Theoretical Insight into the Effect of Steam Temperature on Heavy Oil/Steam Interface Behaviors Using Molecular Dynamics Simulation

The interfacial behavior between heavy oil and steam is one of the vital pointers affecting the development efficiency of steam injection for heavy oil recovery. However, the underlying mechanisms of the interaction between heavy oil and steam at high temperature and pressure remain elusive. Herein, we have investigated the molecular-scale interactions on the interface between heavy oil droplet and steam phase at high temperatures (473 K, 498 K, 523 K, and 548 K) via molecular dynamics simulations. The results show that the interfacial thickness between heavy oil droplet and steam phase increases gradually with temperature, while the interfacial tension decreases constantly. Moreover, high temperature can damage hydrogen bonds, resulting in lower interaction energy between heavy oil droplet and steam phase. The radial distribution function results demonstrate that the interaction between heavy oil fractions and steam phase can be weakened by high temperature. Furthermore, the evolutions of interface are directly observed by the two-dimension density cloud maps at different temperatures, and the mean square displacement and self-diffusion coefficient demonstrate the evolution mechanism of heavy oil fractions and steam. In particular, the heavy oil/steam systems with asphaltenes at the interface are more likely to achieve high diffusivity and emulsifying capacity. This work provides a molecular-level insight for understanding the interfacial interaction mechanisms of heavy oil/steam systems during a steam injection process.