Looking good: initial results published on research to de-risk offshore oil and gas exploration

Published: December 11th 2020

Specialized microbes, that don’t require oxygen, have been discovered feeding on hydrocarbons seeping from underlying geology in the deep sediments of the Scotian Slope, in Nova Scotia’s offshore.

As well, microbial communities – diverse groups of microorganisms that inhabit a common living space – in the examined sediments have been shown to vary according to the type of available energy or food sources found at different depths.

These findings by a multi-disciplinary project team, supported by Genome Atlantic and Genome Alberta, have stirred excitement that the group is on the right track. Currently they are on a three-year $6.5 million mission, funded, in part, by Genome Canada’s Genomics Applications Partnership Program, to help reduce the financial risk of offshore oil and gas exploration. They are using microbial genomics – the study and identification of bacteria via their DNA – in an attempt to characterize the nature of petroleum deposits close to seeps in the seabed.

Their initial discoveries, published Nov. 17, 2020, in Nature Communications, a peer-reviewed, open access scientific journal, are expected to help bring the group closer to its goal of developing genomics tools – bioassays – for identifying different types of bacteria associated with deep water seeps. It is believed the presence of these bacteria can help describe the nature of petroleum deposits below. The information could reduce the costs of commercial offshore exploration by adding extra layers of mapping information to reduce the likelihood of drilling a dry hole.

As a result of the findings, Dr. Jayne Rattray, a member of the project team from the University of Calgary‘s Geomicrobiology Group and one of 17 co-authors of the published study, said they are now honing in “with more intensity” on the anaerobic bacteria (the bacteria breathing without oxygen) they identified. Since these anaerobes are known to degrade crude oil, she said, “they may represent biomarkers for thermogenic hydrocarbons.” Most recoverable oil and gas from sedimentary basins come from thermogenic hydrocarbons, the result of the thermal breakdown of organic matter at high temperature and pressure in the deep subsurface.

Dr. Rattray explained, “Due to their inaccessibility, little is known about the microorganisms inhabiting deep water marine sediments and how they manage to survive in what is termed by scientists as ‘the earth’s deep biosphere.’ ”

The published study is based on data analysis done on 3.4 meters of marine sediment obtained by piston coring the seabed at more than 2,300 meters in water depth in the Scotian Slope, an area at the edge of the Scotian shelf, which covers 120,000 square kilometers, south west of Nova Scotia.

The sediment retrieval work and detailed geochemical analysis was done under the guidance of Adam MacDonald, Director of Petroleum Resources, with the Nova Scotia Department of Energy and Mines, while the application of genomics to track the presence of marine bacteria associated with hydrocarbons was performed by University of Calgary microbiologists, led by Dr. Casey Hubert.

The site was chosen because of its status as a newly discovered cold seep, said Dr. Rattray. In oil and gas exploration, seeps often point to the presence of hydrocarbon deposits. Cold seeps are also known to host a wide array of microorganisms and ecological systems, but how they sustain themselves and what their distributions are, relative to the available hydrocarbons and other nutrients, are unknown.

An innovative combination of geophysical, geochemical, metagenomic and metabolomic expertise was employed in the study. Dr. Rattray said, “metagenomic profiling, a method using genetic material to identify the microorganisms present and their capabilities, was used to show that the microbial community – bacteria and archaea- was structured differently depending on the depth of the sediment analyzed. By comparing the results of the metagenomic analysis with metabolomics data – a method to determine which chemicals are present as substrates or intermediate energy sources – it was found that various microbial community members were actively able to use deeply-sourced thermogenic hydrocarbons for food, without the need for oxygen.”

She added, “The overall findings of the study connect subseafloor microorganisms and the feeding patterns they use, and uncover some surprising new ways that organisms eat hydrocarbons seeping up from deep below.”

Ten of the study’s 17 co-authors are with the Department of Biological Sciences, University of Calgary. Besides Dr. Rattray, they include Drs. Casey Hubert, Anirban Chakraborty, Oyeboade Adebayo, Ryan Groves, Ian Lewis and Xiyang Dong (also with the School of Marine Sciences, Sun Yat-Sen University), along with molecular microbiologist Carmen Li, and undergraduate students Stuart Matthews, and Scott Wang. The other authors are Dr. D. Calvin Campbell, Geological Survey of Canada-Atlantic; Jamie Webb and Martin Fowler, Applied Petroleum Technology (Canada); Natasha Morrison and Adam MacDonald, Nova Scotia Department of Energy and Mines; Dr. Chris Greening, School of Biological Sciences, Monash University, Australia; and Dr. Daisuke Mayumi, Institute for Geo-Resources and Environment, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology, Japan.

The project partners are Genome Atlantic, Genome Alberta, Genome Canada, the Nova Scotia Department of Energy and Mines, the Geological Survey of Canada, Natural Resources Canada, Research Nova Scotia, Nova Scotia Offshore Energy Research Association, Mitacs Canada, Applied Petroleum Technology, the University of Calgary and Saint Mary’s University.