Geoscientist Ruben Juanes takes the notion of “trickle down” farther than most — thousands of meters farther.

Juanes, ARCO associate professor of energy studies, looks at how fluids interact in out-of-the-way places in the earth’s crust where excess carbon dioxide (CO2) might be stowed and untapped oil reserves lurk. Less viscous fluids, he has found, percolate through thicker ones in “viscous fingers” that look like tentacles or drips on the side of a paint can. Juanes explores how these fingers, with the help of gravity, migrate through porous solids. His work is primarily funded by the U.S. Department of Energy and
Eni SpA.

When CO2 dissolves in water, the density of water increases. This seemingly innocuous phenomenon has profound implications for geologic carbon sequestration, in which compressed CO2 is injected in deep porous layers filled with brine. As a result, a configuration with heavy fluid on top leads to an instability that can increase storage capacity of underground reservoirs by a factor of five or more, providing “a huge advantage” in sequestering CO2 to prevent it from contributing to global warming, he says. “Once CO2 is in water, you’ve won the game.”

Knowing how fast CO2 will dissolve in water and how likely it is to leak through an underground fault or to reach an outcrop are key bits of information for engineers. Juanes’ research team has already measured the CO2 capacity for the most promising geological basins in the U.S. and is about to embark on an international project with far-reaching significance. In Abu Dhabi, Juanes will lead a multi-institution collaboration to sequester CO2 on an ambitious scale. “This is a world-class project that could really influence the prospects of sequestration in the Middle East and worldwide,” he says.

Juanes’ work also has implications for the oil industry. To extract viscous crude oil the consistency of honey from porous rock, engineers have typically injected steam into crevices to increase the oil’s temperature and flow. This is energy-intensive, expensive and not always feasible. Juanes has studied the process of “viscous fingering,” which takes place when fluids less viscous than oil are introduced. “With viscous fingering, the two fluids mix more rapidly,” he says. This process allows the oil itself to become less viscous and easier to extract, potentially facilitating the recovery of a whole new energy source. So-called heavy oil “has the potential to shift the geopolitics of oil to areas such as Canada, the U.S., and South America, areas not typically perceived as the biggest oil producers,” he says.

“Addressing these very large-scale problems with important societal ramifications, such as access to energy and striking a balance between energy and the environment, really relies on understanding the fluid dynamics that control these processes at a much smaller scale,” he says.

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