SELF-POTENTIAL

The Self-Potential (SP) method is based on measuring the natural electrical potential difference between two points on the ground. Its origin lies in the flow of fluids through porous media (known as streaming potential), which results from the electrical interaction between the fluid and the electrical double layer at the pore–mineral interface. Natural self-potentials can also be attributed to electrokinetic processes that occur when water circulates through fractures within a reservoir. Additional processes—such as electrochemical or electrothermal effects—may also contribute to self-potential signals, arising from differences in chemical composition and temperature between subsurface fluids.

Measuring self-potential is straightforward. Non-polarizable porous electrodes are used: one remains fixed (the base), while the other is moved along a profile or grid to generate maps of natural potential distribution.