Molecular Dynamics Simulation of CO 2 Diffusion in a Carbonated Water–Decane System

Lei Yuan, Changzhong Zhao, Yongsheng Xu and Yi Zhang
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Lei Yuan: Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024, China
Changzhong Zhao: Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024, China
Yongsheng Xu: Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024, China
Yi Zhang: Key Laboratory of Ocean Energy Utilization and Energy Conservation of Ministry of Education, School of Energy and Power Engineering, Dalian University of Technology, Dalian 116024, China

Energies, 2020, vol. 13, issue 22, 1-16

Abstract: Carbonated water injection (CWI) is a technology with significant sweep efficiency advantages in enhanced oil recovery (EOR), but the mechanism of the microscopic diffusion of CO 2 is still unclear. In this study, the diffusion mechanism of CO 2 from the aqueous phase to the oleic phase in a carbonated water (CW)–decane system was investigated by the molecular dynamics simulation method. This investigation also explored the diffusion capacity and interface properties of the CW–decane system. We found that the movement of CO 2 from the aqueous phase to the oleic phase can be divided into two processes: the accumulation behavior of CO 2 moving from the aqueous phase to the interface, and the dissolution behavior of CO 2 moving from the interface to the decane phase. The increase in the temperature and CO 2 concentration in carbonated water can improve the decane phase’s diffusion ability and reduce the water–decane interfacial tension. The difference in the interactions between water–CO 2 and decane–CO 2 provides a driving force for the diffusion of CO 2 between aqueous and oleic phase. The temperature increase intensifies the degree of diffusion and improves the diffusion rate of CO 2 from the aqueous phase to the oleic phase. The diffusion coefficient results show that CO 2 significantly enhances the oleic phase’s diffusion properties. In addition, the affinity of water for CO 2 is increased by the hydrogen bond, and it provides a mechanism for the accumulation behavior of CO 2 . Further, the temperature significantly improves the CO 2 diffusion ability at the interface, which promotes CO 2 leaving the interface and weakens the accumulation behavior. This work provides useful information for guiding carbonated water injection to improve the recovery mechanism of enhanced oil.

Keywords: carbonated water; CO 2 diffusion; interface; molecular dynamics simulation (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2020
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