Compensated Neutron Log Response Issues

Compensated neutron (CN) logs have been around for many years, and have been used successfully for many petrophysical applications. Although the basic design and general response characteristics of these instruments have remained relatively constant over the years, service companies have refined the response characterizations and have updated their hardware, providing evolutionary improvements. Unfortunately, the general understanding among petrophysicists of how CN instruments work and how best to make use of the log data appears to have lagged or perhaps even worsened in recent years. This paper discusses several obstacles to understanding and interpreting neutron logs and proposes some techniques for avoiding problems. Although this paper is not an exhaustive treatment of CN logging issues, some of the more important ones are discussed. Some alternative ways of looking at the data are presented.