1963 Paper (O)

THE USE OF CORE ANALYSIS DATA TO EXPLAIN THE ABNORMALLY LOW RESISTIVITIES OF SOME HYDROCARBON-PRODUCTIVE SIMPSON SERIES SANDS IN CENTRAL OKLAHOMA

James C. Gauntt and Ralph E. Jenkins: Core Laboratories, Inc.

ABSTRACT

Difficulty in interpretation of the productivity of Simpson Series sands in Central Oklahoma has been common. Low resistivities often have been recorded in zones which have proven to be hydrocarbon productive. In addition to the problems this causes in selecting well completion intervals, producing zone thickness and down-dip acreage evaluation are greatly affected due to incorrect interpretation of oil-water contact positions. Core analysis data often contradict the electric log data in such intervals; however, in some cases, neither is conclusive.

A technique for comparison of core analysis and electric log data, which was recently suggested, was used in a study of some Simpson Series sands in a field in Central Oklahoma. In essence, the technique involves the conversion of core analysis data to theoretical resistivity values required for hydrocarbon productivity, and requires capillary pressure and resistivity measurements on the cores as well as the routine core analysis data. The study involved the analysis of data from ten wells, completed in the Bromide, Tulip Creek, and McLish formations.

A comparison of core data and electric log data indicates that low resistivities often encountered on the logs in hydrocarbon-productive intervals can be explained in terms of the rock properties which are determined by core analysis tests. In several instances the apparent oil-water contact indicated by the log is significantly higher than the oil-water contact determined by such a comparative study.