Study on the combined effect of thixotropy, particle shape, and particle size on cuttings transport in horizontal annuli

Abstract

Several authors have studied the effect of particle shape and size on cuttings transport and have reported different, often contradictory, results. The thixotropic nature of the drilling is seldom considered. This study investigates the effects of particle shape and size on cuttings carrying capability of thixotropic fluids in an attempt to better understand the underlying process. Flow equations are based on the mixture approach and are numerically solved using the CFD methodology. Turbulence is modeled using the buoyant k-epsilon model. A relative velocity equation is developed to model the slip between non-spherical particles and thixotropic fluid. It is concluded that in horizontal annuli, cuttings transport does not have a one to one relationship with particle size and/or particle shape. Instead, cuttings transport has a power-law relationship with the ratio of the product of particle shape and flow rate, and particle size i.e. (sphericity x velocity)/particle diameter.