Mechanism Of The Ternary Complex Drive Surface Active Agent Adsorption And Alkali

This paper studies systematically the adsorption laws of surfactants in the different systems at oil sand of Daqing oil field. The effect of alkali on rheological properties of ASP system, interfacial tension and rock mineral dissolution is also discussed. After resin and asphaltene are dissolved in decane, the relationship between interfacial viscoelasticity of oil/water interface and emulsion stability is investigated.The static adsorption experiments are conducted to study the adsorption isotherms of four surfactants on the oil sand at 45C. The results show their adsorptions are not in accord with Langmuir adsorption isotherm. A maximum is observed when concentration of surfactants is near the range of CMC. At the same surfactant concentration, the larger of molecular weight of the surfactant, the higher of its adsorbance on oil sand. Chemical potential of surfactant molecule in solution determines its absorbance on sand. The higher the chemical potential of surfactant molecule is, the larger its adsorption is. Adsorbance of surfactant is different in different systems. Adsorbance of surfactant in injected water is more than that of in alkaline, polymer and ASP solutions. Alkali and polymer decrease adsorptive loss of surfactant by changing surface properties of rock or competing adsorption sites. The maximum adsorbance of ORS41 and B-100 in ASP system are 14 u mol/g sand and 8 u mol/g sand respectively. The effect of Alkaline and polymer in ASP on surfactant adsorption is synergic and complex. After the wettability of oil sand is changed to oil wetting with silicone oil, the adsorbance of surfactant would increase. The mechanism of the maximum adsorption of surfactant on oil sand is analyzed. The model of surfactant adsorption on oil sand is established by two steps. Adsorption loss of surfactant can be reduced over 30% by mixing sacrificial agents with surfactant or pre-flushing with sacrificial agents. For reducing adsorption of surfactant on oil sand, sacrificial agents are more effective by pre-flushing than mixing with ASP system. The creative points are: establishment of the model for the adsorption of surfactant on oil sand; investigation of the effect of polymer and sacrificial agents on surfactant adsorption in ASP system.The dynamic retention of surfactant in ASP system in natural core is studied, the results(the retention of surfactant is 0.08mg/g sand, which is lower than that of static absorbance.) are in accord with the surfactant loss in actual reservoir. The displacing experiments show that displacement efficiency of water wetting core(water flooding or ASP flooding) is always higher than that of oil wetting core.The static adsorbance of surfactant, NaOH and polymer on oil Sand are 3-6mg/g, 0.4mg/g and 1.2mg/g sand, respectively. During the ASP migrating process, the adsorption mechanisms of the three chemicals are different because of the influnce of the fluid and porous medium on them and the different properties of themselves. The larger retention of components in natural core, the faster of the concentration of the component decrease, and the migration speed of component should be slower. For the first time, this paper put forward that, in ASP flooding, surfactant molecule is adsorbed oriental on the oil-water interface film of remaining oil and oil film of emulsion, and that would increase the retention loss of surfactant. The analysis of the laboratory experiment and four field experiments indicate that alkali and polymer appears in produced fluid firstly with maximum of relative concentration located closely and that of surfactant is produced always with a delay of 0.3PV. These confirm the phenomena of chromatographic separation in ASP flooding.The types and concentrations of alkali affect rheological properties of ASP system. As the increase of the alkali, pseudoplastic behavior and vicoelascility of the solution decrease and linear vicoelasticity regions become narrow. Organic alkali (quaternary ammonium hydrate) is used in ASP system for the first time, which is beneficial...