Friction Pressure Correlations for Oilfield Polymeric Solutions in Eccentric Annulus

Polymer fluids are utilized extensively in the petroleum industry for viscosity enhancement and friction pressure reduction during turbulent flow. Selection of the appropriate correlation for the desired fluid and flow regime is very important for the accurate determination of frictional pressure losses. A range of correlations has been published for predicting frictional losses under annular flow conditions. All these correlations are based on certain assumptions, which limit their application under different operating conditions. This paper presents the results of an experimental study carried out to develop a reliable frictional pressure loss correlation for polymeric solutions in a fully eccentric annulus. Fluids investigated include Water, Guar, Xanthan, and Welan gum under conditions typically encountered in drilling and completion operations. The frictional pressure losses of these polymeric fluids exhibiting drag-reducing characteristics are investigated and analyzed as a function of generalized Reynolds number for each fluid. The experimental set-up includes 200 ft of 1 1/2-in. straight tubing, and 200 ft of (3 1/2-in. × 1 3/4-in.) fully eccentric annuli. Data analysis enabled the development of an improved correlation for polymer solutions in a fully eccentric annulus. Fluids apparent viscosity at 511 sec⁻¹, generalized Reynolds number, and diameter ratio, all of which can be easily determined in the field, were selected as independent variables for the new correlation. Experimental data show that the new correlation estimates friction pressure losses in fully eccentric annuli much better than previously published equations.