Geomaterial-Functionalized Microfluidic Devices for Multiphase Flow in Porous Media
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2020-03-23
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Abstract
Fluid flow, species transport, and chemical reactions in geological formations abound in the exploitation of fossil fuels and geothermal energy, the geological storage of carbon dioxide (CO2), and the disposal of hazardous materials. Reservoir rocks are made of grains, with an extensive surface area, where the physicochemical fluid-solid interactions greatly influence the multiphase flow behavior. The success of the design, implementation, and prediction of engineering activities related to subsurface systems depends on the understanding of the flowing fluids’ properties and their interactions with the surrounding rock surfaces. Microfluidics, which performs laboratory tests in miniaturized flow cells, has exhibited numerous functionalities and potentials to assess subsurface processes. However, a key constraint in the application of microfluidics to flow in porous rocks is the surface discrepancy between microfluidic chips and the actual rocks/soils. This research develops novel microfluidic devices (e.g., ‘surface-mimetic micro-reservoirs’ (SMMRs) functionalized with reflective rock surfaces), which represent multiscale and multi-type of natural rocks/soils. The advanced surface-functionalized microfluidic chips are applied to address the physics of fluids in porous media, which includes rock-fluid interactions. The novel layer-by-layer (LbL) assembly for surface modification is employed to produce rock-forming mineral coatings on microfluidic chip surfaces. Substrates of glass, quartz, and polydimethylsiloxane (PDMS), and the actual microscale flow channels made of glass and PDMS are successfully functionalized with geomaterials of clays and quartz. We characterize the coating stability, nanoscale structures, and wettability of the functionalized substrates and microfluidic chips using dynamic flooding experiments, scanning electron microscope (SEM), optical microscopy, profilometer, atomic force microscopy (AFM), and contact angle measurements. The surface modification technique generates a stable coated surface with tunable hydrophilicity in microfluidic chips and is shown to be universal, reliable, and material-independent. The microfluidic chips functionalized by clay particles are used in two-phase flow experiments, which illustrate the role of the coated clays on flow patterns. Functionalized microfluidic chips enable the real-time and multi-scale evaluation of transport processes in reservoir-mimetic visual models, thus unravelling the intricate interactions between the flowing fluids and rock minerals. The present study provides a path in the development of microfluidic technology-based applications for subsurface energy and environmental research.
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Zhang, Y. (2020). Geomaterial-Functionalized Microfluidic Devices for Multiphase Flow in Porous Mediathesis (Doctoral thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.