Microorganisms that live in the depths of an oil reservoir can withstand such extreme conditions they can be used in harsh chemical processes. Norwegian researchers have been hard at work cataloguing these species with the use of DNA sequencing technologies.
Petroleum reservoirs that lie 2-3 kilometres beneath the seabed hold more than just oil and gas. These deep reservoirs are also home to micro-organisms that have lived in isolation for millions of years, ever since the process of converting organic matter to fossil fuels first began.
The organisms live in some of the most extreme conditions found on Earth, with temperatures as high as the boiling point of water, pressures that are more than 250 times atmospheric pressure, and an environment full of heavy metals and other toxic chemical compounds, without access to light and air. In other words, these microbes (bacteria and Archaea) are tough.
A place where time stands still
The relatives of these organisms once lived on Earth's surface. And because of the limitations imposed by the environment since they were buried, they have not evolved significantly. They have adapted, but even this has happened at an infinitely slow rate. They also propagate very slowly because they have so little access to important nutrients. Their doubling time, or the time a microbial cell needs to divide into two, can be many years.
"Time has basically stood still for these microorganisms, down in the dark," says Alexander Wentzel, a senior scientist at SINTEF.
"But there is a great deal of life down there in the oil, we have found many dozens of different microorganisms," says Anna Lewin, a researcher at the Norwegian University of Science and Technology's (NTNU) Department of Biotechnology. "Some are known from before, but others are new. One characteristic they share is that they are thermophilic, meaning that they love the heat. There are similar organisms in areas where there is volcanic activity, such as in geysers and black smokers."
Wentzel and Lewin and their partners at Statoil have made some startling discoveries since they began their research back in 2008. The microorganisms they have brought up from the black and gooey depths provide interesting answers to questions raised by basic research, and can also be used to improve chemical processes.
"The basic research aspect is interesting when you are looking at such an old and extreme environment. This information provides us a better understanding of what early life was like on Earth and the evolution that has taken place over millions of years," says Lewin. The researchers have thus far studied samples from different oil reservoirs on the Norwegian continental shelf.
"There is a big difference between the microbes that live down in oil reservoirs and the ones found on Earth's surface. But we see surprisingly little difference between the various oil reservoirs," says Lewin.
High temperature enzymes
The microorganisms found in oil reservoirs have a metabolism that is based on thermostable enzymes, which are enzymes that work well at high temperatures. These kinds of enzymes can be used to streamline various chemical processes because they can withstand high temperatures.
"Chemical processes are generally much faster at high temperatures. That means that these enzymes can help to streamline chemical processes, which can make them economically important. The market potential in industrial biotechnology alone is huge. For example, the enzymes could be used in processes involving biomass decomposition, such as wood to produce biofuels and other biorefinery products. The enzymes can help the process go much faster and make it more profitable," says Wentzel.
Another possible application would be in improving CO2 capture, because the enzymes can withstand the extreme temperature variations that are common during the CO2 capture process.
"But these are just two examples of the kinds of things we are looking at," says Wentzel. "The samples from the oil reservoir are a goldmine of enzymes for new and improved biotechnological processes in a whole range of different market segments. We hope that our research and technology can help Norwegian industry develop modern processes to increase our international competitiveness."
First in the world
This is the first time that someone has been able to obtain live samples from an oil reservoir and subject them to such a comprehensive study of microbial communities.
"Extracting these samples is a methodological challenge. The micro-organisms live under such high pressure that if the pressure drops quickly, they simply disintegrate," Wentzel says. "It's also extremely important to avoid contaminating the samples when you are collecting them. We avoid this by making sure the equipment and staff on the oil platform are optimally prepared.
The key was taking samples in special pressurized bottles that were connected directly to the pipes that typically transport oil and gas from the reservoir to the oil platform. During sampling, oil production from the platform had to be stopped.
"Stopping oil production is enormously costly, so that each sample we took is worth its weight in gold. Our close cooperation with Statoil is what has made this possible," says Wentzel.
The researchers are also the first in the world to have used metagenomics with these types of samples. This has given them the opportunity to study a whole community of micro-organisms taken from their natural environment with unprecedented reliability and detail.
The researchers are now working to get samples from several other oil reservoirs so they can confirm their hypotheses and continue their work on enzymes with industrial potential. They have published a number of scientific articles and book chapters about their research, most recently in Environmental Microbiology.
The above story is based on materials provided by The Norwegian University of Science and Technology (NTNU). Note: Materials may be edited for content and length.
- Anna Lewin, Jostein Johansen, Alexander Wentzel, Hans Kristian Kotlar, Finn Drabløs, Svein Valla. The microbial communities in two apparently physically separated deep subsurface oil reservoirs show extensive DNA sequence similarities. Environmental Microbiology, 2014; 16 (2): 545 DOI: 10.1111/1462-2920.12181
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