A Theoretical Analysis of the Effect of Thermal Neutron absorbers on Dual-Detector Porosity Log Measurements

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P.J. McDaniel, J.M. Harris, D.H. Widman,
Sandia National Laboratory

SPWLA TWENTY-FOURTH ANNUAL LOGGING SYMPOSIUM, JUNE 27-30, 1983

1983

Abstract

One of the tools used for the determination of formation porosity is the dual-detector neutron (DDN) porosity log. When used in conjunction with a gamma-ray density log, a cross-plot technique can be used to detect the presence of gas rather than oil or water in the formation. In formations with complex mineralogies, the accuracy of the interpretation of this log has been questioned and shown to be rather unreliable. A possible explanation for this is the uncertainty in a formation’s neutron absorption properties.