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

## TL;DR

This study tracks how microbial communities in oil reservoirs change over three years of bio-chemical flooding, revealing shifts in dominant species and functions.

## Contribution

The study provides new insights into long-term microbial community dynamics in oil reservoirs under bio-chemical flooding.

## Key findings

- Microbial composition and diversity in oil reservoirs changed dynamically during long-term bio-chemical flooding.
- Dominant bacterial community structure altered, with reduced methanogenic archaeal abundance.
- Bacterial metabolic functions remained stable, while archaeal functions changed significantly.

## Abstract

Huge amounts of water and chemicals have been injected into subsurface oil reservoirs in secondary and tertiary oil recovery processes. Although the effects of injected water and chemicals on microbial communities have been investigated, knowledge about their long-term dynamic changes in oil reservoirs remains limited. To address this gap, we used 16S rRNA sequencing from cDNA and chemical analysis to track the dynamic changes in microbial communities in oil reservoirs under a long-term flooding operation over three years and five months using bio-chemical flooding in the Daqing Oilfield, China. Researchers observed dynamic changes in microbial composition and diversity during the flooding process. Long-term bio-chemical drainage leads to alterations in dominant bacterial community structure, with a decrease in methanogenic archaeal abundance. Bacterial metabolic functions remained stable, but archaeal functions changed notably. Our results indicate that the microbial community and its functions in the oil reservoirs have experienced significant dynamic changes under the long-term flooding intervention of bio-chemical flooding, which opens up a new window for further understanding the impact of injected water and chemicals on microbial community in oil reservoirs and expands our knowledge about the role of microbial community changes in reservoirs under the flooding process.