Search

Search Results

• 41. [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

• 42. [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

• 43. [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

• 44. [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

• 45. [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

• 46. [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

• 47. [Image] Evaluation and Design of Downhole Heat Exchangers for Direct Application; Annual Report, May 1, 1976 - July 1, 1977

  	Progress in an experimental and analytical research program to evaluate and improve the design of downhole heat exchangers (DHEs) for direct applications of geothermal energy is reported. Significant progress ...
  	Citation × Citation Citation Abstract Copy Title: Evaluation and Design of Downhole Heat Exchangers for Direct Application; Annual Report, May 1, 1976 - July 1, 1977 Author: Culver, G.G. Year: 1977 Progress in an experimental and analytical research program to evaluate and improve the design of downhole heat exchangers (DHEs) for direct applications of geothermal energy is reported. Significant progress has been achieved in characterizing flows in wells and without perforated casings and DHEs installed, determination of energy extraction rates for conventional DHEs in both cased and uncased wells, and utilization of information obtained to develop and substantiate models of heat transfer within the well. Flow characterization was obtained by experimentally measuring temperature and velocity profiles. In uncased wells, there was a relatively large vertical temperature gradient (approximately 0.5{sup 0}C/m) and insignificant measured vertical flow, while for the same wells when cased the temperature gradient was essentially zero (approximately 0.03{sup 0}C/m) and a large vertically upward flow was measured (9 to 14 cm/s as measured with a hot-film anemometer). These show that a significant connection cell is established after installation of the casing. The energy extraction rates for a conventional DHE both before and after casing of a 60 m deep well was experimentally measured. In the uncased well up to 300 kW was obtained while the cased well produced over 500 kW. Analytical heat transfer models were developed for the cased well both with and without DHEs. For the cased well without a DHE, the model predicts flow rates that agree with the measured value within about 30 percent. Further, the energy extraction rates predicted by the models agree even better with the measured values. These models allow the energy extraction rates of design parameter variations to be evaluated. At this stage, only trends can be shown but with additional substantiation they should produce optimum energy extraction designs Title: Evaluation and Design of Downhole Heat Exchangers for Direct Application; Annual Report, May 1, 1976 - July 1, 1977 Author: Culver, G.G. Year: 1977 Progress in an experimental and analytical research program to evaluate and improve the design of downhole heat exchangers (DHEs) for direct applications of geothermal energy is reported. Significant progress has been achieved in characterizing flows in wells and without perforated casings and DHEs installed, determination of energy extraction rates for conventional DHEs in both cased and uncased wells, and utilization of information obtained to develop and substantiate models of heat transfer within the well. Flow characterization was obtained by experimentally measuring temperature and velocity profiles. In uncased wells, there was a relatively large vertical temperature gradient (approximately 0.5{sup 0}C/m) and insignificant measured vertical flow, while for the same wells when cased the temperature gradient was essentially zero (approximately 0.03{sup 0}C/m) and a large vertically upward flow was measured (9 to 14 cm/s as measured with a hot-film anemometer). These show that a significant connection cell is established after installation of the casing. The energy extraction rates for a conventional DHE both before and after casing of a 60 m deep well was experimentally measured. In the uncased well up to 300 kW was obtained while the cased well produced over 500 kW. Analytical heat transfer models were developed for the cased well both with and without DHEs. For the cased well without a DHE, the model predicts flow rates that agree with the measured value within about 30 percent. Further, the energy extraction rates predicted by the models agree even better with the measured values. These models allow the energy extraction rates of design parameter variations to be evaluated. At this stage, only trends can be shown but with additional substantiation they should produce optimum energy extraction designs Close

• 48. [Image] Low -Altitude Aeromagnetic Survey of a Portion of the Coso Hot Springs KGRA, Inyo County, California

  	A detailed low-altitude aeromagnetic survey of 576 line-mi (927 line-km) was completed over a portion of the Coso Hot Springs KGRA in September 1977. The survey has defined a pronounced magnetic low that ...
  	Citation × Citation Citation Abstract Copy Title: Low -Altitude Aeromagnetic Survey of a Portion of the Coso Hot Springs KGRA, Inyo County, California Author: Fox, R.C. Year: 1978 A detailed low-altitude aeromagnetic survey of 576 line-mi (927 line-km) was completed over a portion of the Coso Hot Springs KGRA in September 1977. The survey has defined a pronounced magnetic low that could help delineate the geothermal system. The magnetic low has an areal extent of approximately 10 C' sq mi (26 sq km). Direct and indirect evidence indicates that this anomaly is due, in part, to magnetite destruction by hydrothermal solutions associated with the geothermal system. The anomaly generally coincides with two other geophysical anomalies which are directly associated with the system: 1) a bedrock electrical resistivity low, and 2) an area of relatively high near-surface temperatures. The highest measured heat flow, 18 HFU, also occurs within its boundary. The magnetic low occurs at the intersection of two major structural zones which coincide with a complementary set of strike-slip fault zones determined from seismic activity. The intersection of these two zones of active tectonism probably served as the locus for emplacement of a pluton at depth, above which are observed the coincidental geophysical anomalies and surface manifestations related to the geothermal system Title: Low -Altitude Aeromagnetic Survey of a Portion of the Coso Hot Springs KGRA, Inyo County, California Author: Fox, R.C. Year: 1978 A detailed low-altitude aeromagnetic survey of 576 line-mi (927 line-km) was completed over a portion of the Coso Hot Springs KGRA in September 1977. The survey has defined a pronounced magnetic low that could help delineate the geothermal system. The magnetic low has an areal extent of approximately 10 C' sq mi (26 sq km). Direct and indirect evidence indicates that this anomaly is due, in part, to magnetite destruction by hydrothermal solutions associated with the geothermal system. The anomaly generally coincides with two other geophysical anomalies which are directly associated with the system: 1) a bedrock electrical resistivity low, and 2) an area of relatively high near-surface temperatures. The highest measured heat flow, 18 HFU, also occurs within its boundary. The magnetic low occurs at the intersection of two major structural zones which coincide with a complementary set of strike-slip fault zones determined from seismic activity. The intersection of these two zones of active tectonism probably served as the locus for emplacement of a pluton at depth, above which are observed the coincidental geophysical anomalies and surface manifestations related to the geothermal system Close

• 49. [Image] Heat Flow of Oregon

  	An extensive new heat flow and geothermal gradient data set for the State of Oregon is presented on a contour map of heat flow at a scale of 1:1,000,000 and is summarized in several figures and tables. ...
  	Citation × Citation Citation Abstract Copy Title: Heat Flow of Oregon Author: Blackwell, D.D. Year: 1978 An extensive new heat flow and geothermal gradient data set for the State of Oregon is presented on a contour map of heat flow at a scale of 1:1,000,000 and is summarized in several figures and tables. The 1:1,000,000 scale heat flow map is contoured at 20 mW/m/sup 2/ (0.5 HFU) intervals. Also presented are maps of heat flow and temperature at a depth of 1 km averaged for 1/sup 0/ x 1/sup 0/ intervals. Histograms and averages of geothermal gradient and heat flow for the State of Oregon and for the various physiographic provinces within Oregon are also included. The unweighted mean flow for Oregon is 81.3 +- 2.7 mW/m/sup 2/ (1.94 +- 0.06 HFU). The average unweighted geothermal gradient is 65.3 +- 2.5/sup 0/C/km. The average heat flow value weighted on the basis of geographic area is 68 +- 5 mW/m/sup 2/ (1.63 +- 0.12 HFU) and the average weighted geothermal gradient is 55.0 +- 5/sup 0/C/km Title: Heat Flow of Oregon Author: Blackwell, D.D. Year: 1978 An extensive new heat flow and geothermal gradient data set for the State of Oregon is presented on a contour map of heat flow at a scale of 1:1,000,000 and is summarized in several figures and tables. The 1:1,000,000 scale heat flow map is contoured at 20 mW/m/sup 2/ (0.5 HFU) intervals. Also presented are maps of heat flow and temperature at a depth of 1 km averaged for 1/sup 0/ x 1/sup 0/ intervals. Histograms and averages of geothermal gradient and heat flow for the State of Oregon and for the various physiographic provinces within Oregon are also included. The unweighted mean flow for Oregon is 81.3 +- 2.7 mW/m/sup 2/ (1.94 +- 0.06 HFU). The average unweighted geothermal gradient is 65.3 +- 2.5/sup 0/C/km. The average heat flow value weighted on the basis of geographic area is 68 +- 5 mW/m/sup 2/ (1.63 +- 0.12 HFU) and the average weighted geothermal gradient is 55.0 +- 5/sup 0/C/km Close

• 50. [Image] Characteristics of Geothermal Wells Located in the Salton Sea Geothermal Field, Imperial County, California

  	We have summarized the geophysical, geochemical, and geothermal characteristics of wells located in the Salton Sea Geothermal Field. Based on the geothermal characteristics of the wells, we have developed ...
  	Citation × Citation Citation Abstract Copy Title: Characteristics of Geothermal Wells Located in the Salton Sea Geothermal Field, Imperial County, California Author: Palmer, T.D. Year: 1975 We have summarized the geophysical, geochemical, and geothermal characteristics of wells located in the Salton Sea Geothermal Field. Based on the geothermal characteristics of the wells, we have developed a subsurface heat profile for the entire geothermal field. We have also drawn maps of temperature contours for specified depths throughout the field Title: Characteristics of Geothermal Wells Located in the Salton Sea Geothermal Field, Imperial County, California Author: Palmer, T.D. Year: 1975 We have summarized the geophysical, geochemical, and geothermal characteristics of wells located in the Salton Sea Geothermal Field. Based on the geothermal characteristics of the wells, we have developed a subsurface heat profile for the entire geothermal field. We have also drawn maps of temperature contours for specified depths throughout the field Close