Full Characterization of CO<sub>2</sub>–Oil Properties On-Chip: Solubility, Diffusivity, Extraction Pressure, Miscibility, and Contact Angle

Carbon capture, storage, and utilization technologies target a reduction in net CO<sub>2</sub> emissions to mitigate greenhouse gas effects. The largest such projects worldwide involve storing CO<sub>2</sub> through enhanced oil recoverya technologically and economically feasible approach that combines both storage and oil recovery. Successful implementation relies on detailed measurements of CO<sub>2</sub>–oil properties at relevant reservoir conditions (<i>P</i> = 2.0–13.0 MPa and <i>T</i> = 23 and 50 °C). In this paper, we demonstrate a microfluidic method to quantify the comprehensive suite of mutual properties of a CO<sub>2</sub> and crude oil mixture including solubility, diffusivity, extraction pressure, minimum miscibility pressure (MMP), and contact angle. The time-lapse oil swelling/extraction in response to CO<sub>2</sub> exposure under stepwise increasing pressure was quantified via fluorescence microscopy, using the inherent fluorescence property of the oil. The CO<sub>2</sub> solubilities and diffusion coefficients were determined from the swelling process with measurements in strong agreement with previous results. The CO<sub>2</sub>–oil MMP was determined from the subsequent oil extraction process with measurements within 5% of previous values. In addition, the oil–CO<sub>2</sub>–silicon contact angle was measured throughout the process, with contact angle increasing with pressure. In contrast with conventional methods, which require days and ∼500 mL of fluid sample, the approach here provides a comprehensive suite of measurements, 100-fold faster with less than 1 μL of sample, and an opportunity to better inform large-scale CO<sub>2</sub> projects.