Potential Utilization of Neutron Logging for Casing Cement Evaluation

Abstract

Verification of casing cement integrity is crucial to ensure that the cement fulfills its purpose of zonal isolation, for optimal production and safety. This thesis introduces cement evaluation technology on the market today and highlights advantages and current limitations of each. The scope of this work was to assess neutron logging for the same purpose, and cases such as good cement, cement with channels, foamed cement and a through-tubing configuration has been modelled in a basic preliminary analysis. Results where compared to highlight relative differences in neutron attenuation. Other aspects of the neutron logging technology are assessed for a comprehensive review.

This preliminary analysis has shown that neutrons have the potential to reach the cement-formation interface and be backscattered to the detector for all cases considered. Neutrons experience large attenuation in liquids present in or near the wellbore, while it is less attenuated for gas and foamed cement. For a single casing configuration, results indicate distinguishable results between good and channeled cement. For a through-tubing configuration it cannot be concluded the same as final energy were either too close to the good cement base case or undetectable.

Assessment of other aspects has shown that adding tracer material to the cement can be beneficial in terms of increased absorption and neutron spectroscopy. While specific neutron sources have HSE concerns, there are available alternatives on the market. Neutron logging could present an increased cost which must be weighed against potential gains of applying this technology as a replacement or complimentary to existing cement evaluation methods.

Based on the outcomes of this thesis, a paper to be published is drafted (Appendix C).