The transport and phase change of a complex fluid mixture under nanoconfinement is of fundamental importance in nanoscience, and limits the recovery efficiency from tight oil reservoirs (<10%). Herein, through experiments and supporting theory we characterize the transport and phase change of a nanoconfined complex fluid mixture. Our nanofluidic platform, nanomodel, replicates shale reservoirs in terms of mean pore size (∼100 nm), permeability (∼μD) and porosity (∼10%). We screen conditions for the most promising shale EOR strategies, directly quantifying their pore-scale efficiency and underlying mechanisms. We find that immiscible gas (N₂) flooding presents a prohibitively large capillary pressure threshold (∼2 MPa). Miscible (CO₂) gas flooding eliminates this threshold leading to film-wise stable oil displacement with high recovery efficiency. Strong capillary forces present barriers as well as opportunities for recovery strategies unique to nanoporous reservoirs by transitioning from a miscible to an immiscible condition locally within the reservoir. These results quantify the fundamental transport and phase change mechanisms applicable to nanoconfined complex fluids, with direct implications in unconventional oil as well as nanoporous media more broadly.

This study was conducted to investigate the phase behaviour of CO2–brine and CO2–oil systems under various operating conditions. Through this study, CO2 solubility measurement tests were carried out for CO2–water, CO2–brine, and CO2–oil mixtures at various equilibrium pressures ranging Peq = 0.7–10.3MPa and temperatures ranging Texp = 21–40°C. Additionally, series of oil swelling/extraction tests were conducted at aforementioned experimental conditions using a see-through high- pressure cell to determine the oil swelling factor at various equilibrium conditions. CO2 solubility measurement tests showed that at constant temperatures, an increase in CO2 solubility value was observed for CO2–water, CO2–brine, and CO2–oil mixtures when the equilibrium pressure increases. Furthermore, as it was expected for all mixtures, the solubility of CO2 reduces with increased temperature. In this study, it was also found that at a constant temperature, the oil swelling factor, SF, increases up to a pressure so called extraction pressure, Pext, at which majority of the light to medium hydrocarbon groups in the oil phase are extracted by CO2 and vaporized into the CO2-rich phase. Additionally, it was observed that for the pressures higher than the extraction pressure, the oil swelling factor reduced with equilibrium pressure because more hydrocarbon components were extracted at higher pressures. The extraction pressure was determined at different experimental temperatures and results revealed that the extraction pressure increases by increasing experimental temperature. Comparison of the CO2 solubility values in oil at extraction pressures corresponding to different experimental temperatures also showed that the major hydrocarbon extraction occurs when a certain amount of CO2 has dissolved in the oil phase which is called threshold CO2 solubility, χth. The defined threshold CO2 solubility was found to be approximately the same for the CO2–oil mixture under this study at different temperatures

Si-glass microfluidics have long provided unprecedented precision, robustness and optical clarity. However, chip fabrication is costly (∼500 USD per chip) and in practice, devices are not heavily reused. We present a method to reduce the cost-per-chip by two orders of magnitude (∼5 USD per chip), rendering Si-glass microfluidics disposable for many applications. The strategy is based on reducing the area of the chip and a whole-chip manifolding strategy that achieves reliable high-pressure high-temperature fluid connectivity. The resulting system was validated at 130 bar and 95 °C and demonstrated in both energy and carbon capture applications. We studied heavy oil flooding with brine, polymer, and surfactant polymer solutions and found the surfactant polymer as the most effective solution which recovered ∼80% of the oil with the least amount of injection while maintaining a relatively uniform displacement front. In a carbon capture application, we measured the dilation of an emerging ionic liquid analog, choline chloride with urea, in gaseous and supercritical CO₂. Previously restricted to niche microfluidic applications, the approach here brings the established benefits of Si-glass microfluidics to a broad range of applications.