1965 Paper I-K

THE UNIVERSAL LOG INTERPRETATION COMPUTER PROGRAM - NUCLEAR LOG EVALUATION-

Hilton B. Evans

ABSTRACT

The methods used to correct the response of the nuclear devices (gamma-ray, neutron and density) for nonideal hole conditions and the parameters calculated from these corrected responses are described.

The influence of mud density, salinity, and barite content, formation fluid salinity and density, mud cake density and thickness, thin beds, lithology, shaliness, casing and other factors on log response is considered for the various devices and the log values are corrected from the appropriate departure curves or relationships.

The gamma-ray device is used to determine bed boundaries, shaliness, and to distinguish between laminated and dispersed shaly formations. Individually, the neutron and density devices provide computed porosities (and densities). In combination, these devices can be used to determine gas saturation, porosity, and shale fraction in shaly formations, and porosity and fractional composition in two-component lithologies. When the acoustic log is also available, porosity and fractional composition of three-component systems can be computed. Dispersed clay and reconnaissance parameter calculations are also possible.