Equivalent circulating density contribution to the plastering effect of casing while drilling technology: analysis of annular fluid velocity and annular pressure through computational fluid dynamics

Abstract

Application of Casing while Drilling (CwD) technology has accelerated in the recent decade. The technology came up with so many benefits and unknowns. The plastering effect of CwD and specific hydraulics conditions constituted the main portion of the research on this technology. The plastering effect has been shown to be beneficial in many aspects and there is an interest to define governing factors on it. In an effort to describe the physics beyond the plastering effect, several components that potentially govern the process are under investigation. This thesis is a theoretical modeling study; and, it is focused on one of the potential conditions for the plastering effect of CwD. Annulus hydraulics is elaborated to investigate the pressure and velocity profiles. While doing so, Computational Fluid Dynamics (CFD) has been used in the form provided by ANSYS. Inc. Fluent commercial software package. The main focus is on the responses of annular fluid velocity and annular pressure to varying geometry with increasing eccentricity. Furthermore, a combination of rotational motion of the inner pipe and eccentricity is studied. Multiple physical explanations of the flow field in diverse conditions are described. Visuals in the form of contour plots and X-Y plots verified physical explanations are presented. The discussions and interpreted results are given in the interpretation of CFD results chapter. The knowledge presented in the results section and the computational models, especially detailed information presented about annular pressure distribution in axial and horizontal plane, is expected to assist in furthering studies as the link between the high equivalent circulating density of CwD and plastering effect is of interest. In summary, hydraulics for the CwD technology is empirically found to be unique, and this can be a major contributor to the plastering effect, which provides significant achievements to the CwD technology.