Sulfide-producing bacteria dominate hydraulically fractured oil, gas wells

ScienceDaily | 7/5/2017 | Staff
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"This is a pretty inhospitable environment of high pressure, salinity and temperature some 2,000 meters underground. You'd think that microbes introduced during the fracturing process would die, but some of them make a good life for themselves," says Mike Wilkins, an environmental microbiologist at The Ohio State University in Columbus and senior researcher on the study. "The industry spends a fair amount of money trying to keep microbes out of these systems."

Hydraulic fracturing, also known as "fracking," involves the high-pressure injection of water, sand, and chemicals into shale formations to create fracture networks that release oil and gas, which are pumped back to the surface and recovered. Practiced for only the last decade, not much is known about the microbial ecosystems in the fracture networks.

Microbes - Problems - Operations - Hydrogen - Sulfide

Sulfide-producing microbes cause multiple problems for drilling operations. Hydrogen sulfide can "sour" a well and must be separated from oil and gas in an expensive process. Sulfides can be toxic to the workers on the drilling pad and can also corrosively degrade metal pipelines. The microbes themselves can gum up the extraction process by filling in the tiny fractures with either biomass or excreted precipitates.

Wilkins' team had previously found that one bacterial family in particular, Halanaerobium, dominated fractured well ecosystems. These bacteria can convert thiosulfates found in the environment to sulfide. The team, along with collaborators at West Virginia University and Pacific Northwest National Lab, decided to track sulfur cycling catalyzed by the microbial community found in a Utica shale formation well near Flushing, Ohio.

Well - Fluids - Fractures - Months - Way

"The well continually pulls up fluids that have been sitting in the fractures for months, so it's a good way to get a chemical and biological look at what's going on down there," says Wilkins. His...
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