980not indicatedDelineate the subsurface geologyThe Raft River Valley occupies an upper Cenozoic structural basin filled with nearly 1600 m of fluvial silt, sand, and gravel. Rapid facies and thickness changes, steep initial dips (30 0C), and alteration make correlation of basin-fill depositional units very difficult. The Raft River geothermal system is a hot water convective system relying on deep circulation of meteoric water in a region of high geothermal gradients and open fractures near the base of the Tertiary basin fill.Subsurface geology of the Raft River geothermal area, Idaho
Field Mapping At Raft River Geothermal Area (1990)Field Mapping1990not indicatedTogether, field and 40Ar/39Ar results suggest that Late Cretaceous extension occurred in the Sevier belt hinterland at the same time as shortening in the eastern foreland and at depth in the hinterland. Sufficient topography must have been present to drive upper-crustal extension in the eastern hinterland.Late Cretaceous extension in the hinterland of the Sevier thrust belt, northwestern Utah and southern Idaho
Field Mapping At Raft River Geothermal Area (1993)Field Mapping1993not indicatedTo determine the importance of Early to Middle Miocene period in the northern Basin and Range region.New apatite fission track cooling age and track length data, supplemented by other information, point to the Early to Middle Miocene as an additional time of very significant extension-induced uplift and range formation. Many ranges in a 700-km-long north-south corridor from the Utah-Nevada-Idaho border to southernmost Nevada experience extension and major exhumation in Early to Middle Miocene time. Reconnaissance apatite ages from the Toiyabe Range and environs (NV) are (approximately)15 Ma and geologic data indicate Early to Middle Miocene extension at Yerington NV (Proffet and Dillis, 1984). Thus, it appears from the available data that the Early to Middle Miocene was an important, and previously little recognized, period of major extension over broad areas of the northern Basin and Range.Fission track evidence for widespread early to Middle miocene extension in the northern Basin and Range province
Flow Test At Raft River Geothermal Area (1979)Flow Test1979usefulTo allow for the lateral and vertical extrapolation of core and test data and bridged the gap between surface geophysical data and core analyses.Temperature and flowmeter logs provide evidence that these fractures and faults are conduits that conduct hot water to the wells. One of the intermediate depth core holes penetrated a hydrothermally altered zone that includes several fractures producing hot water. This altered production zone could be distinguished by several logs.Role of borehole geophysics in defining the physical characteristics of the Raft River geothermal reservoir, Idaho
Flow Test At Raft River Geothermal Area (2004)Flow Test2004usefulGeothermal Resource Exploration and Definition Projects Raft River (GRED II): Re-assessment and testing of previously abandoned production wells. The objective of the U.S. Geothermal effort is to re-access the available wellbores, assess their condition, perform extensive testing of the reservoir to determine its productive capacity, and perform a resource utilization assessment. At the time of this paper, all five wells had been successfully re-entered and were undergoing testing. A LEAMS unit was modified for Raft River and is working extremely well during this flow-test phase.Geothermal Resource Exploration and Definition Projects
Flow Test At Raft River Geothermal Area (2006)Flow Test2006not indicatedDetermine field hydraulic conductivity using borehole impeller flowmeter dataA quantitative evaluation of borehole-impeller flowmeter data leads to estimated field hydraulic conductivity. Data were obtained during an injection test of a geothermal well at the Raft River geothermal test site in Idaho. Both stationary and trolling calibrations of the flowmeter were made in the well. Methods were developed to adjust for variations in hole diameter, impeller speed, and trolling speed. These methods were applied to evaluate water losses into the formation as a function of depth.The flowmeter data were digitized and processed by the computer to obtain plots of apparent field hydraulic conductivity versus depth.FLOWMETER ANALYSIS AT RAFT RIVER, IDAHO
Flow Test At Raft River Geothermal Area (2008)Flow Test2008not indicatedTo confirm resource using flow testsBoth production and injection wells were flow tested. Aslo includes interference testing across the well field.Final Technical Resource Confirmation Testing at the Raft River Geothermal Project, Cassia County, Idaho
Fluid Inclusion Analysis At Raft River Geothermal Area (2011)Fluid Inclusion Analysis2011not indicatedHydrogen isotope values of muscovite (δDMs ∼–100‰) and fluid inclusions in quartz (δDFluid ∼–85‰) indicate the presence of meteoric fluids during detachment dynamics. Recrystallized grain-shape fabrics and quartz c-axis fabric patterns reveal a large component of coaxial strain (pure shear), consistent with thinning of the detachment section. Therefore, the high thermal gradient preserved in the Raft River detachment reflects the transient geotherm that developed owing to shearing, thinning, and the potentially prominent role of convective flow of surface fluids.Preservation of an extreme transient geotherm in the Raft River detachment shear zone
Gamma Log At Raft River Geothermal Area (1979)Gamma Log1979usefulTo allow for the lateral and vertical extrapolation of core and test data and bridged the gap between surface geophysical data and core analyses.Borehole gamma spectrometry can be used to identify anomalous concentration of uranium, thorium, and potassium which are probably due to transportation by hydrothermal solutions. Computer crossplotting was used as an aid to the identification of such rock types as quartzite, quartz monzonite, and biotite schist in the deeper wells. Alteration of biotite schist to chlorite schist was also recognizable on these logs using computer-based analysis.Role of borehole geophysics in defining the physical characteristics of the Raft River geothermal reservoir, Idaho
Geophysical Method At Raft River Geothermal Area (1975)Geophysical Techniques1975not indicatedGeologic and geophysics studies were completed at the Raft River valley.Geological and geophysical studies of a geothermal area in the southern Raft river valley, Idaho
Geophysical Method At Raft River Geothermal Area (1977)Geophysical Techniques1977not indicatedBorehole geophysics were completed at the Raft River valley, Idaho.Borehole geophysics evaluation of the Raft River geothermal reservoir, Idaho
Geothermometry At Raft River Geothermal Area (1973)Geothermometry1973not indicatedAt least 380 hot springs and wells are known to occur throughout the central and southern parts of Idaho.Estimated aquifer temperatures, calculated using the silica and the sodium-potassium-calcium geochemical thermometers, range from 5 to 3700C and averaged 1100C. Estimated aquifer temperatures in excess of 1400C were found at 42 sites.Geothermal investigations in Idaho. Part 1. Geochemistry and geologic setting of selected thermal waters
Geothermometry At Raft River Geothermal Area (1980)Geothermometry1980not indicatedGeothermometer temperatures of shallow samples suggest significant re-equilibration at temperatures below those found in the deep wells. Silica geothermometer temperatures of water samples from the deep wells are in reasonable agreement with measured temperatures, whereas Na-K-Ca temperatures are significantly higher than measured temperatures. The chemical characteristics of the water, as indicated by chloride concentration, are extremely variable in shallow and deep samples. Chloride concentrations of the deep samples range from 580 to 2200 mg/kg.Temperatures, heat flow, and water chemistry from drill holes in the Raft River geothermal system, Cassia County, Idaho
Temperature, thermal-conductivity, and heat-flux data,Raft River area, Cassia County, Idaho (1974-1976)
Ground Gravity Survey At Raft River Geothermal Area (1957-1961)Ground Gravity Survey19571961not indicatedFrom 1957 to 1961 a regional gravity survey was made over the northern part of the Great Salt Lake Desert and adjacent areas in Utah, eastern Nevada, and southeastern Idaho. A total of 1040 stations were taken over an area of about 7000 square miles. The results were compiled as a Bouguer gravity anomaly map with a contour interval of 2 mgal. The Bouguer values ranged from a high of about —120 mgal over the outcrop areas to a low of about —196 mgal over the alluvium-covered graben areas. The gravity high over the Raft River Mountains apparently corresponds with the Raft River Mountains anticline.Regional Gravity Survey of the Northern Great Salt Lake Desert and Adjacent Areas in Utah, Nevada, and Idaho
Ground Gravity Survey At Raft River Geothermal Area (1978)Ground Gravity Survey1978not indicatedTo infer the structure and the general lithology underlying the valleyThe gravity data indicate the approximate thickness of the Cenozoic rocks and location of the larger normal faults.Reconnaissance geophysical studies of the geothermal system in southern Raft River Valley, Idaho
Ground Magnetics At Raft River Geothermal Area (1979)Ground Magnetics1979not indicatedTo investigate anomalous magnetizationThe investigation of anomalous magnetization in the Raft River valley, Idaho
Groundwater Sampling At Raft River Geothermal Area (1974-1982)Groundwater Sampling19741982usefulCollect baseline chemical dataGround-water monitoring near the Raft River site was initiated in 1974 by the IDWR. This effort consisted of semiannual chemical sampling of 22 irrigation wells near the Raft River geothermal development area. This program yielded useful baseline chemical data; however, several problems were inherent. For example, access to water pumped from the wells is limited to the irrigation season (April through September). All the wells are not continuously pumped; thus, some wells that are sampled one season cannot be sampled the next. In addition, information on well construction, completion, and production is often unreliable or not available.Raft River monitor well potentiometric head responses and water quality as related to the conceptual ground-water flow system
Groundwater Sampling At Raft River Geothermal Area (2004-2011)Groundwater Sampling20042011not indicatedCollect new water chemistry data on geothermal fieldFrom mid-2004 to present, US Geothermal Inc. has collected geochemical data from geothermal and monitoring wells in the field, as well as other shallow wells in the area. An additional sampling program was completed in July 2010 to measure a wider range of trace elements and key water isotopes (δ18O, δD, and 3H (Tritium)) in the field. The data indicate that the fluid geochemistry in the field is spatially variable and complex, with two distinct deep geothermal fluid types (high vs. low K, Na, Cl, Ca, Li, F concentrations) and two groundwater fluid types. These differences have been interpreted to reflect deep structural controls on fluid pathways in the field, which has compartmentalized the fluids and limited the degree of mixing between them.FLUID GEOCHEMISTRY AT THE RAFT RIVER GEOTHERMAL FIELD, IDAHO- NEW DATA AND HYDROGEOLOGICAL IMPLICATIONS
Injectivity Test At Raft River Geothermal Area (1979)Injectivity Test1979usefulQuantification of the pressure response prior to 600 minutes is not always possible. Short-duration (< 24-hour) injection or pump tests are conducted with the drilling rig equipment, and long-duration (21-day) injection and pump tests are then conducted with the permanent pumping facilities.Evaluation of testing and reservoir parameters in geothermal wells at Raft River and Boise, Idaho
Isotopic Analysis-Fluid At Raft River Geothermal Area (1977)Isotopic Analysis- Fluid1977not indicatedEstimate deep reservoir temperatureThe oxygen isotope compositions of dissolved sulfate and water from hot springs and shallow drillholes have been tested. Methods are described to calculate the effects of boiling and dilution. The geothermometer, is applied to thermal systems of Yellowstone Park, Wyoming, Long Valley, California, and Raft River, Idaho to estimate deep reservoir temperatures of 360, 240, and 1420C, respectively.Geothermal reservoir temperatures estimated from the oxygen isotope compositions of dissolved sulfate and water from hot springs and shallow drillholes
Isotopic Analysis-Fluid At Raft River Geothermal Area (1982)Isotopic Analysis- Fluid1982not usefulDetermine which reservoir model best matches the isotope data.1) Chemical and light-stable isotope data are presented for water samples from the Raft River geothermal area and nearby. On the basis of chemical character, as defined by a trilinear plot of per cent milliequivalents, and light-stable isotope data, the waters in the geothermal area can be divided into waters that have and have not mixed with cold water. 2) Helium isotope ratios have been measured in geothermal fluids. These ratios have been interpreted in terms of the processes which supply He in distinct isotopic ratios (i.e. magmatic He, ~10 Ra; atmospheric He, Ra; and crustal He, ~0.1 Ra) and in terms of the processes which can alter the isotopic ratio (hydrologic mixing, U-Th series alpha production and weathering release of crustal He, magma aging and tritiugenic addition of 3He). Raft River contains only crustal He indicating no active volcanic sources.Chemical and light-stable isotope characteristics of waters from the raft river geothermal area and environs, Cassia County, Idaho, Box Elder county, Utah
Helium isotopes in geothermal systems- Iceland, The Geysers, Raft River and Steamboat Springs
Magnetotellurics At Raft River Geothermal Area (1977)Magnetotellurics1977usefulMagnetotelluric soundings along a profile extending from the Raft River geothermal area in southern Idaho in Yellowstone National Park in Wyoming reveal a highly anomalous crustal structure involving a conductive zone at depths that range from 18 km in the central part of the eastern Snake River Plain to 7 km beneath the Raft River thermal area and as little as 5 km in Yellowstone. Resistivities in this conductive zone are less than 10 ohm-m and at some sites than 1 ohm-m.Geothermal significance of magnetotelluric sounding in the eastern Snake River Plain-Yellowstone Region
Micro-Earthquake At Raft River Geothermal Area (1979)Micro-Earthquake1979not indicatedRefraction SurveyInterpretation of seismic refraction recordings in the area yielded compressional velocities from near the surface to the crystalline basement at a maximum depth of approximately 1600 m. The results show a complex sequence of sediments and volcanic flows overlying basement. Velocities in the sedimentary section vary laterally. Correlation with well data suggests that zones of higher velocities may correspond to zones where sediments are hydrothermally altered. Flowing hot wells occur near the boundary between inferred shallow altered and unaltered rocks.Seismic refraction study of the Raft River geothermal area, Idaho
Micro-Earthquake At Raft River Geothermal Area (1982)Micro-Earthquake1982not indicatedDevelop a background seismicity before power production beginsLocal seismic networks were established to monitor the background seismicity prior to initiation of geothermal power production. The Raft River study area is currently seismically quiet down to the level of approximately magnitude one.Seismic baseline and induction studies- Roosevelt Hot Springs, Utah and Raft River, Idaho
Micro-Earthquake At Raft River Geothermal Area (2011)Micro-Earthquake2011not indicatedDetermine seismicity before and after reservoir stimulation for EGSThe overall goal is to gather high resolution seismicity data before, during and after stimulation activities at the EGS projects. This will include both surface and borehole deployments to provide high quality seismic data for improved processing and interpretation methodologies. This will allow the development and testing of seismic methods for understanding the performance of the EGS systems, as well as aid in developing induced seismicity mitigation techniques that can be used for a variety of EGS systems in the future.DOE REAL-TIME SEISMIC MONITORING AT ENHANCED GEOTHERMAL SYSTEM SITES
Modeling-Computer Simulations At Raft River Geothermal Area (1977)Modeling-Computer Simulations1977not indicatedSimulate reservoir performanceComputer models describing both the transient reservoir pressure behavior and the time dependent temperature response of the wells were developed. A horizontal, two-dimensional, finite-difference model for calculating pressure effects was constructed to simulate reservoir performance. Vertical, two-dimensional, finite-difference, axisymmetric models for each of the three existing wells were also constructed to describe the transient temperature and hydraulic behavior in the vicinity of the wells.Two-dimensional simulation of the Raft River geothermal reservoir and wells. (SINDA-3G program)
Modeling-Computer Simulations At Raft River Geothermal Area (1979)Modeling-Computer Simulations1979usefulTo evaluate the hydrodynamics of the unconfined aquifer.This study covers about 1000 mi2 (2600 km2) of the southern Raft River drainage basin in south-central Idaho and northwest Utah. The main area of interest, approximately 200 mi2 (520 km2) of semiarid agricultural and rangeland in the southern Raft River Valley that includes the known Geothermal Resource Area near Bridge, Idaho, was modelled numerically. Computed and estimated transmissivity values range from 1200 ft2 per day (110 m2 per day) to 73,500 ft2 per day (6830 m2 per day). It satisfactorily reproduced the historic water-level decline over the period 1952 to 1965.Simulation analysis of the unconfined aquifer, Raft River Geothermal Area, Idaho-Utah
Modeling-Computer Simulations At Raft River Geothermal Area (1980)Modeling-Computer Simulations1980not indicatedFrom refined estimates of reservoir coefficients better predictions of interference effects and long-term drawdown in the wells can be made.Analytic methods have been used during reservoir testing to calculate reservoir coefficients. However, anisotropy of the reservoir due to fractures has not been taken into account in these calculations and estimates of these coefficients need to be refined. In conjunction with the USGS, Faust and Mercer's 3-D finite difference model has been used to simulate the geothermal field. Intera used a 2-D simulator to predict temperatures, pressures over 30 years and movement of dissolved solids in the reservoir.Collection and Analysis of Reservoir Data from Testing and Operation of the Raft River 5 MW Power Plant
Modeling-Computer Simulations At Raft River Geothermal Area (1983)Modeling-Computer Simulations1983usefulPredict flow rate and porosityThe objectives of the physical modeling effort are to: (1) evaluate injection-backflow testing for fractured reservoirs under conditions of known reservoir parameters (porosity, fracture width, etc.); (2) study the mechanisms controlling solute transport in fracture systems; and (3) provide data for validation of numerical models that explicitly simulate solute migration in fracture systems. The fracture network is 0.57-m wide, 1.7-m long, and consists of two sets of fractures at right angles to one another with a fracture spacing of 10.2 cm. A plot of the fractional tracer recovery against quiescent time results in a straight line. This relationship, combined with classical reservoir engineering data, can be used to predict aquifer flow rate and porosity from known injection volumes and tracer recovery.Physical model of a fractured reservoir
Numerical Modeling At Raft River Geothermal Area (1983)Numerical Modeling1983not indicatedThe numerical modeling of the resistivity data is marginal for changes as small as those observed but the results suggest that changes of a few percent could be expected from a fracture zone extending from depth to within 100 m of the surface.Resistivity measurements before and after injection Test 5 at Raft River KGRA, Idaho. Final report
Petrography Analysis At Raft River Geothermal Area (1980)Petrography Analysis1980not indicatedDetermined rocks found in the geothermal field in the late cenozoic sediments.Petrography of late cenozoic sediments, Raft River geothermal field, Idaho
Petrography Analysis At Raft River Geothermal Area (2011)Petrography Analysis2011not indicatedExplore for development of an EGS demonstration projectX-ray diffraction and thin section analyses are being conducted on samples from 5 deep wells, RRG- 1, 2, 3, 7 and 9, to determine the characteristics of the rock types and hydrothermal alteration within the geothermal system. Thin section analyses of samples from RRG-9 document the presence of strong alteration and brecciation at the contact between the Tertiary and basement complex. The Tertiary rocks consist of ash-flow tuffs, lava flows, tuffaceous siltstone, greywacke, and sandstone.Geology and Hydrothermal Alteration of the Raft River Geothermal System, Idaho
Self Potential Measurements At Raft River Geothermal Area (1983)Self Potential Measurements1983not indicatedSelf-potential measurements before and during injection tests at Raft River KGRA, Idaho indicate a small negative change. The magnitude of the change (5 to 10 mV) is near the noise level (5 mV) but they extend over a fairly broad area. The presence of a cathodic protection system clouds the issue of the validity of the changes, however the form of the observed changes cannot be explained by any simple change in the current strength of the protection system. Furthermore, similar changes are observed for two separate tests, months apart. Modeling of the changes indicate that they are likely caused by a fracture extending from the reservoir (1400 m) to close to the surface.Interpretation of self-potential measurements during injection tests at Raft River, Idaho. Final report
Surface Water Sampling At Raft River Geothermal Area (1973)Surface Water Sampling1973not indicatedAt least 380 hot springs and wells are known to occur throughout the central and southern parts of Idaho.One hundred twenty-four of 380 hot springs and wells in the central and southern parts of Idaho were inventoried as a part of the study reported on herein. At the spring vents and wells visited, the thermal waters flow from rocks ranging in age from Precambrian to Holocene and from a wide range of rock types-igneous, metamorphic, and both consolidated and unconsolidated sediments. Twenty-eight of the sites visited occur on or near fault zones while a greater number were thought to be related to faulting. Measured water temperatures at the 124 wells and springs inventoried ranged from 12 to 930C and averaged 500C. Estimated aquifer temperatures, calculated using the silica and the sodium-potassium-calcium geochemical thermometers, range from 5 to 3700C and averaged 1100C. Estimated aquifer temperatures in excess of 1400C were found at 42 sites.Geothermal investigations in Idaho. Part 1. Geochemistry and geologic setting of selected thermal waters
Telluric Survey At Raft River Geothermal Area (1978)Telluric Survey1978not indicatedInfer the structure and the general lithology underlying the valleyThe relative ellipse area contour map compiled from the telluric current survey generally conforms to the gravity map except for lower values in the area of the geothermal system.Reconnaissance geophysical studies of the geothermal system in southern Raft River Valley, Idaho
Thermal And-Or Near Infrared At Raft River Geothermal Area (1974-1976)Thermal And-Or Near Infrared19741976usefulReconnaissance geothermal explorationA TIR survey of the Raft River geothermal area prospect in Idaho where thermal waters move laterally in an alluvial plain and have no visible surface manifestations was undertaken as part of geothermal exploration.Geothermal Reconnaissance From Quantitative Analysis Of Thermal Infrared Imagery
Reconnaissance geothermal exploration at Raft River, Idaho from thermal infrared scanning
Thermal And-Or Near Infrared At Raft River Geothermal Area (1997)Thermal And-Or Near Infrared1997not indicatedLocate geothermal surface manifestationsSeveral examples of the use of TIR to locate geothermal surface manifestations and notes that TIR is more useful in remote areas. The analysis of three TIR images acquired during a diurnal cycle at Raft River is presented. The purpose of these images was to minimize the masking of temperature variations by vegetation and topography.Remote Sensing- Principles And Interpretation
Thermochronometry At Raft River Geothermal Area (1993)Thermochronometry1993not indicatedConstraints on the initial orientation and crustal position of the shear zone have been derived from 40Ar/39Ar thermochronology of mineral suites (hornblende, muscovite, biotite, and k-feldspar) collected within and beneath the shear zone along a 27 km transect parallel to the transport direction.Geologic and thermochronologic constraints on the initial orientation of the Raft River detachment and footwall shear zone
Dating of major normal fault systems using thermochronology- An example from the Raft River detachment, Basin and Range, western United States
Tracer Testing At Raft River Geothermal Area (1983)Tracer Testing1983not indicatedTo develop chemical tracing procedures for geothermal areas.Two field experiments were conducted to develop chemical tracer procedures for use with injection-backflow testing, one on the fracture-permeability Raft River reservoir and the other on the matrix-permeability East Mesa reservoir. Results from tests conducted with incremental increases in the injection volume at both East Mesa and Raft River suggests that, for both reservoirs, permeability remained uniform with increasing distance from the well bore. Increased mixing during quiescent periods, between injection and backflow, at Raft River suggest an area near the well bore that has a hydrologic character different from the far well bore environment.Tracer Recovery and Mixing from Two Geothermal Injection-Backflow Studies
Tracer Testing At Raft River Geothermal Area (1984)Tracer Testing1984not indicatedTracer testing was undertaken at Raft River geothermal area.Preferred methods of analysis for chemical tracers in moderate- and high-temperature geothermal environments
Well Log Techniques At Raft River Geothermal Area (1977)Well Log Techniques1977not indicatedCharacterize the rock using well log data.Information is given on the following logs: dual-induction focused log, including resistivity, sp, and conductivity; acoustic log; compensated neutron; compensated densilog; and caliper. Lithologic breaks for a drill core to a depth of 2840 ft are illustrated.Deep drilling data, Raft River geothermal area, Idaho Raft River geothermal exploration well No. 4