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Design of CO₂-in-Water Foam Stabilized with Switchable Amine Surfactants at High Temperature in High-Salinity Brine and Effect of Oil

Da, Chang, Jian, Guoqing, Alzobaidi, Shehab, Yang, Jonathan, Biswal, Sibani L., Hirasaki, George J., Johnston, Keith P.
Energy & fuels 2018 v.32 no.12 pp. 12259-12267
adsorption, carbon dioxide, carbon sequestration, carbonates, emulsions, flow resistance, foams, fuels, hydraulic fracturing, models, oils, pH, salinity, surfactants, temperature, thermal stability, viscoelasticity, viscosity
The design of surfactants for CO₂-in-water (C/W) foams in carbonate reservoirs above 100 °C has been limited by thermal instability of surfactants, surfactant adsorption to mineral surfaces, and challenges in generating and stabilizing the foams. Here, we have identified a diamine surfactant, C₁₂–₁₄N(CH₃)C₃N(CH₃)₂ (Duomeen CTM), with good thermal stability (>1 month at 135 °C), that stabilizes viscous C/W foam with an apparent viscosity of up to ∼35 cP at 120 °C in 22% total dissolved solid (TDS) brine. Strong foams with excessively high viscosity were reported to be generated with longer-tailed C₁₆–₁₈N(CH₃)C₃N(CH₃)₂ (Duomeen TTM) that formed a viscoelastic aqueous phase. Here, the tail length was shorter for C₁₂–₁₄N(CH₃)C₃N(CH₃)₂ and thus a viscoelastic aqueous phase was not formed, resulting in a weaker CO₂ foam with a more appropriate viscosity for the proposed applications. Moreover, at the lowest superficial velocity studied (4 ft/day), the apparent viscosity for C₁₂–₁₄N(CH₃)C₃N(CH₃)₂ was ∼20 fold lower than that of C₁₆–₁₈N(CH₃)C₃N(CH₃)₂, consistent with the lower viscosity for the aqueous phase. Not only the foam viscosity with C₁₂–₁₄N(CH₃)C₃N(CH₃)₂ was high enough for CO₂ mobility control in enhanced oil recovery (EOR) but also it was low enough to be more favorable with regard to the injection pressure than the excessive high flow resistance associated with C₁₆–₁₈N(CH₃)C₃N(CH₃)₂. In addition, viscous C/W foam was maintained at low fractions of dodecane (model oil) and broke in the presence of large fractions of dodecane, both of which are beneficial to EOR. The oil/water (O/W) emulsions formed with C₁₂–₁₄N(CH₃)C₃N(CH₃)₂ were unstable and broke in 30 min, and the O/W partition coefficient depended greatly on pH at 120 °C in 22% TDS brine. All of these factors suggest that the surfactant C₁₂–₁₄N(CH₃)C₃N(CH₃)₂ is a good candidate for further evaluation and scale up for CO₂ EOR, CO₂ sequestration, and hydraulic fracturing at high salinities and temperatures.