Study shows how to produce natural gas while storing carbon dioxide

UT study shows how to produce natural gas while storing carbon dioxide
Gas hydrates, shown here on the Gulf of Mexico floor, are an ice-like material that form naturally under extreme pressure in low temperature environments where water is abundant. A new study from The University of Texas at Austin has shown that hydrates under the Gulf floor can be tapped for energy while providing safe storage for greenhouse gas emissions. Credit: NOAA

New research at The University of Texas at Austin shows that injecting air and carbon dioxide into methane ice deposits buried beneath the Gulf of Mexico could unlock vast natural gas energy resources while helping fight climate change by trapping the carbon dioxide underground.

The study, published June 27 in the journal Water Resources Research, used computer models to simulate what happens when mixtures of dioxide and air are injected into deposits of methane hydrate, an ice-like, water-rich chemical compound that forms naturally in high-pressure, low-temperature environments, such as deep in the Gulf of Mexico and under Arctic permafrost.

Lead author Kris Darnell, a recent doctoral graduate from the UT Jackson School of Geosciences, said the research is the next step in solving two significant global challenges: and carbon storage.

"Our study shows that you can store carbon dioxide in hydrates and produce energy at the same time," said Darnell, whose research was funded by the University of Texas Institute for Geophysics (UTIG).

In the process, the nitrogen in the injected air sweeps the methane toward a production well and allows carbon dioxide to take its place, researchers said. The beauty of this approach is that it extracts natural gas from methane hydrate deposits and at the same time stores carbon dioxide, a , in a deep environment where it is unlikely to be released into the atmosphere where it could contribute to climate change.

This is not the first time that hydrate deposits have been proposed for carbon dioxide storage. Earlier attempts either failed or produced lackluster results. The new study breaks down the physics behind the process to reveal why previous attempts failed and how to get it right.

The next step, said Darnell, is to test their findings in a lab. The Jackson School and the UT Hildebrand Department of Petroleum and Geosystems Engineering are currently testing the method in a specialized facility in the Jackson School, which is one of the few in the world that can store and test methane hydrate. This work is being led by Peter Flemings, a Jackson School professor and senior UTIG research scientist, and David DiCarlo, a professor in the Hildebrand Department. Both are co-authors on the paper.

UT study shows how to produce natural gas while storing carbon dioxide
The study's lead author, Kris Darnell, at the University of Texas Pressure Core Center in the Jackson School of Geosciences, the only university-based facility that can study methane hydrate cores under pressure. The lab allows researchers to study methane hydrate under the same environmental conditions in which they are found. Credit: University of Texas Institute for Geophysics

"Two things are really cool. First, we can produce to generate energy and sequester CO2," said Flemings. "Second, by swapping the methane hydrate with CO2 hydrate, we disturb the (geologic) formation less, lowering the environmental impact, and we make the process energetically more efficient."

If the process can be shown to work in the field on an industrial scale, it has enormous potential.

Methane hydrate is one of a group of chemical compounds known as gas hydrates in which gas molecules become trapped inside cages of water ice molecules rather than chemically bonding with them. UT and the U.S. Department of Energy (DOE) are working together to study naturally forming methane hydrates with the aim of figuring out their potential as an energy resource. This is important because estimates suggest that methane harvested from hydrate deposits found beneath the Gulf of Mexico alone could power the country for hundreds of years.

In the paper, the authors showed that a process in which one type of molecule trapped in hydrate is exchanged for another (called guest molecule exchange) is a two-stage process and not a single, simultaneous process, as it was previously thought to be.

First, nitrogen breaks down the methane hydrate. Second, the carbon dioxide crystalizes into a slow-moving wave of carbon dioxide behind the escaping gas.

The computer simulations indicate that the process can be repeated with increasing concentrations of carbon dioxide until the reservoir becomes saturated. The authors said that unlike some methods of carbon storage, this provides a ready incentive for industry to begin storing , a major driver of climate change.

"We're now openly inviting the entire scientific community to go out and use what we're learning to move the ball forward," Flemings said.


Explore further

Energy Department seeks methane hydrate proposals

More information: K.N. Darnell et al, Nitrogen-Driven Chromatographic Separation During Gas Injection into Hydrate-Bearing Sediments, Water Resources Research (2019). DOI: 10.1029/2018WR023414
Journal information: Water Resources Research

Citation: Study shows how to produce natural gas while storing carbon dioxide (2019, June 27) retrieved 24 August 2019 from https://phys.org/news/2019-06-natural-gas-carbon-dioxide.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
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Jun 27, 2019
Stop fracking the Earth! The future is renewables.

Jun 27, 2019
Overall, net zero in terms of carbon sequestration, net plus for energy. This will of course require that the wells be capped when the reservoirs are fully tapped.

This isn't a solution for AGCC, but it's a very good delaying tactic.

My wife pointed out that this makes jobs for extraction technology workers, and then I pointed out to her that these technology workers' skills will be needed for asteroid mining. Overall I think this is a minor win, but time will tell.

Jun 27, 2019
Thinking about this a little more I am astonished that the geologists did not already know this, but it seems they were monofocused on petroleum. There should be some red faces out there among these people.

estimates suggest that methane harvested from hydrate deposits found beneath the Gulf of Mexico alone could power the country for hundreds of years.


Why are we not harvesting this ecologically neutral resource right now? Why pay Saudi Arabia, Iran, and Russia for the energy we can get from the Gulf of Mexico on our doorstep? Lots of people look stupid on this one. Sequestering CO2 is the cherry on top. Maybe even the nuts and whipped cream.

Jun 27, 2019
Now, all of that said this is 10 years off for initial implementation, and 20 to 40 years off for wide adoption. And this is right up against the scary timelines for AGCC. But this is one of those times where I think every little bit helps.

Jun 28, 2019
Now, all of that said this is 10 years off for initial implementation, and 20 to 40 years off for wide adoption. And this is right up against the scary timelines for AGCC. But this is one of those times where I think every little bit helps.

It doesn't look like the kind of SF technology that would require that much time to implement. In the end it's about "drilling" the oceans (not deep in the ocean bottom). How hard could that be?

Jun 28, 2019
Tokamaks were first made in the late 1960s. Fusion has been 10 years off ever since.

Jun 30, 2019
Does anyone really believe the extraction industry has the skills or the interest in undertaking such an endeavor and not continue to wreck havoc on the Gulf? We've only seen gross negligence thus far - why would this further intrusion into the deep waters of such a commercially important and environmentally sensitive water resource be treated with a modicum of concern for the environment. More folly as the clock continues to run against us.

Jun 30, 2019
Wonder if they have considered this documented fact:
https://phys.org/...ime.html

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