Analysis of the Effects of Major Drilling Parameters on Cuttings Transport Efficiency for High-Angle Wells in Coiled Tubing Drilling Operations

摘要

Coiled Tubing (CT) Drilling is becoming more popular as the drilling technology is advancing. Most of the CT applications are associated with highly inclined or horizontal well drilling. In such wells, cuttings transport is still remaining as a major challenge. In this study, a layered cuttings transport model is introduced for high-angle and horizontal wells, which can be used for incompressible non-Newtonian fluids as well as compressible non-Newtonian fluids, i.e., foams. A computer program is developed based on the proposed model. The effects of major drilling parameters, such as flow rate, rate of penetration, fluid density, viscosity, gas ratio, cuttings size, cuttings density, wellbore inclination and eccentricity of the CT on cuttings transport efficiency are analyzed. The results are verified with the experimental data obtained at The University of Tulsa – Low Pressure – Ambient Temperature flow loop. The major findings from this study are, the dominating parameter on wellbore cleaning is the flow rate, and, as the viscosity of the fluid is increased, the thickness of the cuttings bed developed in the wellbore is significantly increasing. Also, cuttings properties, fluid density, wellbore inclination and eccentricity have some influence on cuttings transport.