Multi-Sensor through-Casing Density and Saturation Measurement Concepts with a Pulsed Neutron Source: A Modeling Assessment

Abstract

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThe paper discusses an assessment, using Monte Carlo modeling techniques, of the advantages we could derive and challenges we would face in utilizing multiple sensors with a pulsed neutron (PN) source for cased-hole logging to obtain petrophysical parameters. Current PN devices are primarily based on two detectors, with source-detector spacing often similar among the various vendors. We consider four sensors to investigate three measurement types, 1) a pseudo-density through casing concept that shows the potential to distinguish between gas and tight zones, 2) computing oil saturation from Carbon/Oxygen logs with oil present in the borehole, and 3) estimation of Sigma and hence water and steam saturation from PNC logs. We illustrate the advantages of using modeling to study measurement concepts independent of specific tools. We identify areas of further research in basic measurement concepts using pulsed sources and in related radiation transport theory.