Abstract

In gas injection processes it has been already shown that the wettability characteristics of the solid surface and the spreading characteristics of the fluid system hold the key roles. Network modeling has proved to be a useful tool to phenomenological studies of multiphase flow. The objective of the present paper is to describe a network model of three-phase flow in porous media with heterogeneous wettability. Experimental support to validate the model is provided in the study by Laroche (SPE 52067) using micromodels with different wettability patterns.

The developed numerical tool is used to demonstrate the impact of small scale wettability heterogeneities on gas injection efficiency, for various patterns and spatial heterogeneity distributions. The model permits to impose heterogeneous wettability by assigning different water/oil contact angles according to the desired heterogeneity pattern. The initial distribution of oil and water in the network is established by simulating a two-phase displacement, which corresponds to a drainage in the water-wet region and to an imbibition in the oil-wet region. When gas is injected, three phases coexist within the network. The three-phase displacement is dominated by drainage mechanisms. Oil is assumed to flow through wetting films in the oil-wet regions and through spreading films on water in the water-wet regions. The simulations clearly demonstrate the effect of the size and distribution of wettability heterogeneities on water/oil displacement and three-phase gas injection. Also the effect of wettability heterogeneities distribution on water/oil capillary pressure is investigated by simulating quasi-static displacements.

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