Experemental Study On Alkaline/ Surfactant/ High Polymer Concentration Solution

In recent years, alkaline/ surfactant/ high concentration polymer (ASP) pilot test was carried out in Daqing Lamadian oil field. The obvious water reduction and oil increase were achieved. In order to improve the technical and economic benefits, the viscosity, hydraulic diameter Dh, molecular configuration, rheology, viscoelasticity, interfacial tension (IFT), flow characteristics, chromatographic fractionation phenomenon, displacement efficiency, displacement effect, and their factors were studied under the guidance of modern reservoir engineering theory, physicochemical theory,advanced instrumental analysis, and core flooding tests. The results showed that, the higher the concentration of alkaline, the lower the apparent viscosity, the smaller the Dh, and the worse the viscoelasticity. The HPAM molecules in solution exhibited reticular structure, while the molecule showed reticular-sheet structure and reticular-bead structure in A-P solution and S-P solution, respectively. The interfacial activities became worse when increased the polymer concentration, solid liguid ratio, and the adsorption times. The higher the alkaline concentration, the smaller the resistance factort (FR) and residual resistance factor (FRR). The higher the polymer concentration, the larger the FR and FRR with the same core permeability. The increase of polymer concentration led to the increase of viscosity, which resulted in good sweep capacity and high EOR. The high polymer concentration multi-slug ASP system exhibited higher injection pressure, larger sweep volume, and better EOR than that of low polymer concentration single-slug ASP system. Moreover, the chromatographic fractionation phenomenon was much more serious in the former system. Compared to displacement efficiency of chemical agents, the sweep efficiency was more important to the EOR. The ploymer flooding had the best EOR, the non-ionic surfactant Sun/ polymer system was in the middle, and the ASP system had the worst EOR under the same costs. Comprehensively considering from technologic demand and economic efficiency, the promising polymer concentration was 2000mg/L~2500mg/L and the slug size was 0.285PV~0.457PV. In the 4 displacing plans, the pre-slug+main slug+minor slug+protective slug had the best economic and technical effect compared to that of single slug, pre-slug+main slug, and pre-slug+main slug+minor slug, under the condition that all the plans were carried out with same costs.