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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractHydraulic fracturing through coiled tubing (CT) has become an effective and economical stimulation technique for wells with multiple zones to be fractured. Yet, prediction of friction pressure losses of fracturing slurries in coiled tubing presents a unique challenge in the fracturing job design.This paper presents an experimental study of friction pressure losses of fracturing slurries in coiled tubing using a full-scale coiled tubing test loop which consists of 1000 ft 2-3/8″ coiled tubing and 200 ft 2-3/8″ straight tubing sections. The fracturing slurries were prepared with guar-based gels at various polymer and sand concentrations. Based on the experimental results, the characteristics of the flow behavior of fracturing slurries as affected by sand concentration, base gel rheology and centrifugal forces are discussed. A new correlation has been developed and can be used to predict the friction loss increase over base gel friction.The coiled tubing erosion mechanisms (sliding abrasion, random particle impact, and directional particle impact) have been discussed. The abrasion by sliding sand bed is believed to be the dominant erosion mechanism.

TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis paper presents a complete set of friction factor correlations for both Newtonian and non-Newtonian fluids in laminar and turbulent flow in coiled tubing. The friction factor correlation for non-Newtonian fluids in laminar flow is obtained based on theoretical analysis and numerical solutions of the flow equations of a power-law model fluid in curved pipes. The empirical correlation for non-Newtonian fluids in turbulent flow is developed based on full-scale experiments of polymeric fluid systems in various 1", 1-1/2", and 2-3/8" coiled tubing reels. To consider the effect of pipe roughness in coiled tubing, a modified correlation is proposed by combining the Srinivasan et al. correlation for smooth curved pipe and the Chen correlation for rough straight pipe. Examples are given to illustrate the applications and accuracies of the newly developed correlations.

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TX 75083-3836, U.S.A., fax 01-972-952-9435. AbstractThis paper presents a comprehensive theoretical study of the flow of non-Newtonian fluid in coiled tubing using the boundary layer approximation method. First, a boundary layer approximation analysis was applied to the governing equations of continuity and motion of a power law fluid in the curved tubing flow geometry. Momentum integral equations for the boundary layer flow were then derived and solved numerically. The resulting solutions of the velocity field were used to develop a new friction factor correlation in terms of generalized Dean number, coiled tubing curvature ratio, and flow behavior index of the power law model. The new correlation of this study and a previous correlation by Mashelkar and Devarajan were evaluated using experimental data obtained from full-scale coiled tubing flow experiments. An excellent agreement was found between the new correlation and the experimental results. The Mashelkar and Devarajan correlation failed to result in any acceptable agreement with the experimental data, nor did it match the Ito correlation for the Newtonian fluids (n = 1). This work extends the range of applicability of the new correlation to fluids with flow behavior indices as low as 0.25, which would cover most fluids used for coiled tubing operations in the oil and gas industry.