Fig. 4: Carbon capture and sequestration.

Schematic representation of carbon capture and sequestration in reservoirs. The inherent temperature gradient induces thermal diffusion of impurities from the bottom to the cap-rock of the reservoir. During injection, sequestration and storage, CO₂ goes through different thermodynamic states as depicted in the right panel. The temperature and pressure dependence of the Widom line for pure CO₂ was determined by the maxima of the isobaric heat capacity. The area between the blue and red lines represents the transition region between the liquid-like and gas-like subdomains of the supercritical fluid. Image of thermal-power plant by vectorpocket on Freepik.com (https://www.freepik.com/free-vector/heavy-industry-factory-working-thermal-power-plant-station-with-electricity_4758475.htm).