Research On The Characteristics And Demulsification Efficiency Of Biological Demulsifiers Used For The Demulsification Of Oil-in-water Emulsions

Development of oilfields in the middle and later stages has been changed into complex oil-water emulsions because of various enhanced oil recovery technologies.Demulsification treatment of emulsions is an important part of the oil industry.The existing emulsion-breaking methods do not achieve environmentally-friendly,efficient and safe,especially the demulsification of chemicals.Therefore,it is of great significance to solve the three major problems of oilfield production increase,cost reduction,and environmental protection by microbiological demulsifier.This article identifies a method for screening strains.The emulsion-breaking bacteria were screened from the mixed colonies by the oil-discharging ring method combined with the demulsification experiment,and separated and purified by the dilute coating method.By 16S rDNA identification and Phylogenetic tree analysis,it was determined that the screened bacteria were Stenotrophomonas maltophilia and Bacillus thuringiensis,and were named CY-1 and CY-2,respectively.The growth conditions of CY-1 demulsifier and CY-2 demulsifier were optimized and the influencing factors on the demulsification efficacy were examined.The optimal growth conditions of CY-1 and CY-2 are:24 h of fermentation time,pH of medium 6.5,culture temperature at 30℃ and 140 rpm of shaker speed with no added carbon source.The time of complete demulsification of CY-1 and CY-2 was 56 h and 32 h,respectively,and the best demulsifier dosage in the 5 mL emulsion was 3 mL for both of them.The effective demulsification components of CY-1 demulsifier and CY-2 demulsifier were analyzed.The demulsification rate of CY-1 suspension and the whole CY-2 culture demulsifier reached to 100%,which indicated that CY-1 demulsifier was a bacterial cell,and CY-2 demulsifier were synergistic of bacterial metabolites and cells.The polysaccharides and protein substances in the clear liquid of CY-2 have demulsification capacity.The results of thermal stability analysis showed that the CY-1 demulsifier and the CY-2 demulsifier contained protein,sugar,and lipids.Infrared analysis showed that the difference peak was at 1729 cm-1,which was proved to be the C=O stretching vibration peak belonging to the group of proteinaceous substances.At the same time,the absorption of proteinaceous substances occured at 275 nm by UV spectroscopy analysis.The demulsification mechanism of the emulsion was analyzed from three aspects:demulsification process,Zeta potential and emulsion stability,oil-water interfacial tension and emulsion breaking effect.The Zeta potential of the emulsion did not change regularly with changes in the dosage and demulsification rate of the biological demulsifier;the interfacial tension decreased with increase dosage of the biological demulsifier,and the formed interfacial film strength was lower than the original interfacial film which caused the interfacial film been hence the oil,the oil entrapped inside was released,and the oil-water was separated and achieved demulsification.