| As an effective chemical enhanced oil recovery method, alkaline-surfactant-polymer (ASP) flooding, is able to significantly reduce waterflood residual oil saturation and has been applied in both conventional and unconventional (viscous oils) oilfields. Among these challenges associated with ASP flooding technique, the screening and development of ASP flooding surfactants is always a top priority. This study is focused on development of high performance surfactant formulations for an Alkaline-surfactant-polymer (ASP) flooding field test. Interfacial tension (IFT) measurement, phase behavior tests, aqueous stability/solubility assessment, and core flooding were undertaken to develop and screen this formulation using commercially available surfactant products.;Two surfactant formulations were successfully screened in our study. They are both surfactant mixtures. One is LAS1/CS/AS (4/5/1 in weight percent), and the other is LAS3/AS (5/5 in weight percent). The laboratory evaluation shows that both surfactants are able to: (1) achieve ultralow interfacial tension with order of magnitude of 10-3 mN/m in a wide range of alkali concentrations. Ultralow water/oil IFT is required to significantly reduce capillary pressure and waterflood residual oil saturation; (2) show excellent aqueous stability necessary to ensure surfactant propagation deep into reservoir with low retention; (3) form middle microemulsion or Winsor Type III microemulsion phase at different oil water ratios; (4) recovery around 90 percent waterflood residual oil saturation by injecting merely 0.3 pore volume ASP slug followed by polymer drive. |
