SPACE–TIME EVOLUTION OF A RADIOACTIVE LABEL DURING THE INJECTION OF A TRACER INTO A WELL

The results of modeling the flow of an indicator radioactive liquid in a well with account for convective and diffu- sive mass transfer, as well as the decay of the tracer substance, are presented. Based on the asymptotic method, an analytical solution to the problem has been constructed for the case of arbitrary radial velocity distribution in the borehole, computational experiments have been performed, and the results of analyzing the contribution by various processes to the formation of concentration fields during the movement of the tracer tag in the process of liquid injection have been provided. It is shown that the main criterion determining the evolution of a rectangular label is convective-diffusive processes whose contribution is determined by the Ma number. To account for the contribution of decay processes, it is necessary to use an additional criterion, Fi. The contribution of radioactive decay leads to a decrease in am- plitude values, and the shape of the label is determined by the values of the convective-diffusive number and time. New patterns have been established for the formation of fields of radioactive elements during the movement of the tag along the borehole. It is shown that the evolution of a "rectangular" radioactive tracer tag in the initial state is accompanied by its lag relative to the injected liquid and the formation of a tail part where the maximum concentration values are basically observed. The developed mathematical model and software can be used to create a simulator which is used to carry out the planning and interpretation of the results of tracer analysis in the diagnostics of the well′s technical condition, casing faults, annular circulation, and tracer injection to determine the characteristics of formations.

Author:  A. I. Filippov, M. A. Zelenova, R. G. Gubaidullin
Keywords:  radioactive tracer, convective diffusion, asymptotic method, concentration field, well
Page:  946