Estimating Diffusion Coefficients And Visualizing Interactions In Propane-Heavy Oil Systems

• Author / Creator

  Athar, Khan S

• Unconventional oil (mainly heavy oil, extra heavy oil and bitumen) represents a significant share of global oil reserves. Due to their high viscosity, efficient recovery of oil from these reserves is challenging and remains an issue of ongoing global research. Thermal recovery methods are generally accepted as viable and successful. These methods rely on heat for viscosity reduction. Their high energy requirement has lead the industry to investigate solvent based recovery methods as alternatives. Among solvent based recovery methods, vapour extraction (VAPEX) is gaining most attention. VAPEX has immense potential for heavy oil recovery due to its low energy requirement and low GHGs emission. Experimental and numerical studies of VAPEX have indicated its technical and economic viability. In VAPEX, in-situ viscosity reduction is due to molecular diffusion of solvent in heavy oil. One of the most important uncertainty of VAPEX is the mixing rate of light hydrocarbon solvent molecules with heavy hydrocarbons (high density and high viscosity). This mixing rate is quantified as diffusion coefficient (D) or diffusivity and determines the effectiveness of VAPEX. Measuring diffusion coefficient is difficult, especially at in-situ conditions, i.e. at high temperature and pressure. There is no universally acceptable method of measuring diffusion coefficient. Therefore, it is inferred through the data obtained from experimental methods, with the pressure decay (PD) technique being the most convenient and simple. In the first part of this research, numerical and experimental approaches are used to estimate unknown parameters from PD data. The results provide new insights from PD data analysis including the identification of different stages in diffusion process. PD data from high temperature and high pressure tests is analyzed and divided into three regions based on different slopes; early-time, transition and late-time regions. Due to very limited data available in literature, solubility and diffusivity of propane and butane in heavy oil at high temperatures and high pressures are also estimated. Also, the effects of i) temperature and solvent type on diffusion coefficient of solvent in heavy oil, ii) solvent solubility and diffusion time in heavy oil, and iii) the corresponding viscosity reduction are investigated and discussed in this study. In the second part of this research, we conduct visualization tests in a customized visual cell to investigate interactions between liquid propane (C3(l)) and a heavy oil sample during soaking process at different experimental conditions. The results show how different mechanisms lead to the complete mixing of heavy oil with C3(l). The results of this study are of direct relevance to in situ recovery of heavy oil. They help in understanding propane-based recovery processes and diffusion processes in heavy oil and bitumen systems. Also, the results can be applied in the simulation of VAPEX and other solvent-based recovery processes.

• Subjects / Keywords

  • VAPEX
  • Propane
  • Heavy Oil
  • Visualization
  • Diffusion

• Graduation date

  Spring 2019

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/r3-1330-hc96

• License

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