Investigating the impact of drillpipe's rotation and eccentricity on cuttings transport phenomenon in various horizontal annuluses using computational fluid dynamics (CFD)

Drillpipe eccentricity is a common issue in horizontal drilling operations. The eccentricity is a non-manipulative parameter by itself but its impact is a function of various parameters such as rate of penetration (ROP), fluid flow rate (Q), cuttings bed height, wellbore path and drillpipe rotation. The goal of this study is to observe the cutting's accumulation in different eccentric annuluses by employing a multiphase Eulerian flow model including a Herschel-Bulkley drilling fluid. Turbulence was implemented using Reynolds Stress Model which reveals proper results, especially on asymmetric and complex cases. All of these are developed and calculated through a comprehensive Computational Fluid Dynamics (CFD) simulations to solve the governing equations in the multiphase medium. A sensitivity analyzes were implemented from concentric to 75% eccentric cases accompanying different variations of fluid flow rate, ROP, and drillpipe rotation. The results demonstrated that further eccentricity from a certain amount will abruptly increase the cutting's accumulation which is a function of bed height, ROP/Q, and drillpipe rotation. However, rotation's impact is negligible above a certain speed of rotation after which the sudden increase of cutting's accumulation caused by eccentricity is not observable.