Could Hydraulically Fractured Shales Represent a Viable Repository for Geologic Carbon Sequestration?
Speaker: Andres Clarens, University of Virginia
Series: CEE Departmental Seminars
Location: Engineering Quad E219
Date/Time: Monday, April 14, 2014, 12:15 p.m. - 1:30 p.m.
Oil and gas production from hydraulically fractured shale formations is an abundant new source of omestically available energy for the U.S. It will also result in significant CO2 emissions with important climate implications. We want to understand whether fractured shale formations could represent a significant repository for CO2 once they are depleted of hydrocarbons. Geologic carbon sequestration has been studied extensively in saline aquifers with shales often acting as caprocks. But the pressure and temperature profiles of many of the largest shale formations in the US and the emergence of technology to increase the permeability of these shales led us to ypothesize that the fractured shales themselves could represent an attractive repository. We developed a modeling framework to estimate the sequestration capacity for a shale formation based on historical CH4 production and applied it to the portions of the Marcellus formation found in Pennsylvania. The results suggest that the Marcellus shale in Pennsylvania alone could store between 10.4 and 18.4 Gigatonnes of CO2 between now and 2030. This would be over 50% of total annual US CO2 emissions from stationary sources. The mass transfer and sorption kinetics results indicate that CO2 injection proceeds several times faster than CH4 production. Model estimates were most sensitive to the permeability of the formation and assumptions about the ultimate ratio of adsorbed CH4 to CO2. It was assumed that only the sorbed CO2 would stay in the formation over time. These estimates for sequestration capacity suggest that the approach merits further study to understand the viability of this approach and opportunities to leverage existing infrastructure. Other synergies could exist in terms of monitoring. Related impacts associated with induced seismicity and leakage would need to be explored to understand the full potential of this approach. The sequestration capacity estimated using this model supports continued exploration into this pathway for producing carbon neutral energy.
Andres Clarens is an Assistant Professor of Civil and Environmental Engineering at the University of Virginia. His research is focused broadly on anthropogenic carbon flows and the ways that CO2 is manipulated, reused, and sequestered in engineered systems. To carry out this work, his group studies environmental surface processes, complex fluids, flow through porous media, and aqueous chemistry as they relate to carbon sequestration, enhanced oil recovery, and hydraulic fracturing. The results of his work are important for developing strategies for mitigating the emissions that are driving climate change and for understanding how infrastructure systems must be adapted to meet these changes. He is the recipient of the National Science Foundation CAREER award and the American Chemical Society Petroleum Research Fund Young Investigator Award. He received a B.S. in Chemical Engineering from the University of Virginia and an M.S.E. and Ph.D. in Environmental Engineering from the University of Michigan. In his spare time, Prof Clarens also enjoys running, backpacking, fly-fishing, and traveling.