Self Potential Method (M-10)

1. Q: How does it work?
   A: A natural voltage difference is present between points on the earth's surface. This voltage can be due to subsurface water flow through porous media but can also be caused by dissimilar metals or materials in the subsurface (a battery effect) or spatial or temporal discontinuities in global electrical currents.

2. Q: What is the geologic model?
   A: A conduit or channel controlling the preferential flow of water.
   

3. Q: What are the requirements?
   A: A low-noise base station, non polarizing electrodes, a high impedance voltmeter, and light-weight high-quality wire to link the two potential points. Small holes are dug at each station to place the electrode in a uniform medium. Interpretation is usually qualitative and subjective if the anomalies are small. To bypass geologic factors, two surveys, one at low pool and one at high pool, are often required for reservoir leakage studies. A leak may be due to sheet flow and the resultant anomaly undetectable.
   

4. Q: What are the pitfalls?
   A: Interference such as buried metallic objects, abrupt resistivity changes, or two- or three-dimensional effects should be accounted for.Telluric noise, especially at high latitudes, may have to be recorded. Buried metals (unless those are the targets) will interfere.

5. Q: What logistics are needed?
   A: Crew size is usually one person. The equipment is simple and lightweight.
   
6. Q: What are the deliverables?A:Plan map of station locations, profiles of SP values, contour maps of values if sufficient data is acquired, very specific base location information (for repeat surveys if necessary), and a narrative discussion of the work.
   
7. More detailed information.