Micro‐PIV measurements of multiphase flow of water and liquid CO₂ in 2‐D heterogeneous porous micromodels

Abstract

We present an experimental study of pore‐scale flow dynamics of liquid CO2 and water in a two‐dimensional heterogeneous porous micromodel, inspired by the structure of a reservoir rock, at reservoir‐relevant conditions (80 bar, 21°C). The entire process of CO2 infiltration into a water‐saturated micromodel was captured using fluorescence microscopy and the micro‐PIV method, which together reveal complex fluid displacement patterns and abrupt changes in velocity. The CO2 front migrated through the resident water in an intermittent manner, forming dendritic structures, termed fingers, in directions along, normal to, and even opposing the bulk pressure gradient. Such characteristics indicate the dominance of capillary fingering through the micromodel. Velocity burst events, termed Haines jumps, were also captured in the heterogeneous micromodel, during which the local Reynolds number was estimated to be ∼21 in the CO2 phase, exceeding the range of validity of Darcy's law. Furthermore, these drainage events were observed to be cooperative (i.e., across multiple pores simultaneously), with the zone of influence of such events extending beyond tens of pores, confirming, in a quantitative manner, that Haines jumps are nonlocal phenomena. After CO2 completely breaks through the porous section, shear‐induced circulations caused by flowing CO2 were also observed, in agreement with previous studies using a homogeneous porous micromodel. To our knowledge, this study is the first quantitative measurement that incorporates both reservoir‐relevant conditions and rock‐inspired heterogeneity, and thus will be useful for pore‐scale model development and validation.

Energy Conversion Reveals Regime Transition of Imbibition in a Rough Fracture

“…Equation states that for log 10 Ca > −7.19, the surface energy together with external work is transformed into the kinetic energy and dissipated energy, which is different from the energy conversion indicated in equation . Equation also suggests that for log 10 Ca > −7.19, the amount of dissipated energy can be calculated only if the velocity field is determined, which would require velocity measurement technologies, such as particle image velocimetry (Li et al, ).…”

High‐Speed Quantification of Pore‐Scale Multiphase Flow of Water and Supercritical CO2 in 2‐D Heterogeneous Porous Micromodels: Flow Regimes and Interface Dynamics

“…A brief overview of the methodology is reported in this section, and the reader is kindly referred to our previous studies using a similar apparatus (Chen et al, ; Fakhari et al, ; Kazemifar et al, ; Li et al, , ) and to the supporting information for additional technical details.…”

“…A growing experimental, numerical, and theoretical effort has been recently devoted to the study of immiscible fluid displacement in porous media at the pore scale. Typical techniques include the use of X‐ray microcomputed tomography (micro‐CT) and magnetic resonance imaging for the visualization of flow patterns in complex geometries (Perrin & Benson, ; Song et al, , among others), and the use of fluorescent microscopy and microscopic particle image velocimetry (micro‐PIV) for quantitative measurements in 2‐D microfluidic models, or so‐called micromodels (Armstrong & Berg, ; Blois et al, ; Karadimitriou et al, ; Kazemifar et al, , ; Li et al, ; Roman et al, ; Zhang, Oostrom, Grate, et al, ; Zhang, Oostrom, Wietsma, et al, ). Lenormand et al () performed a series of experiments in a homogeneous micromodel (i.e., featuring a regularly arranged porous structure) for a large parameter space.…”

“…In addition to nonwetting phase saturation, characterization of the fluid‐fluid interfacial area is critical for understanding many heat, momentum, and mass transfer processes, including shear‐induced flow, dissolution, exsolution, and subsequent chemical reactions (Kazemifar et al, ; Li et al, ; Liu et al, ; Zhang, Oostrom, Wietsma, et al, ; Zuo et al, ), all of which occur at the interface. Pore‐scale processes may affect long‐term CO 2 solubility and mineral trapping.…”

“…From a pore‐scale perspective, the macroscopic movement of the displacement front is understood as an ensemble of high‐speed interfacial burst events occurring within individual pores, termed Haines jumps (Haines, ). Typical Haines jumps occur at the time scale of milliseconds and can appreciably affect a length scale of up to 30 pore diameters (Armstrong & Berg, ; Li et al, ). Several studies have shown that Haines jumps play a key role in drainage processes by effectively creating nonlocal velocities of large magnitudes, enhancing inertial effects, affecting displacement regimes, and eventually shaping macroscopic fluid morphology (Armstrong & Berg, ; Li et al, ; Moebius & Or, ).…”