Buoyant Displacement flow of non-Newtonian Fluids in an Inclined Duct: Experimental, mathematical and numerical approaches (K. Alba, Schlumberger Copenhagen Denmark)

Buoyant displacement flows with two miscible fluids in pipes and 2D channels inclined at an angle are studied with the main applications found in the processes present in the construction and completion of oil & gas wells. Detailed experimental, mathematical and numerical approaches are employed in an integrated fashion. The displacements are at low Atwood numbers and high Peclet numbers, so that miscibility effects are mostly observable after instability and via dispersive mixing. The experiments were first conducted for Newtonian fluids (using water-based solutions) and then for non-Newtonian fluids (using Carbopol to study viscoplastic effects). For the regimes where the fluid layers are well segregated by stabilizing transverse buoyancy force, a mathematical model following a Weighted Residual approach is developed to predict the front velocity, displacement efficiency and flow stability. Finally CFD simulations are carried out for 2D channel geometry using code PELICANS developed in IRSN (French Nuclear Safety Research Institute) to compare against experimental and mathematical results.