KU research has identified combinations of surfactants and polyelectrolyte nanoparticles that improve the stability of CO2 foam for enhanced oil recovery (EOR).
When an oil reservoir is drilled, its natural pressure will only expel a small portion of the oil to the surface. When the natural pressure is exhausted, surface pumps can be used to draw additional quantities of oil from the reservoir. However, the physical properties of the oil and the surrounding rock limit the amount that can be recovered in this way. "Tertiary recovery" or "Enhanced Oil Recovery" (EOR) methods improve oil production by flushing out the remaining oil through injection of other fluids or chemicals that facilitate the movement of oil through the rock. One of these methods involves the injection of carbon dioxide (CO2) foam that contains a surfactant (detergent that releases oil clinging to rock). This foam, however, is inherently unstable and tends to perform poorly under many real-world conditions. The present invention introduces polyelectrolyte and polyelectrolyte complex nanoparticles into the mixture to improve the performance and stability of the surfactant and CO2 foam.
This invention is intended for use in subterranean oil production, specifically as an improved method of Enhanced Oil Recovery.
Polyelectrolytes and their complexes have been shown to improve the stability of CO2 foam when used in oil recovery. Their addition improves the performance of typical surfactants and provides greater stability to the foam when it is exposed to shear forces and direct contact with crude oil over extended periods of time.
Stabilizing CO2 foam improves its vertical and areal sweep efficiencies. This allows oil producers to extract more oil from a reservoir that would otherwise be considered depleted, thus extending its useful lifespan. Increased use of CO2 in oil recovery also facilitates greenhouse gas management by allowing oil producers to incorporate subterranean carbon sequestration into their production process.
Typical applications of CO2 in EOR methods can be limited due to problems such as viscous fingering and gravity override. CO2 foams are used to avoid these problems but the foams are inherently unstable, especially in the presence of crude oil. KU research has identified polyelectrolyte nanoparticles that protect and stabilize the foams under these detrimental conditions.
Stabilization of surfactant foams could also be useful in the detergent industry.