Normalization of Cased-Hole Neutron Logs, Slaughter Field, Cochran, and Hockley Counties, TX

Abstract

Summary Currently accepted methods of normalizing cased hole neutron logs to porosity were determined to be unusable under conditions encountered during a reservoir study of the Texaco Bob Slaughter Block and nearby leases in Slaughter Field, Cochran, and Hockley Counties, TX. A new method for normalizing a large number of neutron logs was developed that is applicable in a wide range of situations. The method uses statistical parameters derived from available core and modern log suites to transform dependably the neutron log response. Unlike earlier techniques, a linear transform equation is developed for each log being normalized. The method calculates the slope of the transform equation by comparing the standard deviation of the neutron values to a reference log with similar characteristics over a specified depth interval. The intercept of the transform line is then calculated from average porosity values for a specific interval, but not necessarily the same interval used to calculate the standard deviation. The technique eliminates inaccuracies in the normalization process created by tool differences, scale factors, and hole size. The effect of changes in lithology and formation fluid on the resulting porosity values are also minimized.