This study analyzes the changes in solubility and mass distribution of three alkyl amine surfactants in pure, supercritical carbon dioxide (ScCO2) and in supercritical carbon dioxide methane (ScCO2 - ScCH4) mixtures under high-pressure conditions at 40 or 60 degrees C. It was observed that highly methylated surfactant structures have the highest solubility in ScCO2, up to 1 wt % at 40 degrees C, and, exponentially declined with addition of methane in the system. Moreover, methylated surfactant structures with lower molecular weights have greater solubility in the presence of methane than higher molecular weight structures due to the weak solvation power of methane. On the other hand, for surfactant structures with hydroxylated terminals, the surfactant solubility in ScCO2 was found to be 1 order of magnitude lower compared to methylated terminals, and the solubility remained leveled with the presence of methane.