Multiphase boundary of C16+ heavy n-alkanes and CO2 systems

• Published in: Petroleum exploration and development 2017-02, Vol.44 (1), p.105-110
• Main Authors: LIU, Xiaolei, QIN, Jishun, HAN, Haishui, LI, Shi, JI, Zemin
• Format: Article
• Language: English
• Subjects: bubble point pressure; C16+ heavy n-alkanes; CCE experiment; CO2; multiphase boundary
• ISSN: 1876-3804; 1876-3804
• DOI: 10.1016/S1876-3804(17)30013-7

N-eicosane, N-tetracosane, N-octacosane and N-dotriacontane, which are heavy n-alkanes, were selected to form binary systems with CO2. The bubble point pressures of each system were obtained through a series of constant component expansion (CCE) experiments. Variation laws and mechanisms of multiphase boundary of heavy n-alkanes-CO2 systems were studied. As CO2 fraction increased, the bubble point pressure of heavy n-alkanes-CO2 systems increased greatly, and the bubble point pressure increased linearly with temperature. When CO2 molar fraction is less than 50%, the bubble point pressure of the heavy n-alkanes-CO2 systems decreased slightly with the increase of carbon number, and the decrease of pressure amplitude decreased with the decrease of CO2 mole fraction. When CO2 molar fraction was 75%, the bubble point pressure of different heavy n-alkane systems increased slightly with the increase of carbon number. When CO2 molar fraction was less than 50%, with the increase of the carbon number, the influence of temperature variation on the bubble point pressure of systems decreased. When CO2 molar fraction was equal to 75%, with the increase of the carbon number, the influence of temperature variation on the bubble point pressure of heavy n-alkanes-CO2 systems did not change. On the analysis of micro scale, the reason for variation laws above is that the long chains and large intermolecular interval of heavy n-alkane has ability to accommodate CO2 molecules and its chain is prone to twist.