Pipe Rotation Improves Hole Cleaning and Cement-Slurry Placement: Mathematical Modeling and Field Validation

Abstract Placing the cement slurry in the entire annulus, in both the wide and narrow sides, is essential to achieving effective zonal isolation. Well conditions, such as deviated wellbore geometry, eccentric annulus, and gelled drilling fluid, pose unique challenge in achieving this objective. It is known in the industry that pipe movement helps improve hole cleaning and cement-slurry placement. However, the quantitative effect of pipe rotation on hole cleaning and cement-slurry placement for a given eccentricity, flow rate, and geometry was not well studied. Hence, it was difficult to design a primary cement job where the effects of all these parameters were considered at the same time and optimized for best results. The effective velocity and pressure drop in an eccentric annulus with and without pipe rotation is modeled for Herschel-Bulkley fluid. This is then extended to evaluate the effect of pipe rotation on hole cleaning and cement-slurry placement. The modeling clearly demonstrates the improvement in hole cleaning from pipe rotation in an eccentric annulus. Now there is a tool available to study the interaction of various factors on hole cleaning and optimize them for the well in question. The results from the modeling study have been compared with field data. The comparisons show a good match between the improvement in cement-slurry placement predicted that was inferred from the cement bond logs. The study clearly indicated the importance of using representative rheological model and input values. The modeling results and field validation are presented and discussed. The work presented in this paper should help the industry optimize the various factors during a cement job to help maximize hole cleaning and cement-slurry placement in the wide and narrow sections of the annulus. This should help in achieving zonal isolation for the life of the well and reduce operating expenses by reducing remedial jobs.