Study On The Demulsification Effect And Mechanism Of Water-in-oil Emulsion By Biological Demulsifying Bacteria Regulated By Carbon Source

With the increasing demand for oil energy in China,oil exploration will produce millions of tons of water-in-oil type crude oil emulsions every year.Due to its high content of natural surface active substances and various chemical surfactants added during crude oil extraction,its stability increases dramatically and the water in crude oil emulsions is difficult to be separated by centrifugation.Conventional water-in-oil emulsion dewatering methods have the disadvantages of high energy consumption,poor universality,large chemical dosage and high chemical toxicity.In recent years,the development of environment-friendly bio-emulsion breaking technology has been rapid.In view of the increasing demand for environment-friendly emulsion breakers in the oil and gas field extraction industry for crude oil emulsion dewatering and refining,and the problems of high production cost,low dewatering efficiency and imperfect emulsion breaking mechanism of bio-emulsion breakers in the current bio-emulsion breaking technology,this study innovatively proposes the use of water-soluble organic matter as raw material to produce emulsion breakers by using bio-emulsion breaking bacteria screened in the laboratory.In this study,we innovatively proposed to use water-soluble organic matter as raw material to produce emulsion breaker,and also studied the bio-milk-breaking bacteria cultured with oil-soluble organic matter to explore its emulsion-breaking effect on water-in-oil model emulsion and improve the dewatering efficiency,and then analyzed the emulsion-breaking mechanism of water-in-oil emulsion by bio-milk-breaking bacteria regulated by different carbon sources.The main research contents and results are as follows.Different kinds of water-soluble carbon sources and oil-soluble carbon sources were selected to culture biological demulsifier.The influence of carbon source types on the demulsifier effect and characteristics of the bacteria was explored,and the biological demulsifier mechanism regulated by carbon source was studied.(1)Thirteen different carbon sources were used to culture the demulsifier TD-4,and the influence of carbon sources on the demulsifier effect and demulsifier characteristics of the bacteria was studied.The results showed that carbon source had significant influence on the growth and metabolism process and demulsification effect of biodemulsification bacteria.The bacteria TD-4 can make good use of the water-soluble carbon sources glucose,sodium acetate,sucrose,etc.,and the water-soluble carbon sources can not metabolize TD-4 to produce biphilic bioactive substances,but it shows a good demulsification effect.The effective demulsification component is the bacterial cell with surface activity.When the oil soluble organic matter was used as the carbon source,the biomass of TD-4 was very high,and it could produce a large number of biosurfactant substances,showing strong demulsification ability.The effective demulsification components were mainly bacterial somatic cells and their surface-active lipopepins.On the whole,the demulsification effect of oil-soluble carbon source culture is better than that of water-soluble carbon source culture.(2)Lactic-breaking bacteria cultured with different carbon sources have different lacticbreaking properties.When the optical density of oil-soluble carbon source paraffin oil culture of lactic-breaking bacteria TD-4 is OD600=2,its emulsion breaking efficiency of water-in-oil model emulsion can reach 100%.The emulsion-breaking efficiency of TD-4 with the watersoluble carbon source sodium acetate was also 100%at the concentration of OD600=2.5.The oil and water separated by the two carbon sources were clear and turbidity-free.The emulsion breaking effect of oil-soluble carbon source cultivated emulsion breaking bacteria is not affected by high temperature and pressure,and the emulsion breaking speed is faster and the emulsion breaking ability is stronger.The emulsion breaking activity of emulsion breaking bacteria cultivated with water-soluble carbon source was completely lost after high temperature and high pressure treatment,and the emulsion breaking activity was more sensitive to high temperature and the emulsion breaking speed was slower.(3)Three typical carbon sources,sodium acetate,glucose and paraffin oil,were used to cultivate lactic-breaking bacteria to study the biological lactic-breaking mechanism regulated by carbon sources.When the water-soluble carbon source was used to culture the lacticbreaking bacteria TD-4,the lactic-breaking ability of the lactic-breaking bacteria was related to the cell activity of the bacteria,and the lactic-breaking effect was significantly and positively correlated with cell surface hydrophobicity(MATH),and high MATH could make the lacticbreaking cells reach the oil-water interface faster,but the spatial structure of the protein on the surface of the bacteria might be the dominant factor to make the lactic-breaking bacteria TD-4 cultured with water-soluble carbon source have the lactic-breaking ability.Under the action of the protein structure on the cell surface of the bacterium,the bacterium cells at the oil-water interface keep aggregating small droplets through adsorption and bridging,and then the oilwater interface membrane breaks down and the droplets are aggregated,and finally achieve emulsion breaking.The emulsion breaking effect of the oil-soluble carbon source cultivated by the emulsion breaking bacteria is dominated by its metabolic production of bio-surface active lipopeptides,and the contribution of the bacterial cells to the emulsion breaking effect is small.This surface active substance can be dissolved in the oil phase and rapidly enter into the oilwater interfacial membrane,competitively replacing the emulsifier molecules on the interfacial membrane,showing strong interfacial activity,which in turn reduces the strength of the interfacial membrane and destabilizes the emulsion to achieve emulsion breaking.