Displacement of Non-Newtonian Fluids in Annular Spaces
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A successful cement job is determined by the displacement efficiency. Displacement of drilling fluids in horizontal annuli is a critical element in the completion of wellbores. Optimum displacement requires an understanding of flow patterns, frictional pressure losses and mutual interaction of mud, spacers, and cement in annular spaces. Modelling this complex behaviour is difficult, and requires a fundamental understanding of fluid mechanics, rheology, and computational techniques. Nevertheless, it is essential to understand the flow propagation to guarantee displacement success. A Computational Fluid Dynamics (CFD) model has been developed, and simulations have been performed in order to analyze the operational downhole conditions during primary cementing. The simulations accounted for complexities such as non-Newtonian fluids and eccentricity in annuli for both single-phase and multiphase flow of mud-cement-spacer. The study identifies the fluid displacement and failure modes associated with fluid displacement due to high eccentricity. For single-phase analysis, the numerical analysis shows +/- 5 % accuracy compared to experimental data and study of Zhigarev et al. Multiphase simulations show that the studied fluid train of drilling mud-spacer-cement display adequate displacement efficiency. Although, an increase of modelling complexity should be performed in order to obtain more accurate representation. Data acquired from the multiphase simulations should be verified against experimental work, in order to justify the feasibility of the CFD model used for product design and analysis in specific conditions. Overall, a CFD approach for analysis of primary cementing may yield adequate information in order to improve cementing to ensure sufficient zonal isolation, which is necessary for well integrity.