The drilling solids content is an important consideration in Coiled Tubing Drilling (CTD) operations. This paper presents an experimental investigation of the effects of drilling solids on frictional pressure losses in Coiled Tubing (CT) using a sophisticated full-scale coiled tubing test facility for an industry – university joint research project. The facility consists of seven reels of coiled tubing with diameters of 1", 1-1/2", and 2-3/8", fluid mixing and pumping equipment, and data acquisition system. Fluids investigated include solid-free polymer solutions at various concentrations, and real drilling fluids currently used in the drilling industry. The rheological properties of test fluids were evaluated using Fann and Bohlin viscometers. Standard industry drilling solids (Rev Dust) were added to the drilling fluids to simulate the effect of drilling solids on frictional pressure losses. Flow tests results indicate that as solids concentration increases, the frictional pressure losses increase significantly. The effect of lubricants on friction reduction in coiled tubing was also investigated. It was observed that the lubricants investigated could effectively reduce the friction pressure loss in coiled tubing. The analysis of experimental data has been focused on the effect of solids concentration, lubricant concentration, coiled tubing geometry as well as drilling fluid rheology.

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