Abstract：Based on the fluid and solid two-phase flow dynamics and erosion theory, sand-carrying erosion model was established for outer wall of coiled tubing(CT) in horizontal section. The erosion rate of sand particle was calculated through Grand and Tabakoff formula. The calculation result was verified with the experimental data for the computational fluid dynamics(CFD)numerical model. Then, this model was applied to study the erosion law of outer wall of CT, such as curved tube and straight tube, the mass flow, the size of sand particle, the inject pressure,the volume of fracturing fluid injection and the viscosity of fracturing fluid. The result shows that the erosion of curving CT is more serious than that of straight CT, and also the erosive wear is the most serious in the small gap between the CT and the casing.With the increase of mass flow, erosion rate of outer wall of CT increased dramatically. The size of sand particle has great effect on the erosion of outer wall of CT. The erosion rate of the CT rapidly grows with the increase of fluid injection volume.

Keywords: coiled tubing; fluid and solid two-phase flow; erosion; outer wall; annular sand fracturing