Effects Of Laponite Particles On The Stability Of Produced Water From ASP (Alkaline/Surfactant/Polymer) Flooding

In recent years, with the increase of oil exploitation, the major oil fields in China have entered tertiary recovery phase. And the ASP flooding technology has been widely applied in Daqing, Shengli oil field which enhances oil recovery over20%. However, the treatment of produced water from ASP flooding is another problem to be solved. The produced water contains large amounts of oil displacement agent (alkali, surfactant and polymer), which formed a complex emulsion system with strong emulsification, high stability and biorefractory. As a result that it is difficult to deal with. Currently, it has a major breakthrough that the displacment agent affects the stability of the produced water from ASP flooding. Actually, the crude oil carries some clay particles which has certain surfactants when flowing through the stratum. And the clay particle is an important factor affecting the stability of oil wastewater.Laponite particles were simulated as clay minerals of stratum in this article. Firstly laponite particles with different concentrations were put in ASP flooding produced water to investigate its effect on the system stability. And the zeta potential, oil-water interfacial tension, size of oil droplets and apparent viscosity were determined under the conditions of different concentration of displacement agents and laponite to investigate its mechanism.The results are as follows:(1) With the NaOH concentration increasing (<300mg/L), the negatively charged zeta potential of oil droplets increased, the interfacial tension, viscoelastic modulus and the oil droplets size decreased, eventually leading that the stability of produced water gradually increased; with concentrations of NaOH increasing (>300mg/L), the zeta potential remained stable, while the interfacial tension and viscoelastic modulus gradually decreased and the size of oil droplets increased, as a result that the stability of produced water deteriorated. It is illustrated that the effect of NaOH on the oil droplet size is dominant at high concentrations. With increasing the oil droplet size, the emulsion stability is deteriorated. The WPS, with the increase of its concentration, the negatively charged zeta potential gradually increased, and the interfacial tension, viscoelastic modulus and oil droplet size decreased, eventually the emulsion stability gradually increased. It was indicated that WPS affected the stability of produced water through combining effects of zeta potential, interfacial properties and oil droplet diameter; for HPAM, with the concentration increasing, the negatively charged zeta potential and viscosity of the system increased, while the interfacial properties and particle size of the oil droplets were not changed obviously, eventually the emulsion stability enhanced. It was indicated that HPAM enhanced the emulsion stability by influencing the zeta potential of oil droplets and the system viscosity.(2) When laponite was at low concentrations (<150mg/L), with the increase of its concentration, the negatively charged zeta potential and viscoelastic modulus gradually increased, the interfacial tension decreased, oil water emulsion stability enhanced; at high concentration (>200mg/L), with increasing its concentration, the negatively charged zeta potential remained stable, the interfacial tension increased, the viscoelastic modulus decreased, and the results were that the emulsion destabilized. It was proved that the laponite decreased the emulsion stability primarily through increasing the interfacial tension and reducing the viscoelastic modulus.