Study on Enhancing Oil Recovery by Indigenous Microorganisms in a Heavy Oil Reservoir

The feasibility of enhancing oil recovery in Xinjiang oilfield with heavy oil reservoir was studied. The results showed that main microbial populations in the reservoir were saprophytic, hydrocarbon-oxidizing, nitrate-reducing bacteria, sulfate-reducing bacteria, and fermentative. Given optimized carbon and nitrogen sources, the indigenous microorganisms generated gases, which mostly were CO2, and amount of gases could reach 1.3 times volume as nutrient solution. The effect of MEOR was evaluated by a sand pack experiment, and the oil recovery was 9.5%. The test with the injection of nutrient and air was carried out. Field performance monitoring and product ion tracking results showed: (1)the indigenous microorganisms were activated with the number increased 2-3, and microbial population structure changed apparently; (2)The content of CO2 and CH4 in the gas of oil well changed slightly; (3)the properties formation water were changed, the content of HCO3- in formation water varied greatly, and emulsion were found. (4)Although Indigenous Microbial Flooding Technology may be a potential technique for the development of oilfields, that biogas generated by microbes is not the primary mechanism of Indigenous Microbial Flooding Technology is determined.