ABSTRACT
Resistivity methods constitute a major group of measurements in petroleum formation evaluation. They determine an important physical property of a material. For many years, resistivity logs were the only logging method which would directly and quantitatively respond to the presence of hydrocarbon in the formation material. Many surface electrical measurements and a large percentage of downhole geophysical measurements are some form of quantitative resistivity measurement. Engineering and scientific measurements demand quantification. Resistance is commonly used in sedimentary mineral exploration because the fluid content of a sand is not very important. The single point resistance curve, however, is an excellent stratigraphic curve. It is sensitive to the sands, the degree of shaliness, and the redox state. It must not be called “resistivity,” however.
