ERSC 3V93 Lecture Notes - Lecture 37: Clay Minerals, Lithification, Equipotential
3 May 2016
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Document Summary
Geological materials show large variation (1024) in resistivity. Resistivity of earth materials: the low resistivity phase dominates the overall resistivity, overall resistivity is very sensitive to the geometry (distribution of the fluid) Factors that decrease resistivity: add more pore fluid. Increase salinity of pore fluid (more ions to conduct i) Fracture rocks to create extra pathways for current flow: add clay minerals, keep fluid content constant, but improve interconnection between pores. Factors that increase resistivity: remove pore fluid, lower salinity of pore fluid, compaction: less pathways for electric current flow, lithification: block pores by deposition of minerals, keep fluid content constant, but decrease pore. We use resistivity ( ) rather than resistance (r) as a measure of ability of material to conduct electrical current. Single electrode planted in the earth with circuit completed by second infinitely distant electrode current flow is radially away from positive electrode.
