Search

Search Results

• 1. [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

• 2. [Image] Geology of the Colado Geothermal Area, Pershing County, Nevada

  	The Colado geothermal area in south-central Pershing County, Nevada is defined by hot water wells in alluvium just west of the West Humboldt Range. Geothermal gradient holes have encountered temperatures ...
  	Citation × Citation Citation Abstract Copy Title: Geology of the Colado Geothermal Area, Pershing County, Nevada Author: Sibbett, B.S. Year: 1980 The Colado geothermal area in south-central Pershing County, Nevada is defined by hot water wells in alluvium just west of the West Humboldt Range. Geothermal gradient holes have encountered temperatures up to 113.5/sup 0/C at a depth of 76 m (250 ft) with a gradient reversal in the alluvium below this depth. The West Humboldt Range consists mainly of Triassic to Jurassic slaty shale to quartzite of the Auld Lang Syne Group. Carbonate rocks of the Jurassic Lovelock Formation have been thrust over pelitic rocks on the south end of the area. Erosional remnants of Tertiary tuffs and sediments overlay the metasediments in the West Humboldt Range. The principal structures are high-angle faults striking north-northwest, northeast and north-south. The horst-to-graben transition along the range front consists of several step faults trending irregularly north. The structural pattern in the west edge of the range probably continues to the west under the Quaterary alluvium where the source of the hot water is located. Thermal waters probably rise along a major fault intersection in the Mesozoic rocks then spread out in an aquifer in the alluvium. Several thrust faults are exposed south of Coal Canyon, and a structural break in the Mesozoic rock exists under the canyon. Several low-angle faults are present north of Coal Canyon but their effect, if any, on the geothermal occurrence is not known; DOE/ID/12079-8; ESL-38 Title: Geology of the Colado Geothermal Area, Pershing County, Nevada Author: Sibbett, B.S. Year: 1980 The Colado geothermal area in south-central Pershing County, Nevada is defined by hot water wells in alluvium just west of the West Humboldt Range. Geothermal gradient holes have encountered temperatures up to 113.5/sup 0/C at a depth of 76 m (250 ft) with a gradient reversal in the alluvium below this depth. The West Humboldt Range consists mainly of Triassic to Jurassic slaty shale to quartzite of the Auld Lang Syne Group. Carbonate rocks of the Jurassic Lovelock Formation have been thrust over pelitic rocks on the south end of the area. Erosional remnants of Tertiary tuffs and sediments overlay the metasediments in the West Humboldt Range. The principal structures are high-angle faults striking north-northwest, northeast and north-south. The horst-to-graben transition along the range front consists of several step faults trending irregularly north. The structural pattern in the west edge of the range probably continues to the west under the Quaterary alluvium where the source of the hot water is located. Thermal waters probably rise along a major fault intersection in the Mesozoic rocks then spread out in an aquifer in the alluvium. Several thrust faults are exposed south of Coal Canyon, and a structural break in the Mesozoic rock exists under the canyon. Several low-angle faults are present north of Coal Canyon but their effect, if any, on the geothermal occurrence is not known; DOE/ID/12079-8; ESL-38 Close

• 3. [Image] Planning, Drilling, Logging, and Testing of Energy Extraction Hole EE-1, Phases I and II

  	Energy Extraction Hole No. 1 (EE-1) is the second deep hole drilled into the Precambrian-age granitic rocks of the Jemez Mountains of north-central New Mexico. EE-1 was drilled to intersect a hydraulic ...
  	Citation × Citation Citation Abstract Copy Title: Planning, Drilling, Logging, and Testing of Energy Extraction Hole EE-1, Phases I and II Author: Pettitt, R.A. Year: 1977 Energy Extraction Hole No. 1 (EE-1) is the second deep hole drilled into the Precambrian-age granitic rocks of the Jemez Mountains of north-central New Mexico. EE-1 was drilled to intersect a hydraulic fracture extending outward from near the bottom of previously drilled hole GT-2, thus completing the underground circulation loop required for the hot dry rock geothermal energy extraction experiment. Directional drilling techniques were used to intersect the fracture zone. In addition, high-temperature instrumentation and equipment development, hydraulic fracturing experiments, pressure-flow testing of the fracture systems, and fracture mapping and borehole-ranging technique activities were conducted. The drilling, logging, and testing operations in EE-1 are described Title: Planning, Drilling, Logging, and Testing of Energy Extraction Hole EE-1, Phases I and II Author: Pettitt, R.A. Year: 1977 Energy Extraction Hole No. 1 (EE-1) is the second deep hole drilled into the Precambrian-age granitic rocks of the Jemez Mountains of north-central New Mexico. EE-1 was drilled to intersect a hydraulic fracture extending outward from near the bottom of previously drilled hole GT-2, thus completing the underground circulation loop required for the hot dry rock geothermal energy extraction experiment. Directional drilling techniques were used to intersect the fracture zone. In addition, high-temperature instrumentation and equipment development, hydraulic fracturing experiments, pressure-flow testing of the fracture systems, and fracture mapping and borehole-ranging technique activities were conducted. The drilling, logging, and testing operations in EE-1 are described Close