Development of Solvent Selection Criteria Based on Diffusion Rate, Mixing Quality, and Solvent Retrieval for Optimal Heavy-Oil and Bitumen Recovery at Different Temperatures Open Access
- Other title
- Type of item
- Degree grantor
University of Alberta
- Author or creator
- Supervisor and department
Babadagli, Tayfun (Civil & Environmental Engineering)
- Examining committee member and department
Huazhou, Li (Civil & Environmental Engineering)
Ergun Kuru (Civil & Environmental Engineering)
Department of Civil and Environmental Engineering
- Date accepted
- Graduation date
Master of Science
- Degree level
Heavy-oil and bitumen recovery requires high recovery factors to offset the extreme high cost of the process. Attention has been given to solvent injection for this purpose and it has been observed that high recoveries are achievable when combined with steam injection. Heavier (“liquid”) solvents (liquid at ambient conditions) are especially becoming more popular to be used in these processes due to availability and transportation. “Liquid” solvents are advantageous as they yield a better mixing quality (especially with very heavy-oils and bitumen) but a lower diffusion rate than lighter solvents like propane or butane. Despite this understanding, there is still not a clear screening criterion for solvent selection considering both diffusion rate and the quality of the mixture.
Therefore, two main solvent selection criteria parameters—diffusion rate and mixing quality—were proposed to evaluate solvent injection efficiency at different temperatures for a defined set of solvent-heavy oil pairs of varying properties and composition. Diffusion rate, viscosity, and density reduction were among the test carried out through bulk liquid-liquid interaction.
Then, core experiments at different temperatures were performed on Berea sandstone samples using the same set of oil-solvent pairs already defined to obtain the optimum carbon size (solvent type)-heavy oil combination that yields the highest recovery factor and the least asphaltene precipitation. Based on the fluid-fluid (solvent-heavy oil) interaction experiments and heavy-oil saturated rock-solvent interaction tests, the optimal solvent type was determined considering the fastest diffusion and best mixing quality for different oil-solvent combinations.
In all these applications, the retrieval of expensive solvent is essential for the economics of the process. This led to a micro scale analysis to clarify the dynamics of solvent retrieval from matrix under variable temperatures at atmospheric pressure. The reasons of the entrapment of the solvent during this process were investigated for different wettability conditions, solvent type, and heating process carrying out visualization experiments on micromodels.
The experimental and semi-analytical outcome of this research would be useful in determining the best solvent type for a given oil and in understanding the key factors that influence the quality of mixtures, including: (1) viscosity reduction and probable asphaltene precipitation, (2) the optimal solvent type considering the fastest recovery rate and ultimate recovery for different heavy oil-solvent combinations at different temperatures, and, (3) the visualization of the solvent recovery mechanisms at the pore scale.
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