Numerical simulation of the cutting-carrying ability of supercritical carbon dioxide drilling at horizontal section

The density of supercritical carbon dioxide is relatively heavy, close to liquid density; its viscosity is small and close to gas viscosity. In order to research the cutting-carrying ability of supercritical carbon dioxide drilling in horizontal section, a mathematical model was built describing cutting-carrying process in the horizontal eccentric annulus with supercritical carbon dioxide; at the same time, the physical model was built according to the characteristics of horizontal eccentric annulus. The cutting-carrying law in horizontal section at different viscosities and densities of supercritical carbon dioxide was simulated with CFD simulation software. The cutting-carrying ability of supercritical carbon dioxide increases with increasing density and viscosity, but there exists a critical density, when the density of supercritical carbon dioxide is smaller than that, the cutting-carrying ability will decrease apparently, and the smaller the density of supercritical carbon dioxide is, the worse the cutting-carrying ability will be. We can control the back pressure of wellhead to change the density of supercritical carbon dioxide in the wellbore while drilling and to comply with the cutting-carrying request, but the ground pump pressure should be appropriate to avoid higher load.