Creation of a dual-porosity and dual-depth micromodel for the study of multiphase flow in complex porous media

Abstract

Silicon-based microfluidic devices, so-called micromodels in this application, are particularly useful laboratory tools for the direct visualization of fluid flow revealing pore-scale mechanisms controlling flow and transport phenomena in natural porous media. Current microfluidic devices with uniform etched depths, however, are limited when representing complex geometries such as the multiple-scale pore sizes common in carbonate rocks. In this study, we successfully developed optimized sequential photolithography to etch micropores (1.5 to 21 μm width) less deeply than the depth of wider macropores (>21 μm width) to improve the structural realism of an existing single-depth micromodel with a carbonate-derived pore structure. Surface profilimetry illustrates the configuration of the dual-depth dual-porosity micromodel and is used to estimate the corresponding pore volume change for the dual-depth micromodel compared to the equivalent uniform- or single-depth model. The flow characteristics of the dual-depth dual-porosity micromodel were characterized using micro-particle image velocimetry (μ-PIV), relative permeability measurements, and pore-scale observations during imbibition and drainage processes. The μ-PIV technique provides insights into the fluid dynamics within microfluidic channels and relevant fluid velocities controlled predominantly by changes in etching depth. In addition, the reduction of end-point relative permeability for both oil and water in the new dual-depth dual-porosity micromodel compared to the equivalent single-depth micromodel implies more realistic capillary forces occurring in the new dual-depth micromodel. Throughout the imbibition and drainage experiments, the flow behaviors of single- and dual-depth micromodels are further differentiated using direct visualization of the trapped non-wetting phase and the preferential mobilization of the wetting phase in the dual-depth micromodel. The visual observations agree with the relative permeability results. These findings indicate that dual-porosity and dual-depth micromodels have enhanced physical realism that is pertinent to oil recovery processes in complex porous media.

Oil-water flow regimes in 4-mm borosilicate glass and fluorinated ethylene propylene channels: Effects of wall wettability

“…At the lower diameter range of mini-channels, oil-water flow regimes depend on whether oil or water first fills the channel, and stratified flows were not observed due to the increased importance of surface tension over gravity [28,29]. At even smaller size micro-scales, capillary forces governed imbibition in fabricated, pore-scale geometries [30,31]. the Eö numbers in the glass and FEP are 0.4 and 0.6, respectively.…”

Optical measurements of oil release from calcite packed beds in microfluidic channels

“…Since then, a variety of 2D micromodels have been developed, from various materials such as glass (Grate et al 2012;Karadimitriou et al 2012), silicon (Gunda et al 2011;Grate et al 2013;Song and Kovscek 2015) and polymers (Berejnov et al 2008;Sollier et al 2011;Ma et al 2012;Wu et al 2015). To better represent the fluid processes occurring in 3D porous media, so called 2.5D (Xu et al 2017;Yu et al 2019) and dual porosity/ depth micromodels (Buchgraber et al 2012;Yun et al 2017) were also established. In micromodels with dimensionality higher than 2, visualization of the rock and the fluids generally requires the use of dedicated imaging techniques and/or adaptation of the materials; examples are the application of X-ray computer tomography using brines enriched in heavy metal ions (Berg et al 2013;Reynolds et al 2017) or the use of glass beads together with two immiscible fluids having the same refractive index in optical microscopy studies (Krummel et al 2013;do Nascimento et al 2019).…”

A Novel True Triaxial Apparatus for Testing Shear Seepage in Gas-Solid Coupling Coal

“…Xu et al studied the evolution process of shear microcracking, expansion, and macroscopic failure of gas-containing coals under the compression-shear load condition using a self-developed microscopic shear testing device for coal rock [35]. Other scholars have combined numerical simulation with physical experiments to study the motion of microfluids in pore fractures [36][37][38][39].…”