Browsing by Author "Chen, Shengnan Nancy"

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    Dissolution and Exsolution Kinetics of Ethane/Bitumen and Vapor-Liquid Equilibrium of Ethane/Bitumen/Water System for Applications to Solvent-Aided Recovery Processes
    (2024-09-17) Turkman, Shakerullah; Hassanzadeh, Hassan; Nassar, Nashaat; Chen, Shengnan Nancy
    This thesis presents an experimental study on the dissolution and exsolution kinetics and vapor-liquid equilibrium of ethane/bitumen system applicable to solvent aided recovery processes. In heavy oil and bitumen recovery, dissolution occurs across the gas-liquid interface when gaseous solvents are injected to enhance oil recovery. On the other hand, when gas-saturated oil undergoes a pressure drop, exsolution (degassing) of gaseous solvents happens from the heavy oil phase, whereby the supersaturation aiding the oil recovery. The phase behavior and thermophysical properties of solvent/bitumen system are also of crucial importance for heavy oil and bitumen in-situ recovery techniques. This thesis experimentally examines the dissolution and exsolution kinetics of ethane/bitumen system, phase equilibria of ternary ethane/water/bitumen mixtures, and related thermophysical properties to address an evident knowledge gap in the literature. First, a PVT setup was used to measure the exsolution/dissolution kinetics of ethane and bitumen systems across the test temperature range of 80–140 ℃, and a pressure difference of 0.69 and 0.35 MPa. An analytical model was adopted to analyze the experimental data for the estimation of the exsolution and dissolution coefficients. The diffusivity values for the exsolution and dissolution processes were estimated to be in the range of (2.65-10.48) × 10-8 m2/s and (0.73-6.18) × 10-9 m2/s, respectively, at a pressure difference of 0.69 MPa, and (1.61-8.33) × 10-8 m2/s and (0.89-10.78) × 10-9 m2/s, respectively, at a pressure difference of 0.35 MPa. The results indicated that the exsolution process was faster than dissolution at both pressure differences. Additionally, the liquid phase shrinkage (exsolution) and liquid phase swelling (dissolution) increased with increasing temperature, indicating that the dominant factor is the transport property (diffusion coefficient). Next, the experimental studies vapor-liquid equilibria (VLE) of a ternary system of ethane/water/bitumen were performed. The phase behavior and thermophysical properties (density and viscosity) were measured by varying the feed fractions of ethane and water while keeping bitumen composition constant at temperatures ranging from 190-210 °C and at 2.5 MPa pressure. The cubic-plus-association equation of state (CPA EoS) was used to model the phase equilibria and feed composition was chosen based on the model to study the VLE region. The model accurately predicted the existing phase equilibria, and experimental results confirmed vapor-liquid equilibrium (VLE). The vapor phase comprises ethane and water, while liquid phase (hydrocarbon-rich) primarily consists of bitumen (up to 75% mole fraction), along with ethane and water. The CPA model and stability analysis was used to construct ternary diagrams at three different temperatures 190, 200, and 210 °C and pressure at 2.5 MPa. The phase boundaries between different regions were determined using stability analysis.
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    Investigation of Gravity Drainage of Heavy Oil into a Flowing Solvent Layer in Porous Media
    (2024-04-23) Shaygan, Kaveh; Yarranton, Harvey W.; Yarranton, Harvey W.; Kantzas, Apostolos; Natale, Giovanniantonio; Chen, Shengnan Nancy; Yang, Daoyong (Tony)
    The condensing solvent bitumen recovery process is a promising alternative to steam-assisted processes in terms of greenhouse gas emissions and energy consumption reduction. In this process, the solvent vapor injected into the reservoir condenses when it contacts the colder bitumen and the bitumen diffuses into the condensed liquid. The process has been piloted but field implementation is impeded by the absence of a reliable model to upscale laboratory measurements to the field scale. The details of the underlying physical mechanisms of this process (gravity drainage and mass transfer) are not fully understood, and predictive models are lacking. This thesis focuses on the little-investigated role of solvent flow rate, permeability and irreducible water saturation in condensing solvent processes. In order to better understand and represent the mechanisms controlling the process, a packed Hele-Shaw type apparatus was partially filled with bitumen with a sloped interface and liquid toluene was flowed on top of the bitumen layer at a fixed flow rate. The experiments were performed with silica sands and glass beads with and without irreducible water saturation. Toluene volumetric flow rates between 0.5 to 15 cm³/min and permeabilities within the range of 47 to 254 D were considered. Bitumen and solvent recoveries were measured over time and the change in bitumen profile was tracked with a camera. The key mechanisms of the process were verified to be diffusion of bitumen into solvent through convective mass transfer and convective flow of the resulting mixture in the drainage layer by gravity. The high dilution (high flow rate) data were predicted with an analytical model obtained from the solution of Fick’s second law of diffusion for the effective mass transfer of bitumen into the flowing drainage layer according to Darcy’s law. The full range of data was matched with a numerical model based on convective mass transfer of bitumen into the drainage layer using a correlated convective mass transfer coefficient derived from effective molecular diffusivity and Darcy flow. The correlation has only one adjustable parameter which was constant for steady-state mass transfer in the semi-infinite acting regime. Neither model required mechanical dispersion even in presence of irreducible water. A square root dependence of mass flux versus permeability was observed, consistent with molecular diffusion with no mechanical dispersion.