Effect Of Rheology Of Oil-water Interface Demulsifier On The Demulsification Performance Of Heavy Oil Emulsion Demulsifier

The reserves of heavy oils is plentiful, but its viscosity is high and contain a lot of natural emulsifier, which result in the heavy oil would form the emulsion. Now, the most commonly used method is chemical demulsification, i.e. the demulsifier is added into the crude oil emulsion to achieve the separation of the oil and water. There are many researches about the demulsification mechanism, but many of them main focus on one property of the demulsifier, or just focus on the structure of the demulsifier, which make the demulsification mechanism of demulsifier don't form a whole. Therefore, it is hard to explain the reason of the demulsification completely. To solve the problem, the demulsification mechanism of effect of demulsifier on the heavy oil emulsion was researched in the paper.The heavy oil used in the paper came from bohai oilfield, the properties of the heavy oil was investigated firstly:the water content ratio was 25%, the density of water-free oil was 0.987g/cm3, the content of the four components in the oil was:asphaltenes was 6.7%, resin was 14.3%, saturate was 48.7%, arene was 25%, the viscosity achieved maximal value when the water content was 50%, with the water content continued to increase, the viscosity began to decrease. Combined with the properties of the heavy oil, some oil-soluble demulsifier were selected (branched, straight) through the bottle test, taken the dehydration ratio after 1.5h as evaluation index, it was found that all the good performance demulsifier were the branched:T-1, T-2, T-3, P, E, D-1, D-2. After 90 min, the lowest dehydration ratio was 68%, the highest dehydration ratio was 100%.The strength of oil-water interface film of demulsifier were measured. Although the dilational modulus had a relationship with the dehydration ratio of demulsifier, the most of the demulsifier, which behaved good demulsification performance, could reduced the dilational modulus value of interfacial film to below 6 mN/m. However, some poor demulsifier also could reduced the dilational modulus value to below 6 mN/m. The dilational modulus was divided into elastic modulus and loss modulus to research, it was found that the elastic modulus had a good relationship with the dehydration ratio of demulsifier, the demulsifier had high dehydration ratio when it could reduced the elastic modulus to below 5 mN/m, conversely, the dehydration ratio of demulsifier was poor. The loss modulus had not relationship with the dehydration ratio of demulsifier.Taken the time which the 50% water was separated as the evaluation index. The seven demulsifiers:T-1, T-2, T-3, P, E, D-1 and D-2's dehydration rate were measured. The loss modulus had a good relationship with the dehydration rate, the dehydration rate increased with the decrease of the loss modulus. Because the loss modulus was proportional to the interfacial viscosity, the interfacial viscosity decreased with the decrease of loss modulus, which made the adsorption, rearrangement rate of the demulsifier increased, so the dehydration rate also increased. In addition, the dynamic interfacial tension of seven demulsifiers were also measured, the diffusion, adsorption and rearrangement values of demusifiers were achieved. The dehydration rate increased with the increase of diffusion, adsorption and rearrangement ability of demulsifer. Because the rupture rate constant of interfacial film increased when the diffusion, adsorption and rearrangement ability of demulsifier increased.The demulsifiers which had different structures were employed, then bottle test and the nuclear magnetic were done, it is found that the proportion of ethylene oxide (EO) in the demulsifier had a important influence on the dehydration property. The demulsifier had high dehydration ratio when the EO in the range from 30%-60%, the dehydration ratio began to decrease as the EO was not in the range. In addition, the dehydration rate reached the maximum when EO was about 55%, once the EO decreased or increased, the dehydration rate decreased.The effect of the demulsifier on the interfacial film mainly focus on the interaction between demulsifier and asphaltenes. The competitive adsorption rule of demulsifier and asphaltenes at the oil-water interface was presented by the oil/water contact angle measurement:the asphaltene interfacial film was broken by the demulsifier, then the demulsifier molecules would adsorbed at the interface to form a new interfacial film. Which made the contact angle increased.According to the demulsification mechanism, the XF and ECP series demulsifiers with different proportion of EO were carried out demulsification, it was found that the demulsifier which EO content was medium had high dehydration ratio, the dehydration rate of demulsifier was the fastest when the EO was about 50%. The results confirmed the feasibility of this paper's coclusion.