Microbial Diversity in High-Temperature Heavy Oil Reservoirs

Abstract

The microbial community in oil reservoirs plays important roles in carbon, sulfur, and nitrogen cycling. We identified the microbial composition, abundance, and diversity in two heavy oil wells (W1 and W2) located at Liaohe oilfield, China, that were flooded with higher temperatures, forming a decreasing gradient-temperature field (DGTF) from the steam chamber to the original surrounding formation. The two wells were connected to each other at a depth of 650 m and with temperatures of 249 °C (W1) and 259 °C (W2) in the steam chamber. Water and oil samples were collected from both wells, and 16S rRNA genes were sequenced using Illumina MiSeq (Illumina, San Diego, CA). The number of operational taxonomic units (OTUs) was 5499 and 5938 for W1 and W2, respectively, at 97% clustering. In both wells, the dominant bacterial phylum was Proteobacteria. Euryarchaeota and Crenarchaeota were the only two archaeal phyla detected. Terrimonas and Fluviicola were more abundant in the water sample W1–W, whereas Thermomonas, Nitrosomonas, and Sphingobacterium were more abundant in the oil sample W2-O. Aquificae was the only phylum detected in these wells that had not been detected in other oilfields. Excluding exogenous contamination, the results of this study showed abundant in-situ microbial diversity. The heavy oil reservoir has a large DGTF in higher temperature heavy oil reservoirs, potentially affecting the inner environment.

Keywords:

• Heavy oil reservoir
• high temperature
• SAGD
• microbial diversity
• indigenous microorganism

Acknowledgments

The authors are grateful to Ning Hong, Wu-Yang Sun, Weiguo Hou, and Shang Wang for their help in laboratory experiments. The authors would like to thank Dr Yong Guo, Jianping Yang, and Hongyuan Wang for their valuable discussion and suggestions.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This work was financially supported by the National Natural Science Foundation of China [41373086 and 41373126], National Science and Technology Major Project [Nos. 2016ZX05050011 and, 2016ZX05040002], New Century Excellent Talent Supporting Project by MOE [NCET-09-0765], and Excellent Talent Fund of China University of Petroleum-Beijing [KYJJ2012-01-10].