Exploration Technique: Self Potential
|Exploration Technique Information|
|Exploration Group:||Geophysical Techniques|
|Exploration Sub Group:||Electrical Techniques|
|Parent Exploration Technique:||Electrical Techniques|
|Information Provided by Technique|
|Lithology:||SP technique originally applied to locating sulfide ore-bodies.|
|Stratigraphic/Structural:||Detection and tracing of faults.|
|Hydrological:||Determination of fluid flow patterns: electrochemical coupling processes due to variations in ionic concentrations, and electrokinetic coupling processes due to fluid flow in the subsurface.|
|Thermal:||Location of near-surface thermal anomalies: thermoelectric coupling processes due to variations in temperature in the subsurface.|
|Low-End Estimate (USD):|| 907.48|
90,748 centUSD/ mile
|Median Estimate (USD):|| 6,473.05|
647,305 centUSD/ mile
|High-End Estimate (USD):|| 18,000.00|
1,800,000 centUSD/ mile
|Low-End Estimate:|| 15.02 days|
0.0411 years/ 10 mile
|Median Estimate:|| 23.33 days|
0.0639 years/ 10 mile
|High-End Estimate:|| 42.91 days|
0.117 years/ 10 mile
|Cost/Time Dependency:||Electrode Spacing, Size, Terrain, Weather|
- "The self-potential (SP) survey ultimately generates a profile or map of contours of equipotential surfaces. The SP method may be applied to characterizing shallow conductive bodies or subsurface fluid flow. '"`UNIQ--ref-00000000-QINU`"''"`UNIQ--ref-00000001-QINU`"'" cannot be used as a page name in this wiki.
- The given value was not understood.
- "The self-potential technique enables characterization of faults that may provide a conduit for the flow of geothermal fluids. This is due to a few factors: 1) thermoelectric coupling is generated when a temperature gradient exists across a rock body or geological contact (due to thermal fluid or thermal diffusion into the surrounding rock), and 2) the electrokinetic coupling which results from the flow of fluid through a porous medium (such as a thermal fluid-filled fault) causing an electric potential gradient. Steep self-potential anomaly gradients may be indicative of these structures.'"`UNIQ--ref-00000002-QINU`"''"`UNIQ--ref-00000003-QINU`"'" cannot be used as a page name in this wiki.
- The given value was not understood.
The SP field equipment consists of two non-polarizing electrodes connected by insulated cable and a high impedance voltmeter. Non-polarizing electrodes are used in order to minimize the effects of noise at the soil/electrode interface. The electrodes are porous pots containing a metallic electrode immersed in a salt solution , commonly copper sulfate or lead chloride.
The survey grid and electrode spacing are specific to the particular survey design and depends on the resolution and depth of investigation desired. However, there are two electrode configurations and these are the dipole configuration (a.k.a. leapfrog or gradient configuration) and the fixed-base configuration. The dipole configuration involves recording a measurement and then moving the electrodes along a survey line, maintaining a fixed spacing. The trailing electrode becomes the leading electrode as the electrodes are leap-frogged along the line. The positive voltmeter lead is always connected to the leading electrode to maintain proper polarity. For the fixed-base configuration, one electrode remains stationary and the other electrode is moved to different measurement locations using a cable reel. The fixed-configuration electrode array may result in lower error overall, but its application in the field may be more challenging due to long wire lengths and transporting the cable reel.
The electrodes are generally buried at a depth of less than 0.5 meters. It is crucial to monitor the contact resistance of the electrodes at each station as this is an indicator of the electrical contact between the soil and the electrode. A low contact resistance is desired for better electrical contact with the soil. At times, it is necessary to water the soil in the vicinity of the electrode to reduce the contact resistance, but this should be done with caution in an SP measurement as noise may be introduced to the measurement.
Field notes record the voltage between the electrodes at each specified electrode spacing and station position (1mV resolution is sufficient), and should also indicate the condition of the soil, if water was used to water the electrode contact surface, nearby cultural infrastructure, nearby surface bodies of water and any other condition relevant to a surface electrical measurement.
- (Corwin and Hoover 1979) "The self-potential method in geothermal exploration"
- (Sharma 1997) "Environmental and Engineering Geophysics"
- (Kaufman and Anderson 2010) ""Self-Potential Method." In Principles of Electrical Methods in Surface and Borehole Geophysics"
- Beowawe Hot Springs Area
- Blue Mountain Geothermal Area
- Central Nevada Seismic Zone Geothermal Region
- Coso Geothermal Area
- Cove Fort Geothermal Area
- Dixie Hot Springs Area
- Haleakala Volcano Area
- Hualalai Northwest Rift Area
- Kilauea East Rift Geothermal Area
- Kilauea Summit Area
- Mauna Loa Southwest Rift Area
- Mokapu Penninsula Area
- Mt Princeton Hot Springs Geothermal Area
- Mt St Helens Area
- Neal Hot Springs Geothermal Area
- Northern Basin and Range Geothermal Region
- Northwest Basin and Range Geothermal Region
- Roosevelt Hot Springs Area
- Roosevelt Hot Springs Geothermal Area
- Steamboat Springs Area
- Twenty-Nine Palms Geothermal Area
- Valles Caldera - Redondo Geothermal Area
- Walker-Lane Transition Zone Geothermal Region