Bacteria could make oil extraction less disruptive to environment
More than a mile beneath Decatur, where temperatures reach 122 degrees and no light penetrates, lives a community of bacteria happily munching on iron and other geological delicacies.
The bacteria, known as Halomonas, thrive in extreme conditions — little oxygen, few nutrients, very salty water and enormous pressures that would kill most other organisms. And they only reproduce once every 100,000 years or so.
Halomonas bacteria have been found in deep sea trenches and the Great Salt Lake, and one of their most interesting traits is that they metabolize hydrocarbons — essentially, they eat oil.
Their presence in the porous sandstone formations of the Illinois Basin could help scientists find new ways to extract oil with less disruption to the environment, University of Illinois researchers report.
The study, published this month in the journal Environmental Microbiology, is the first to examine microbes at such depths in sandstone formations, where 60 percent of the world's oil reserves lie, said Yiran Dong, a UI postdoctoral researcher and lead author of the study. Only one other study plumbed those depths, at a gold mine in South Africa. But that was igneous rock, which is very different from sandstone and other types of sedimentary rock where oil, gas and drinking water is typically stored, said Bruce Fouke, UI professor of geology and microbiology and principal investigator on the study.
"We knew that there were organisms that could metabolize hydrocarbons, but no one knew if those organisms were present in sandstone, and in the kind of sandstone where you get reservoirs like the North Slope of Alaska," rich in oil and gas, Fouke said. "These are things I'd dreamt of and hoped for."
The majority of living things on Earth lie below the planet's surface — organisms that could hold the key to medical discoveries, evolution and potential life on other planets, Fouke said.
"We call it the deep subsurface biosphere," he said. "The greatest reservoir of life on Earth is in the subsurface. We know almost nothing about what's living down there.We drill oil and gas wells all the time. We drill holes to get water to drink. But almost nothing's been known of what the indigenous habitat is composed of and who's living down there."
The scientists examined underground microbial life at a well drilled near Decatur for an $82 million carbon sequestration project led by the Midwest Geological Sequestration Consortium and funded by the Department of Energy. The project has already injected 680,000 metric tons of carbon dioxide — a byproduct of ethanol production at Archer Daniels Midland Co. — 7,000 feet underground to test the effectiveness of carbon storage as a way to reduce greenhouse gases.
Fouke, an affiliate of the UI Institute for Genomic Biology, secured grant money from the UI Energy Biosciences Institute to use the well for his study.
He and his colleagues took water samples from the pores of a sandstone reservoir 1.1 miles deep — about 2,500 feet lower than the carbon sequestration zone.
The work was technically challenging and expensive, as it's difficult to obtain a clean sample from such depths, Dong said. They used a "Quicksilver" probe developed by the oil services company Schlumberger that greatly reduces contamination from mud and other microbes.
Dong and her colleagues then used new DNA technologies to understand what the bacteria there do and how they survive. Their analysis showed the bacteria can use iron and nitrogen to meet their dietary needs. (A relative, Halomonas titanicae, is actually consuming the iron superstructure of the Titanic.)
They also found evidence strongly suggesting the bacteria are capable of eating hydrocarbons and turning toxic oil byproducts into less harmful substances, she said.
Other Halomonas bacteria were used to help clean up the 1989 Exxon Valdez oil spill in Alaska and may be playing a role in the cleanup of the 2010 BP spill in the Gulf of Mexico.
Their oil-refining ability also could make it easier to extract oil that is now too thick to pump out of underground sandstone deposits, Dong said. Oil companies now use steam or chemicals to force it out. But the bacteria naturally break down the oil, making it lighter and easier to pump, with no chemical byproducts, thus reducing the environmental impact.
"Unconventional heavy oil is the big target," Fouke said. "There's great interest now in being able to harness the power of microbes to find oil and gas, to break down oil and gas in the subsurface and actually being able to refine it, and to be able to use the microbes that live down there to help us extract it."
The bacteria are like a "fingerprint" that could help the geologists and chemists pinpoint where to drill, he said.
The microbe's ability to consume iron could shed light on evolution in the early days of Earth before the emergence of photosynthesis, as well as potential life on other oxygen-deprived planets, Dong and Fouke said.
The study's results could also lead to new ways to approach human medicines, said Fouke, who is already working on a project with the Mayo Clinic to find potentially life-saving biochemistry in coral reefs.
Sallie Greenberg of the Illinois State Geological Survey said the study will also help scientists working on carbon sequestration better understand the subsurface environment, which is important "to ensure safe and viable storage activities."