Abstract

The microbial communities and diversities in production water from three high-temperature, water-flooded petroleum reservoirs in the same injection area of the Chenghai area of Dagang oil field in China and their recycled injection water sample were characterized by polymerase chain reaction denaturing gradient gel electrophoresis (PCR-DGGE) analysis. Results show that microbial sequences mainly belonged to the divisions Proteobacteria, Bacteroidetes, Spirochaetes,Firmicutes and Euryarchaeota. Many mesophilic and thermophilic microorganisms were found in samples of produced water and injection water. Thermoanaerobcter,Desulfotomaculum, Methanolinea, Methanomethylovorans and Geoglobus were detected in all samples. Mesophilic microorganisms found in the samples of produced water, mainly belonged to Brevundimonas, Agrobacterium,Pseudomonas, Sphingomonas, Acinetobacte, Dechloromonas, Clostridium andMethanobacterium. All of them were detected in the injection water samples, exceptBrevundimonas and Methanobacterium, which indicates that injection exploration may be the main reason why mesophilic bacteria  was detected in high-temperature petroleum reservoirs of Dagang. Results suggest that reinjection of water not only introduces enormous mesophilic microbe into high-temperature petroleum reservoirs, but also cause thermophilic microorganisms cross-contamination among wells in the same injection area.

Key words: Petroleum reservoir, recycled injection water, DGGE, microbial community, cross-contamination.