Speaker
Description
Polymer solutions are widely employed to regulate flow behavior in porous media and thereby enable fine control of multiphase displacement in systems such as energy production, materials shaping and chemical processing. However, continuous polymer injection often suffers from high injection pressure, large chemical consumption and strong adsorption, which has motivated the development of polymer–water slug strategies as a more efficient and economical way to control non-Newtonian multiphase flows. Existing studies have mainly relied on numerical simulations and macroscopic displacement experiments, and a pore-scale, visual understanding of how these processes affect operational efficiency and the trapping and remobilization of the displaced phase remains limited.
In this work, we conduct pore-scale water–polymer–post-water slug displacement experiments on a microfluidic platform and synthesize a fluorescently labeled polyacrylamide to enable in situ visualization of the polymer phase. The porous structure is a numerically reconstructed dual-permeability medium in which strong preferential flow develops in the high-permeability region, making the sweep enhancement induced by the polymer slug in the low-permeability region directly observable. Topological analysis of the displaced phase shows that, at relatively high capillary number (Ca), viscoelastic oscillations of the polymer phase cause a large amount of displaced fluid to remain trapped inside pores as droplets, a behavior further confirmed by comparison with non-viscoelastic glycerol solutions used as a Newtonian reference. In addition, we observe that the reduction in the size of trapped clusters during polymer-slug displacement becomes more pronounced under lower Ca conditions. By combining pressure-drop measurements with spatiotemporal fluorescence mapping of polymer concentration, we find that, at low Ca, both the temporal fluctuations and spatial heterogeneity of polymer concentration are substantially amplified. This trend is consistent with the evolution of trapped clusters, indicating that, under low-Ca conditions, cluster breakup and the associated improvement in displacement performance are primarily governed by the spatiotemporal fluctuations of polymer concentration.
To further quantify these phenomena, we perform miscible water–polymer displacement experiments in capillary tubes and use fluorescence intensity to determine the polymer concentration. By comparing the experimentally measured mixing length with theoretical predictions, we show that macromolecular Taylor dispersion of the polymer, together with miscible viscous fingering, jointly generates a more disordered concentration field at low flow rates. Together, the experiments and analysis guide the design of polymer slug length and injection conditions and establish a microfluidic framework for optimizing pore-scale multiphase non-Newtonian flows in complex porous media.
| References | [1] Xie, C.; Qi, P.; Xu, K.; Xu, J.; Balhoff, M. T. Oscillative Trapping of a Droplet in a Converging Channel Induced by Elastic Instability. Phys. Rev. Lett. 2022, 128 (5), 054502. [2] Zhang, Y.; Zhao, X.-Z.; Han, P.-H.; Zhang, L.-Y.; Weitz, D. A.; Feng, Y.-J. Visualization of Adaptive Polymer Flow and Displacement in Medium-Permeable 3D Core-on-a-Chip. Petroleum Science 2023, 20 (2), 1018–1029. [3] Xie, C.; Lei, W.; Balhoff, M. T.; Wang, M.; Chen, S. Self-Adaptive Preferential Flow Control Using Displacing Fluid with Dispersed Polymers in Heterogeneous Porous Media. J. Fluid Mech. 2021, 906, A10. |
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| Country | China |
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