Combination of non-ionic and cationic surfactants in generating stable CO₂ foam for enhanced oil recovery and carbon storage

Surfactant-stabilized CO₂ foam is a promising technology to reduce CO₂ mobility in geologic CO₂ storage and CO₂ enhanced oil recovery processes. In this study, various combinations of a non-ionic surfactant, Alkyl polyglycoside, along with cationic surfactants were ingeniously examined to enhance carbon storage and facilitate oil recovery through CO₂-based foam flooding. Specifically, for the first time, the investigation focused on the impact of altering the alkyl chain length and counter-ion type of the cationic surfactants. The surfactant combinations were first screened based on surfactant characterization, surface and interfacial tension studies and bulk foam experiments. The interfacial tension studies showed that, in combination with Alkyl polyglycosides, the C₁₆ (cetyltrimethylammonium bromide and cetyltrimethylammonium chloride) alkyl chain length cationic surfactants exhibited less interfacial tension values than the C₁₂ (dodecyltrimethylammonium bromide and dodecyltrimethylammonium chloride) alkyl chain length cationic surfactant. The bulk foam experiments established that Alkyl polyglycosides/C₁₆ combination showed higher foamability and foam stability than Alkyl polyglycosides/C₁₂ combination. The bulk foam investigation showed that the optimized concentration of Alkyl polyglycosides/cationic-surfactant was 0.3/0.15 wt%. The surfactant combinations screened from these studies were evaluated for EOR coreflooding experiments at 1250 psi and 60 ℃. The incremental oil recovery obtained for baseline CO₂ and Alkyl polyglycosides/cetyltrimethylammonium bromide foam flooding was 18.5% and 32.7%, respectively. The estimated carbon storage potential for baseline CO₂ g and Alkyl polyglycosides/cetyltrimethylammonium bromide foam flooding was 11.9% and 23.7%, respectively. The combination of Alkyl polyglycosides cetyltrimethylammonium bromide surfactant was demonstrated as an effective solution for increased oil recovery and carbon storage.