Immiscible Flow of Viscous Oil and Water in Porous Media: A Network Simulation Study

ABSTRACT

The problem of two-phase flow at elevated temperatures and with a viscous hydrocarbon phase is addressed through network modelling techniques. A three-dimensional complex network is constructed, starting from publicly available data form Imperial College and adapted to fit the needs of the task at hand. The model attempts to provide a realistic description of the complex porous-space of both unconsolidated sands and consolidated sandstones. The void space is represented by pores that are connected to each other by throats. Weibull distributions are utilized in order to compute the pore radius, throat radius, and throat length distributions. The generated network is then fed to the flow-simulator software to simulate the immiscible two phase flow of viscous oil and water in Berea sandstone and typical oil sands.
The simulator solves the fundamental equations of two-phase immiscible flow inside the network and elucidates the effect of temperature and oil viscosity on wettability and interfacial tension. Subsequently the model attempts to elucidate the interplay among the viscous, capillary, and gravitational forces on relative permeability, resistivity index and capillary pressure functions. Simulation runs demonstrated piston-like displacement, pore body late filling, and snap-off mechanisms. At strong wetting conditions the model assumes a continuous film of the wetting phase on the walls of the network elements which in turn guarantees low wetting-phase saturation after forced drainage. Wetting-phase trapping occurs merely due to non-wetting-phase bypassing during forced drainage.
Drainage and imbibition of water and viscous oil are simulated in a network generated based on actual Berea sandstone and Athabasca type oil sand data. Predicted transport properties are presented and compared, whenever possible, with experimental data obtained from the literature and are in good agreement with each other. The effect of wettability and interfacial tension alteration is investigated. The results are in good agreement with physical expectations.

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