Effect of Network Topology on Relative Permeability; Network Model and Experimental Approaches

Walid Mohamed Mahmud

doi:10.11648/j.ogce.20170505.14

Abstract

The effect of topological properties on imbibition relative permeabilities and residual saturations was previously studied by utilizing quasi-static network model topologies extracted from actual sandstones 3D micro-tomographic images. Non-wetting fluid in imbibition displacements can be disconnected by snap-off as a result of swelling of wetting films in the corners of pores and throats. The findings showed that the effect of topology on imbibition relative permeabilities depends on the level of snap-off. For strongly wetting conditions where snap-off dominates the displacement the effect of network topology is significantly smaller than for weakly wet conditions where snap-off is suppressed. The findings were valid for random networks and for networks displaying short-range pore-throat and longer-range spatial correlations. The aim of this study is to validate network model findings by comparing them with laboratory measurements of relative permeabilities. Laboratory measured data include imbibition relative permeability for sandstones of similar petrophysical properties to Fontainebleau sandstone used to extract 3D micro-tomographic images. Laboratory measurements were made at ambient conditions on core samples of different diameters and different porosities and permeabilities. Experimental measurements were in good qualitative agreement with stochastic networks that match the full coordination number distribution and geometric properties of networks obtained from 3D micro-CT images. Experimental measurements were also in good agreement with networks displaying both short-range pore-throat correlations and longer-range spatial correlations.

Highlights

Network models, including those that utilize the quasistatic algorithm as in this study, are used to model multiphase flow at small scale to predict macroscopic properties such as relative permeability, residual saturations and capillary pressure
It was suggested that the computations of some petrophysical properties, such as permeability, formation factor and mercury injection capillary pressure, on digitized image of a small rock fragments cut from a core plug are consistent with laboratory measurements performed on the same plug or plugs of similar microstructure and petrophysical properties even though the computations and measurements are performed at significantly different scales [1, 2, 15]
The effect of network topology on computed transport properties has previously been investigated for drainage and imbibition displacements [2, 3, 4, 15]

Summary

Introduction

Network models, including those that utilize the quasistatic algorithm as in this study, are used to model multiphase flow at small scale to predict macroscopic properties such as relative permeability, residual saturations and capillary pressure. The effect of network topology on computed transport properties has previously been investigated for drainage and imbibition displacements [2, 3, 4, 15]. For strongly wetting conditions where the displacement is dominated by snap-off the sensitivity of relative permeability to network topology is considerably reduced. This conclusion is valid for both random and correlated networks [3]

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Results

Conclusion