ABSTRACT
The use of the resistivity systems, suites and techniques and their interpretation are most important in hydrocarbon usage. The resistivity systems and techniques are important to petroleum evaluation, of course, because of the usual extremely high resistivity contrast between hydrocarbons and the accompanying formation waters. The accuracy of the deep and the shallow resistivity determinations is controlled by the effective depth of invasion of the borehole fluid. The resistivity gradient method for estimating permeability makes use of the differences of density between the waters of the pore space and the hydrocarbon. It also makes use of the great differences of resistivity of the pore water and the hydrocarbon. In small grained sands, a fining upward sequence will often result in a gradually lower resistivity upward. This may indicate a lowering of the depositional energy, with time. The length of the single-point curve electrode is analogous to the spacing of the multi-electrode resistivity curves.
