Apart from giving new life to an old field, the use of CO₂ as an injection makes EnCana's Weyburn site the world's largest greenhouse gas sequestration project. From 2000 to 2004, the Weyburn project was the site of a world-scale research initiative operated under the auspices of the International Energy Agency, which studies the sequestration of CO₂ in an oil reservoir. The study concluded that Weyburn is a suitable reservoir for long-term storage of CO₂.

Under the right temperature, pressure and oil composition conditions, CO₂ can act as a solvent, cleaning oil trapped in the microscopic pores of the reservoir rock. This miscible process greatly increases the recovery of oil from a reservoir compared to the recoveries normally seen by waterflooding. The Weyburn unit is an ideal candidate for CO₂ flooding due to the following reasons:

• the waterflood has been very successful and provides confidence that the geology of the reservoir is likely suitable for CO₂ flooding;
• the Weyburn oil swells with the addition of CO₂ and has a large viscosity reduction factor;
• reduced spacing created by the existence of horizontal wells will make the CO₂ process very efficient; and
• the reservoir pressure required for miscibility can be readily achieved at the reservoir temperature and with Weyburn oil.

Read about the IEA GHG Weyburn-Midale CO₂ Monitoring and Storage Project.