4D microvelocimetry reveals multiphase flow field perturbations in porous media

• 成果类型: Article
• 署名作者: Bultreys, Tom; Ellman, Sharon; Schlepuetz, Christian M.; Boone, Matthieu N.; Pakkaner, Gulce Kalyoncu; Wang, Shan; Borji, Mostafa; Van Offenwert, Stefanie; Goudarzi, Niloofar Moazami; Goethals, Wannes; Winardhi, Chandra Widyananda; Cnudde, Veerle
• 署名单位: Ghent University; Swiss Federal Institutes of Technology Domain; Paul Scherrer Institute; Ghent University; Utrecht University
• 刊物名称: PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
• ISSN/ISSBN: 0027-10704
• DOI: 10.1073/pnas.2316723121
• 发表日期: 2024-03-19
• 关键词: haines jumps; slow drainage; 2-phase flow; DYNAMICS; sandstone; Visualization; displacement; velocimetry; hysteresis; energy

摘要

Many environmental and industrial processes depend on how fluids displace each other in porous materials. However, the flow dynamics that govern this process are still poorly understood, hampered by the lack of methods to measure flows in optically opaque, microscopic geometries. We introduce a 4D microvelocimetry method based on high- resolution X-ray computed tomography with fast imaging rates (up to 4 Hz). We use this to measure flow fields during unsteady-state drainage, injecting a viscous fluid into rock and filter samples. This provides experimental insight into the nonequilibrium energy dynamics of this process. We show that fluid displacements convert surface energy into kinetic energy. The latter corresponds to velocity perturbations in the pore-scale flow field behind the invading fluid front, reaching local velocities more than 40 times faster than the constant pump rate. The characteristic length scale of these perturbations exceeds the characteristic pore size by more than an order of magnitude. These flow field observations suggest that nonlocal dynamic effects may be long-ranged even at low capillary numbers, impacting the local viscous- capillary force balance and the representative elementary volume. Furthermore, the velocity perturbations can enhance unsaturated dispersive mixing and colloid transport and yet, are not accounted for in current models. Overall, this work shows that 4D X- ray velocimetry opens the way to solve long- standing fundamental questions regarding flow and transport in porous materials, underlying models of, e.g., groundwater pollution remediation and subsurface storage of CO2 and hydrogen.