3. What are the properties of CO2?

Pure carbon dioxide is an invisible, odourless gas. When put under pressure or in very cold conditions, it can transform into a liquid or solid. At temperatures below minus 78.5°C, carbon dioxide becomes a solid (also known as "dry ice").

The CO2 that is pipelined to Saskatchewan from North Dakota for injection into the Weyburn and Midale oilfields is 95% pure; it contains a few other components that are produced in the coal gasification process. The CO2 is pipelined under high pressure, which transforms the gas into a liquid-like state (also called a "dense phase") that can be better injected into the two oil reservoirs.