Abstract
Efficient reservoir management requires that the latest pulsed neutron capture (PNC) tool technology be comparable with the older measurement results to provide continuity, precision, and accuracy in the monitoring program. A new sigma processing technique was developed for the dual-burst pulse neutron capture measurements that maintains the resolution and repeatability of the new-generation tools but provides results needed for reconciliation with the older generation tools used for more than 20 years in reservoir monitoring. The sigma processing technique is described relative to the old and new generation tools, which utilize radically different approaches. General considerations of repeatability and accuracy are discussed which apply to PNC logs and their use in both stand-alone and time-lapse techniques.
More than 35 cases have been evaluated with the new processing technique. Examples are presented to show reservoir monitoring results obtained in a variety of formation lithologies, formation fluids, and borehole environments to illustrate the robustness of the technique. These cases include detailed analytic studies between the PNC tools. The results indicate that the new sigma processing can provide direct time-lapse reservoir monitoring continuity and yield accurate reservoir saturation analysis.
