| When the concentration reaches a certain value, the viscosity of viscoelastic surfactant increased significantly. With a certain degree of mobility control and the ability of reducing oil-water interfacial tension, Viscoelastic surfactant could become a well-displacing agent to replace the surfactant/polymer flooding. In this paper, based on the actual reservoir, study the properties of viscoelastic surfactant for EOR in porous media for the first time. The main contents are as follows:(1)Study the static adsorption law of viscoelastic surfactant on the surface of the different minerals and dynamic retention law in porous media.The results show that the viscoelastic surfactant dynamic retention in porous media is generally10-2-10mg/g, far less than its static adsorption capacity (100～102mg/g).(2)Study the injection and mobility control of the viscoelastic surfactant in porous media. The results show that viscoelastic surfactant has a good degree of the injection and mobility control in middle-low permeability reservoir.(3)Study the rheological properties of viscoelastic surfactant in porous media by the core flow experiments. The results show that effective viscosity of viscoelastic surfactant in porous media consists of shear viscosity and extensional viscosity. There exists a critical shear rate. Equivalent shear rate below the critical shear rate, shearing is dominant.While equivalent shear rate above the critical shear rate, stretching effect is significant.(4)Through core flooding physical model experiments, study the oil displacement efficiency of viscoelastic surfactant. The results show that viscoelastic surfactant and surfactant/polymer system has considerable oil displacement efficiency. Viscoelastic surfactant has a good potential for application in middle-low permeability reservoir.Research about viscoelastic surfactant in this paper enriched EOR theory of middle-low permeability reservoir and provided technical support for the development of high water cut reservoir. |
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