The Study On The Stability Of Water Produced From ASP Flooding And Treatment Technology Exploring

Water resource shortage and water pollution are serious in our country. With the oilfield such as Shengli, Daqing in our country entering the period of Enhanced Oil Recovery (EOR), the alkaline/surfactant/polymer (ASP) flooding technology has been successfully used in oilfield in order to increase the crude oil recovery, but more and more ASP produced water is produced. Produced water from ASP flooding containing large quantities of residual chemicals (alkali, surfactant and polymer), crude oil and suspended substances is a complex and stable emulsion system, and it is difficult to treat. Before reinjection and discharge, ASP produced water must be treated and measure up to a given standard. However, now there was no appropriate treatment method for such wastewater at home and abroad.After the preparation of simulated ASP produced water, the effects of residual oil displacement agents on oil-water separation of simulated produced water, zeta potentail, oil-water interfacial rheology and oil droplet size were investigated, and then the stability mechanism of ASP produced water was analyzed. And on that basis, the treatment on simulated produced water from ASP by using treating-agent of alkaline white mud was studied, and the precipitate was characterized by FTIR and SEM. And then the treatment conditions and reaction mechanism were approached. It was found that:(1) When HPAM concentration is low (3.0×106 HPAM< 300 mg/L,5.0×106 HPAM<200 mg/L,1.2×107 HPAM<200 mg/L), the flocculation of HPAM is the dominant factor, while the high viscosity of produced water and zeta potential of oil droplet play a significant role at high HPAM concentration, therefore the emulsion stability of produced water is initially degraded and then enhanced with the increase of HPAM concentration. The adsorption of WPS on oil-water interface decreases interfacial tension and increases zeta potential, and thus enhances the emulsion stability remarkably. NaOH can react with acid components of crude oil and form interface active substances, and the adsorption of these substances on oil-water interface can decrease interfacial tension, viscoelastic modulus and increase zeta potential, so the emulsion stability of produced water is enhanced gradually with the increase of NaOH concentration up to 300 mg/L and then weakened with the further increase of NaOH concentration.(2) It is effective to treat simulated produced water from ASP by using alkaline white mud treating-agent. When initial oil concentrations of produced water are between 300 mg/L and 2700 mg/L and under the selected treatment conditions, the oil concentrations after treatment are close to the demand of national integrated wastewater discharge standard. And the selected treatment conditions through tests are as follows:dosage is 8000-9000 mg/L, pH is 11-12.5, stirring intensity is 200-350 r/min, stirring time is 90-180 s, settling time is above 20 min and temperature is 15-40℃. And the treatment mechanism of alkaline white mud treating-agent is maybe related to the property of new phase hydroxide by surmising.