Breaking down the bubbly: Micromodels redefine how bubbles characterize CO2 gas flow

March 21, 2013
Micromodels redefine how bubbles characterize CO2 gas flow
No, it's not a Lego: This Lab-on-a-Chip micromodel (left) was designed to mimic the pore structure and permeability of Mt. Simon sandstone. Unlike conventional studies using only X-ray tomography, which is limited to determining pore structure, EMSL’s model pore system, with controlled geometry and enhanced visibility, can incorporate fluorescence microscopy to study CO2 bubble formation with high-impact details, such as showing exsolved CO2 gas mobility (right), providing a new view of critical gas saturation during geological CO2 sequestration.

One of the most noteworthy concerns for the U.S. Department of Energy is controlling atmospheric carbon dioxide to mitigate its effects on global climate and, in turn, energy consumption. Geological formations, such as the Mt. Simon Sandstone Reservoir in the Illinois basin, offer potential storage for captured CO2—the challenge is knowing that, once packed in saline aquifers or depleted oil and gas fields, the CO2 will stay there. Using EMSL's Microfabrication and Subsurface Flow and Transport capabilities, as well as fluorescence microscopy and image analysis, scientists crafted a micromodel in a silicon wafer to mimic Mt. Simon sandstone's low-permeability pore structure.

The unique pore-scale model can be operated in supercritical conditions, allowing flow properties of exsolved, or separated, CO2 and carbonated water to be observed during depressurization in reservoir pressure and temperature conditions (9 MPa and 45°C, respectively)—not unlike when, upon opening, CO2 (and potentially H2O) escape from a soda bottle. The work showed how interfacial tension and pore geometry affect bubble formation, morphology, and mobility as CO2 exsolves into gas. Contrary to existing definitions of critical gas saturation—the onset of gas production—bubbles formed long before gas flow was detected downstream in the micromodel. At this newly defined minimum , a snap-off mechanism produced mobile gas bubbles along the model's water flow paths, transporting the dispersed exsolved gas and leading to intermittent gas flow. The mobile bubbles do not interact very well, blocking water flow and repressing a mobile gas phase. With such low permeability and the flow barrier created from exsolved CO2, geological CO2 sequestration may prove a viable, potentially favorable, storage option. Moreover, this research could evolve to examine how CO2 may or may not enhance oil recovery methods currently used by the oil and gas industry.

To learn more about the work being done analyzing CO2 bubbles and geological sequestration at EMSL, check out "User Spotlight: The Escape Potential of CO2" at

Explore further: Ohio CO2 sequestration test well completed

More information: Zuo, L. et al. 2013. Micromodel Investigations of CO2 Exsolution from Carbonated Water in Sedimentary Rocks. Advances in Water Resources 53:188-197. DOI: 10.1016/j.advwatres.2012.11.004.

Related Stories

Carbon study could help reduce harmful emissions

February 14, 2008

Earth scientists at The University of Manchester have found that carbon dioxide has been naturally stored for more than a million years in several gas fields in the Colorado Plateau and Rocky Mountains of the United States.

Study tracks safety of underground CO2 storage

December 13, 2011

( -- In a paper published today in the Proceedings of the National Academy of Sciences, an international team of geoscientists, including Simon Fraser University groundwater expert Dirk Kirste, ...

Use of microfluidic chips a first in bitumen-gas analysis

February 29, 2012

A University of Toronto research team has developed a process to analyze the behavior of bitumen in reservoirs using a microfluidic chip, a tool commonly associated with the field of medical diagnostics. The process may reduce ...

Effect of CO2 on the integrity of well cement examined

March 5, 2013

Geologic carbon storage is the separation and capture of carbon dioxide (CO2) from large stationary sources, such as power plants, followed by injection into deep geologic formations. Long-term storage of CO2 pre-supposes ...

Recommended for you

Test racetrack dipole magnet produces record 16 tesla field

November 30, 2015

A new world record has been broken by the CERN magnet group when their racetrack test magnet produced a 16.2 tesla (16.2T) peak field – nearly twice that produced by the current LHC dipoles and the highest ever for a dipole ...

Turbulence in bacterial cultures

November 30, 2015

Turbulent flows surround us, from complex cloud formations to rapidly flowing rivers. Populations of motile bacteria in liquid media can also exhibit patterns of collective motion that resemble turbulent flows, provided the ...

CERN collides heavy nuclei at new record high energy

November 25, 2015

The world's most powerful accelerator, the 27 km long Large Hadron Collider (LHC) operating at CERN in Geneva established collisions between lead nuclei, this morning, at the highest energies ever. The LHC has been colliding ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.