The Peculiarities of Oil Displacement in the Process of Oscillating Injection of Polymer Solution into the Bed with Layered Heterogeneity

Abstract

The authors study the filtration flow of polyethylene oxide (PEO) water solutions of molecular weights 4∙106 and 6∙106 within the concentration range from 0 to 0.05% when exposed to an oscillating hydrodynamic field. Photographs characterizing the displacement of oil (with a viscosity of 10 to 50 mPa. s) with PEO water solutions from model porous formations with layered heterogeneity have been obtained. They have made it possible to specify the effectiveness of different oil displacement modes. It is shown that pumping a polymer solution into porous heterogeneous strata, while exposing it to oscillating hydrodynamic field, proved to yield a higher oil displacement ratio, as compared with a stationary oil displacement mode. The authors find out the conditions providing the positive influence on elastic deformations effects in the process of enhanced oil recovery by using polymer solutions. If elastic deformations take place, the filtration flow of polymer solutions should be carried out in the oscillating mode, whereas the frequency of the oscillating effect on the filtration flow should correspond to the dissipative function maximum. The stated results of the polymer solution flow research, under model conditions of a porous bed, have confirmed the nonlinearity mechanism of the polymer solutions filtration flow. In essence, the molecular and macromolecular non-linearity mechanism of the polymer solutions filtration flow means that in a porous medium under the influence of quasi-regular longitudinal velocity gradients, there arise self-sustained oscillations of reversible macromolecular deployment; the deployed macromolecules, in turn, influence the structure of the filtration flow, both on the molecular and macromolecular levels. Deformation oscillations of macromolecules and dissolubility of dynamic macromolecular structures formed under the influence of tensile currents result in the energy dissipation increase and the filtration flow nonlinearity. The nonlinearity of polymer solutions filtration flow ensures the alignment of the frontal advance of the polymer solutions within a porous bed with a layered heterogeneity and, consequently, higher oil displacement efficiency.