Competitive adsorption behaviors of carbon dioxide and n-dodecane mixtures in 13X molecular sieve

The CO2 cyclic injection has been proven to be effective to enhance tight oil recovery under constant reservoir temperature and down hole pressure conditions. However, the enhance tight oil recovery mechanism was unclear, especially the adsorption of the CO2 and alkane in the surface. Therefore, it is great important to study the adsorption mechanism of CO2 and alkane mixtures in tight oil. In this study, a new experimental method and apparatus have been designed to test the change of the mole fraction of CO2 and n-C-12 before and after the adsorption equilibrium. Then, the adsorption amount of CO2 and n-C-12 was obtained by a mathematical method. Moreover, the adsorption character of CO2 and n-C-12 mixtures in 13X molecular sieve and the effect of pressure on the adsorption and amount were studied. The results show that the adsorption of CO2 and the desorption of n-C-12 follow the Langmuir adsorption. This study provides a straightforward method to experimentally determine the adsorption properties of the tight oil, which can be used to evaluate enhanced tight oil recovery by CO2 injection.