Downhole Evaluation with Neutron Activation Measurement

A system for monitoring a subterranean well structure at least partially composed of a first doping material, the system comprising:

• a logging tool at least partially within the subterranean well structure, the logging tool comprising a neutron source and a gamma ray detector;
• a motor coupled to the logging tool that moves the logging tool relative to the well structure at a velocity that depends on:
• a distance between the neutron source and the gamma ray detector;
• and
• a gamma decay half-life corresponding to the first doping material;
• and
• a data processing apparatus communicably coupled to the gamma ray detector, the data processing apparatus comprising a processor and a memory device coupled to the processor, the memory device containing a set of instructions that, when executed by the processor, cause the processor to:
• receive a counted number of activation gamma rays;
• determine a ratio between the counted number of detected activation gamma rays and an expected number of detected activation gamma rays;
• and
• determine information corresponding to a characteristic of the well structure based on the ratio.