CO2-Soluble Nonionic Surfactants for Enhanced CO2 Storage via In Situ Foam Generation

Geologic carbon storage (GCS) is a rapidly evolving technologywith the potential to reduce the environmental impact of fossil fuelusage. Saline aquifers, which comprise a sandstone matrix with brinecontained in the pores, make up much of the pore space available forCO(2) storage in the United States. When CO2 isinjected in saline aquifers, however, capillary fingering occurs,and only a small percentage of the pore space is filled with CO2. This fingering effect is due to the low viscosity of CO2, which is roughly ten times less viscous than brine. To addressthis problem, we tested the ability of inexpensive, commercially availablenonionic surfactants to be dissolved in injected CO2 andincrease the apparent viscosity of CO2 by generating CO2-in-water foams in situ. We focused our study on nonionictridecyl ethoxylate surfactants with the number of ethoxylate groupsranging from 11 to 18 (TDA-11, TDA-13, TDA-15, TDA-18). These surfactantsexhibited sufficient CO2-solubility and were shown to reducethe CO2-brine interfacial tension (IFT), stabilize bulkCO(2)-in-brine foams, and reduce the mobility of CO2 during core floods of CO2 in brine-saturated Berea sandstone.The surfactants did not alter the wettability of the Berea sandstone.Modeling results showed that in a reservoir field injection scenario,the presence of TDA-11 (0.1 wt %) increased both the CO2 storage resource and storage efficiency by 17%. Simulations alsoshowed that the lateral extension area of the plume was reduced by23% and that CO2 saturation within the plume increasedby 26%.