High-performance displacement by microgel-in-oil suspension in heterogeneous porous media: Microscale visualization and quantification

Hypothesis: Preferential flow in porous media is commonly encountered and decreases the multiphase displacement efficiency. Here, we synthesized microgel-in-oil in suspension and demonstrated that microgel-in-oil as a novel additive could present self-adaptive transport behavior and introduce a novel multiphase displacement mode for improving displacement efficiency in heterogeneous porous media. Experiments: We investigated the microgel-in-oil formation process and characterized their morphology with fluorescence microscopy and Cryo-SEM. The suspension displacement performance in heterogeneous porous media was evaluated using a microfluidic chip containing a preferential flow pathway (PFP) and a parallel matrix region. The displacement results of microgel-in-oil were compared to plain microgel particles and analyzed from pore-scale particle transport behavior to macroscopic multiphase flow patterns. Findings: The results show that suspension with moderate microgel-in-oil yields the optimal displacement efficiency. Fewer microgel-in-oil cannot alter the flow direction, while too many microgel-in-oil would block the PFP region. The topological analysis identified that suspensions with moderate microgel-in-oil content could achieve the strongest sweeping and carrying abilities that contribute to the highest displacement efficiency. The synergistic transport of microgel-in-oil and plain microgel particles would result in local pressure fluctuations to divert displacing fluid from PFP into the matrix region, which explains the above flow behavior. (C) 2022 Elsevier Inc. All rights reserved.

Automated summary

In this study, microgel-in-oil suspension was synthesized and found to improve the displacement efficiency of multiphase flow in heterogeneous porous media. The optimal efficiency was achieved with a moderate content of microgel-in-oil, which demonstrated strong sweeping and carrying abilities. Synergistic transport of microgel-in-oil and plain microgel particles was observed to divert displacing fluid and alter the flow behavior. These findings provide insights into the self-adaptive transport behavior of microgel-in-oil and its potential application in enhancing multiphase displacement efficiency.