Search

Search Results

• 1. [Image] Dipole-Dipole Resistivity Surveys, Roosevelt Hot Springs KGRA. Final Report, Volume 2

  	Dipole-dipole Resistivity surveys were conducted at Roosevelt Hot Springs KGRA. Three different dipole spacings were used; 99km of traverse line were surveyed with 100m dipoles, 50km with 300m dipoles, ...
  	Citation × Citation Citation Abstract Copy Title: Dipole-Dipole Resistivity Surveys, Roosevelt Hot Springs KGRA. Final Report, Volume 2 Author: Ward, S.H. Year: 1976 Dipole-dipole Resistivity surveys were conducted at Roosevelt Hot Springs KGRA. Three different dipole spacings were used; 99km of traverse line were surveyed with 100m dipoles, 50km with 300m dipoles, and 44km with 1km dipoles. The objectives of the Resistivity surveying were to detect and delineate regions of low Resistivity associated with fracturing, brines, high temperatures, and clay alteration. The Resistivity of rocks that are typical of hydrothermal environments is due to two main conduction mechanisms: (1) electrolytic conduction through pores and fractures; and (2) surface conduction due to a thin zone of cations attracted to those mineral surfaces with net negative charges (especially clay minerals). For saturated rocks, the Resistivity due to electrolytic conduction is a function of the effective porosity of the fractured rock, of the temperature, and of the salinity of the fluid filling the pores and fractures. The Resistivity decreases as the effective porosity, water saturation, salinity, and temperature increase. The presence of clay minerals and pyrite will also decrease the Resistivity Title: Dipole-Dipole Resistivity Surveys, Roosevelt Hot Springs KGRA. Final Report, Volume 2 Author: Ward, S.H. Year: 1976 Dipole-dipole Resistivity surveys were conducted at Roosevelt Hot Springs KGRA. Three different dipole spacings were used; 99km of traverse line were surveyed with 100m dipoles, 50km with 300m dipoles, and 44km with 1km dipoles. The objectives of the Resistivity surveying were to detect and delineate regions of low Resistivity associated with fracturing, brines, high temperatures, and clay alteration. The Resistivity of rocks that are typical of hydrothermal environments is due to two main conduction mechanisms: (1) electrolytic conduction through pores and fractures; and (2) surface conduction due to a thin zone of cations attracted to those mineral surfaces with net negative charges (especially clay minerals). For saturated rocks, the Resistivity due to electrolytic conduction is a function of the effective porosity of the fractured rock, of the temperature, and of the salinity of the fluid filling the pores and fractures. The Resistivity decreases as the effective porosity, water saturation, salinity, and temperature increase. The presence of clay minerals and pyrite will also decrease the Resistivity Close

• 2. [Image] Downhole Electrical Detection of Hydraulic Fractures in GT-2 and EE-1

  	Electrical geophysical methods including mise a la masse and self-potential (SP) for determination of hydraulic fracture characteristics were used at the hot dry rock geothermal project. Electrical and ...
  	Citation × Citation Citation Abstract Copy Title: Downhole Electrical Detection of Hydraulic Fractures in GT-2 and EE-1 Author: Kintzinger, P.R. Year: 1977 Electrical geophysical methods including mise a la masse and self-potential (SP) for determination of hydraulic fracture characteristics were used at the hot dry rock geothermal project. Electrical and induction logs indicated that the resistivity contrast between the granite and 200/sup 0/C water at the 2926-m (9600-ft) depth is a factor of 1000 or more. Thus the water in a hydraulic fracture, formed to connect two adjacent deep holes, is a good conductor compared to the confining granite. Mise a la masse-type measurements were made to help determine the characteristics for hydraulic fractures formed in each of the two geothermal holes GT-2 and EE-1. Once a hydraulic fracture has been formed, mise a la masse effects are obtained both with the fracture pressurized above hydrostatic and when depressurized to hydrostatic. This indicates that once the fracture has been created, enough natural propping exists that a conductive zone persists even when the fracture is deflated. A fracture was formed in a 18-m (60-ft) zone immediately below 1957 m (6420 ft) in EE-1. Later a set of SP logs was run in this zone with no pressure, with pressure building, with pressure decreasing, and again with the fracture depressurized. Results show that during times of change of parameters in hydraulically fractured regions in the hole, natural SP logging helps to determine the position of the fracture. However, after a fracture has come to equilibrium with fluid parameters such as temperature, pressure, salinity, and pH, an effect of the fracture may not be evident. Self-potential logs provide an excellent method for locating the bottom of steel casing that has been set in the hole Title: Downhole Electrical Detection of Hydraulic Fractures in GT-2 and EE-1 Author: Kintzinger, P.R. Year: 1977 Electrical geophysical methods including mise a la masse and self-potential (SP) for determination of hydraulic fracture characteristics were used at the hot dry rock geothermal project. Electrical and induction logs indicated that the resistivity contrast between the granite and 200/sup 0/C water at the 2926-m (9600-ft) depth is a factor of 1000 or more. Thus the water in a hydraulic fracture, formed to connect two adjacent deep holes, is a good conductor compared to the confining granite. Mise a la masse-type measurements were made to help determine the characteristics for hydraulic fractures formed in each of the two geothermal holes GT-2 and EE-1. Once a hydraulic fracture has been formed, mise a la masse effects are obtained both with the fracture pressurized above hydrostatic and when depressurized to hydrostatic. This indicates that once the fracture has been created, enough natural propping exists that a conductive zone persists even when the fracture is deflated. A fracture was formed in a 18-m (60-ft) zone immediately below 1957 m (6420 ft) in EE-1. Later a set of SP logs was run in this zone with no pressure, with pressure building, with pressure decreasing, and again with the fracture depressurized. Results show that during times of change of parameters in hydraulically fractured regions in the hole, natural SP logging helps to determine the position of the fracture. However, after a fracture has come to equilibrium with fluid parameters such as temperature, pressure, salinity, and pH, an effect of the fracture may not be evident. Self-potential logs provide an excellent method for locating the bottom of steel casing that has been set in the hole Close