Several fluid replacement operations take place during and after an oil well drilling operation, such as: the replacement of the drilling fluid by the completion fluid and the displacement of cleaning plugs or chemical treatment plugs. In such operations it is important to minimize the contamination of a fluid by the other to maintain the designed physical properties of the new fluid displaced.
This work presents a numerical simulation study of the operations related to the replacement of a fluid by another inside the well. The effects of density and rheology differences between the fluids are analyzed (Newtonian fluids displacing non-Newtonian fluids and vice-versa). The studies are based on the numerical solution of the governing equations for a two phase system and the subsequent evolution of the interface shape between the two fluids.
The present work details design criteria and fluid contamination predictions to some of the typical completion operations. Some displacement procedures are recommended to minimize contamination.