Abstract

This paper discusses a laboratory evaluation of the feasibility of different chemical flooding strategies and a simulation study to optimize the feasible strategies for a west-central Saskatchewan heavy oil reservoir. The integrated experimental approach was composed of oil/brine interfacial tension (IFT) measurements, polymer viscosity measurements, wetting tendency measurements, and sandpack coreflood tests. The experimental results showed that the equilibrium interfacial tension between reservoir oil and formation brine could be lowered to an ultralow level (0.05 mN/m) by adding a certain concentration of alkali and surfactant into the brine. The addition of alkali and surfactant caused the wettability characteristics in all tested systems to become oil-wet. All of the polymer solutions exhibited pseudo-plastic behaviour, i.e., the apparent viscosity decreased with increasing shear rate. A series of sandpack coreflood tests were carried out to investigate the recovery performance of alkali + surfactant, polymer, and alkali + surfactant + polymer (ASP) floods. Enhanced oil recoveries (from the chemical flood and extended waterflood) varied significantly from 0.71 to 14.65% OOIP. The coreflood results suggest that in enhanced waterflooding for recovering viscous heavy oil, mobility control by polymer is more important than IFT reduction by alkaline/surfactant. In the simulation study, the relative permeability curves were obtained through history matching. Then, as the sensitive operating parameters, the ASP slugs and polymer concentrations were tuned to show their effects on enhanced heavy oil recovery (EHOR). In summary, ASP flooding provides synergistic effects that can maximize the recovery performance.

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