Annular flow analysis by tracers in drilling operations

A study of drilling fluid flow in the annular space and drill pipe by residence time distribution analysis using a tracer is presented. This is a new method which can be used to assess the rate of removal of cuttings during the drilling process. eld trials were conducted to evaluate the technical feasibility and potential application. The results are analyzed using the flow behavior, carrying capacity of the drilling fluid, and hole cleaning conditions. Analysis of tracer response indicates the presence of anomalous flow in both trials, characterized by two fluid volume fractions traveling with different velocities. The magnitude of these volume fractions is related directly to the carrying capacity of the drilling fluid (hence, the hole cleaning conditions) which is explained. The dispersion coefficient, as well as other distribution functions, is suggested to measure the overall behavior of fluid in a drill-hole. ethod is compared with empirical correlations employed in the industrial practice and potential advantages are demonstrated using tracers.