Some Preliminary Investigations of Quantitative Interpretations of Radioactivity Logs
- Robert E. Bush (Lane-Wells Co.) | E.S. Mardock (Well Surveys Inc.)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- January 1950
- Document Type
- Journal Paper
- 19 - 34
- 1950. Original copyright American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Copyright has expired.
- 2.4.3 Sand/Solids Control, 5.6.1 Open hole/cased hole log analysis, 4.3.4 Scale, 5.6.2 Core Analysis, 6.5.4 Naturally Occurring Radioactive Materials, 1.6.9 Coring, Fishing, 5.5.2 Core Analysis
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The objective of this paper is to present practical methods of applyingradioactivity logs to problems of interest both to those engaged in evaluatingfundamental reservoir data as well as to those engaged in subsurface structuralwork. The basic theories underlying the operation of radioactivity loggingmethods are briefly discussed along with some of the problems arising in theinterpretation of the log. Relative methods of quantitative interpretation aredescribed, with a discussion of relative reference lines and specific examplesare given showing the application of these relative quantitative interpretationmethods. To show the variation of the methods described, specimen wellspenetrating formations widely divergent in point of geologic age were selectedto demonstrate the application. A relative reference line is determined for theNeutron Curve and by comparison to known petrophysical data such as porositiesfrom diamond cores, a direct quantitative relationship is developed. Theapplication of this relative calibration curve to logs of unknown wells willpermit a reasonably accurate determination of porosity in limestone anddolomite formations. Specific examples are given showing the application ofthese relative methods of interpretation to logs of the Smackover limestone inLouisiana, the Edwards limestone and dolomites of South Texas, and Permiandolomites of West Texas.
Radioactivity logs have been used extensively by the petroleum industry fora number of years and recognition of their value has grown steadily, not onlyas tools to aid in the solution of specific stratigraphic problems, but also aspotential sources of the basic data necessary for the estimation of net pay andreserves. The value of radioactivity logs for stratigraphic work has beenpointed out in the literature, and now has long been recognized by theindustry, but the quantitative application of the logs has advanced but littlebeyond the stage of a strong conviction that radioactivity logging curves willsome day provide the information on such important quantities as the porosityand the liquid saturation of the formations.
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