Dynamic Changes in Microbial Communities in Oil Reservoirs Under a Long-Term Bio-Chemical Flooding Operation

Area of Science:

• Microbial Ecology
• Petroleum Geochemistry
• Environmental Science

Background:

• Subsurface oil reservoirs undergo extensive water and chemical injection for enhanced oil recovery (EOR).
• Limited understanding exists regarding the long-term effects of these injections on microbial community dynamics within reservoirs.

Purpose of the Study:

• To investigate the dynamic changes in microbial communities and their functions in an oil reservoir under long-term bio-chemical flooding.
• To assess the impact of over three years of continuous bio-chemical flooding on reservoir microbial ecology.

Main Methods:

• Utilized 16S rRNA sequencing from cDNA to analyze microbial community composition and diversity.
• Conducted chemical analysis of reservoir samples.
• Monitored changes over a period of three years and five months in the Daqing Oilfield.

Main Results:

• Observed significant dynamic shifts in microbial composition and diversity throughout the flooding period.
• Documented alterations in the dominant bacterial community structure and a decrease in methanogenic archaeal abundance.
• Found that bacterial metabolic functions remained relatively stable, while archaeal functions exhibited notable changes.

Conclusions:

• Long-term bio-chemical flooding interventions cause significant dynamic changes in the oil reservoir's microbial community and its functional profile.
• These findings enhance understanding of how injected water and chemicals impact reservoir microbes and their roles in flooding processes.