Preventing buoyancy-driven flows of two Bingham fluids in a closed pipe - Fluid rheology design for oilfield plug cementing

The mechanically unstable situation of a heavy Bingham fluid resting on top of a light Bingham fluid in an inclined closed-ended pipe can be stabilise d if the fluids have sufficiently large yield stresses. This paper focuses on determining the yield stresses that are sufficient to keep the fluids st atically stable for a given fluid density difference, pipe diameter and pip e inclination. The results are applicable to a broad class of practically o bservable flows. This situation provides an idealised model for the oilfiel d process of plug cementing.