| The oil production of DaQing oil field has been in the middle-last development time. With the inputting water more and more, the water content ratio of outputted liquid form oil well is increasing high. The average water content ratio of middle region in DaQing oilfield is over 90%. The outputted liquid mainly is oil in water emulsion. When it reach the ground , it must be add into high efficient demulsifier to separate water and oil. Now, the common used demulsifiers in oil field are SP, AP, AE, AR and so on, but every demulsifier has its limitation .To some oil in water emulsions with special high water cut ,there are some defects such as low dewatering efficiency, high dewatering temperature and slow dewatering speed. In accordance with the oil of the ninth oil -extracting factory of DaQing oilfield and in order to overcome such defects, we compounded three different demulsifiers firstly, then taking of synergetic effect among demulsifiers to make composition with the three different demulsifiers. We can get different composition system with different oil, and use the outcomes to direct the production.The component A is a kind of polyether with quite high molecular weight and narrow molecular weight distribution. Using self-made initial agent to make copolymerization with double metal cyanide catalysts and ethylene oxide, propylene oxide, we can compound out different products with different molecular weight and different molecular weight distribution and so to observe and study the effects of some factors to the molecular weight and molecular weight distribution of the products, such as the kind of assistant catalyst, copolymerization temperature , inputting speed, adding amount of catalyst and the method of setting off. With the oil dewatering experiment, we can learn that when the molecular weight of the compound is higher and molecular weight distribution is narrower, the dewatering efficiency is higher.The compound B is a kind of polyether from ethylene oxide and propylene oxide taking polyethylene polymine as initial agent. It is a kind of highly branched compound and has quite good dewatering efficiency to oil with comparatively lowwater cut. We can get the best prescription through choosing among the prescriptions of initial agent, catalyst, ethylene oxide and propylene oxide The B has very good devvatering efficiency to oil with 20% water cut at quite low density and temperature. The infra-red spectrum, HNMR spectrum, and GPC spectrum of polyether show that the molecular weight distribution of polyether taking acetate calcium as catalyst is comparatively narrow.The component C is a kind of cationic surfactant compounding form cationic monomer DC and polyacrylamide with persulphate-fatty amine as catalyst. It can neutralize the negative charges on the liquid flim of oil in water emulsion, and encourage oil drop getting together separating. Reasonable concentration of cations and comparatively high molecular weight are main factors effecting devvatering efficiency of component C.In accordance with some questions such as the low using efficiency of sole demulsifier to oil of the ninth oil extracting factory, we use the three demulsifiers compounding together and choose out the best prescription to oil with different water cuts. The dewatermg efficiencies are all over 95% and the higher the dewatering speed the lower the dewatering temperature. With analyzing the mechanism of compounded demulsifiers , we can get two conclusions:1. Changing the nature of interfacial film in emulsion, reducing interface tension and the life of liquid drop.2. Neutralizing the negative charges on the liquid film, encouraging oil drop getting together quickly.In April 2002, we took on-spot test at Longyi conjunction place. It locate in LongHuPao oilfield and can handle outputted liquid 1200m everyday. The average water cut of oil is 80%. After adding demulsifiers 40mg/L to it, the dewatering temperature reduced from 55C to 40C and water cut reduced to 0.2%. They all conformed to standard about the...
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