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• 1. [Image] Geothermal Exploration of the Puga and Chumathang Geothermal Fields, Ladakh, India

  	Puga and Chumathang Geothermal fields are situated near the collided junction of the Indian and Asian Crystal plates and thermal activity in these fields is attributed to the widespread igneous activity ...
  	Citation × Citation Citation Abstract Copy Title: Geothermal Exploration of the Puga and Chumathang Geothermal Fields, Ladakh, India Author: Shanker, R. Puga and Chumathang Geothermal fields are situated near the collided junction of the Indian and Asian Crystal plates and thermal activity in these fields is attributed to the widespread igneous activity of Upper Cretaceous to late Tertiary age. A deep suture zone, recognised in between these two fields and the associated faults provide channels for the upward migration of the thermal fluids. High concentrations of Cl, F, Si02, B, Na, Li, Rb, Cs in thermal fluids signify contribution of magmatic bodies towards heat, and fluid supply. These fields are characterized by high heat flow conditions (13 HFU), abnormal shallow geothermal gradients (0.7 - 2.5 c/m) , high base temperature (220 - 270 C) as obtained by alkalia and Ne-K-Ca geothermometry and low resistivity values (2-20 ohm.m.). Low resistivity zones occupy on an area of three and one sq.km. and extend down to maximum depths of 300 m. and 130 m. at Puga and Chumathang respectively. Shallow drilling (28-130 m.) has established the existence of wet steam reservoirs under moderate pressure (2-4.5 kg/cm^2). Hot fluid (95-135 C) discharges from eight flowing wells ranged from 7.5 to 30 t/h. These thermal fluids are stored in the partly consolidated fluvioglacial deposits of Quarternary to Recent age. The occurrence of a limestone layer in the country rock at Puga brightens the prospects of getting good reservoir at depth. In both these fields two aquifers have been recognised, each having sizeable potential for retaining ground water. The ground water recharge is mainly through snow melt from glaciers in the case of Puga field and principally from Indus river in the case of Chumathangfield Title: Geothermal Exploration of the Puga and Chumathang Geothermal Fields, Ladakh, India Author: Shanker, R. Puga and Chumathang Geothermal fields are situated near the collided junction of the Indian and Asian Crystal plates and thermal activity in these fields is attributed to the widespread igneous activity of Upper Cretaceous to late Tertiary age. A deep suture zone, recognised in between these two fields and the associated faults provide channels for the upward migration of the thermal fluids. High concentrations of Cl, F, Si02, B, Na, Li, Rb, Cs in thermal fluids signify contribution of magmatic bodies towards heat, and fluid supply. These fields are characterized by high heat flow conditions (13 HFU), abnormal shallow geothermal gradients (0.7 - 2.5 c/m) , high base temperature (220 - 270 C) as obtained by alkalia and Ne-K-Ca geothermometry and low resistivity values (2-20 ohm.m.). Low resistivity zones occupy on an area of three and one sq.km. and extend down to maximum depths of 300 m. and 130 m. at Puga and Chumathang respectively. Shallow drilling (28-130 m.) has established the existence of wet steam reservoirs under moderate pressure (2-4.5 kg/cm^2). Hot fluid (95-135 C) discharges from eight flowing wells ranged from 7.5 to 30 t/h. These thermal fluids are stored in the partly consolidated fluvioglacial deposits of Quarternary to Recent age. The occurrence of a limestone layer in the country rock at Puga brightens the prospects of getting good reservoir at depth. In both these fields two aquifers have been recognised, each having sizeable potential for retaining ground water. The ground water recharge is mainly through snow melt from glaciers in the case of Puga field and principally from Indus river in the case of Chumathangfield Close

• 2. [Image] Geothermal Exploration of the Parbati Valley Geothermal Field, Kulu District, Himachal Pradesh, India

  	The Parbati Valley Geothermal Field is divided into five sectors and out of these a geothermal exploration program has been launched in two sectors - Manikaran and Kasol. This field lies to southwest of ...
  	Citation × Citation Citation Abstract Copy Title: Geothermal Exploration of the Parbati Valley Geothermal Field, Kulu District, Himachal Pradesh, India Author: Jangi, B.L. The Parbati Valley Geothermal Field is divided into five sectors and out of these a geothermal exploration program has been launched in two sectors - Manikaran and Kasol. This field lies to southwest of the Central Crystalline axis where profuse igneous activity has taken place during Tertiary Times. This activity appears to be the main source of heat supply to the field, although contribution of some-heat through radioactive disintegration can not be ruled out. A tear fault with one kilometre displacement, picked up in the Parbati Valley, and fractures related to it may be providing the ultimate major channels for the upward movement of the hot fluids while joints in the country rock serve as immediate channels for these fluids. Spontaneous polarisation and resistivity geophysical surveys pointed to the presence of some significant zones of thermal activity and possible shallow sub-surface channels for movement of thermal fluids at Manikaran whereas resistivity surveys pointed to the existence of shallow hot zone at Kasol. Surface manifestations of thermal activity at Manikaran and Kasol are in the form of hot springs recording temperatures from 37 C to 96 C. The base temperatures of thermal fluids of Manikaran sector as calculated from Na-K-Ca and silica thermometry comes to 197 to 203 C and 131 to 138 C respectively. The average geothermal gradients in the drill holes at Manikaran vary from .0.12 C/m to .14 C/m in the depth range 0-76 m. and at Kasol from +0.16 C to +1.25 C/m in the depth ranges of 0 to 40 m. Beyond these depths reversal of gradients is noticed Title: Geothermal Exploration of the Parbati Valley Geothermal Field, Kulu District, Himachal Pradesh, India Author: Jangi, B.L. The Parbati Valley Geothermal Field is divided into five sectors and out of these a geothermal exploration program has been launched in two sectors - Manikaran and Kasol. This field lies to southwest of the Central Crystalline axis where profuse igneous activity has taken place during Tertiary Times. This activity appears to be the main source of heat supply to the field, although contribution of some-heat through radioactive disintegration can not be ruled out. A tear fault with one kilometre displacement, picked up in the Parbati Valley, and fractures related to it may be providing the ultimate major channels for the upward movement of the hot fluids while joints in the country rock serve as immediate channels for these fluids. Spontaneous polarisation and resistivity geophysical surveys pointed to the presence of some significant zones of thermal activity and possible shallow sub-surface channels for movement of thermal fluids at Manikaran whereas resistivity surveys pointed to the existence of shallow hot zone at Kasol. Surface manifestations of thermal activity at Manikaran and Kasol are in the form of hot springs recording temperatures from 37 C to 96 C. The base temperatures of thermal fluids of Manikaran sector as calculated from Na-K-Ca and silica thermometry comes to 197 to 203 C and 131 to 138 C respectively. The average geothermal gradients in the drill holes at Manikaran vary from .0.12 C/m to .14 C/m in the depth range 0-76 m. and at Kasol from +0.16 C to +1.25 C/m in the depth ranges of 0 to 40 m. Beyond these depths reversal of gradients is noticed Close

• 3. [Image] Conceptual Design of Commercial 50 MWe(Net) Geothermal Power Plants at Heber and Niland, California. Final Report

  	The scope of work of this study includes conceptual designs, corresponding capital cost estimates and engineering and construction schedules for two 50 MWe (net) commercial-scale geothermal power plants. ...
  	Citation × Citation Citation Abstract Copy Title: Conceptual Design of Commercial 50 MWe(Net) Geothermal Power Plants at Heber and Niland, California. Final Report Author: Bechtel Corporation Year: 1976 The scope of work of this study includes conceptual designs, corresponding capital cost estimates and engineering and construction schedules for two 50 MWe (net) commercial-scale geothermal power plants. In order to develop and illustrate the concepts involved, the reservoir and site conditions of the geothermal field near Heber, California, which has moderate-temperature low-salinity brine, were used for one of the power plants. The conditions of the field near Niland, California (or the Salton Sea Geothermal Field), which has high-temperature high-salinity brine, were used for the other plant. Both fields are located in the Imperial Valley in Southern California. The two plants give perspective on plant design and capital costs for the range of hydrothermal resources that are of economic interest for electric power generation Title: Conceptual Design of Commercial 50 MWe(Net) Geothermal Power Plants at Heber and Niland, California. Final Report Author: Bechtel Corporation Year: 1976 The scope of work of this study includes conceptual designs, corresponding capital cost estimates and engineering and construction schedules for two 50 MWe (net) commercial-scale geothermal power plants. In order to develop and illustrate the concepts involved, the reservoir and site conditions of the geothermal field near Heber, California, which has moderate-temperature low-salinity brine, were used for one of the power plants. The conditions of the field near Niland, California (or the Salton Sea Geothermal Field), which has high-temperature high-salinity brine, were used for the other plant. Both fields are located in the Imperial Valley in Southern California. The two plants give perspective on plant design and capital costs for the range of hydrothermal resources that are of economic interest for electric power generation Close

• 4. [Image] Drilling plan: Raft River Geothermal Exploratory Hole No. 3

  	The program, plans, and procedures to be used in drilling and completion of the Raft River Geothermal Exploratory Hole No. 3(RRGE-3) are described. RRGE-3 will be located in the Raft River valley of south ...
  	Citation × Citation Citation Abstract Copy Title: Drilling plan: Raft River Geothermal Exploratory Hole No. 3 Author: Industrial Applications Division , Nevada Operations Office Year: 1976 The program, plans, and procedures to be used in drilling and completion of the Raft River Geothermal Exploratory Hole No. 3(RRGE-3) are described. RRGE-3 will be located in the Raft River valley of south central Idaho, southeast of Burley, and approximately 16 miles south of Malta, Idaho. The third exploratory hole will be drilled to provide data to further investigate and evaluate the geothermal reservoir, as well as to optimize the location of possible future resource and/or injection wells, and to develop methods to reduce the cost of geothermal wells. Plans call for drilling to a total depth of approximately 6,000 ft., or to the depth at which it is either indicated from temperature and test flow data and from logs that an acceptable hot water resource is available or that the hole is accepted as a possible reinjection well. (LBS) Title: Drilling plan: Raft River Geothermal Exploratory Hole No. 3 Author: Industrial Applications Division , Nevada Operations Office Year: 1976 The program, plans, and procedures to be used in drilling and completion of the Raft River Geothermal Exploratory Hole No. 3(RRGE-3) are described. RRGE-3 will be located in the Raft River valley of south central Idaho, southeast of Burley, and approximately 16 miles south of Malta, Idaho. The third exploratory hole will be drilled to provide data to further investigate and evaluate the geothermal reservoir, as well as to optimize the location of possible future resource and/or injection wells, and to develop methods to reduce the cost of geothermal wells. Plans call for drilling to a total depth of approximately 6,000 ft., or to the depth at which it is either indicated from temperature and test flow data and from logs that an acceptable hot water resource is available or that the hole is accepted as a possible reinjection well. (LBS) Close

• 5. [Image] Exploration Methods for Hot Dry Rock. Report of the Panel Held June 22, 1976

  	The geological and geophysical characteristics of hot dry rock (HDR) necessary for an effective exploration program were discussed. The type of HDR project discussed, that being developed by the Los Alamos ...
  	Citation × Citation Citation Abstract Copy Title: Exploration Methods for Hot Dry Rock. Report of the Panel Held June 22, 1976 Author: West, F.G. (comp.) Year: 1977 The geological and geophysical characteristics of hot dry rock (HDR) necessary for an effective exploration program were discussed. The type of HDR project discussed, that being developed by the Los Alamos Scientific Laboratory (LASL), would utilize hydraulic fracturing to develop a large surface area in rock of low permeability, 10/sup -6/ darcys, and at temperatures greater than 200/sup 0/C. A better definition of the thermal regime in the crust and mantle at reconnaissance (hundreds to tens of kilometers) and exploration (tens of kilometers to 1 km) scales is needed. Geophysical methods capable of deep investigation would be used with the near-surface geologic information to extrapolate conditions at the depth of interest. Detection of HDR per se may be difficult because the contrast in physical properties of HDR and other rock is not always unambiguous, but boundaries between rock environments can be delineated. When patterns and coincidence of various types of geophysical anomalies and geologic maps are used, the probability of the detection of HDR is greatly increased, especially when a consistent picture is described. Various geophysical methods are required to detect these anomalies: (a) electromagnetic techniques can map deep electrically conductive structures, which to some extent can be used to infer isotherms. (b) Bouguer gravity maps corrected for regional topography are found to correlate with large silicic intrusive bodies, which are often associated with high heat flow. (c) isotherms and open crack systems at depth can be inferred from seismic wave attenuations, dispersions, and delay times. (d) heat flow measurements are useful as a primary tool and as a check on the results of other methods. Abstracts for individual presentations by the twelve panel members are included. 111 references Title: Exploration Methods for Hot Dry Rock. Report of the Panel Held June 22, 1976 Author: West, F.G. (comp.) Year: 1977 The geological and geophysical characteristics of hot dry rock (HDR) necessary for an effective exploration program were discussed. The type of HDR project discussed, that being developed by the Los Alamos Scientific Laboratory (LASL), would utilize hydraulic fracturing to develop a large surface area in rock of low permeability, 10/sup -6/ darcys, and at temperatures greater than 200/sup 0/C. A better definition of the thermal regime in the crust and mantle at reconnaissance (hundreds to tens of kilometers) and exploration (tens of kilometers to 1 km) scales is needed. Geophysical methods capable of deep investigation would be used with the near-surface geologic information to extrapolate conditions at the depth of interest. Detection of HDR per se may be difficult because the contrast in physical properties of HDR and other rock is not always unambiguous, but boundaries between rock environments can be delineated. When patterns and coincidence of various types of geophysical anomalies and geologic maps are used, the probability of the detection of HDR is greatly increased, especially when a consistent picture is described. Various geophysical methods are required to detect these anomalies: (a) electromagnetic techniques can map deep electrically conductive structures, which to some extent can be used to infer isotherms. (b) Bouguer gravity maps corrected for regional topography are found to correlate with large silicic intrusive bodies, which are often associated with high heat flow. (c) isotherms and open crack systems at depth can be inferred from seismic wave attenuations, dispersions, and delay times. (d) heat flow measurements are useful as a primary tool and as a check on the results of other methods. Abstracts for individual presentations by the twelve panel members are included. 111 references Close

• 6. [Image] Exploration Criteria for Low Permeability Geothermal Resources: Final Report

  	The overall project objective was to analyze low permeability geothermal systems related to high temperature plutons in the upper crust in order to ascertain those characteristics of these systems which ...
  	Citation × Citation Citation Abstract Copy Title: Exploration Criteria for Low Permeability Geothermal Resources: Final Report Author: Norton, D. Year: 1977 The overall project objective was to analyze low permeability geothermal systems related to high temperature plutons in the upper crust in order to ascertain those characteristics of these systems which could be detected by surface and shallow subsurface exploration methods. Analyses were designed to integrate data and concepts from the literature, which relate to the transport processes, together with computer simulation of idealised systems Title: Exploration Criteria for Low Permeability Geothermal Resources: Final Report Author: Norton, D. Year: 1977 The overall project objective was to analyze low permeability geothermal systems related to high temperature plutons in the upper crust in order to ascertain those characteristics of these systems which could be detected by surface and shallow subsurface exploration methods. Analyses were designed to integrate data and concepts from the literature, which relate to the transport processes, together with computer simulation of idealised systems Close

• 7. [Image] Dipole-Dipole Resistivity Survey of a Portion of the Coso Hot Springs KGRA, Inyo County, California

  	A detailed electrical resistivity survey of 54 line-km was completed at the Coso Hot Springs KGRA in September 1977. This survey has defined a bedrock resistivity low at least 4 sq mi (10 sq km) in extent ...
  	Citation × Citation Citation Abstract Copy Title: Dipole-Dipole Resistivity Survey of a Portion of the Coso Hot Springs KGRA, Inyo County, California Author: Fox, R.C. Year: 1978 A detailed electrical resistivity survey of 54 line-km was completed at the Coso Hot Springs KGRA in September 1977. This survey has defined a bedrock resistivity low at least 4 sq mi (10 sq km) in extent associated with the geothermal system at Coso. The boundaries of this low are generally well defined to the north and west but not as well to the south where an approximate southern limit has been determined. The bedrock resistivity low merges with an observed resistivity low over gravel fill east of Coso Hot Springs. A complex horizontal and vertical resistivity structure of the surveyed area has been defined which precludes the use of layered-earth or two-dimensional interpretive models for much of the surveyed area. In general the survey data indicate that a 10 to 20 ohm-meter zone extends from near surface to a depth greater than 750 meters within the geothermal system. This zone is bordered to the north and west by bedrock resistivities greater than 200 ohm-meters and to the south by bedrock resistivities greater than 50 ohm-meters. A combination of observed increases in: (1) fracture density (higher permeability), (2) alteration (high clay content), and (3) temperatures (higher dissolved solid content of ground water) within the bedrock low explain its presence Title: Dipole-Dipole Resistivity Survey of a Portion of the Coso Hot Springs KGRA, Inyo County, California Author: Fox, R.C. Year: 1978 A detailed electrical resistivity survey of 54 line-km was completed at the Coso Hot Springs KGRA in September 1977. This survey has defined a bedrock resistivity low at least 4 sq mi (10 sq km) in extent associated with the geothermal system at Coso. The boundaries of this low are generally well defined to the north and west but not as well to the south where an approximate southern limit has been determined. The bedrock resistivity low merges with an observed resistivity low over gravel fill east of Coso Hot Springs. A complex horizontal and vertical resistivity structure of the surveyed area has been defined which precludes the use of layered-earth or two-dimensional interpretive models for much of the surveyed area. In general the survey data indicate that a 10 to 20 ohm-meter zone extends from near surface to a depth greater than 750 meters within the geothermal system. This zone is bordered to the north and west by bedrock resistivities greater than 200 ohm-meters and to the south by bedrock resistivities greater than 50 ohm-meters. A combination of observed increases in: (1) fracture density (higher permeability), (2) alteration (high clay content), and (3) temperatures (higher dissolved solid content of ground water) within the bedrock low explain its presence 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 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

• 9. [Image] Geothermal Resource and Reservoir Investigations of U. S. Bureau of Reclamation Leaseholds at East Mesa, Imperial Valley, California

  	The study included five parts: geology, seismicity, well testing, reservoir simulation, and geochemistry. Included in appendices are: production test data and discussion, interference tests, production ...
  	Citation × Citation Citation Abstract Copy Title: Geothermal Resource and Reservoir Investigations of U. S. Bureau of Reclamation Leaseholds at East Mesa, Imperial Valley, California Author: Howard, J. Year: 1978 The study included five parts: geology, seismicity, well testing, reservoir simulation, and geochemistry. Included in appendices are: production test data and discussion, interference tests, production tests in the northern portion of the East Mesa KGRA, conversion tables, chemical analysis of fluids from East Mesa wells, and results of laboratory studies of scale samples taken from the vertical tube evaporator. (MHR) Title: Geothermal Resource and Reservoir Investigations of U. S. Bureau of Reclamation Leaseholds at East Mesa, Imperial Valley, California Author: Howard, J. Year: 1978 The study included five parts: geology, seismicity, well testing, reservoir simulation, and geochemistry. Included in appendices are: production test data and discussion, interference tests, production tests in the northern portion of the East Mesa KGRA, conversion tables, chemical analysis of fluids from East Mesa wells, and results of laboratory studies of scale samples taken from the vertical tube evaporator. (MHR) Close

• 10. [Image] Geothermal Energy: Residential Space Heating

  	The purpose of this study, which was carried out under the auspices of the DGRST, was to determine the best way to use geothermal hot water for residential space heating. It quickly became apparent that ...
  	Citation × Citation Citation Abstract Copy Title: Geothermal Energy: Residential Space Heating Author: Delegation Generale a la Recherche Scientifique et Technique 35 rue Saint-Dominique, 75007 Paris Year: 1977 The purpose of this study, which was carried out under the auspices of the DGRST, was to determine the best way to use geothermal hot water for residential space heating. It quickly became apparent that the type of heating apparatus used in the housing units was most important and that heat pumps could be a valuable asset, making it possible to extract even more geothermal heat and thus substantially improve the cost benefit of the systems. Many factors play a significant role in this problem. Therefore, after a first stage devoted to analyzing the problem through a manual method which proved quite useful, the systematic consideration of all important aspects led us to use a computer to optimize solutions and process a large number of cases. The software used for this general study can also be used to work out particular cases: it is now available to any interested party through DGRST. This program makes it possible to: (1) take climatic conditions into account in a very detailed manner, including temperatures as well as insolation. 864 cases corresponding to 36 typical days divided into 24 hours each were chosen to represent the heating season. They make it possible to define the heating needs of any type of housing unit. (2) simulate and analyze the behavior in practice of a geothermal heating system when heat is extracted from the well by a simple heat exchanger. This simulation makes it possible to evaluate the respective qualities of various types of heating apparatus which can be used in homes. It also makes it possible to define the best control systems for the central system and substations and to assess quite accurately the presence of terminal controls, such as radiators with thermostatically controlled valves. (3) determine to what extent the addition of a heat pump makes it possible to improve the cost benefit of geothermal heating. When its average characteristics and heating use conditions (price, coefficient of performance, length of utilization, electrical rates, etc.) are taken into account, the heat pump should not be scaled for maximum heating power. Consequently, the program considers several possible sizes, with different installation schemes, and selects for each case the value which corresponds to the lowest cost of heating Title: Geothermal Energy: Residential Space Heating Author: Delegation Generale a la Recherche Scientifique et Technique 35 rue Saint-Dominique, 75007 Paris Year: 1977 The purpose of this study, which was carried out under the auspices of the DGRST, was to determine the best way to use geothermal hot water for residential space heating. It quickly became apparent that the type of heating apparatus used in the housing units was most important and that heat pumps could be a valuable asset, making it possible to extract even more geothermal heat and thus substantially improve the cost benefit of the systems. Many factors play a significant role in this problem. Therefore, after a first stage devoted to analyzing the problem through a manual method which proved quite useful, the systematic consideration of all important aspects led us to use a computer to optimize solutions and process a large number of cases. The software used for this general study can also be used to work out particular cases: it is now available to any interested party through DGRST. This program makes it possible to: (1) take climatic conditions into account in a very detailed manner, including temperatures as well as insolation. 864 cases corresponding to 36 typical days divided into 24 hours each were chosen to represent the heating season. They make it possible to define the heating needs of any type of housing unit. (2) simulate and analyze the behavior in practice of a geothermal heating system when heat is extracted from the well by a simple heat exchanger. This simulation makes it possible to evaluate the respective qualities of various types of heating apparatus which can be used in homes. It also makes it possible to define the best control systems for the central system and substations and to assess quite accurately the presence of terminal controls, such as radiators with thermostatically controlled valves. (3) determine to what extent the addition of a heat pump makes it possible to improve the cost benefit of geothermal heating. When its average characteristics and heating use conditions (price, coefficient of performance, length of utilization, electrical rates, etc.) are taken into account, the heat pump should not be scaled for maximum heating power. Consequently, the program considers several possible sizes, with different installation schemes, and selects for each case the value which corresponds to the lowest cost of heating Close