CO2 injections have been successfully used in enhanced oil recovery. The CO2 from natural or industrial source is injected into the reservoir either as continuous gas or as water-altering-gas injection also known as WAG. Because of the special properties of the CO2 it is able to improve oil recovery by lowering the interfacial tension (IFT), swelling the oil, reducing the oil viscosity and by mobilizing the lighter components of the oil. However, the low viscosity of the CO2 compared to the targeted oil causes viscous fingering and the low density of the CO2 might lead the CO2 to migrate to top part of the porous media not reaching the targeted oil. These issues have led to study of CO2 in water foams as more viscous injection media.
Hydrophilic/CO2-philic balance is used to design surfactants for CO2-water foams
CO2 in water foams, require surfactants that can stabilize the CO2 - water interphase at reservoir conditions. The design of surfactants for CO2 -water foams is based on the concept of hydrophilic/CO2- philic balance (HCB). This is very similar to the hydrophilic/lipophilic balance (HLB) used to describe surfactant behaviour in oil-water systems. Selected surfactant must have a CO2-philic moieties that interact highly with CO2. Also, economical aspects as well as environmental effects need to be considered. Several different types of surfactants and even nanoparticles have been proposed and tested for CO2-water foam stabilization.
To study the effect of surfactant addition to CO2 – water system, interfacial tension measurements are required. In addition to surfactant concentration, other factors like pressure, temperature and salinity of the water effect on IFT values. For these reasons, it is crucial to measure interfacial tension at high pressures and controlled measurement environment.
Hear Prof. Sandro da Rochas short talk about the CO2-in-water foams and how to design surfactants for these systems and explain the measurements in a short (15 min) video.
In enhanced oil recovery wettability plays an important role as that determines the interactions between the solid (rock) and the liquids in the reservoirs (crude oil, brine). Wettability has been recognized as one of the key parameters controlling the remaining oil-in-place.