An Analysis Accounting for the Combined Effect of Drillstring Rotation and Eccentricity on Pressure Losses in Slimhole Drilling

Abstract

Abstract Knowledge of the distribution of pressure losses is a key factor to the design of a slimhole well. However, predicting annular pressure losses-the major partis difficult because drillstring motion makes nonnegligible complex contributions that have not been accounted for up to now. Flow in an eccentric annulus with eccentricity varying in the axial direction is studied. The effect of rotation induced transverse vibrations is included by allowing time periodic variations of eccentricity. The resulting model predictions can reproduce trends observed in field data.