Wellbore Hydrodynamic Model

Abstract

ABSTRACT Efficient bottomhole cleaning has been shown to significantly contribute to the increase in ROP. A detailed investigation into cutting dislodgment and movement may give insight on how to potentially increase the bottomhole cleaning ability of a well. This cleaning ability can be predicted by the use of a Scouring Model. The hydrodynamic (scouring) model consists of a progression of mathematical relationships relating the drilling fluid hydrodynamic forces to a well cutting resting on a well bottom. These relationships are made assuming ideal conditions in order to decrease (the complexity of the fluid hydrodynamics of the well bottom. The forces considered that act upon a well cutting are the hydrodynamic drag lift forces, and the submerged weight of the cutting. These forces can be related to the angle of repose which is dependent upon the cutting type (Sandstone, Shale, etc.). These forces can be described as functions of the cutting size and density, fluid density, and fluid velocity. The relationship between the hydrodynamic forces and the angle of repose will thus give an equation predicting the critical incipient velocity. This critical velocity is the velocity required by the fluid to initiate movement of the well cutting and thus inherently predicts the cleaning ability of the well bottom by the drilling fluid.