Prediction of Dynamic Cuttings Behavior of Eccentric Annulus in High-Inclination Well Based on Numerical Simulation

Abstract

Abstract. The unique geometry of high-angle wellbores promotes the deposition of drill cuttings at the bottomhole, leading to the formation of cuttings beds. This accumulation increases friction torque and reduces the rate of penetration of the drilling string, and even causes other severe accidents. Therefore, it is necessary to study the cutting transport mechanism of high-inclination wells and improve the efficiency of wellbore cleaning. In this study, an eccentric annulus model closely representing the actual drilling conditions of high-inclination wells was established based on the Eulerian model for two-phase flow, while simultaneously accounting for drill pipe rotation and orbital motion. Numerical simulations were subsequently performed to investigate the cuttings transport behavior in drilling fluid. We verified the improvement degree of the drilling pipe orbital motion of the wellbore cleaning (the thickness of the cuttings bed has decreased by 50%) and clarified the cuttings transport mechanism in the real-drilling environment of the high-inclination well by comparing it with the drill pipe static model and the drill pipe rotation model. The results indicated that wellbore cleaning efficiency can be improved by appropriately increasing the well deviation angle, drill pipe orbital velocity, drill pipe rotation velocity, drilling fluid displacement, and drilling fluid viscosity. According to the research results, it can be used to predict the behavior of cuttings in high-inclination wells and provide theoretical support for wellbore cleaning and safe drilling.