Methods to quantitatively determine the separate amounts of oil and gas in a geological formation adjacent to a cased well using measurements of formation resistivity. The steps include obtaining resistivity measurements from within a cased well of a given formation, obtaining the porosity, obtaining the resistivity of formation water present, computing the combined amounts of oil and gas present using Archie's Equations, determining the relative amounts of oil and gas present from measurements within a cased well, and then quantitatively determining the separate amounts of oil and gas present in the formation. Resistivity measurements are obtained from within the cased well by conducting A.C. current from within the cased well to a remote electrode at a frequency that is within the frequency range of 0.1 Hz to 20 Hz.
FEDERALLY-SPONSORED RESEARCH AND DEVELOPMENT
This invention was made with Government support under DOE Grant No. DE-FG06-84ER13294, entitled "Validating the Paramagnetic Logging Effect", Office of Basic Energy Sciences, of the U.S. Department of Energy. The government has certain rights in this invention. The basic concept for the invention described herein was conceived during the funding provided by the above grant.
Ongoing research to measure resistivity through casing has been provided on a co-funded basis from: (a) U.S. Department of Energy Grant No. DE-FG19-88BC14243 entitled "Proof of Feasibility of Thru Casing Resistivity Technology"; (b) U.S. Department of Energy (DOE) Grant No. DE-FG22-90BC14617 entitled "Proof of Concept of Moving Thru Casing Resistivity Apparatus"; (c) U.S. Department of Energy Grant No. DE-FG22-93BC14966 entitled "Fabrication and Downhole Testing of Moving Through Casing Resistivity Apparatus"; and (d) Gas Research Institute (GRI) Contract No. 5088-212-1664 entitled "Proof of Feasibility of the Through Casing Resistivity Technology". The government and the GRI have certain rights in this invention. The application herein was filed during periods of time funded by (a) and (b) and (c) above.