Abstract: A method for injecting carbon dioxide into a well is shown, in which carbon dioxide is supplied at the well site in a tank maintained at sufficient pressure to keep the carbon dioxide in the liquid state. As the carbon dioxide is withdrawn from the tank and transferred to the high pressure well pump, supplemental cooling is provided intermediate the tank and pump to maintain the carbon dioxide in the liquid state. The supplemental cooling is provided by passing the carbon dioxide withdrawn from the tank through a heat exchanger, the cooling effect being provided by separating a liquid-vapor stream from a predominantly liquid stream of carbon dioxide, expanding the liquid-vapor stream in the heat exchanger to cool the heat exchanger, and passing the predominantly liquid stream separately through the heat exchanger to cool the predominantly liquid stream.