CO2-in-Water Foam at Elevated Temperature and Salinity Stabilized with a Nonionic Surfactant with a High Degree of Ethoxylation

The utilization of nonionie surfactants for stabilization of CO2 foams has been limited by low aqiieous solubilities at.elevated temperatures: and salinities. In this work, a norricinic surfactant C12-14(EO)(22) with a high degree of ethoxylation resulted in a high cloud point temperature of 83 degrees C even in 90 g/L NaCl brine: Despite the relatively high hydrophilic-CO2-philic balance, the surfactant adsorption at the C-W interface lowered the interfacial tension to mN/m at a CO, density of g/rriL, as determined withrcaptive bubble tensiometry. The adsorption was sufficient to stabilize a CO2-in-water (C/W) foam with an apparent viscosityof similar to 7 cP at 80 degrees C, essentially up to the cloud point temperature, in the presence of 90 g/L NaCl brine in a 30 darcy sand pack. In a 1.2 darcy glass bead pack the apparent viscosity of the foam in the presence of 0.8% total dissolved solids (TDS) brine reached the highest viscosity of similar to 350 cP at 60% foam quality (volume percent CO2) at a low superficial velocity of 6 ft/day. Shear-thinning behavior was observed in both the glass bead pack and the sand pack irrespective of the pernieability difference. In addition, C12-14(EO)(22) stabilized C/W foam with an apparent viscosity of 80-100 cP in a 49 niclarcy dolomite core formed through a coinjection and a surfactant-alternating-gas prodess. The dodecane-0.8% TDS brine partition co-efficient for C12-14(EO)(22) was below 0.1 at 40 degrees C and 1 atm. The formation of strong foam in the porous media and the low oil-brine partition coefficient indicate C12-14(EO)(22) has potential for CO2-enhanced oft recovery.