Experimental Study on the Efficiency of Cuttings Carrying with Supercritical CO2

Abstract Supercritical carbon dioxide (SC-CO2) has the characteristics of high density, low viscosity and high diffusivity, and higher penetration rate can be achieved with SC-CO2. But the law of cuttings carrying is not clear, in order to make clear the influence of pump displacement, well incline, cuttings diameter, wellbore temperature and pressure on cuttings carrying efficiency, the laboratory experiments was carried out to simulate the cuttings carrying with SC-CO2 in annulus. The result shows that the cuttings carrying efficiency decreases when pump displacement decreases and cuttings diameter increases, and it decreases with the increasing of well incline at first, and then increases. Wellbore temperature and pressure have much more influence on cuttings carrying efficiency, and it decreases when the wellbore pressure increases, if keeping the wellbore temperature and pump displacement in constant; and it increases when wellbore temperature increases, if keeping the wellbore pressure and pump displacement in constant. So the wellbore temperature can be adjusted to compensate the cuttings carrying efficiency's changes caused by pressure changes, and the excess annulus velocity should be in consideration to avoid erosion of casing, drilling pipe and other down hole tools.