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• 1. [Image] The Cody Hydrothermal System

  	The hot springs of Colter's Hell are the surface manifestations of a much larger hydrothermal system. That system has been studied to define its extent, maximum temperature, and mechanism of operation. ...
  	Citation × Citation Citation Abstract Copy Title: The Cody Hydrothermal System Author: Heasler, H.P. Year: 1982 The hot springs of Colter's Hell are the surface manifestations of a much larger hydrothermal system. That system has been studied to define its extent, maximum temperature, and mechanism of operation. The study area covers 2700 km/sup 2/ (1040 mi/sup 2/) in northwest Wyoming. Research and field work included locating and sampling the hot springs, geologic mapping, thermal logging of available wells, measuring thermal conductivities, analyzing over 200 oil and gas well bottom-hole temperatures, and compiling and analyzing hydrologic data. These data were used to generate a model for the hydrothermal system Title: The Cody Hydrothermal System Author: Heasler, H.P. Year: 1982 The hot springs of Colter's Hell are the surface manifestations of a much larger hydrothermal system. That system has been studied to define its extent, maximum temperature, and mechanism of operation. The study area covers 2700 km/sup 2/ (1040 mi/sup 2/) in northwest Wyoming. Research and field work included locating and sampling the hot springs, geologic mapping, thermal logging of available wells, measuring thermal conductivities, analyzing over 200 oil and gas well bottom-hole temperatures, and compiling and analyzing hydrologic data. These data were used to generate a model for the hydrothermal system Close

• 2. [Image] Interactive Fracture Design Model

  	A computer program is described that can be used to design a fracture stimulation treatment for a geothermal reservoir. The program uses state-of-the-art methods to calculate the temperature of the fracture ...
  	Citation × Citation Citation Abstract Copy Title: Interactive Fracture Design Model Author: Petroleum Training and Technical Services Year: 1980 A computer program is described that can be used to design a fracture stimulation treatment for a geothermal reservoir. The program uses state-of-the-art methods to calculate the temperature of the fracture fluid as a function of time and distance in the fracture. This information is used to determine the temperature dependent properties of the fracture fluid. These fluid properties are utilized to calculate the fracture geometry as a function of time. The fracture geometry and temperature distribution of the fracture fluid are coupled so the subroutines that calculate these distributions have been made interactive Title: Interactive Fracture Design Model Author: Petroleum Training and Technical Services Year: 1980 A computer program is described that can be used to design a fracture stimulation treatment for a geothermal reservoir. The program uses state-of-the-art methods to calculate the temperature of the fracture fluid as a function of time and distance in the fracture. This information is used to determine the temperature dependent properties of the fracture fluid. These fluid properties are utilized to calculate the fracture geometry as a function of time. The fracture geometry and temperature distribution of the fracture fluid are coupled so the subroutines that calculate these distributions have been made interactive Close

• 3. [Image] Formation Temperature Gauge Feasibility Study. Volume II, Interim Report

  	The present status of the formation temperature gauge feasibility study is reported. It also demonstrates the feasibility of the technique in the simplified situations examined to date both analytically ...
  	Citation × Citation Citation Abstract Copy Title: Formation Temperature Gauge Feasibility Study. Volume II, Interim Report Author: IRT Corporation Year: 1977 The present status of the formation temperature gauge feasibility study is reported. It also demonstrates the feasibility of the technique in the simplified situations examined to date both analytically and experimentally. The first section deals with the theory underlying the technique. The next three sections describe the temperature gauge, the simplified model calculations of the gauge response, and the preliminary experimental measurements performed to verify the results of the computational study. The final section describes the formation temperature test stand designed to demonstrate the feasibility of the technique in the geothermal well geometry. This test stand has been assembled and measurements of the gauge response will begin shortly. These are outlined at the end of this report Title: Formation Temperature Gauge Feasibility Study. Volume II, Interim Report Author: IRT Corporation Year: 1977 The present status of the formation temperature gauge feasibility study is reported. It also demonstrates the feasibility of the technique in the simplified situations examined to date both analytically and experimentally. The first section deals with the theory underlying the technique. The next three sections describe the temperature gauge, the simplified model calculations of the gauge response, and the preliminary experimental measurements performed to verify the results of the computational study. The final section describes the formation temperature test stand designed to demonstrate the feasibility of the technique in the geothermal well geometry. This test stand has been assembled and measurements of the gauge response will begin shortly. These are outlined at the end of this report Close

• 4. [Image] A Geological and Geophysical Study of the Geothermal Energy Potential of Pilgrim Springs, Alaska

  	The Pilgrim Springs geothermal area, located about 75 km north of Nome, was the subject of an intensive, reconnaissance-level geophysical and geological study during a 90-day period in the summer of 1979. ...
  	Citation × Citation Citation Abstract Copy Title: A Geological and Geophysical Study of the Geothermal Energy Potential of Pilgrim Springs, Alaska Author: Turner, Donald L. [ed.] Year: 1980 The Pilgrim Springs geothermal area, located about 75 km north of Nome, was the subject of an intensive, reconnaissance-level geophysical and geological study during a 90-day period in the summer of 1979. The thermal springs are located in a northeast-oriented, oval area of thawed ground approximately 1.5 km{sup 2} in size, bordered on the north by the Pilgrim River. A second, much smaller, thermal anomaly was discovered about 3 km northeast of the main thawed area. Continuous permafrost in the surrounding region is on the order of 100 m thick. Present surface thermal spring discharge is {approx} 4.2 x 10{sup -3} m{sup 3} s{sup -1} (67 gallons/minute) of alkali-chloride-type water at a temperature of 81 C. The reason for its high salinity is not yet understood because of conflicting evidence for seawater vs. other possible water sources. Preliminary Na-K-Ca geothermometry suggests deep reservoir temperatures approaching 150 C, but interpretation of these results is difficult because of their dependence on an unknown water mixing history. Based on these estimates, and present surface and drill hole water temperatures, Pilgrim Springs would be classified as an intermediate-temperature, liquid-dominated geothermal system; UAG-R-271 Title: A Geological and Geophysical Study of the Geothermal Energy Potential of Pilgrim Springs, Alaska Author: Turner, Donald L. [ed.] Year: 1980 The Pilgrim Springs geothermal area, located about 75 km north of Nome, was the subject of an intensive, reconnaissance-level geophysical and geological study during a 90-day period in the summer of 1979. The thermal springs are located in a northeast-oriented, oval area of thawed ground approximately 1.5 km{sup 2} in size, bordered on the north by the Pilgrim River. A second, much smaller, thermal anomaly was discovered about 3 km northeast of the main thawed area. Continuous permafrost in the surrounding region is on the order of 100 m thick. Present surface thermal spring discharge is {approx} 4.2 x 10{sup -3} m{sup 3} s{sup -1} (67 gallons/minute) of alkali-chloride-type water at a temperature of 81 C. The reason for its high salinity is not yet understood because of conflicting evidence for seawater vs. other possible water sources. Preliminary Na-K-Ca geothermometry suggests deep reservoir temperatures approaching 150 C, but interpretation of these results is difficult because of their dependence on an unknown water mixing history. Based on these estimates, and present surface and drill hole water temperatures, Pilgrim Springs would be classified as an intermediate-temperature, liquid-dominated geothermal system; UAG-R-271 Close

• 5. [Image] Thermal Drawdown and Recovery of Singly and Multiply Fractured Hot Dry Rock Reservoirs

  	To calculate heat extraction and thermal recovery in hot dry rock geothermal reservoirs, a computer code was written to solve the differential equations for rock-water heat conduction and convection by ...
  	Citation × Citation Citation Abstract Copy Title: Thermal Drawdown and Recovery of Singly and Multiply Fractured Hot Dry Rock Reservoirs Author: Wunder, R. Year: 1978 To calculate heat extraction and thermal recovery in hot dry rock geothermal reservoirs, a computer code was written to solve the differential equations for rock-water heat conduction and convection by finite differences. Temperature versus time functions for multiple fractures separated by various spacings are presented in dimensional and in nondimensional plots. The results were specialized for the limiting case of a single fracture in unbounded rock and for the other limiting case where the rock is so extensively fractured that thermal breakthrough phenomena can occur. Fracture temperatures were calculated during the thermal recovery following various extraction periods. For the single-fracture case these temperature recoveries could, with slight approximation, be represented as a single curve depending only upon the ratio of the total elapsed time and the extraction time Title: Thermal Drawdown and Recovery of Singly and Multiply Fractured Hot Dry Rock Reservoirs Author: Wunder, R. Year: 1978 To calculate heat extraction and thermal recovery in hot dry rock geothermal reservoirs, a computer code was written to solve the differential equations for rock-water heat conduction and convection by finite differences. Temperature versus time functions for multiple fractures separated by various spacings are presented in dimensional and in nondimensional plots. The results were specialized for the limiting case of a single fracture in unbounded rock and for the other limiting case where the rock is so extensively fractured that thermal breakthrough phenomena can occur. Fracture temperatures were calculated during the thermal recovery following various extraction periods. For the single-fracture case these temperature recoveries could, with slight approximation, be represented as a single curve depending only upon the ratio of the total elapsed time and the extraction time Close

• 6. [Image] A Thermodynamic Model of the Hydrolysis of Microcline in Acid Sulfate Solutions

  	A theoretical model of the hydrolysis of microcline by a hydrothermal solution has been determined for a closed system at constant temperature. Hypothetical solution compositions and temperatures were ...
  	Citation × Citation Citation Abstract Copy Title: A Thermodynamic Model of the Hydrolysis of Microcline in Acid Sulfate Solutions Author: Dedolph, R.E. Year: 1976 A theoretical model of the hydrolysis of microcline by a hydrothermal solution has been determined for a closed system at constant temperature. Hypothetical solution compositions and temperatures were chosen to match the known geothermal system at Roosevelt Hot Springs, Utah. The calculated reaction paths indicate that the overall reaction process is an exchange of potassium from the reactant mineral, microcline, for hydrogen from the solution. Aluminum is nearly conserved among solid phases. The amount of microcline reacted per kilogram of solution before overall equilibrium is reached is a function of temperature and initial solution pH. Since the system is closed and at constant temperature natural conditions are not reproduced well enough to apply the model as a geothermometer. The reaction paths suggest qualitative models of alteration mineral zoning patterns that are similar to zoning at Roosevelt Hot Springs, Utah; Steamboat Springs, Nevada, and Butte, Montana. The models presented view alteration zoning as a function of temperature and pH gradients within homogeneous host rocks where microcline and quartz are abundant Title: A Thermodynamic Model of the Hydrolysis of Microcline in Acid Sulfate Solutions Author: Dedolph, R.E. Year: 1976 A theoretical model of the hydrolysis of microcline by a hydrothermal solution has been determined for a closed system at constant temperature. Hypothetical solution compositions and temperatures were chosen to match the known geothermal system at Roosevelt Hot Springs, Utah. The calculated reaction paths indicate that the overall reaction process is an exchange of potassium from the reactant mineral, microcline, for hydrogen from the solution. Aluminum is nearly conserved among solid phases. The amount of microcline reacted per kilogram of solution before overall equilibrium is reached is a function of temperature and initial solution pH. Since the system is closed and at constant temperature natural conditions are not reproduced well enough to apply the model as a geothermometer. The reaction paths suggest qualitative models of alteration mineral zoning patterns that are similar to zoning at Roosevelt Hot Springs, Utah; Steamboat Springs, Nevada, and Butte, Montana. The models presented view alteration zoning as a function of temperature and pH gradients within homogeneous host rocks where microcline and quartz are abundant Close

• 7. [Image] Geological and Geophysical Analysis of Coso Geothermal Exploration Hole No. 1 (CGEH-1), Coso Hot Springs KGRA, California

  	The Coso Geothermal Exploration Hole number one (CGEH-1) was drilled in the Coso Hot Springs KGRA, California from September 2 to December 2, 1977. Chip samples were collected at ten foot intervals and ...
  	Citation × Citation Citation Abstract Copy Title: Geological and Geophysical Analysis of Coso Geothermal Exploration Hole No. 1 (CGEH-1), Coso Hot Springs KGRA, California Author: Galbraith, R.M. Year: 1978 The Coso Geothermal Exploration Hole number one (CGEH-1) was drilled in the Coso Hot Springs KGRA, California from September 2 to December 2, 1977. Chip samples were collected at ten foot intervals and extensive geophysical logging surveys were conducted to document the geologic character of the geothermal system as penetrated by CGEH-1. The major rock units encountered include a mafic metamorphic sequence and a leucogranite which intruded the metamorphic rocks. Only weak hydrothermal alteration was noted in these rocks. Drillhole surveys and drilling rate data indicate that the geothermal system is structurally controlled and that the drillhole itself was strongly influenced by structural zones. Water chemistry indicates that this geothermal resource is a hot-water rather than a vapor-dominated system. Several geophysical logs were employed to characterize the drillhole geology. The natural gamma and neutron porosity logs indicate gross rock type and the acoustic logs indicate fractured rock and potentially permeable zones. A series of temperature logs run as a function of time during and after the completion of Drilling were most Useful in delineating the zones of maximum heat flux. Convective heat flow and temperatures greater than 350/sup 0/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 Title: Geological and Geophysical Analysis of Coso Geothermal Exploration Hole No. 1 (CGEH-1), Coso Hot Springs KGRA, California Author: Galbraith, R.M. Year: 1978 The Coso Geothermal Exploration Hole number one (CGEH-1) was drilled in the Coso Hot Springs KGRA, California from September 2 to December 2, 1977. Chip samples were collected at ten foot intervals and extensive geophysical logging surveys were conducted to document the geologic character of the geothermal system as penetrated by CGEH-1. The major rock units encountered include a mafic metamorphic sequence and a leucogranite which intruded the metamorphic rocks. Only weak hydrothermal alteration was noted in these rocks. Drillhole surveys and drilling rate data indicate that the geothermal system is structurally controlled and that the drillhole itself was strongly influenced by structural zones. Water chemistry indicates that this geothermal resource is a hot-water rather than a vapor-dominated system. Several geophysical logs were employed to characterize the drillhole geology. The natural gamma and neutron porosity logs indicate gross rock type and the acoustic logs indicate fractured rock and potentially permeable zones. A series of temperature logs run as a function of time during and after the completion of Drilling were most Useful in delineating the zones of maximum heat flux. Convective heat flow and temperatures greater than 350/sup 0/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 Close

• 8. [Image] Potential of Low-Temperature Geothermal Resources in Northern California. Report No. TR13

  	Economically feasible uses for geothermal heat at temperatures too low for conventional electrical power generation at present are delineated. Several geothermal resource areas in northern California that ...
  	Citation × Citation Citation Abstract Copy Title: Potential of Low-Temperature Geothermal Resources in Northern California. Report No. TR13 Author: Hannah, J.L. Year: 1975 Economically feasible uses for geothermal heat at temperatures too low for conventional electrical power generation at present are delineated. Several geothermal resource areas in northern California that have development potential are described, and applications of the heat found in each area are suggested. Plates are included of the following field study areas: the east side of the Sierra-Cascade Range north of Bishop, and the northern Coast Range from San Francisco Bay to Clear Lake. The counties included in the study area are Mo doc, Lassen, Sierra, Plumas, Placer, Alpine, Mono, Mendocino, Lake, and Sonoma. (LBS) Title: Potential of Low-Temperature Geothermal Resources in Northern California. Report No. TR13 Author: Hannah, J.L. Year: 1975 Economically feasible uses for geothermal heat at temperatures too low for conventional electrical power generation at present are delineated. Several geothermal resource areas in northern California that have development potential are described, and applications of the heat found in each area are suggested. Plates are included of the following field study areas: the east side of the Sierra-Cascade Range north of Bishop, and the northern Coast Range from San Francisco Bay to Clear Lake. The counties included in the study area are Mo doc, Lassen, Sierra, Plumas, Placer, Alpine, Mono, Mendocino, Lake, and Sonoma. (LBS) Close

• 9. [Image] Assessment of low- to moderate-temperature geothermal resources of Nevada. Final report, April 1978-June 1979

  	The ultimate goal of the project was to produce a geothermal resource map of Nevada that provided detailed information on low- to moderate-temperature geothermal systems, and that also evaluated their ...
  	Citation × Citation Citation Abstract Copy Title: Assessment of low- to moderate-temperature geothermal resources of Nevada. Final report, April 1978-June 1979 Author: Trexler, D.T Year: 1979 The ultimate goal of the project was to produce a geothermal resource map of Nevada that provided detailed information on low- to moderate-temperature geothermal systems, and that also evaluated their potential for direct non-electric utilization. The investigation consisted of these six tasks: edit and verify existing USGS GEOTHERM file for springs and wells in Nevada; supplement GEOTHERM file with NBMG data; digitize the location of springs and wells on 1:250,000 scale maps of Nevada; update water chemistry by sampling areas devoid of data; field check springs and wells designated as hot or warm; and prepare a 1:500,000 scale map of Nevada that evaluates geothermal resource areas of potential for direct use. This report described the completed tasks, delineates problems encountered, and presents additional miscellaneous information that augments the investigation. The information shown on the accompanying map can be divided into two categories: spot data and regional assessment (or potential evaluation). Specific geochemical information, such as temperature, pH, and chemical species, is represented by approximately 300 circle and diamond-shaped symbols. Thirty-seven larger regions were evaluated for their potential for direct-use on the basis of a numerical technique, which is fully described in this report. An additional 15 sites were designated as areas that may provide a basis for investigations, but that lack sufficient data for a detailed potential evaluation at this time. ; NVO-01556-1 Title: Assessment of low- to moderate-temperature geothermal resources of Nevada. Final report, April 1978-June 1979 Author: Trexler, D.T Year: 1979 The ultimate goal of the project was to produce a geothermal resource map of Nevada that provided detailed information on low- to moderate-temperature geothermal systems, and that also evaluated their potential for direct non-electric utilization. The investigation consisted of these six tasks: edit and verify existing USGS GEOTHERM file for springs and wells in Nevada; supplement GEOTHERM file with NBMG data; digitize the location of springs and wells on 1:250,000 scale maps of Nevada; update water chemistry by sampling areas devoid of data; field check springs and wells designated as hot or warm; and prepare a 1:500,000 scale map of Nevada that evaluates geothermal resource areas of potential for direct use. This report described the completed tasks, delineates problems encountered, and presents additional miscellaneous information that augments the investigation. The information shown on the accompanying map can be divided into two categories: spot data and regional assessment (or potential evaluation). Specific geochemical information, such as temperature, pH, and chemical species, is represented by approximately 300 circle and diamond-shaped symbols. Thirty-seven larger regions were evaluated for their potential for direct-use on the basis of a numerical technique, which is fully described in this report. An additional 15 sites were designated as areas that may provide a basis for investigations, but that lack sufficient data for a detailed potential evaluation at this time. ; NVO-01556-1 Close

• 10. [Image] Geological and Geophysical Analysis of Coso Geothermal Exploration Hole No. 1 (CGEH-1), Coso Hot Springs KGRA, California

  	The Coso Geothermal Exploration Hole number one (CGEH-1) was drilled in the Coso Hot Springs KGRA, California, from September 2 to December 2, 1977. Chip samples were collected at ten foot intervals and ...
  	Citation × Citation Citation Abstract Copy Title: Geological and Geophysical Analysis of Coso Geothermal Exploration Hole No. 1 (CGEH-1), Coso Hot Springs KGRA, California Author: Galbraith, R.M. Year: 1978 The Coso Geothermal Exploration Hole number one (CGEH-1) was drilled in the Coso Hot Springs KGRA, California, from September 2 to December 2, 1977. Chip samples were collected at ten foot intervals and extensive geophysical logging surveys were conducted to document the geologic character of the geothermal system as penetrated by CGEH-1. The major rock units encountered include a mafic metamorphic sequence and a leucogranite which intruded the metamorphic rocks. Only weak hydrothermal alteration was noted in these rocks. Drillhole surveys and drilling rate data indicate that the geothermal system is structurally controlled and that the drillhole itself was strongly influenced by structural zones. Water chemistry indicates that this geothermal resource is a hot-water rather than a vapor-dominated system. Several geophysical logs were employed to characterize the drillhole geology. The natural gamma and neutron porosity logs indicate gross rock type and the acoustics logs indicate fractured rock and potentially permeable zones. A series of temperature logs run as a function of time during and after the completion of drilling were most useful in delineating the zones of maximum heat flux. Convective heat flow and temperatures greater than 350/sup 0/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 Title: Geological and Geophysical Analysis of Coso Geothermal Exploration Hole No. 1 (CGEH-1), Coso Hot Springs KGRA, California Author: Galbraith, R.M. Year: 1978 The Coso Geothermal Exploration Hole number one (CGEH-1) was drilled in the Coso Hot Springs KGRA, California, from September 2 to December 2, 1977. Chip samples were collected at ten foot intervals and extensive geophysical logging surveys were conducted to document the geologic character of the geothermal system as penetrated by CGEH-1. The major rock units encountered include a mafic metamorphic sequence and a leucogranite which intruded the metamorphic rocks. Only weak hydrothermal alteration was noted in these rocks. Drillhole surveys and drilling rate data indicate that the geothermal system is structurally controlled and that the drillhole itself was strongly influenced by structural zones. Water chemistry indicates that this geothermal resource is a hot-water rather than a vapor-dominated system. Several geophysical logs were employed to characterize the drillhole geology. The natural gamma and neutron porosity logs indicate gross rock type and the acoustics logs indicate fractured rock and potentially permeable zones. A series of temperature logs run as a function of time during and after the completion of drilling were most useful in delineating the zones of maximum heat flux. Convective heat flow and temperatures greater than 350/sup 0/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 Close