Guicai Zhang

The original purpose of our work was finding commercial foaming agents for high‐salinity reservoirs. During the study, the commercial lauramide amide oxide solution displayed different foaming properties in high‐salinity water (salinity 220,000 mg/L) at different aging times and relatively low temperature (25 °C). Foam volume decreases drastically first with the increase of aging time. Then, with further aging, foam volume increases. However, in low‐salinity water or at high temperature, no obvious foam volume variation was observed. Lauric acid in the commercial surfactant plays a key role. Under proper temperature and pH conditions, lauric acid will react with Ca²⁺. Calcium laurate generated from lauric acid in the commercial form and Ca²⁺ from water influences the foaming property significantly. At the beginning of calcium laurate generation, surfactants adsorb on calcium laurate and decelerate the diffusion velocity of lauramide amide oxide from the bulk phase to the air–water interface. With the increase of aging time, calcium laurate gathers, thus adsorption of lauramide amide oxide by calcium laurate decreases. Hence, the foaming volume increases.