Abstract

In the recently developed "DeProF" model steady-state twophase flow in porous media (SS2 PM) is modelled as a composition of three flow patterns, namely CPF (connected-oil pathway flow), GD (ganglion dynamics), and DTF (drop traffic flow). The key difference between these prototype flow patterns is the degree of disconnection of the non-wetting phase (‘oil’). The observed flow is usually a mixture of the basic prototype flows. Each flow pattern prevails over mesoscopic-scale regions of the porous medium (ranging from a few to several hundred pores), whereas the macroscopic flow is homogeneous.

The predictive capability of the DeProF model was used to investigate the effect of pore network geometry and topology on the pore scale mechanisms of two-phase flow in pore networks. The domain of the values of the operational parameters Ca and r, for which two-phase flow is sustained, is determined by performing simulations of two-phase flows in 2-D and 3-D pore networks and for various combinations of fluids. Macroscopic interstitial physical quantities that characterize two-phase flow are computed.

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.

A recently developed theoretical model3,4,5,6, predicts the relative permeabilities using the concept of decomposition in prototype flows (DeProF); it accounts for the pore-scale mechanisms and the network wide cooperative effects, and is sufficiently simple and fast for practical purposes. The sources of non-linearity and other complex effects, are satisfactorily modeled. The quantitative and qualitative agreement between existing sets of data and the corresponding theoretical predictions of the DeProF model is very good5,6.

In the DeProF model it is assumed that the macroscopic flow can be decomposed into the two prototype flows, CPF and DOF. The latter comprises Ganglion Dynamics (GD) and Drop Traffic Flow (DTF), regimes which have been observed experimentally1,2. Each prototype flow has the essential characteristics of the corresponding flow patterns, in suitably idealized form, and so the pore scale mechanisms are incorporated in the prototype flows. The cooperative effects among ganglia and drops are also incorporated in DOF, by making suitable use of a modified version of the effective medium theory7.

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