Supercritical Carbon Dioxide

Definition - What does Supercritical Carbon Dioxide mean?

Supercritical carbon dioxide (CO2) is a fluid state of CO2 where it is heated and held at or above its critical temperature and pressure. In this supercritical phase, CO2 exhibits properties and behaviors between that of a liquid and a gas. In particular, supercritical CO2 possesses liquid-like densities with gas-like diffusivity, surface tension and viscosity.

When CO2 exceeds temperatures of 87.9°F (31.1°C) and is subjected to pressures above 1071 psi (7.39 MPa), it enters the supercritical phase. This phase of CO2 is commonly used as a solvent in chemical extraction processes due to its high solubility, low toxicity and minimal net effect on the environment.

Corrosionpedia explains Supercritical Carbon Dioxide

Supercritical CO2 is commonly used in the oil and gas industry for gas injections during enhanced oil recovery (EOR) techniques. Oil can typically remain in the reservoir during water flooding due to a lack of contact between the water and the oil. Supercritical CO2, although low in viscosity, is highly miscible with oil and is used to sweep the reservoir for oil deposits not extracted by water flooding.

CO2 gas injection techniques can have corrosive side effects. When supercritical CO2 reacts with water, carbonic acid (H2CO3) is formed. Carbonic acid lowers the pH in the reserve and creates an environment that is corrosive to metal equipment.

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