Foam can mitigate the associated problems with the gas injection by reducing the mobility of the injected gas. The presence of an immiscible oleic phase can adversely affect the foam stability. Nevertheless, under miscible conditions gas and oil mix in different proportions forming a phase with a varying composition at the proximity of the displacement front. Therefore, it is important to understand how the compositional variations of the front affect the foam behavior. In this study through several core-flood experiments under miscible condition, three different regimes were identified based on the effects of the mixed-phase composition on CO2 foam-flow behavior: In Regime 1 the apparent viscosity of the in-situ fluid was the highest and increased with increasing x(CO2). In Regime 2 the apparent viscosity increased with decreasing x(CO2). In Regime 3 the apparent viscosity of the fluid remained relatively low and insensitive to the value of x(CO2). (c) 2017 American Institute of Chemical Engineers AIChE J, 64: 758-764, 2018