The vast potential for permanently storing carbon dioxide underground by using it for enhanced oil recovery can only be realized if produced or captured CO2 can be economically transported long distances via pipeline. And the only way that can happen is if the CO2 is compressed into a “supercritical” or “dense-phase” fluid — a state that is somewhat compressible like a gas but flows and can be pumped like a liquid. When CO2 is in a supercritical state, much more of it can economically flow through a pipeline to the producing field. And when it gets there, the dense-phase CO2 can be injected into an oil production zone, where it has the unique ability to flow through permeable rock formations, bond with and “swell” trapped oil molecules, and free the oil to move to the production well, then up to the surface. Given that CO2-based EOR is destined to become a much more significant activity in the energy industry, it’s time for a fun-filled review of the thermodynamics of fluids as it relates to the transportation of CO2 and its use in the production of crude oil. (Wait! Don’t leave! This will be easy to follow! We promise!) Today, we continue our series on the rapidly evolving CO2 market and why it matters to crude oil producers.