Critical Cuttings Transport Velocity in Inclined Annulus: Experimental Studies and Numerical Simulation

摘要

In drilling horizontal wells and extended reach wells effectiverntransport of drill cuttings is critical. Cuttings deposition andrnaccumulation could lead to formation of deposit bed(s) inside thernannulus, causing stuck drillpipe, eccentric borehole, poorrnpenetration rate, etc. Experimental investigations reported in thernliterature previously focused on evaluation of cuttings transportrnperformance in directional wells, as functions of mud flow rate,rnmud rheology, angle of inclination, pipe rotation, flow regime, etc.rnEmpirical correlations were also developed for critical flow raternfor different flow conditions.rnIn this study, both experimental investigation and numericalrnsimulation were performed to determine the critical cuttingsrntransport velocity in inclined annulus, for different flow conditions.rnExperiments were carried out in a flow-loop, using a novel dataacquisition-rnand-analysis system. The behavior of drill cuttings atrnboth steady-state and unsteady-state flow conditions werernrecorded by a CCD video camera system. The captured imagesrnwere then analyzed to obtain the velocity profile, the crosssectionalrndistribution, and average velocity of cuttings in annulus.rnResults from this experimental investigation were comparedrnagainst those predicted by an unsteady-state cuttings transportrnnumerical model developed in-house. The numerical modelrndeveloped for the study allows for the interaction between therndrill cuttings and drilling fluid, and follows broadly the two-layerrnmodel reported in the literature. It enabled the determination ofrnpressure, fluid and cuttings velocity, fluid and cuttingsrnconcentration distributions inside the annulus at different times.rnThe model was run using parameters similar to experimentalrnconditions. Its results agree closely with experimental data forrnthe critical flow rate for cuttings transport in inclined borehole, forrnthe majority of cases.