As coiled tubing is presently utilized for a multitude of projects in the field, the necessity of estimating the friction pressure of the working fluids in the reeled portion of the coiled tubing string becomes extremely important. Past authors have shown the significant difference in friction pressure between straightened and reeled coiled tubing.

This work discusses the experimental investigation of five different polymeric solutions and one drilling mud in three different coiled tubing sizes. The analysis of the frictional pressure loss data includes the effect of fluid rheology, coiled tubing curvature, and tubing diameter.

The intent of the analysis is to arrive at a correlation describing frictional pressure loss behavior of polymer solutions and drilling muds in reeled as well as straightened tubing.

The experimental setup includes 3000 ft of 2 3/8 in. reeled tubing, 5000 ft of 1 1/2 in. reeled tubing, and 1500 ft of 1 in. reeled tubing. Straightened sections of tubing are also utilized in the setup for comparison and modelling of data.

The experimental results are compared with correlations developed by earlier investigators including Mashelkar, McCann, Ito, and Shah. The analysis of the data led to the development of a new model for polymer solutions and a model for drilling muds. The model for polymer solutions is recommended for power law type, pseudoplastic fluids with a power law index less than one, while the model developed for drilling mud was developed for only one concentration of mud. However, the drilling mud correlation suggests the form that other concentrations of drilling mud may follow.

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