Study On Selecting High Efficiency De-emulsifying Bacteria And De-emulsification Experiment

The feasibility of applying biosurfactants to the de-emulsification and dewatering technology of the produced liquid of oilfield was studied in this paper. The produced hquid was from Kelamayi Oilfield No. 81 station and contains 50% water. The study includes several main parts: (1) the condition to prepare crude oil emulsion used in this study;(2) selecting de-emulsifying bacteria;(3) separating and identifying the de-emulsifying bacteria;(4) optimizing the cultivating conditions of the de-emulsifying bacteria. The experiment results showed that: (1) under the condition of low agitating intension, the stability of the crude oil emulsion was related with the agitation intension and time. The crude oil emulsion was stable when the volume ratio of oil and water was 1:1 and the agitating intension and time were 900rpm and 15min, respectively. The dewatering efficiency was high when the dosage of chemical de-emulsifier was 40mg/L. The emulsion made under such conditions could be used as the model crude oil emulsion in the course of selecting de-emulsifying bacteria. (2) The reported bacteria with de-emulsifying ability could not effectively demulsify the crude oil emulsion made from the produced liquid from Kelamayi Oilfield No. 81 station. The reasons were that simple emulsion containing kerosens was studied before. But the crude oil emulsion contains many natural polymeric emulsifiers which made the interface film very stable. So the reported bacteria could not change the characteristics of oil-water interface and demulsify the emulsion. (3) The species of bacteria were complex in the activated sludge foaming of the activated sludge treatment system and their metabolites were various. Foam was the important characteristic when surfactants were present. These surfactants could improve the fluidity of oil-water interface of the crude oil emulsion and demulsify it. But it was rather difficult to separate pure de-emulsifying bacteria from it. (4) After culture and domestication by using liquid paraffin as the single carbon source, the Sinkiang oilfield soil dipped in the oil for a long time would produce some surfactants to emulsify liquid paraffin. These surfactants could change thequality of oil-water interface of the crude oil emulsion and greatly reduce the interface intension and demulsify the emulsion. Bacterium TR-1 was separated from the mixed bacteria and had great de-emulsifying ability. The dewatering efficiency and rate was superior to the mixed bacteria. The bacteria was belongs to Sphingomonas paucimobilis by primary identification and had no toxicityto little mouse. Its de-emulsifying ability was stable and descendible. When the dosage of bacteria and dry powder were 200mg/L, the de-emulsifying efficiency in 150min was 93% and 84%, respectively. And the oil contained in the de-emulsified water was 26mg/L. Bacterium TR-1 could be manufactured and applied in industry with further study.