Storing Carbon Dioxide in Fracked Shale Formations

Scientists estimate that about 10 to 18 gigatonnes of carbon dioxide could be stored in the Marcellus formation alone after the extraction of methane gas. The US has several other large shale formations that could provide additional storage.

They apply their model to the Marcellus Shale geological formation in Pennsylvania and find that the fractured rock has the potential to store roughly 50 percent of the US carbon dioxide emissions produced from stationary sources between 2018 and 2030.

Andres Clarens, an assistant professor of civil and environmental engineering at University of Virginia's School of Engineering and Applied Science, and graduate student Zhiyuan Tao report their findings in Environmental Science and Technology.

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They base their model on historical and projected methane production, along with published data and models for estimating the carbon dioxide capacity of the formations.

Clarens says that production records are available for how much methane gas producers have already extracted from the Marcellus Shale, as well as estimates of how much more they expect to extract. That provides a basis for determining how much space will be left in the formation when the methane is gone, he says. Clarens says gas would be adsorbed into the pores of the shale and held securely.

"This would be a way of eating our cake and having it too," Clarens says. "We can drill the shale, pump out the gas, and pump in the carbon dioxide. I think this will get policymakers' attention."

He says his work deals with the chemical feasibility of the idea, and that additional studies must be performed to examine the economical, political, and logistical implications.

"My field is carbon management-high-pressure carbon dioxide chemistry," he says. "Right now, we are emitting huge levels of carbon dioxide, and we need new ideas on ways to store the waste."

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Clarens, who says he has no connection with the oil and gas industry, knows some in the environmental movement oppose hydraulic fracturing because of possible risks to ground and surface waters. However, he thinks this type of extraction is inevitable in many places and it is important to preemptively develop new strategies for handling the environmental implications, especially those related to carbon dioxide.

"There are a lot of people who say we need to get away from carbon-based fuels, and that may be possible in a few decades, but right now, fossil fuels power everything," he says. "Finding ways to harvest these non-conventional fossil fuel sources without contributing to climate changes is a difficult but important challenge."

By. Matt Kelly