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Research Papers: Petroleum Engineering

Experimental and Theoretical Determination of Diffusion Coefficients of CO2-Heavy Oil Systems by Coupling Heat and Mass Transfer

[+] Author and Article Information
Sixu Zheng

Petroleum Systems Engineering,
Faculty of Engineering and Applied Science,
University of Regina,
Regina, SK S4S 0A2, Canada

Daoyong Yang

Petroleum Systems Engineering,
Faculty of Engineering and Applied Science,
University of Regina,
Regina, SK S4S 0A2, Canada
e-mail: tony.yang@uregina.ca

1Corresponding author.

Contributed by the Petroleum Division of ASME for publication in the JOURNAL OF ENERGY RESOURCES TECHNOLOGY. Manuscript received February 25, 2016; final manuscript received June 3, 2016; published online July 12, 2016. Editor: Hameed Metghalchi.

J. Energy Resour. Technol 139(2), 022901 (Jul 12, 2016) (15 pages) Paper No: JERT-16-1112; doi: 10.1115/1.4033982 History: Received February 25, 2016; Revised June 03, 2016

By treating heavy oil as multiple pseudocomponents, techniques have been developed to experimentally and theoretically determine diffusion coefficients of CO2-heavy oil systems by coupling heat and mass transfer together with consideration of swelling effect. Experimentally, diffusion tests have been conducted for hot CO2-heavy oil systems with three different temperatures under a constant pressure by using a visualized pressure-volume-temperature (PVT) setup. The swelling of liquid phase in the PVT cell is continuously monitored and recorded during the measurements. Theoretically, a two-dimensional (2D) mathematical model incorporating the volume-translated Peng–Robinson equation of state (PR EOS) with a modified alpha function has been developed to describe heat and mass transfer for hot CO2-heavy oil systems. Heavy oil sample has been characterized as three pseudocomponents for accurately quantifying phase behavior of the CO2-heavy oil systems, while the binary interaction parameters (BIPs) are tuned with the experimentally measured saturation pressures. The diffusion coefficient of hot CO2 in heavy oil is then determined once the discrepancy between the experimentally measured dynamic swelling factors and theoretically calculated ones has been minimized. During the diffusion experiments, heat transfer is found to be dominant over mass transfer at the beginning and reach its equilibrium in a shorter time; subsequently, mass transfer shows its dominant effect. The enhanced oil swelling mainly occurs during the coupled heat and mass transfer stage. CO2 diffusion coefficient in heavy oil is found to increase with temperature at a given pressure, while it can be explicitly correlated as a function of temperature.

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Figures

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Fig. 1

(a) Schematic of PVT setup for diffusion tests and (b) a digital image of the PVT cell

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Fig. 2

(a) Schematic diagram of the diffusion cell and (b) cell-centered control volumes

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Fig. 3

Measured and calculated dynamic swelling factors based on (a) constant diffusion coefficient and (b) diffusion coefficient as a function of viscosity and a constant for tests #1–3, respectively

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Fig. 4

Measured diffusion coefficient as a function of temperature

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Fig. 5

Calculated temperature profile in liquid phase for test #1: (a) t = 60 s, (b) t = 150 s, (c) t = 300 s, and (d) t = 600 s

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Fig. 6

CO2 mole fraction in liquid phase for test #1: (a) t = 1 hr, (b) t = 5 hrs, (c) t = 10 hrs, (d) t = 50 hrs, (e) t = 90 hrs, and (f) t = 126 hrs

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Fig. 7

CO2 mole fraction in liquid phase for test #2: (a) t = 1 hr, (b) t = 5 hrs, (c) t = 10 hrs, (d) t = 50 hrs, (e) t = 90 hrs, and (f) t = 126 hrs

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Fig. 8

CO2 mole fraction in liquid phase for test #3: (a) t = 1 hr, (b) t = 5 hrs, (c) t = 10 hrs, (d) t = 50 hrs, (e) t = 90 hrs, and (f) t = 126 hrs

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Fig. 9

CO2 mole fraction in liquid phase along the height of the PVT cell for test #3

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