Research On Emulsification And Demulsification For ASP Flooding Produced Liquid In The N1 Block

The alkali-surfactant-polymer (ASP) flooding is an important tertiary oil recovery technology. As a result of chemical agent emulsification and synergy during oil displacement process, the serious oil-water emulsification is evolved followed enhanced recovery ratio. Owing to difficult demulsification, it is necessary to develop effective demulsification method in accordance with ASP flooding produced liquid.The lease test of ASP flooding in N1 Block of Daqing oilfield, is a strong base ASP flooding industry field trial with the largest scale localization of surfactant manufactures in domestic. This paper aims at the extremely difficult oil-water separation of the ASP flooding produced liquid in N1 Block. The influence law of oil displacement agent on emulsion property, oil displacement agent and solid particles on oil-water separation are studied. Based on the evaluation for demulsifying effect of chemistry demulsification, gravity settling, centrifugation, ultrasonic treatment and microwave radiation, XJ-1 demulsifier with fine demulsifying effect on produced liquid is optimized. Then the adaptability of demulsifier, thermal chemical settlement and centrifugation on demulsification is determined. Thus the optimum demulsification parameter suit for different oil displacement agent content of ASP flooding produced liquid in N1 Block is got.The main research conclusions drawn in this paper include:(1) Superfluous negative charge is left on the oil-water interface of ASP flooding produced liquid. Zeta potential decreases with the increase of surfactant content, and increases with the increase of alkali content. The dynamic tension of oil-water interface for ASP produced liquid decreases with the increase of surfactant and alkali content, while polymer affects the dynamic interfacial tension little.(2) Surfactant and polymer affect the emulsification degree of ASP produced liquid more notable than alkali does. Bead size of oil droplets decreases significantly with the increase of surfactant content in the case of no polymer and alkali, and the emulsification degree increases. Emulsification degree increases with the increase of polymer and alkali content at the low content of surfactant.(3) Quartzite and Calcium base montmorillonite particles can be adsorbed on the oil-water interface, so it has remarkable hinder effect for the coalescence of oil droplets and it influences the oil-water separation features of produced liquid.(4) The RSN value range of demulsifier suit for the ASP produced liquid in N1 Block is 15～19. XJ-1 demulsifier has fine demulsifying effect on ASP produced liquid. While dosage less than 150mg/L, the oil content of water phase and water content of oil phase for ASP produced liquid can respectively be reduced to 2000mg/L and 5% during the static settlement of 90 minutes. For three kinds of ASP flooding produced fluid with low, medium and high oil displacement agent content, the optimum demulsifier dosage is respectively 50mg/L,75mg/L and 150mg/L.(5) Under the condition of adding proper XJ-1 demulsifier, the best removal temperature of free water for ASP flooding produced fluid in N1 Block is 40℃, with the settling time 30min, and the suitable thermo-chemical dehydrating temperature is 65℃. The water content of oil phase can achieve to below 0.5%, which is the water content control index of crude oil for external transport, after 24h thermal chemical settlement with 65 "C temperature.(6) Centrifugal processing has significant effect on water-oil separation of ASP produced liquid in N1 Block. Under the condition of adding proper XJ-1 demulsifier, the optimum centrifugal acceleration is 984G, with centrifugal processing time of 10min and centrifugal processing temperature of 40℃. The oil content of water phase and water content of oil phase can respectively be reduced to below 200mg/L and 1% after centrifugal separation.(7) Mechanical oscillation coalescence obviously has improved effect on water-oil separation of ASP produced liquid in N1 Block. The suitable effect time of mechanical coalescence is 0.5min. Ultrasonic wave processing and microwave radiation do not have apparent effect on water-oil separation of ASP produced liquid in N1 Block.