New Calibration and Conversion Techniques for Radioactivity Logs
- V.J. Mercier (The Western Co.) | W.H. Redford (Lane-Wells Co.)
- Document ID
- Society of Petroleum Engineers
- Journal of Petroleum Technology
- Publication Date
- September 1957
- Document Type
- Journal Paper
- 11 - 15
- 1957. Original copyright American Institute of Mining, Metallurgical, and Petroleum Engineers, Inc. Copyright has expired.
- 4.3.4 Scale, 5.6.1 Open hole/cased hole log analysis, 4.1.5 Processing Equipment, 1.11.2 Drilling Fluid Selection and Formulation (Chemistry, Properties), 4.1.2 Separation and Treating
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A new approach to an old problem has made it possible to analyze and quantitatively evaluate a radio-activity log in a relatively short time, whereas in the past it was necessary to calculate and plot a "neutron-derived porosity curve" then transpose that information to other logs.
The new calibration technique is discussed and introduces the terms "radiation units", "environmental units" and "well strata index". The application of these units to each radioactivity log, regardless of detector type, source spacing or well condition, is explained and illustrated.
Neutron curve conversion charts are introduced. The accompanying charts provide a means for comparing neutron curve responses obtained under empty or liquid-filled openhole (uncased borehole) conditions, in borehole ranging from 4 to 9 in. in diameter, with several types of neutron logging instruments operated at various source to detector spacings.
Given the neutron curve response under one set of borehole conditions the charts may be used to determine the response which would be obtained in similar rock under a different set of borehole conditions. In this way the neutron curve of a given well may be converted to obtain the curve which would have resulted had the borehole conditions been altered. Similarly, several neutron curves obtained under different well conditions may be converted to a common basis to determine whether or not certain formations observed in the several wells are alike.
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