Direct-Current Resistivity Survey

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Exploration Technique: Direct-Current Resistivity Survey

Exploration Technique Information
Exploration Group: Geophysical Techniques
Exploration Sub Group: Electrical Techniques
Parent Exploration Technique: Electrical Techniques
Information Provided by Technique
Lithology: Rock type, mineral and clay content may be inferred.
Stratigraphic/Structural: Determination of fracture zones, faults, depth to groundwater aquifers.
Hydrological: Resistivity influenced by porosity, permeability, fluid saturation, fluid type and phase state of the pore water.
Thermal: Resistivity influenced by temperature.[1]
Cost Information
Low-End Estimate (USD): 4,827.00482,700 centUSD
4.827 kUSD
0.00483 MUSD
4.827e-6 TUSD
/ mile
Median Estimate (USD): 16,109.001,610,900 centUSD
16.109 kUSD
0.0161 MUSD
1.6109e-5 TUSD
/ mile
High-End Estimate (USD): 45,000.004,500,000 centUSD
45 kUSD
0.045 MUSD
4.5e-5 TUSD
/ mile
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Direct-Current Resistivity Survey:
Direct-current (DC) resistivity is an active source electrical technique in which current is applied to the ground using electrodes and the earth response (voltage or potential difference) is recorded. This survey generates a geoelectric section of apparent resistivity and enables an inference of subsurface geology.
Other definitions:Wikipedia Reegle


 
Introduction
A DC Resistivity Survey generates a ‘geoelectric’ section , which is a model of the electrical properties of the subsurface.[1] This enables an inference of rock and fluid type as well as structure. The depth of investigation for a DC survey ranges from 1.5 km – 2 km. [2]
 
Use in Geothermal Exploration
DC Resistivity surveys can be performed in a variety of ways, depending on the electrode array geometry utilized. The most common electrode array geometries for geothermal exploration are the Schlumberger Array, Wenner Array and Dipole-Dipole Array. [2]

DC Resistivity can be used to find “hidden” geothermal resources (blind systems with no surface hydrothermal manifestations) in conjunction with other geophysical techniques such as Self Potential and Magnetotellurics. [2] Low resistivity anomalies may correspond to high temperature regions of a geothermal reservoir, fracture zones, or areas with hydrothermal alteration. [3] The depth to and thickness of the cap rock overlying the geothermal reservoir may be determined with a DC Resistivity survey. [4] Conversely, the low resistivity signature may relate to outflow zone of a geothermal system located in steep terrain. [3]

 
Field Procedures
The field equipment required for a DC resistivity survey are the current and receiver electrodes, insulated wire, a transmitter (current source) and the receiver instrument. The electrodes used for a DC survey are typically metal stakes which need to be driven a few tens of centimeters (~30-50 cm) into the ground. There are typically four electrodes which are arranged in a collinear array and various electrode geometries exist as shown below.

The choice of which electrode array to use (i.e. Schlumberger array, Wenner array, pole-dipole array, dipole-dipole array, gradient array) depends on the target of investigation, its expected depth and geometry, signal strength, sensitivity of the array to vertical and lateral changes in resistivity, background noise levels, and the sensitivity of the instrument.

DC Resistivity electrode arrays[5]

 
Environmental Mitigation Measures
A DC Resistivity survey is minimally invasive and the main environmental impacts are associated with access to the survey stations. Line cutting may be required in areas of thick vegetation in order to lay out the cable.
 
Physical Properties

 
Data Access and Acquisition
Schematic diagram showing the basic principle of DC Resistivity measurements[1]

 
Best Practices
• It may be necessary to water the electrodes with pure or salt water to lower contact resistance at the electrode interface.

 
Potential Pitfalls
• Near surface inhomogeneities in electrical resistivity strongly affect apparent resistivity measurements. These variations may mask or obscure the deeper electrical response. [6]

• Resistivity models are non-unique, meaning there are many combinations of subsurface parameters which can fit the resistivity model. It is recommended to apply other geophysical techniques or constraints in conjunction with DC Resistivity survey.

• DC Resistivity surveys do not provide direct information regarding fluid transport or permeability structure of the geothermal reservoir. [2]It is not possible to directly derive the temperature of the resource from a DC survey.

• Field work may be time-consuming, laborious and expensive because of the efforts required in moving the wire and electrodes while performing the survey.

• The proximity to cultural noise such as buried pipelines and metal fences may impact measurements. [7]

• Electrode polarization and contact resistance may impact data quality. [7]

• Any breaks in the insulated cable may cause current leakage in wet weather conditions.




Page Area Activity Start Date Activity End Date Reference Material
Direct-Current Resistivity At Beowawe Hot Springs Area (Garg, Et Al., 2007) Beowawe Hot Springs Area


Direct-Current Resistivity At Brady Hot Springs Area (Combs 2006) Brady Hot Springs Area


Direct-Current Resistivity At Central Nevada Seismic Zone Region (Pritchett, 2004) Central Nevada Seismic Zone Geothermal Region


Direct-Current Resistivity At Clear Lake Area (Skokan, 1993) Clear Lake Area


Direct-Current Resistivity At Cove Fort Area (Warpinski, Et Al., 2002) Cove Fort Geothermal Area


Direct-Current Resistivity At Cove Fort Area (Warpinski, Et Al., 2004) Cove Fort Geothermal Area


Direct-Current Resistivity At Cove Fort Area - Liquid (Combs 2006) Cove Fort Geothermal Area


Direct-Current Resistivity At Cove Fort Area - Liquid (Warpinski, Et Al., 2004) Cove Fort Geothermal Area


Direct-Current Resistivity At Haleakala Volcano Area (Thomas, 1986) Haleakala Volcano Area


Direct-Current Resistivity At Honokowai Area (Thomas, 1986) Honokowai Area


Direct-Current Resistivity At Hualalai Northwest Rift Area (Thomas, 1986) Hualalai Northwest Rift Area


Direct-Current Resistivity At Kawaihae Area (Thomas, 1986) Kawaihae Area


Direct-Current Resistivity At Kilauea Southwest Rift And South Flank Area (Thomas, 1986) Kilauea Southwest Rift And South Flank Area


Direct-Current Resistivity At Kilauea Summit Area (Keller, Et Al., 1979) Kilauea Summit Area


Direct-Current Resistivity At Lahaina-Kaanapali Area (Thomas, 1986) Lahaina-Kaanapali Area


Direct-Current Resistivity At Lualualei Valley Area (Thomas, 1986) Lualualei Valley Area


Direct-Current Resistivity Survey At Beowawe Hot Springs Area (Garg, Et Al., 2007) Beowawe Hot Springs Area


Direct-Current Resistivity Survey At Blue Mountain Area (Fairbank Engineering Ltd, 2005) Blue Mountain Area


Direct-Current Resistivity Survey At Brady Hot Springs Area (Combs 2006) Brady Hot Springs Area


Direct-Current Resistivity Survey At Central Nevada Seismic Zone Region (Pritchett, 2004) Central Nevada Seismic Zone Geothermal Region


Direct-Current Resistivity Survey At Clear Lake Area (Skokan, 1993) Clear Lake Area


Direct-Current Resistivity Survey At Coso Geothermal Area (1977) Coso Geothermal Area 1977 1977


Direct-Current Resistivity Survey At Cove Fort Area (Warpinski, Et Al., 2002) Cove Fort Geothermal Area


Direct-Current Resistivity Survey At Cove Fort Area (Warpinski, Et Al., 2004) Cove Fort Geothermal Area


Direct-Current Resistivity Survey At Cove Fort Area - Liquid (Combs 2006) Cove Fort Geothermal Area


Direct-Current Resistivity Survey At Cove Fort Area - Vapor (Warpinski, Et Al., 2002) Cove Fort Geothermal Area


Direct-Current Resistivity Survey At Cove Fort Area - Vapor (Warpinski, Et Al., 2004) Cove Fort Geothermal Area


Direct-Current Resistivity Survey At Dixie Valley Geothermal Area (Laney, 2005) Dixie Valley Geothermal Area 2003 2003


Direct-Current Resistivity Survey At Haleakala Volcano Area (Thomas, 1986) Haleakala Volcano Area


Direct-Current Resistivity Survey At Honokowai Area (Thomas, 1986) Honokowai Area


Direct-Current Resistivity Survey At Hualalai Northwest Rift Area (Thomas, 1986) Hualalai Northwest Rift Area


Direct-Current Resistivity Survey At Kawaihae Area (Thomas, 1986) Kawaihae Area


Direct-Current Resistivity Survey At Kilauea East Rift Geothermal Area (FURUMOTO, 1976) Kilauea East Rift Geothermal Area 1973 1975


Direct-Current Resistivity Survey At Kilauea East Rift Geothermal Area (Kauahikaua & Klein, 1978) Kilauea East Rift Geothermal Area 1973 1976


Direct-Current Resistivity Survey At Kilauea East Rift Geothermal Area (Thomas, 1986) Kilauea East Rift Geothermal Area 1978 1986


Direct-Current Resistivity Survey At Kilauea Southwest Rift And South Flank Area (Thomas, 1986) Kilauea Southwest Rift And South Flank Area


Direct-Current Resistivity Survey At Kilauea Summit Area (Keller, Et Al., 1979) Kilauea Summit Area


Direct-Current Resistivity Survey At Lahaina-Kaanapali Area (Thomas, 1986) Lahaina-Kaanapali Area


Direct-Current Resistivity Survey At Lightning Dock Area (Cunniff & Bowers, 2005) Lightning Dock Area


Direct-Current Resistivity Survey At Lightning Dock Area (Warpinski, Et Al., 2002) Lightning Dock Area


Direct-Current Resistivity Survey At Long Valley Caldera Geothermal Area (Pribnow, Et Al., 2003) Long Valley Caldera Geothermal Area 2003


Direct-Current Resistivity Survey At Lualualei Valley Area (Thomas, 1986) Lualualei Valley Area


Direct-Current Resistivity Survey At Marysville Mt Area (Blackwell) Marysville Mt Area


Direct-Current Resistivity Survey At Mauna Loa Northeast Rift Area (Thomas, 1986) Mauna Loa Northeast Rift Area


Direct-Current Resistivity Survey At Mauna Loa Southwest Rift Area (Thomas, 1986) Mauna Loa Southwest Rift Area


Direct-Current Resistivity Survey At Mokapu Penninsula Area (Thomas, 1986) Mokapu Penninsula Area


Direct-Current Resistivity Survey At Mt Princeton Hot Springs Area (Richards, Et Al., 2010) Mt Princeton Hot Springs Geothermal Area 2010 2010


Direct-Current Resistivity Survey At Northern Basin & Range Region (Pritchett, 2004) Northern Basin and Range Geothermal Region


Direct-Current Resistivity Survey At Nw Basin & Range Region (Pritchett, 2004) Northwest Basin and Range Geothermal Region


Direct-Current Resistivity Survey At Raft River Geothermal Area (1975) Raft River Geothermal Area 1975 1975


Direct-Current Resistivity Survey At Raft River Geothermal Area (1983) Raft River Geothermal Area 1983 1983


Direct-Current Resistivity Survey At Roosevelt Hot Springs Area (Combs 2006) Roosevelt Hot Springs Area


Direct-Current Resistivity Survey At Soda Lake Area (Combs 2006) Soda Lake Area


Direct-Current Resistivity Survey At Stillwater Area (Laney, 2005) Stillwater Area


Direct-Current Resistivity Survey At Valles Caldera - Redondo Geothermal Area (Wilt & Haar, 1986) Valles Caldera - Redondo Geothermal Area 1986


Direct-Current Resistivity Survey At Valles Caldera - Sulphur Springs Geothermal Area (Wilt & Haar, 1986) Valles Caldera - Sulphur Springs Geothermal Area 1986


Direct-Current Resistivity Survey At Walker-Lane Transitional Zone Region (Pritchett, 2004) Walker-Lane Transition Zone Geothermal Region


Electrical Resistivity At Coso Geothermal Area (1972) Coso Geothermal Area 1972 1972


Electrical Resistivity At Kilauea East Rift Geothermal Area (KELLER, Et Al., 1977) Kilauea East Rift Geothermal Area 1973 1973


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