Paper: The Use of the Thermal Neutron Decay Time Log in West Texas

The Thermal Decay Time (TDT) log is used to detect hydrocarbons through casing. When used with a porosity log obtained in open or cased hole a water saturation can be calculated. The TDT water saturation computed in high porosity and high salinity situation approached the accuracy obtained from an openhole suite of logs. Since a high salinity and low porosity situation exists in many areas of West Texas, special interpretation techniques must be used to compute a semi-quantitative water saturation in these horizons. Examples of logs recorded in West Texas attest to the validity of these interpretation techniques.