Study on surfactant/polymer flooding technology for under-productive oil layers in development zone of the north Saertu of Daqing Oilfield

Because of low permeability and serious heterogeneity in the under-productive oil layers in development zone of the north Saertu of Daqing oilfield, the effect of water flooding is becoming worse and worse. The viscosity, interracial tension and stability of 4 kinds of surfactant/polymer (SP) systems was evaluated in the paper and refining petroleum sulfonate/polymer system was chosen. Moreover, the flooding effect, injection parameters, viscosity and combination of slug of this SP system have been studied. The result showed that the SP flooding system had a very good performance. At the same time, the whole plug and the plug injected by order of low, middle and high viscosity have a better effect. Besides, the earlier the profile modification, the better the effect of increasing oil. The recommended injection mode is: inject Cr³⁺(0.05~0.08 PV) cross-linked polymer gel first, and then inject SP solution (0.33~0.49 PV) whose polymer and surfactant concentration are 1 200 mg/L and 0.2% respectively. Using such formula and the combination of slug, oil recovery could be increased by more than 15% compared with using water flooding.