Pore-Level Simulation of Heavy Oil Reservoirs; Competition of Capillary, Viscous, and Gravity Forces

ABSTRACT

The advancing high resolution scanning technology has formed a concrete basis for simulation of pore events within microstructures. Interactions between capillary, gravity, and viscous forces result in complex flow phenomena affecting pore-scale physics and phase distributions during different displacement scenarios. Consequently, a myriad of techniques has been proposed to deal with all effective forces and dynamically simulate pore scale multi-phase flow physics. In this regard, the significance of each force, particularly viscous forces, on pore-level flow morphology is not yet well studied. Here, the Navier-Stokes equation along with a VOF volume tracking advection equation is applied for simulation of two-phase displacement scenarios considering gravity, capillary, and viscous forces. A pore-throat pair is used as a simple pore-level geometry to conduct a comprehensive sensitivity analysis and investigate the effect of viscosity, IFT, contact angle and velocity on the trapping amount of non-wetting phase. The results are in good agreement with available experimental data and confirm that in pore-level transport phenomena, the amount of residual trapping is a function of pore-throat geometry and wettability and is not affected greatly by interfacial tension or differences of viscosity. The analysis also demonstrates that within microscale porous media images the gravity role is negligible due to low Bond number values. A pore morphology-based quasi-static approach is then applied to a multi-pore micro-tomographic sandstone image to simulate drainage, and imbibition processes and investigate the effect of geometry, contact angle, and IFT on the amount of heavy oil residual trapping.

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