Sean Brennan is co-project lead for the Carbon and Energy Storage, Emissions, and Economics Project at the U.S. Geological Survey. His main areas of expertise include sedimentology, stratigraphy, low-temperature geochemistry, and subsurface fluid systematics. His research has focused on assessing non-energy gases in the subsurface, creating assessment methodologies and completing assessments of subsurface fluid resources, and working to understand the creation, migration, and entrapment of various naturally occurring fluids.