Study On Biological De-Emulsifier Exploitation And De-Emulsification Efficiency

Petroleum-field emulsions, which are produced in the process of exploration, production and recovery, represent a major environmental and processing problem for the petroleum industry. Biological demulsifier as a biological agent, will become a novel method of petroleum-field emulsions demulsifer instead of chemical demulsifier for its high efficiency, low cost, high adoptability, environment-friendly, repeated use. In this project, a novel type of de-emulsifying bacterium was exploited. Two high efficiency de-emulsifying strains were isolated and identified. The factors affecting their growth and de-emulsification efficiency, the de-emulsification approaches and active composition, and the field application were also studied.A set of high efficiency and convenient method is established to isolate de-emulsification strain, based on the high surface activity bacterial strain selection with the bio-de-emulsification approaches. We have isolated two strains with high and steady de-emulsification activity. The average de-emulsification rates of O/W model emulsions were more than 85.0%. The two strains are both belonging to bacillus mojavensis by traditional and molecular genetic identification. The proliferation of passage of the de-emulsifying strains shows high stability. The effect of culture conditions on the de-emulsification efficiency and the growth situation of this de-emulsifying strain were comprehensively considered, so the most favorable culture conditions were determined as follows: pH 6.5 ~ 9, temperature 30±2℃, stirring speed 140±20 rpm, culturing time 18 ~ 20h. The most favorable carbon resource was the mixture of glucose (10g/l) and liquid paraffin (2 ~ 4%(v/v)). The most favorable nitrogen resource was NH4NO3 (4.0 g/l) and yeast (1.0 g/l).Studies on the conditions of de-emulsification, we found that the de-emulsification rate with the changes of contacting time was approximate first order reaction, the best proportion of the whole bacteria culture and O/W model emulsions for de-emulsifying were 1:5. And this biological de-emulsifier could de-emulsify in environment with pH5~9.The de-emulsification ability of this biological de-emulsifier originated from the surface active substance produced in metabolites, and independent of bacterial cell form. But the presence of bacterial cells is helpful for de-emulsifying process, the de-emulsifying efficiency decreased after centrifuging and discarding the bacterial cells. The de-emulsifying ability was not influenced by freeze-thaw and ultrasonication, but the de-emulsifying activity was lost after autoclave. The de-emulsifying efficiency decreased after protease or urea treatment. This indicated that the active substance is protein. The de-emulsifying active substances were crudely extracted by organic solvent, PEG and salting-out method. And the possibility of polysaccharides as doubting de-emulsifying activity substances was excluded.In field experiments, compared to chemical de-emulsifier, this kind of biological de-emulsifier had high adoptability and better dewatering for petroleum-field emulsions. So this biological de-emulsifier has great prospect for further exploitation and utilization.