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.
The challenge of theoretical and numerical studies of annular fluid flow with varying eccentricity is mainly a result of the required coordinate systems. Computational-fluid-dynamics (CFD) modeling provides the state-of-the-art approach of investigating fluid flow in such complex geometries. In this study, results from a series of numerical simulations for the fully developed laminar flow of non-Newtonian power-law fluids in concentric and eccentric annular geometries are used to investigate the effect of eccentricity, flow-behavior index, and diameter ratio (ratio of the outer diameter of the inner tubing to the inner diameter of the outer tubing) on axial frictional pressure losses.The frictional pressure-loss gradients predicted by the CFD simulations were verified by comparing with the published studies and flow data from a field-scale experimental setup. At a constant flow rate, it is confirmed that frictional pressure losses decrease with increasing eccentricity. A good agreement was obtained with the Haciislamoglu and Langlinais (1990) correlation, and the results of this study, especially at low values of eccentricity. At very high eccentricities, data from the CFD model yield lower frictional pressure loss compared to Haciislamoglu and Langlinais (1990) correlation. This type of expression is obtained and the improved data of this study is incorporated.Next, this paper presents the results of an experimental study carried out to investigate frictional pressure-loss behavior of dragreducing polymer solutions, flowing turbulently through an eccentric annulus. The experimental setup includes 30 ft of 3½ × 2 3 ⁄8-in., 200 ft of 3½ × 1¾-in., 69 ft of 5½ × 4-in., and 79 ft of 5 × 3½-in. fully eccentric annuli. Data analysis enabled the development of a new correlation using fluid apparent viscosity at 511 sec -1 , generalized Reynolds number, and diameter ratio, all of which can be easily determined in the field as independent variables. These new correlations for laminar and turbulent flow of drag-reducing polymer solutions present an improvement to existing correlations, and also permit undemanding hydraulic-program calculations for varying annular configurations.
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