ISSN 打印: 1091-028X
ISSN 在线: 1934-0508

多孔介质期刊

DOI: 10.1615/JPorMedia.v17.i12.60
pages 1093-1108

A NEW MATHEMATICAL MODEL FOR THE SOLVENT CHAMBER EVOLUTION IN THE VAPOR EXTRACTION PROCESS

Xinfeng Jia
Faculty of Engineering and Applied Science, University of Regina, Regina, SK, S4S 0A2, Canada
Fanhua Zeng
University of Regina
Yongan Gu
Petroleum Systems Engineering Faculty of Engineering and Applied Science University of Regina Regina, SK S4S 0A2 Canada

ABSTRACT

Extensive physical modeling of vapor extraction (VAPEX) has been studied in the past two decades, yet the theoretical modeling of VAPEX has not gained much progress. The major VAPEX mechanisms, i.e., oil viscosity reduction through solvent dissolution and gravity drainage, occur mainly in a thin solvent − heavy oil transition zone. Therefore, modeling ofthe transition zone is the key to model the VAPEX process. Current analytical models are based on some potentially unreliable assumptions for the transition zone, such as steady-state mass transfer and constant boundary moving velocity. Numerical models cannot fully capture the physical features because the gridblock is usually much larger than the transition-zone thickness. This paper develops a new mathematical model for the VAPEX transition zone that is simplified as a piecewise linear profile and updated step by step. In each step, first, a solvent concentration distribution is calculated by using Fick's second law. Then the oil drainage velocity is computed by using Darcy's law. Finally, the momentary boundary moving velocity is estimated by using a mass balance equation. The VAPEX model is not only able to describe the evolution ofthe solvent chamber, but also characterize the dynamic oil properties across the transition zone. Compared with numerical simulation, this new model shows more sensitivity to the diffusion coefficient.

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