Foam flow in a layered, heterogeneous porous medium: A visualization study

- Nanoparticles increase foam stability in both bulk and porous media.
- Foam improves sweep efficiency with and without crude oil.
- High oil recoveries are observed in heterogeneous media due to immiscible foams.

Foams can divert flow from high permeability regions to low permeability regions in heterogeneous porous media. In this work, we present a visualization study of foam flow through a two-layer, heterogeneous model, where the performance of foam stabilized by surfactant-nanoparticle mixtures is evaluated. An in-house, 2D sandpack holder was fabricated with a transparent front plate to visualize foam displacement mechanisms. It was packed with two layers of silica sand which resulted in a permeability contrast of 6:1. Foam flow and oil displacement experiments were performed using either surfactants or surfactant-nanoparticle blends. Foam flow experiments revealed that inclusion of nanoparticles increases the resistance factor (RF) by a factor of 1.95 over that of the surfactant foams. In oil displacement experiments, the water flood recoveries were low (∼46% of the original-oil-in-place, OOIP) due to channeling through the top high-permeability region, leaving the bottom low-permeability region completely unswept. Foam flooding with an immiscible gas led to an improvement in sweep efficiency and resulted in an oil recovery as high as 80% OOIP. Foams stabilized by the surfactant-nanoparticle blend outperform surfactant-stabilized foams by 9% OOIP incremental oil. This study is the first-of-its-kind to visually demonstrate flow diversion due to nanoparticle-stabilized foam in a heterogeneous, porous system. Flow phenomena such as cross-flow between layers and foam phase separation are discussed. Complementary experiments such as static foam tests and confocal laser scanning microscopy are also performed to understand the effect of nanoparticles on foam stability.

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