Viscous liquid recovery by injection of Newtonian and viscoelastic materials in a sand porous media

The primary motivation of this work was the enhanced oil recovery in porous media. Polymeric solutions are largely used in tertiary oil recovery and it is of great interest to understand the role played by their properties in the recovery process. It is largely accepted that these solutions can increase the recovery efficiency compared to the water-flooding operation, but some doubts still remain. When polymers are added to a solvent, the viscosity of the mixing increases, and the solution becomes non-Newtonian, exhibiting shear-thinning behaviour and viscoelasticity. Thus, conducting tests that isolate all important parameters is not easy, and this is the goal here. A compact sand porous media was used, which was previously saturated with oil-based solutions. Such oil was recovered by the injection of Newtonian water-based or viscoelastic solutions. Diluted polyethylene oxide solutions, with concentration much lower than ten times the overlap concentration, were used. Below such concentration, elastic turbulence is not observed, and the so-called Saffman–Taylor problem is the main point here. The primary data are the fraction of unrecovered mass m until the displacing fluid breakthrough. The lost mass m was recorded as a function of the capillary number Ca, viscosity ratio R μ , and Weissenberg number Wi . It was shown that for the cases evaluated in this work, the capillary effects were negligible, and therefore, R μ and Wi were the only parameters that control the flow behaviour. For the Newtonian scenario, the not recovered mass m felt from 77.5%, for R μ = 41.82 , to 20%, for R μ = 0.52 , leading to an increase in the recovery ratio of 57.5%. For a fixed viscosity ratio, m felt with Wi until reaching an asymptotic value. For R μ = 1 , the increase of Wi from W i = 0.49 to W i ≥ 5 leads to an increase in the recovery ratio of 35%, showing that more elastic fluids can improve the efficiency of the process.