Abstract

The motion of oil ganglia and droplets in chamber-and-throat pore networks in two-phase flow in porous media can be modeled without or with wetting films. The existence of wetting films around ganglia and droplets is favored by small contact angles (say, smaller than ca. 10 deg) and wall roughness.

The predictive model DeProF (Decomposition into Prototype Flows) considers steady-state two-phase flow in porous media as a composition of three flow patterns, namely connected-oil pathway flow, ganglion dynamics and drop traffic flow. The key difference between these prototype flow patterns is the degree of disconnection of the non-wetting phase (‘oil’) which, in turn, affects the relative magnitude of the rate of energy dissipation caused by capillary effects compared to that caused by viscous stresses. The observed flow is usually a mixture of the basic prototype flows.

In the present work DeProF is used to investigate the effect of the wetting film on two-phase flow in typical 3-D pore networks by including wetting films around droplets. The effects of the wetting film are assessed by comparing the values of key physical characteristics of two-phase flow, specifically, the interfacial area per unit volume, the mechanical power dissipation p.u.v., the degree of disconnectedness of the non-wetting phase, and the energy utilization factor, which are obtained with and without wetting films.

Introduction

Two-phase flow in porous media (2 FPM) occupies a central position in enhanced oil recovery, the behavior of liquid organic pollutants near the source in contaminated soils, etc. It has been experimentally observed1,2 that during two-phase flow the disconnected oil contributes significantly (and in certain cases of practical interest even exclusively) to the flow. Furthermore, the flowrate vs pressure gradient relation is found to be strongly non-linear, and to be strongly affected by the physical parameters that pertain to the fluid-fluid interfaces.

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