Systematic sensitivity analysis of cuttings transport in drilling operation using computational fluid dynamics approach

Hole cleaning and cuttings transport play a vital role in the drilling operation. Various drilling problems such as a reduction in penetration rate, an increase in the torque and drag, and an increase in the potential of differential sticking are often related to poor cuttings transport from a wellbore. Multiple parameters, including the fluid rheology, mud velocity, cuttings size, and drill pipe inclination generally influence the cuttings transport performance. Although several experimental and modelling research works have been conducted in this area, the interactions among the parameters during cuttings transport have not been adequately investigated. This study focuses on interactions between the drilling parameters. Cuttings transport in the wellbore represents a solid-liquid multiphase flow phenomenon. In this research work, Computational Fluid Dynamics (CFD) model was employed to simulate the cuttings transport behaviours in a horizontal wellbore. The Eulerian-Eulerian multiphase flow model was adopted to describe the flow characteristics in the wellbore annular section. Design of Experiment (DoE) was used to systematically study the sensitivity and interactions among the operating parameters. It was observed that the mud viscosity, mud velocity, and drill pipe rotation have a positive impact, whereas an increase in cuttings size and eccentricity in annular clearance show a significant adverse effect on cuttings transport performance. According to the results, the cuttings between 1 mm to 2 mm are difficult to clean, compared to larger cuttings. The study also revealed important interaction effects between the parameters. Although both drilling mud viscosity and velocity show a positive effect, the interaction among them exhibits a negative influence on cuttings transport.