Surface properties and adsorption behavior of cocamidopropyl dimethyl amine oxide under high temperature and high salinity conditions

Zwitterionic surfactants play an increasingly important role in chemical enhanced oil recovery because of their excellent temperature resistance and salinity tolerance, high interfacial activity at low concentrations, and other properties. However, due to cationic and anionic centers attached to the same molecule, the adsorption mechanism of zwitterionic surfactants on rock surfaces is complicated, especially in high temperature and high salinity reservoirs. In this paper, the adsorption behavior of cocamidopropyl dimethyl amine oxide (CAO) on air/liquid and solid/liquid interfaces was systematically investigated under high temperature and high salinity conditions. These harsh conditions caused the critical micelle concentration (cmc) of CAO aqueous solutions and surface tension at the cmc to decrease. The contact angle of the crude oil/liquid/solid three-phase system increased due to surfactant adsorption, which was followed by the alteration of rock wettability. The considerable amount of static and dynamic adsorption indicated that the adsorption capacity of CAO was strong and that the adsorption mechanism on the solid/liquid interface was consistent with multilayer adsorption.