Ballentine has shown that by measuring noble gas isotopes, he can identify and quantify the processes controlling the origin, migration, and interaction of subsurface water, hydrocarbons, and fluids.
He has applied noble gas tools and principles to understand how natural gas fields form inside Earth, the role of groundwater in forming hydrocarbon reservoirs, and the origins of different gases on the planet. Ballentine also has developed quantitative techniques to understand how carbon dioxide behaves in the subsurface, including its role in the crustal carbon cycle, and how carbon-rich fluids have supported subsurface life over geological timescales.