Numerical simulation of cuttings transport capability of supercritical carbon dioxide in horizontal wells

Key words:  drilling  supercritical CO₂  horizontal well  cuttings carrying capability  rotation of drill pipe  eccentricity

Abstract:

Supercritical CO₂ can be one of the most promising drilling and completion fluids, so it is of fundamental and practical importance to investigate its cuttings carrying mechanism. Numerical simulation was conducted to investigate the effects of various factors on CO₂ 's cuttings carrying capability, including temperature, pressure, rotation speed and cuttings size and production rate, in which the cuttings size distribution at the annulus entrance was set based on the measurement data in the experiments. In addition, the influence of coupled relationship between the density and viscosity of CO₂ as a function of temperature and pressure and the rotation of drill pipe was considered in the numerical simulation. The results show that the cuttings carrying capability of CO₂ can be improved by reducing temperature or increasing pressure, and the simulation results are consistent with that of the experiments. It is also found that the rotation speed of drill pipe has little influence on the cutting carrying capability, and the minimum of cuttings carrying capability appeared when the annulus eccentricity equals 0.8. The cuttings carrying capability can also be improved by increasing the displacement capacity or reducing the penetration rate, while viscofier can be added to improve the cuttings carrying capability of CO₂ in horizontal well drilling.