Study On The Stability Mechanism And Treatment Of Polymer/Surfactant Flooding Produced Liquid In Henan Oilfield

According to the processing order, the treatment technology of Xiaermen oil-water treatment center in Henan oilfield includes demulsification process and waste water treatment process which involves the demulsication of W/O crude oil emulsion and treatment of O/W waste water.Synthetic W/O crude oil emulsion and W/O waste water were prepared in laboratory respectively, electromicroscope, stability analyzer, laser particle analyzer, Zeta potential meter, interfacial tension meter and interfacial rheometer were employed to study the influence of polymer/surfactant on stability and interfacial properties of synthetic W/O crude oil emulsion and W/O waste water to investigate the stability mechanism of the emulsions.The density increasing of polymer/surfactant can decrease the mean particle size of synthetic W/O crude oil emulsion and thus enhance the stability of the emulsion. Synthetic W/O crude oil emulsion stabilized by polymer/surfactant is mainly stabilized by polymer by increasing the interfacial elasticity and viscosity; polymer contributes more to the stability of W/O crude oil emulsion compared with surfactant.Surfactant can disperse the emulsified oil droplets, the mean particle size of oil droplets decrease when surfactant concentration increases. Transmission light decreases when surfactant concentration increases which indicates that stability of O/W waste water increases. Zeta potential increases when polymer/surfactant concentration increases. O/W waste water is stabilized by increasing the electric charge of emulsified oil droplets by surfactant mainly; surfactant contributes more to the stability of O/W waste water compared with polymer.The demulsifier SP169I, AP221, TA1031, PR929 and NYC9 are proved to be effective in demulsification of synthetic W/O crude oil emulsion stabilized by polymer/surfactant, the dewatering rate is high, the separated water is clean and the interface condition is neat. The decomponition rate constant of the five demulsifiers has a size order:SP169I>PR929> NYC9>AP221>TA1031. The optimum demulsifer dosage of SP169I, PR929 and NYC9 is 80～120mg·L-1. The sensibility of the three demulsifiers has a size order:NYC9>PR929> SP169I.The balance interfacial tension of oil-demulsifier solution is more important than the dynamic interfacial tension in the demulsification process. The interfacial elasticity decreases with the addition of demulsifier. The demulsification mechanism is that demulsifer can adsorb at the oil-water interface and decrease the interfacial elasticity.Polymer/surfactant flooding waste water is harder to treat than polymer flooding waste water while polymer flooding waste water is harder to treat than water flooding waste water. Polymer/surfactant flooding waste water gets more difficult to treat when polymer/surfactant concentration increases. Initial oil & suspension concentration have a linear relationship with oil & suspension concentration after flocculation treatment. Flocculant and demulsifier have a synergistic effect to treat waste water, oil & suspension concentration after treatment and the flco decrease which can lighten the burden of filtration and washed water system in the waste water treatment process.As to the field emulsion, water content of the purified oil from the triphase separator with demulsier concentration of 100mg-L"1 has a size order:NYC9>PR929>SP169I while oil concentration of the separated waste water has a size order:SP169I>NYC9> PR929. Water content of the purified oil from the triphase separator and oil concentration of the separated waste water increase with polymer/surfactant concentration in field produced liquid.Oil & suspension concentration of field waste water containg 46.2mg·L-1 polymer and 50.0mg·L-1 surfactant after treatment with 6mg·L-1 CPAM+20mg·L-1 RPDE A are less than 30mg·L-1. Oil & suspension concentration of field waste water containg 98.7mg·L-1 polymer and 102.5mg·L-1 surfactant after treatment with 6mg·L-1 CPAM+20mg·L-1 RPDE A are less than 50mg·L-1, Oil & suspension concentration can be further reduced to less than 10mg·L-by filtration with quartz sand.