The Screening And Evaluation Of Generated Biopolymer Bacterium

As having many excellent performance, biopolymers is often used as oil displacement agent, profile control agent and drilling fluid in recent years. However, the research on screening of the generated biopolymer bacterium under reservoir conditions is relatively small. Finding bacterium with more adaptation to the environment and higher yield, and developing biopolymer with better temperature tolerance and stability is the most fundamental way to solve the problem, and also is one of the items by scholars at home and abroad to study microbial.Aiming at the kernel problem for generated biopolymer bacterium, this paper founded research method that combined bacterium screening, fermentation and culturing, performance evaluation. One bacterium (numbered BHs) with the performance to generate biopolymer and short ferment period was separated from oil-water mixture sample of Daqing oilfield. This bacterium was a facultative anaerobe, and compatible with Daqing oilfield reservoir well. The optimum conditions for the bacteria fermentation determined through experiments: the culture temperature is 35℃, the air flux is 0.2m³/h, and the range of pH value is 7～8.Different carbon sources, inorganic nitrogen sources and mineral elements were used to confect the culture mediums, and BH₈ was inoculated in these mediums to culture, the viscosities of the fermentation fluid were tested to choose the culture medium which has the biggest viscosities. The biggest level of each factors and the best medium formula components were obtained through analyzing the influence of different levels of medium factor formula on viscosities of the fermentation fluid in orthogonal experimental way.BH₈ bacteria grew well in porous media, and produced biopolymers. BH₈ made a good sealing effect on hypertonic layer. Results of profile modification experiments indicate that biopolymer can seal hypertonic layer effectively after it is injected into the core, which improved the injection pressure quite a lot. Flooding experiments showed that after water flooding to 98% of the water cut, injecting the BH₈ and the nourished fluid into the core for 3days, then water flooding can enhance oil recovery by 10 percent.