The researchers of IIT-Madras have found that supercritical carbon dioxide can be a good agent for simultaneous carbon dioxide sequestration and enhanced oil recovery (EOR) from depleted reservoirs when the gas is used along with surfactants in a ‘surfactant-alternating gas (SAG) injection’ approach.
What is a Supercritical carbon dioxide (CO2)?
- 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.
- In this process, carbon dioxide gas is injected in the reservoir, where it becomes supercritical, followed by injection of water or surfactant solution.
Key findings
- The IIT-Madras study shows that the use of supercritical carbon dioxide for EOR resulted in greater storage of carbon dioxide for both water-alternating gas (WAG) and SAG approaches.
- However, SAG performed better at all pressures and temperatures as surfactant solution alters the interfacial tension between the oil and water phases, leading to a higher oil recovery percentage and more effective storage of carbon dioxide.
- The researchers also found that the reservoir pressure and temperature had a strong effect on the flow dynamics.
- The use of supercritical carbon dioxide reduces oil viscosity, induces in situ swelling of the oil, and reduces the interfacial tension of the in-situ fluid system.
