Visualizing Interactions Between Liquid Propane and Heavy Oil

In this study, we use a custom-designed visual cell to investigate nonequilibrium interactions between liquid propane (C_3(l)) and a heavy oil sample (7.2 deg API) at varying experimental conditions. We inject C_3(l) into the visual cell containing the heavy oil sample (pressure-buildup process) and allow the injected C_3(l) to interact with the oil sample (soaking process). We measure visual-cell pressure and visualize the C₃/heavy oil interactions during the pressure-buildup and soaking processes. Nonequilibrium interactions occurring at the interfaces of C_3(l)/heavy oil and C_3(l)/C_3(g) are recorded with respect to time. The results show that the complete mixing of heavy oil with C_3(l) occurs in two stages. First, upward extracting flows of oil components from bulk heavy oil phase toward C_3(l) phase form a distinguished layer (L₁) during the soaking process. The extracted oil components become denser over time and move downward (draining flows) toward the C_3(l)/heavy oil interface due to gravity. The gradual color change of L₁ from colorless (color of pure C_3(l)) to black suggests the mixing of oil components with C_3(l). After L₁ appears to be uniform, a second layer (L₂) is formed above L₁ in the bulk C_3(l) phase. Extracting and draining flows become active once again, leading to the mixing of oil components from L₁ into L₂. At final conditions, heavy oil and C_3(l) appear to be mixed and form a single uniform phase.