Energy Institute Faculty Profile: Brian Ellis

Tuesday, January 10, 2017
Nick Soberal, Science Communication Fellow

Brian Ellis is an Assistant Professor of Civil and Environmental Engineering at the University of Michigan.  His lab studies topics at the intersection of geology and energy technology, focusing on the ways modern energy developments like hydraulic fracturing impact our underground environment. Ellis explores how water-rock interactions in the subsurface environment control the fate and transport of fluids in low-permeability fractured rocks. Special areas of interest to Ellis’ research group include geologic storage of carbon dioxide and resource extraction from unconventional oil and natural gas reservoirs.

When Princeton researcher Robert Socolow would discuss his seminal 2004 paper on climate change stabilization wedges, he often referred to the suggested portfolio of mitigation strategies as a “silver buckshot” approach to stabilizing atmospheric CO2 concentration, in contrast to the notion that there was one silver bullet approach that would address the increasingly urgent problem of climate change.

Brian Ellis, an Assistant Professor of Civil and Environmental Engineering, remembers this assessment from when he was pursuing his Ph.D. at Princeton and, while it is not the direct inspiration for his research, it does represent the niche that he believes his research fills. The Ellis lab conducts research that examines emerging subsurface energy technologies and water quality impacts from energy development activities.

Ellis’ lab models subsurface conditions by studying core samples from geologic reservoirs. They use a variety of imaging techniques, especially CT scans and scanning electron microscopy, to improve mathematical models for chemical reactions and the movement of chemical species underground. Included in these investigations are efforts to understand the role of energy resource-development activities, such as hydraulic fracturing- also known as fracking- in mobilizing metals and naturally-occurring radioactive elements deep underground. They also study the storage security of CO2 stored underground, one potential approach toward mitigating anthropogenic, or man-made, carbon emissions.

“My feeling is that if we, as a society or as researchers, want to move the ball forward and mitigate CO2 emissions to the atmosphere at a scale that matters,” Ellis said about carbon sequestration, “then I think geologic storage of CO2 has to be part of the mix.”

According to Ellis, the main challenges to large-scale carbon sequestration are cost and public acceptance. Currently available CO2 capture technology is expensive and long term storage security is an issue, especially with the threat of earthquakes and carbon dioxide plumes like the 1986 Lake Nyos eruption still present in people’s minds.

Ellis describes this as the NUMBY (Not Under My Backyard) effect, noting that people may not fully understand the processes involved in subsurface drilling or deep carbon injection, and that the public may accept or reject energy innovation without fully understanding its risks and benefits.

The risks of underground energy exploration in a given area aren’t always readily apparent. Leaking carbon dioxide into a freshwater aquifer produces carbonic acid. As Ellis describes it, carbon dioxide in water is not necessarily dangerous (this is, after all, what we consume when we drink a carbonated beverage). The problems arise later when the carbonic acid begins to alter the geochemistry of the underground environment. Carbonic acid can drive the pH of the soil from its natural levels of around 6.5 down to 3 or 4 - about the level of many soft drinks (which would rapidly damage your teeth if not for their protective enamel.)  Underground, carbonic acid can dissolve previously stable materials, releasing minerals into the water. It can also affect the integrity of the underground rock structures and increase the mobility of heavy metals or other elements once these are dissolved.

Ellis’ lab is taking steps to further understand the geochemical processes that may affect the success of carbon sequestration, including investigating how the natural variations of mineral structures and composition impact their permeability and reactive fracturing behavior. Using a combination of modeling and imaging techniques, they perform and model experiments that require days to weeks in order to understand water-rock interactions and the movement of fluids and dissolved minerals. The group’s studies are actively bridging the gap between scientific investigation and public understanding, and their results have been published in a number of journals.

Improving our understanding of the these underground processes is a necessary step toward ensuring the safe deployment of large scale CO2 storage. Research efforts that seek to prevent and mitigate CO2 (or methane) leakage from wells is also needed. Dr. Ellis’ work has shown how distribution of carbonate minerals along rock fractures can influence the evolution of the rock’s permeability over time. In some cases, mineral dissolution may even result in reduced permeability due to particle clogging. One key challenge is scaling up the experimental observations from the laboratory scale so that they may better predict behavior in the field -- this remains an active area of research for the Ellis lab.

This research could change the way we think about carbon sequestration or even just contribute to making hydraulic fracturing a safer practice. To Dr. Ellis, “Carbon sequestration activities are only successful if the carbon dioxide stays where we put it.” Technology improvements and better public understanding are needed for large scale deployment; the research conducted in Professor Ellis’ lab could help move toward this goal.

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