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• 1. [Image] Pressure transient testing of a manmade fractured geothermal reservoir: an examination of fracture versus matrix dominated flow effects

  	The data analysis is in terms of a diffusion equation that determines the flow of water and hence the pressure in the main fracture system, associated joints, and the matrix permeability. The fits of the ...
  	Citation × Citation Citation Abstract Copy Title: Pressure transient testing of a manmade fractured geothermal reservoir: an examination of fracture versus matrix dominated flow effects Author: Fisher, H.N. Year: 1980 The data analysis is in terms of a diffusion equation that determines the flow of water and hence the pressure in the main fracture system, associated joints, and the matrix permeability. The fits of the flow data to type curve solutions of the diffusion equation with pressure-dependent properties for various flow geometries are presented. The following points are considered in detail. (1) The limits on the fracture geometry, aperture, and diffusing areas are determined from the diffusion parameters. (2) Dependence of the parameters (impedance, diffusivity) of the flow-through systems are related to the inflation of the major fractures. (3) The rock properties are related to the reservoir compressibility and permeability. In particular, laboratory experiments have shown that the properties of all sizes of cracks from large single fractures to the microstructure are pressure dependent if the fluid pressure is near the confining stress. The effects of this pressure dependence on the form of the type curves are included. (4) The competition of flow into the various types of porosity (main fractures, joints, and microstructure) and the effect on the interpretation of type curves are considered. The approach described makes an important departure from conventional pressure-transient reservoir analysis in that pressure-dependent properties are incorporated into a numerically simulated generation of type curves resulting from one- and two-dimensional diffusion. In addition, the problem of specifying a unique flow geometry where both matrix and fracture-dominated, non-Darcy flow effects are possible is analyzed using a large amount of field and laboratory data in conjunction with a theoretical treatment that reviews the existing state of the art in reservoir mechanics.; LA-8535-MS Title: Pressure transient testing of a manmade fractured geothermal reservoir: an examination of fracture versus matrix dominated flow effects Author: Fisher, H.N. Year: 1980 The data analysis is in terms of a diffusion equation that determines the flow of water and hence the pressure in the main fracture system, associated joints, and the matrix permeability. The fits of the flow data to type curve solutions of the diffusion equation with pressure-dependent properties for various flow geometries are presented. The following points are considered in detail. (1) The limits on the fracture geometry, aperture, and diffusing areas are determined from the diffusion parameters. (2) Dependence of the parameters (impedance, diffusivity) of the flow-through systems are related to the inflation of the major fractures. (3) The rock properties are related to the reservoir compressibility and permeability. In particular, laboratory experiments have shown that the properties of all sizes of cracks from large single fractures to the microstructure are pressure dependent if the fluid pressure is near the confining stress. The effects of this pressure dependence on the form of the type curves are included. (4) The competition of flow into the various types of porosity (main fractures, joints, and microstructure) and the effect on the interpretation of type curves are considered. The approach described makes an important departure from conventional pressure-transient reservoir analysis in that pressure-dependent properties are incorporated into a numerically simulated generation of type curves resulting from one- and two-dimensional diffusion. In addition, the problem of specifying a unique flow geometry where both matrix and fracture-dominated, non-Darcy flow effects are possible is analyzed using a large amount of field and laboratory data in conjunction with a theoretical treatment that reviews the existing state of the art in reservoir mechanics.; LA-8535-MS Close

• 2. [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

• 3. [Image] Thermal Fracture Effects in Geothermal Energy Extraction

  	Heat and water exchange between the primary crack and a lateral thermal fracture are analyzed by means of numerical modeling on a high-speed computer. Three-dimensional heat flow in the rock is coupled ...
  	Citation × Citation Citation Abstract Copy Title: Thermal Fracture Effects in Geothermal Energy Extraction Author: Demuth, R.B. Year: 1979 Heat and water exchange between the primary crack and a lateral thermal fracture are analyzed by means of numerical modeling on a high-speed computer. Three-dimensional heat flow in the rock is coupled to a two-dimensional approximation for the time-varying convective patterns that result from both forced flow and buoyancy. The physical and mathematical bases for the study are described together with the numerical technique for solution. The report includes listing of three versions of the computer code and some results of representative calculations Title: Thermal Fracture Effects in Geothermal Energy Extraction Author: Demuth, R.B. Year: 1979 Heat and water exchange between the primary crack and a lateral thermal fracture are analyzed by means of numerical modeling on a high-speed computer. Three-dimensional heat flow in the rock is coupled to a two-dimensional approximation for the time-varying convective patterns that result from both forced flow and buoyancy. The physical and mathematical bases for the study are described together with the numerical technique for solution. The report includes listing of three versions of the computer code and some results of representative calculations Close

• 4. [Image] Transient well testing in two-phase geothermal reservoirs

  	A study of well test analysis techniques in two-phase geothermal reservoirs has been conducted using a three-dimensional, two-phase, wellbore and reservoir simulation model. Well tests from Cerro Prieto ...
  	Citation × Citation Citation Abstract Copy Title: Transient well testing in two-phase geothermal reservoirs Author: Aydelotte, S.R. Year: 1980 A study of well test analysis techniques in two-phase geothermal reservoirs has been conducted using a three-dimensional, two-phase, wellbore and reservoir simulation model. Well tests from Cerro Prieto and the Hawaiian Geothermal project have been history matched. Using these well tests as a base, the influence of reservoir permeability, porosity, thickness, and heat capacity, along with flow rate and fracturing were studied. Single and two-phase transient well test equations were used to analyze these tests with poor results due to rapidly changing fluid properties and inability to calculate the flowing steam saturation in the reservoir. The injection of cold water into the reservoir does give good data from which formation properties can be calculated. Title: Transient well testing in two-phase geothermal reservoirs Author: Aydelotte, S.R. Year: 1980 A study of well test analysis techniques in two-phase geothermal reservoirs has been conducted using a three-dimensional, two-phase, wellbore and reservoir simulation model. Well tests from Cerro Prieto and the Hawaiian Geothermal project have been history matched. Using these well tests as a base, the influence of reservoir permeability, porosity, thickness, and heat capacity, along with flow rate and fracturing were studied. Single and two-phase transient well test equations were used to analyze these tests with poor results due to rapidly changing fluid properties and inability to calculate the flowing steam saturation in the reservoir. The injection of cold water into the reservoir does give good data from which formation properties can be calculated. Close

• 5. [Image] Geothermal investigations at selected thermal systems of the northern Wasatch Front Weber and Box Elder Counties, Utah. Report of investigation No. 141

  	Numerous thermal springs are present along the Wasatch Front from Utah valley on the south to the state line on the north. These systems are just west of the Wasatch Mountains at the eastern edge of the ...
  	Citation × Citation Citation Abstract Copy Title: Geothermal investigations at selected thermal systems of the northern Wasatch Front Weber and Box Elder Counties, Utah. Report of investigation No. 141 Author: Murphy, P. Year: 1979 Numerous thermal springs are present along the Wasatch Front from Utah valley on the south to the state line on the north. These systems are just west of the Wasatch Mountains at the eastern edge of the Basin and Range physiographic province and within the active seismic zone referred to as the Intermountain Seismic Belt. This Report of Investigation is a summary of UGMS investigations at four northern Wasatch Front geothermal systems: Utah, Crystal (Madsen), and Udy hot springs; and the Little Mountain - south system. All of these resources are deep circulation systems and the water is heated by the normal heat flow of the Basin and Range Province. Heat from volcanic sources is not believed to contribute to the warming of any northern Wasatch Front springs. Data collected under the DOE/DGE state coupled program are presented for use by individuals interested in these systems; DOE/ET/28393-18 Title: Geothermal investigations at selected thermal systems of the northern Wasatch Front Weber and Box Elder Counties, Utah. Report of investigation No. 141 Author: Murphy, P. Year: 1979 Numerous thermal springs are present along the Wasatch Front from Utah valley on the south to the state line on the north. These systems are just west of the Wasatch Mountains at the eastern edge of the Basin and Range physiographic province and within the active seismic zone referred to as the Intermountain Seismic Belt. This Report of Investigation is a summary of UGMS investigations at four northern Wasatch Front geothermal systems: Utah, Crystal (Madsen), and Udy hot springs; and the Little Mountain - south system. All of these resources are deep circulation systems and the water is heated by the normal heat flow of the Basin and Range Province. Heat from volcanic sources is not believed to contribute to the warming of any northern Wasatch Front springs. Data collected under the DOE/DGE state coupled program are presented for use by individuals interested in these systems; DOE/ET/28393-18 Close

• 6. [Image] Geothermal Energy Resource Assessment

  	This report covers the objectives and the status of a long-range program to develop techniques for assessing the resource potential of liquid-dominated geothermal systems. Field studies underway in northern ...
  	Citation × Citation Citation Abstract Copy Title: Geothermal Energy Resource Assessment Author: Wollenberg, H.A. Year: 1975 This report covers the objectives and the status of a long-range program to develop techniques for assessing the resource potential of liquid-dominated geothermal systems. Field studies underway in northern Nevada comprise a systematic integrated program of geologic, geophysical, and geochemical measurements, necessary to specify a drilling program encompassing heat flow holes, deep calibration holes, and ultimately, deep test wells. The status of Nevada field activities is described. The areas under study are in a region characterized by high heat flow where temperatures at depth in some geothermal systems exceed 180 C. Areas presently being examined include Beowawe Hot Springs in Whirlwind Valley. Buffalo Valley Hot Springs, Leach Hot Springs in Grass Valley, and Kyle Hot Springs in Buena Vista Valley. Geologic studies encompass detailed examinations of structure and lithology to establish the geologic framework of the areas. The geothermal occurrences are characterized by zones of intense fault intersection, which furnish permeable channelways for the introduction of meteoric water into regions of high temperature at depth Title: Geothermal Energy Resource Assessment Author: Wollenberg, H.A. Year: 1975 This report covers the objectives and the status of a long-range program to develop techniques for assessing the resource potential of liquid-dominated geothermal systems. Field studies underway in northern Nevada comprise a systematic integrated program of geologic, geophysical, and geochemical measurements, necessary to specify a drilling program encompassing heat flow holes, deep calibration holes, and ultimately, deep test wells. The status of Nevada field activities is described. The areas under study are in a region characterized by high heat flow where temperatures at depth in some geothermal systems exceed 180 C. Areas presently being examined include Beowawe Hot Springs in Whirlwind Valley. Buffalo Valley Hot Springs, Leach Hot Springs in Grass Valley, and Kyle Hot Springs in Buena Vista Valley. Geologic studies encompass detailed examinations of structure and lithology to establish the geologic framework of the areas. The geothermal occurrences are characterized by zones of intense fault intersection, which furnish permeable channelways for the introduction of meteoric water into regions of high temperature at depth Close

• 7. [Image] Geologic Interpretation of the Geothermal Potential of the North Bonneville Area

  	Possible geothermal development for the township of North Bonneville, Washington is being investigated because of the proximity of the town to hot springs in a geologic province of good geothermal potential. ...
  	Citation × Citation Citation Abstract Copy Title: Geologic Interpretation of the Geothermal Potential of the North Bonneville Area Author: Nielson, D.L. Year: 1980 Possible geothermal development for the township of North Bonneville, Washington is being investigated because of the proximity of the town to hot springs in a geologic province of good geothermal potential. Surface expression of geothermal resources is provided by conduits through an impermeable reservoir cap and is therefore generally structurally controlled. Near North Bonneville the geologic formations that underlie potential drilling sites are the Eagle Creek formation and the Ohanpecosh Formation. The Lower Miocene Eagle Creek Formation is composed of poorly consolidated volcanic conglomerates, sandstOnes, tuffs, and includes a few minor interbedded lava flows. The Eocene-Oligiocene Ohanapecosh (Weigle) Formation in its nearest exposures to North Bonneville is composed of Volcaniclastics and lava flows. The Ohanapecosh has been altered to zeolites and clays and is therefore Well consolidated and impermeable. The lack of permeability provides the necessary reservoir cap for any geothermal system that may be present at depth. This formation, to the northeast, in the Wind River drainage is greater than 19,000 ft. thick. Circulation of geothermal heated water from this thick sequence of impermeable strata must be associated with penetrating fracture zones Title: Geologic Interpretation of the Geothermal Potential of the North Bonneville Area Author: Nielson, D.L. Year: 1980 Possible geothermal development for the township of North Bonneville, Washington is being investigated because of the proximity of the town to hot springs in a geologic province of good geothermal potential. Surface expression of geothermal resources is provided by conduits through an impermeable reservoir cap and is therefore generally structurally controlled. Near North Bonneville the geologic formations that underlie potential drilling sites are the Eagle Creek formation and the Ohanpecosh Formation. The Lower Miocene Eagle Creek Formation is composed of poorly consolidated volcanic conglomerates, sandstOnes, tuffs, and includes a few minor interbedded lava flows. The Eocene-Oligiocene Ohanapecosh (Weigle) Formation in its nearest exposures to North Bonneville is composed of Volcaniclastics and lava flows. The Ohanapecosh has been altered to zeolites and clays and is therefore Well consolidated and impermeable. The lack of permeability provides the necessary reservoir cap for any geothermal system that may be present at depth. This formation, to the northeast, in the Wind River drainage is greater than 19,000 ft. thick. Circulation of geothermal heated water from this thick sequence of impermeable strata must be associated with penetrating fracture zones Close

• 8. [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

• 9. [Image] Modeling Heat and Mass Transfer at the Mesa Geothermal Anomaly, Imperial Valley, California. Final Project Report

  	The geothermal reservoir modeling effort at the University of Colorado is reviewed briefly. Technical accomplishments during the final funding period 1 April 1978 to 30 November 1978 are described. It ...
  	Citation × Citation Citation Abstract Copy Title: Modeling Heat and Mass Transfer at the Mesa Geothermal Anomaly, Imperial Valley, California. Final Project Report Author: Kassoy, D.R. Year: 1979 The geothermal reservoir modeling effort at the University of Colorado is reviewed briefly. Technical accomplishments during the final funding period 1 April 1978 to 30 November 1978 are described. It is concluded that a physically viable mathematical model of an unexploited geothermal system can be constructed in terms of the fault zone controlled charging of the thermally active section of a reservoir Title: Modeling Heat and Mass Transfer at the Mesa Geothermal Anomaly, Imperial Valley, California. Final Project Report Author: Kassoy, D.R. Year: 1979 The geothermal reservoir modeling effort at the University of Colorado is reviewed briefly. Technical accomplishments during the final funding period 1 April 1978 to 30 November 1978 are described. It is concluded that a physically viable mathematical model of an unexploited geothermal system can be constructed in terms of the fault zone controlled charging of the thermally active section of a reservoir Close

• 10. [Image] Hot Dry Rock Energy Extraction Field Test: 75 Days of Operation of a Prototype Reservoir at Fenton Hill, Segment 2 of Phase I

  	Results from the first extensive field test of a man-made hot dry rock (HDR) geothermal reservoir in low permeability crystalline rock are presented. A reservoir with a small heat transfer area was utilized ...
  	Citation × Citation Citation Abstract Copy Title: Hot Dry Rock Energy Extraction Field Test: 75 Days of Operation of a Prototype Reservoir at Fenton Hill, Segment 2 of Phase I Author: Tester, J.W. (ed.) Year: 1979 Results from the first extensive field test of a man-made hot dry rock (HDR) geothermal reservoir in low permeability crystalline rock are presented. A reservoir with a small heat transfer area was utilized to study the characteristics of a prototype HDR system over a shortened lifetime. The resulting accelerated thermal drawdown was modeled to yield an effective area of 8000 m/sup 2/. In addition to the thermal effects, this test provided an opportunity to examine equipment operation, water permeation into the formation, geochemical interaction between the circulating fluid and the rock and flow characteristics including impedance and residence time distributions. Continuous monitoring for induced seismic effects showed that no activity to a Richter threshold of -1.0 was detected during the 75-day experiment Title: Hot Dry Rock Energy Extraction Field Test: 75 Days of Operation of a Prototype Reservoir at Fenton Hill, Segment 2 of Phase I Author: Tester, J.W. (ed.) Year: 1979 Results from the first extensive field test of a man-made hot dry rock (HDR) geothermal reservoir in low permeability crystalline rock are presented. A reservoir with a small heat transfer area was utilized to study the characteristics of a prototype HDR system over a shortened lifetime. The resulting accelerated thermal drawdown was modeled to yield an effective area of 8000 m/sup 2/. In addition to the thermal effects, this test provided an opportunity to examine equipment operation, water permeation into the formation, geochemical interaction between the circulating fluid and the rock and flow characteristics including impedance and residence time distributions. Continuous monitoring for induced seismic effects showed that no activity to a Richter threshold of -1.0 was detected during the 75-day experiment Close