Microfluidic Study of In-Situ Recovery of Bitumen in Solvent-Based Processes

• Author / Creator

  Keshmiri, Kiarash

• Viscosity reduction is critically important for heavy oil extraction and experimental studies have shown this can be achieved by injection of a light solvent into a reservoir and dilution of heavy oil in place. Solvent-based methods have challenges like slow diffusion process and oil production rate as well as high cost of solvent. There is presently a lack of understanding regarding the pore-scale mechanisms involved in dilution of bitumen. Therefore, microfluidic as the science of fluid flow in micro-scale, has a great potential to play a significant role in the investigation and development of solvent-based heavy oil extraction methods. However, microfluidic is limited in applicability due to materials and operating condition.In the first section of this work, possibility of using poly(dimethylsiloxane) (PDMS) microchannels in solvent-based bitumen extraction methods is studied. Swelling ratio of PDMS samples in different organic solvents and diluted bitumen were evaluated. We were particularly interested in the kinetic of swelling, deformation, and discoloration of PDMS. The hypothesis was that a PDMS microchip can still be used if the experiment time is much shorter than the time it takes for PDMS discoloration and deformation. The effect of surface coating on bitumen resistivity and compatibility of PDMS slabs was also studied.Choosing the best material for micromodel fabrication, this thesis focuses on the experimental observation and characterization of solvent-based bitumen extraction. In the second section, a microchannel was used to measure hexane diffusion in bitumen with tremendously tiny amount of solvent and bitumen compared with prevalent methods. Semitransparent nature of bitumen facilitates the application of light transmission imaging during the time and relating intensities to solvent concentration. Diffusion mass transfer was studied with consideration of Fickian and Single-File mass transfer mechanisms and corresponding equation was applied to calculate diffusion coefficient. The accuracy of Fickian mass transfer mechanism was confirmed with calculating values of fitting parameter (i.e. nw) in addition to superimposition of data for both techniques. Comparison between constant and concentration dependent coefficients revealed that application of constant value causes up to 100 times larger coefficients specially at high (>0.85) and low (<0.15) hexane concentration. Diffusion of n-alkane solvent in bitumen leads to asphaltene precipitation and flow of diluted bitumen in the porous media.Understanding of fluid flow in porous media is critically important for heavy oil and bitumen recovery. Therefore, capillary filling of pure liquids and diluted bitumen were experimentally monitored using white light microscope and compared with Washburn theoretical model. In addition, capillary filling of bitumen samples in periodically constricted microchannels was compared with Navier-Stokes equation. Glass microchannels were treated with two silanes which changed the water contact angle from 15° (untreated) to 115° (treated) microchannels. For all the samples, a linear relation between square of propagation distance and time was found as expected in the case of Washburn model. Experimental results indicated slower velocity compared to theoretical prediction due to simplifications of the Washburn model. Dynamic contact angles were measured and compared with predicted values using image processing.Solvent diffusion in bitumen causes in-situ upgrading and asphaltene precipitation which causes pore clogging and prevents diluted oil to drain towards the production well. Understanding of asphaltene precipitation and deposition improves the efficiency of solvent-based extraction methods and solvent selection. In the last section of this study, micromodel was used to study asphaltene deposition. Detection point of asphaltene deposition showed faster precipitation from n-pentane compared with n-decane. Structure of asphaltene precipitates were evaluated with Helium Ion Microscopy (HIM). A high-resolution total internal reflection fluorescence (TIRF) microscopy was used to identify the morphology of precipitates and results compared with HIM. While precipitated asphaltene with heavier solvent had larger particles, light solvent formed higher aggregation and formation damage, accordingly.

• Subjects / Keywords

  • Wettability
  • Solvent-Based Process
  • Image Processing
  • Capillary Flow
  • Diffusion Coefficient
  • Asphaltene Precipitation and Deposition
  • Microfluidic

• Graduation date

  Spring 2019

• Type of Item

  Thesis

• Degree

  Doctor of Philosophy

• DOI

  https://doi.org/10.7939/r3-ss3n-hs89

• License

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