Pore-scale investigations of Enhanced Oil Recovery and CO2 Transport using Microfluidics
Creators: Yang, Junyi
Publisher: name: University of Alberta Library
Year: 2023

<p>This thesis focuses on applying the microfluidic approach to study two major applications regarding the subsurface pore-scale flow, namely enhanced oil recovery (EOR) and carbon capture and sequestration (CCS). The microfluidic method enables the visualization of fluid flow in $\mu$m scale, which helps to illustrate the fundamental physics of the pore-scale flow. Such technique also allows precise manipulation of fluids and rapid response. </p>

<p>Targeting enhanced oil recovery (EOR) applications (Chapter 2), we study the effect of wettability on the oil recovery rate and invasion morphology of viscous oil displaced by different aqueous floods using microfluidics. The porous network of the microfluidic device replicates a complex sandstone structure with an average pore length of 283.5 $\mu$m. For comparison, we performed systematic experiments by injecting flood to displace oil in both hydrophilic and hydrophobic microfluidic chips. The results show that the hydrophilic microfluidic rock has a remarkable increase in oil recovery by a factor of $\approx 1.44$, compared to the hydrophobic case. In addition, we observe a more pronounced lateral growth of displacing pattern of aqueous flood for the hydrophilic surface. Finally, we quantitatively explain the increasing factor in the recovery rate and finger width for the hydrophilic vs. hydrophobic rock-liked porous networks by incorporating the contact angle into a scaling analysis.</p>

<p>To investigate CO2 transport in brine near reservoir conditions (Chapter 3), we perform microfluidic experiments of supercritical-CO2 dissolution in different concentrations of brine (0 - 1 M) under various liquid flow rates (15, 30, 45, 60 $\mu$L/min). In this work, a silicon-glass microfluidic device is fabricated for the desired high-pressure (P = 8 MPa) and temperature (T = 50 $^{\circ}$C) application. We observe the supercritical-CO2 bubble shrinkage in the brine and report a volumetric mass transfer coefficient, $k<em>La$. The volume reduction of supercritical-CO2 bubbles is less than 30%. Furthermore, $k</em>La$ = 50.3 -- 144.0 $s^{-1}$ drastically increases with liquid flow rate ($\dot{Q}<em>L$ = 15 -- 60 $\mu$L/min) and only has a slight positive correlation with brine salinity $S</em>{NaCl}$ (0 -- 1 M) because the flow is advection-dominated. We apply a mass transfer model based on the penetration theory to estimate the bubble film and cap contribution to the total $k_La$, and find a more significant contribution from the liquid film (by a factor of 1.78) due to a larger surface area and frequent renewal of the film.</p>

<p>In summary, we demonstrate the potential of utilizing the microfluidic technique to investigate pore-scale phenomenon, including the multiphase displacement mechanism (regarding EOR application) and the mass transfer process (regarding CCS application). Finally, we conclude our work with a research outlook, particularly concerning the microfluidic investigations on CO2-EOR and salt precipitation in the future. </p>