Cuttings transport evaluation in deviated wells

Cuttings transport efficiency is a measure of the extent to which cuttings are carried to the surface from a drilled hole. It quantifies the success achieved in freeing a well of drilled cuttings. It is also related to the carrying capacity of a drilling mud. Cuttings transport efficiency in vertical and deviated wellbores has been reported to depend on the following factors: hole geometry and inclination, average fluid velocity, fluid flow regime, drill pipe rotation, pipe eccentricity, fluid properties and rheology, cuttings size and shape, cuttings concentration, cuttings transport velocity, rate of penetration and multiphase flow effect. In this study, the effects of mud flow rate, rate of penetration, annular clearance, mud and cuttings densities on annular fluid velocity, transport ratio and mean mud density are investigated for highly deviated wells. Equations are developed and used to generate graphs. These equations and graphs could be applied in the field during directional drilling to determine annular fluid velocity, mud flow rate, transport ratio and mean mud density.