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Charles Werth Gives Plenary Talk at US DOE Basic Research Needs Workshop

February 2017

Induced seismicity and fracturing are among the challenges to large-scale carbon storage in the energy-water nexus, according to a presentation given by Professor Charles Werth at the “Basic research needs for the energy-water nexus: New approaches to ensure robust and secure energy and water systems workshop.” Werth, leader of the Geochemical Reactions Theme and a professor at the University of Texas-Austin (UTA), highlighted approaches that he and GSCO2 colleagues are using to address these challenges and better understand how carbon dioxide (CO2) reacts with and flows in “geometrically and mineralogically complex systems.”

Werth and graduate student Samantha Fuchs (UTA) evaluated the effects of surface mineralogy, surface charge, and surface roughness on the contact angle of supercritical CO2 in brine under reservoir conditions. They conducted experiments in collaboration with former graduate student Julien Botto (UTA), Assistant Geologist Jared Freiburg, Assistant Geochemist Peter Berger, and Professor Bruce Fouke (University of Illinois at Urbana-Champaign [UIUC]). The results of their work suggest that “surface roughness, not mineralogical heterogeneity, dominated supercritical CO2 contact angle results.”

Werth and Fuchs recently expanded this effort in a new collaboration with Assistant Professors Ange-Therese Akono (UIUC) and Nicolas Espinoza (UTA). They are aging rock samples in supercritical CO2 and brine for up to 60 days and evaluating how changes in mineralogy and wettability during aging affect hardness and fracture toughness. Espinoza is a member of the Center for Frontiers of Subsurface Energy Security, one of the two other Energy Frontier Research Centers investigating challenges to carbon storage in the subsurface.

Over time, the combination of supercritical CO2 and brine can induce seismic activity by weakening the clays that bind larger sedimentary grains together, said Werth. “When CO2-saturated brine reacts with clay minerals, it weakens the rock, making it easier for the rock to slip among fractures already present.”

Geophysics Rock samples like the one shown above are aged in CO2-saturated brine at 2,900 psi and 140°F for 60 days. This allows the larger grains to be seen more clearly by eroding away clay present in the sample, according to Werth. The image on the left is before aging, and the image on the right is after aging. Photo Credit: Samantha Fuchs and Charles Werth, UTA.

To understand how fluid flows through pore space, Professor Albert Valocchi, who leads the Pore-Scale Pressure Transmission Theme, and post-doc Yu Chen (UIUC) are working with scientists at the National Energy Technology Laboratory (NETL) to create high-resolution, three-dimensional images of rock cores using X-ray computed tomography (CT). These images are used to create model pore networks, which can then be used to test and expand multiphase flow theory. In a recent effort, Valocchi, Chen, Werth, and Fuchs worked with Physical Scientist Angela Goodman, Research Engineer Dustin Crandall, and researcher John Tudek (NETL) to simulate CO2 contact angles obtained from CT images with those predicted from Lattice-Boltzmann modeling. Valocchi is also working with Professor Kenneth Christensen, post-docs Yaofa Li and Farzan Kazemifar, and Research Assistant Professor Gianluca Blois (University of Notre Dame) “to explore mechanisms controlling CO2 displacement of brine” in heterogeneous micromodel experiments.

Werth said that these different research efforts contribute to the bigger picture of reactive transport in porous media, and the basic science challenges being addressed are applicable to carbon storage, as well as other areas within the energy-water nexus. “The GSCO2 has brought together people with different expertise to focus on fundamental challenges,” he added. “The research of the Center can apply to many areas of energy resources in the subsurface.”

The full title of Professor Werth’s presentation was “Energy-water nexus challenges for subsurface resource extraction and storage.” The “Basic research needs for the energy-water nexus: New approaches to ensure robust and secure energy and water systems workshop” was sponsored by the US Department of Energy, Office of Science, and held in Bethesda, Maryland, on January 4–6, 2017.

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