An extended analysis method for two-pulse tracer logging

Radioactive tracer logs are commonly used logs for quantitative determination of injection profiles. In particular, the velocity-shot method is used for quantitative analysis. In this technique, the transit time for the passage of a slug of radioactive tracer material between two stationary detectors is measured. From such transit times, the velocity of the fluid is calculated at various depths in the wellbore, yielding an injection profile. The accuracy of the velocity-shot method, however, is diminished by variations in wellbore diameter or by fluid exiting the wellbore between detector locations. To increase the accuracy of radioactive tracer logging, the two-pulse method was developed. In wellbore-model experiments, pulses of a tracer material were injected into a fluid stream in a circular pipe with fluid exiting through perforations. The pulses were also monitored above and below abrupt diameter changes. The accuracies of the two-pulse and velocity-shot methods in a region of wellbore-diameter change or in a fluid-loss zone are compared on the basis of these experiments