| Microbial enhanced oil recovery (MEOR), is a new method for EOR, which is still at its phase needing to be studied and tested. According to the screening standard adapted to MEOR, this technique has a great potential on enhancing oil recovery, especially efficient to reservoir of high-parraffin content or high-viscosity oil. Many researchers have studied and carried out field tests on MEOR, but it is not very clear about the choice of different microorganisms used in MEOR, the mechanism of MEOR, the growth, the reproduction of microorganisms and their movement in Porous Media. Also, the complete field test on MEOR is less than their laboratory study.Focusing on the keys of MEOR, a method of microbial token and mechanism for microbial oil displacement based on the system and the combination of modern apparatus analysis with chemical analysis in this paper has been established. Four microbial strains that can grow with hydrocarbon as the carbon source has been separated from Daqing oil field. This paper also has studied their bio-characteristics, their optimized conditions of growth and reproduction, their metabolizing regulation, and the composition of their metabolite. Lab and field test were carried through, and rational results were gained.The strain T01,T02 and T03 that has an approximate growth temperature can produce gas(carbon dioxide), acid(acetic acid mainly), and bio-surfactant (rhamnoilpid). With a matched proportion, they have been mixed, which was named SF67. Studies have been done on their compatibility, their symbiosis, and their capability of reproduction. The result showed that they have an excellent compatibility with each other.The mixed bacteria SF67 can degrade saturated hydrocarbon and aromatic hydrocarbon in crude oil, decreasing the paraffiin content and the viscosity of crude oil. Also, they can reduce the interfacial tension between oil and water and the acid value of crude oil. Micro-scale model displacement test showed that the mechanism that the microbial fermentation liquid started up the residual oil after water filooding was to peel off oil film, to change the wettability of porous media, and to emulsify and take off the oil. The analysis on wettability indicated that the contact angle can be reduced from 140°to 50°due to the metabolism of SF67.Core displacement shows that oil recovery can be improved 9.6% or 10% by using MEOR under the reservior condition of Fang-6 cone .The field test has been implemented on the microbial injection project, which had been optimized by numerical simulation according to the laboratory data and the geological property of Fang-6.In the MEOR field test, the injected bacteria have been found from the producing well, whose number was about 100 cells/ml, indicating SF67 can grow and move under the formation. The water cut has been decreased from 65.7% to 59.4%. Meanwhile, the incremental oil amount of each well is 0.8 tons/d. All the results show a good potential for MEOR.The screen and the study on microorganism used in FOR in this paper have built a strong base for the further research on MEOR. Moreover, the analysis on metabolite and metabolizing regulation of MEOR has extended anti of microorganisms and the understanding on mechanism enriched the MEOR theory.
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