New 'lab on a chip' could accelerate carbon storage efforts

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Scientists at Stanford University have developed a new solution to the challenge of ensuring that when carbon dioxide (CO .)₂) is injected underground, it really stays still.

For decades, climate models have predicted that extreme heat waves like those experienced by millions of people this summer will become much more common at the level of planetary warming gases now in Earth’s atmosphere. As emissions and temperatures continue to rise, there is a growing scientific consensus that countries need to actively remove and manage CO₂ for the world to avoid warming beyond the 1.5 degree Celsius threshold above pre-industrial levels.

One widely studied method of keeping carbon removed from the atmosphere over the long term involves injecting CO₂ into rock formations deep underground. But there are still questions to be resolved.

Minerals dissolve in a 3 mm square sample of Marcellus shale during acid injection. Dynamic flow and reactive transport experiments were performed using the fluorescent microscopy technique, which allows clear images to be taken every 100 microseconds. Credit: Ling et al. 2022, Proceedings of the National Academy of Sciences / Stanford University

“Injection of carbon dioxide into storage formations can cause complex geochemical reactions, some of which can cause dramatic structural changes in rock that are difficult to predict,” said Ilenia Battiato, the study’s principal investigator and assistant professor of energy resources engineering in the School of Earth Sciences, Energy. & Stanford Environment (Stanford Earth).

Chain reaction

Earth scientists for years have simulated fluid flow, reactions, and rock mechanics to try to predict how CO . injection will occur₂ or other fluids will affect certain rock formations.

Existing models, however, do not reliably predict the full interactions and consequences of geochemical reactions, which often result in tighter seals by effectively connecting pathways with dissolved minerals—but can also cause cracks and wormholes that allow buried carbon dioxide to affect drinking water. or escape into the atmosphere, where it will contribute to climate change. “These reactions are everywhere. We need to understand them because they control the effectiveness of the seal,” said Battiato.

One of the main modeling challenges centers on the vast timescales and spatial scales over which the interaction processes unfold simultaneously underground. Some reactions fail in less than a second, while others continue for months or even years. As the reaction progresses, the mixture develops and the concentration of various minerals in each particular rock patch, and changes in the geometry and chemistry of the rock surface, affect the fluid chemistry, which in turn affects fractures and possible leak paths.

Lab on a chip

New solution, explained August 1 at Proceedings of the National Academy of Sciences, using a microfluidic device, or what scientists often refer to as a “laboratory on a chip.” In this case, the researchers call it “rock on chip”, because the technology involves embedding a small piece of shale rock into a microfluidic cell.

To demonstrate their device, the researchers used eight rock samples taken from the Marcellus shale in West Virginia and the Wolfcamp shale in Texas. They cut and polish rock chips into pieces no larger than a few grains of sand, each containing varying amounts and compositions of reactive carbonate minerals. The researchers placed the samples into a polymer chamber sealed in glass, with two small holes left open for injection of the acid solution. High-speed cameras and microscopes allow them to observe step by step how chemical reactions cause individual mineral grains in the sample to dissolve and rearrange.

Miniature research ideas that once required large laboratories cut across Earth science, biomedicine, chemistry, and other fields, said study co-author Anthony R. Kovscek, Keleen and Carlton Beal Professors at Stanford Earth and senior fellow at Stanford’s Precourt Institute for Energy. “If you can see it, you can describe it better. These observations have a direct relationship to our ability to assess and optimize designs for safety,” he said. Today, Kovscek says geologists at the drill site can examine rock under a microscope, but no current technology comes close to the level of detail that is possible with this new device: “There’s nothing like this to actually see how grain shape changes.” .”

Optimize for security

Improving reactive transport models is an increasingly pressing issue, given the role carbon removal plays in government plans to tackle climate change and hundreds of millions of dollars now flowing into nascent technology from private investors. Existing projects to remove CO₂ directly from the atmosphere operates only at pilot scale. Those capturing emissions at source are more common, with more than 100 projects under construction worldwide and the US government now preparing to spend $8.2 billion through a bipartisan infrastructure bill for carbon capture and storage from industrial facilities.

Not all carbon storage plans involve burying carbon underground. However, those involving geological storage can be helped and possibly made more stable and secure with the new Stanford technology. “Researchers need to incorporate this knowledge into their models to make good predictions about what will happen after you inject CO2.₂to make sure it stays there and doesn’t do weird things,” Battiato said.

Going forward, Battiato and colleagues plan to use the same platform to study geochemical reactions triggered by the injection of wastewater from oil production, desalination plants, or industry, as well as hydrogen, which is part of the US and EU plans to cut emissions by 2050. underground hydrogen is often touted as a promising solution to the formidable and persistent challenge of ensuring safe storage of highly flammable gas on a large scale, testing it even on a pilot scale will require better screening tools and an understanding of biogeochemical reactions .

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Reactions that store carbon underground can cause cracks, which is good news

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Further information:
Investigating multiscale dissolution dynamics in natural rocks through microfluidics and compositional analysis, Proceedings of the National Academy of Sciences2022. doi.org/10.1073/pnas.2122520119

Provided by Stanford University

Quote: New ‘Lab on a chip’ could accelerate carbon storage efforts (2022, 2 August) retrieved 2 August 2022 from https://phys.org/news/2022-08-lab-chip-carbon-storage-efforts.html

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