Abstract

This paper depicts the laboratory results as well as reservoir surveillance and well production performance of microbial flooding in Fuyu oilfield, China. A four-spot water flooding has been applied from 1973, and various measures to increase production has been implemented since 1981. However, 1/3 non-absorbing reservoir and the invalid circulation of injection water lead to low production rate, high water cut, big flooding difference and low sweep efficiency.

To reduce water channeling, the Microbial Enhanced Oil Recovery (MEOR) test was initialed in Fuyu oilfield, China, in 1992. A microorganism named CJF-002 fed on nutrient was discovered as huff-puff test from 1996~2001. To replace the nutrient with high cost, a new nutrient was developed, using cornstarch as main raw material from 2002~2004. Furthermore, multi-slug microbial flooding was conducted at 22 injection-production well groups in 2005. The cell count of CJF-002 was more than 10^7cells/ml, and injection pressure less than 10MPa. The concentration of CJF-002 and crude oil composition in the sample was analyzed in laboratory before and after MEOR. Moreover, injection profiles monitoring and tracer tests were compared. Finally, the results of laboratory and tests were contrasted with well production performances.

The results observed microbial propagation under reservoir conditions with temperature 30°C and PH 7.5. The effect of injection profile modification was confirmed, which was helpful for plugging the high permeable zones and reducing water channeling. The agreement is obtained with the well production performances. Among them, 87.3% wells indicated a 50~100% oil production increase and an 8% water cut decrease. The water-drive laws curve shows the characteristic of drop, which means the improvement of development effect. The tests show that the composite indigenous microorganism oil displacement technology can enhance the oil yield of mature oilfield and recovery ratio, and it is an effective stimulation measures.

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