Effect of Eccentricity and Rotation on Annular Frictional Pressure Losses With Standoff Devices

Abstract

Abstract Pressure drop estimates are critical for components of the drilling process. During drilling and cementing operations, many stand-off devices, such as centralizers, reamers, and turbulators, are widely used. Few studies have explored the pressure losses arising from these attached devices in the drillstring or casing string with eccentricity and rotation, and these pressure losses are assumed to be negligible. Eccentricity between the wellbore and the stand-off devices, rotation, and the complicated geometrical designs of these devices, which relatively irregular and complicated, increase the complexity of the frictional pressure loss calculations. This study examines the effect of the various geometrical parameters of the commonly used devices, eccentricity, and rotation of the devices, flow rate, and rheological properties on the annular pressure loss using c computational fluid dynamics (CFD). For laminar flow, the 3D Navier-Stokes equation is used. The turbulent flow is based on k- model. This paper presents the results of the study of the alteration and effects of various rheology models on the flow profile and annular pressure losses. This parametric study explores the importance of eccentricity and device rotation and presents a simple set of comprehensive equations and guidelines to calculate the pressure losses for commonly used devices. These equations and guidelines are useful in the determination of the number of devices and of their optimum placement in the string. Although the annular pressure loss against these devices may be negligible, at times incremental pressures from the large number of stand-off devices or in a narrow clearance extended reach wells are potentially detrimental to the well. This paper also presents case studies in which the pressure losses were not negligible and stresses the importance of considering the pressure losses encountered using these devices.