Laboratory Study Displacement Efficiency of Viscoelastic Surfactant Solution in Enhanced Oil Recovery

Polymer/surfactant combination solutions, were easy to suffer chromatographic separation effect when injected into a relatively low permeability reservoir for the poor injection ability. In addition, the long chain polymer molecules are easy to be cracked:when passing through the porous media with low pore throat radius. These problems limit the polymer/surfactant combination flooding used in the poor reservoirs for enhanced oil recovery (EOR). The conventional viscoelastic surfactant (VES) is mainly used in fracturing or drilling. In this paper, we present a novel viscoelastic surfactant, VES-JS, which is designed for EOR It has a unique ability that allows it. to have viscoelasticity like the polymer solution and the capacity to deduce the interfacial tension (IFT) value of oil,and water to order 10(-2) similar to 10(-3) mN/m. For the self-assemble ability, it can reform network structure when it stiff in the porous media. Under the reservoir condition, 65 degrees C, 100 x 10(-3) mu m(2), VES-JS shows good viscoelasticity and ultra low IFT which can improve the displacement efficiency. An experimental investigation of VES flooding was conducted by a series of core flooding. The effects of reservoir permeability, VES concentration, injection rate, injection volume, injection time, and reservoir heterogeneity on displacement efficiency were evaluated. The results indicate that under the experiment conditions, VES flooding can improve oil recovery ratio from 10.64% to 24.72%. Moreover, under the comparable experiment conditions, VES flooding can get recovery increment 17.18%, while polymer flooding is 10.56% and surfactant flooding is 8.64%, which is close to the ratio of the polymer/surfactant combination flooding 17.35%. These exciting results show a strong potential for the VES used in relatively low permeability reservoirs for EOR.