Displacing fluids in downhole conditions and for long distances is a complex task, affecting several steps on well construction. Cementing gains relevance in the moment that fluid contamination compromises cement sheath integrity and consequently zonal isolation.

Density and rheology design for all the fluids involved are essential to achieve operational success. Properties hierarchy and preferred flow regimes have been empirically defined and tend to provide reasonable generic results. Challenging operations, including ultra deepwaters and their narrow operational windows scenarios, require further knowledge of the physics involved in order to prevent undesirable events

This article presents the in house development of a software for annular two-phase flow, which analyzes fluid displacement in typical vertical and directional offshore wells, for Newtonian and non Newtonian liquids, laminar and turbulent flow regimes. The formulation proposed provides accurate results for a wide range of input parameters, including the cases in which the ratio between the inner and outer radii of the annulus is small. Operational guidelines for fluid and placement schedules are provided.

The computational work is validated by unique results obtained from an experimental test rig where detailed displacement tests were conducted. Contamination degrees were measured after the displacement of a sequence of fluids through 1192 m of vertical well. Effect of fluid density and rheology hierarchy, flow regimes and displacement concepts were investigated. The results provide relevant information for the industry and fundamental understanding on displacement of Newtonian and non Newtonian liquids through annular sections.

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