From nonionic to zwitterionic: Novel CO2-responsive zwitterionic wormlike micelles based on zwitterionic surfactant and bola-type asymmetric diamine

Abstract

CO2 enhanced oil recovery (CO2-EOR) is one of the CO2 utilization methods which can also geo-sequestrate greenhouse gases. Due to the weak adsorption on rock surface and excellent viscoelasticity performance, CO2-responsive zwitterionic wormlike micelles (WLMs) has been recognized as a promising method to control CO2 channeling. A novel CO2 responsive zwitterionic WLMs was developed by blending N-octadecyl-N,N-dimethyl-3-ammonio-2-hydroxy-1-propane-sulfonate (OHSB), N,N,2,2-tetramethyl-1,3-propanediamine (TADPA) and sodium salicylate (NaSal). The responsive behaviors induced by varying agents (CO2 and HCl) are systematically studied by rheology tests and cryo-TEM measurements. The molecular structures of products are confirmed by 1H and 13C NMR. Moreover, the responsive mechanism is discussed in detail. The OHSB/NaSal/TADPA system shows morphological transformations between spherical micelles (a good flowing capacity) and WLMs (conducive to plugging) before and after purging CO2. The viscoelasticity and molecular structure of the system with CO2 bubbling is different from that with HCl titration, because TADPA molecules can react with CO2 to form a novel zwitterionic product: NH+(CH3)2-CH2-C(CH3)2-CH2-NHCO2− (TAH+DPACO2−, 78.95 %–83.52 %). This work provides a new strategy for the design of CO2-responsive zwitterionic WLMs and their applications in CO2 utilization schemes, including clean fracturing, mobility control, and CO2 foam flooding, etc.