Research On Oil-water Interfacial Dilational Rheology Of Chemical Flooding Systems

There are many interface phenomena in the process of chemical flooding, so the interfacial rheological technique has a broad application prospect in the field of chemical flooding. We can obtain the micro process information of oil-water interface through the study of interfacial rheological properties, which contributes to better explain the mechanism of chemical flooding. In this paper, the interfacial dilational rheological technology was used to investigate surface rheological properties of foam flooding systems and interfacial rheological properties of oil/water systems. At the same time, the relationship between oil-water interfacial rheology and alkaline flooding recovery was also studied.To study the relationship between foam performance and surface parameters, sodium dodecyl sulfate(SDS)/long chain alcohol systems and long chain alkyl three methyl ammonium chloride systems were investigated. The result show that due to different matching of long chain alcohol molecules and SDS molecules, foaming volume and drainage half-life of SDS solution will increase at first then decrease with addition of lauryl alcohol, myristyl alcohol, cetyl alcohol and stearyl alcohol. Surface tension of the systems will decrease at first and then increase, while dilational modulus, elastic modulus and surface viscosity of the systems will increase at first then decrease. With the growth of hydrophobic chain, foaming volume and drainage half-life of LTAC, TTAC, CTAC and OTAC decrease in turn, surface tension increases in turn, dilational modulus and elastic modulus decreases in turn, while the value of viscous modulus is always very small. Foamability of foam flooding systems is controlled by surface tension and surface viscoelasticity. Stability of foam flooding systems is mainly affected by surfacial rheological properties, and there is significant linear relationship between drainage half-life and elastic modulus.To study the influence of experimental condition, crude oil composition and water composition on oil-water interfacial rheology, Zhuangxi oil/water system was investigated. The result show that the appropriate experiment condition was obtained as follows:8000s equilibrium time,1.0μL amplitude of oil drop and10s oscillation period. The interfacial film could be seen as elastic film. Dilational modulus of oil-water interface pass through a distinct maxima as a function of Zhuangxi crude oil concentration. Among fractions of Zhuangxi crude oil, asphaltene fraction has the most significant effect on oil-water interfacial dilational rheology. Dilational modulus of oil-water interface decrease with increasing concentration of NaCl. Dilatational modulus decreases after adding surfactants of ORS-41and OP series, but the contribution of viscous modulus on dilational modulus increases.In order to research on the mechanism of alkali flooding from the point of interfacial rheology, the alkaline flooding system of Zhuangxi crude oil was investigated. The result show that weather alkaline flooding can enhance oil recovery mainly depends on its interfacial dilational rheology, rather than interfacial viscosity and interfacial tension.