A Novel Tripod Methodology of Scrutinizing Two-Phase Fluid Snap-Off in Low Permeability Formations from the Microscopic Perspective

According to the requirements of carbon-neutral development, this study explores the comparison and new discussion of replacing nitrogen with carbon dioxide in the conventional two-phase microfluid flow. Thus, carbon dioxide application in various fields can be more precise and convenient. This research uses an artificially continuously tapering micro model to mimic the natural rock channel in low permeability formation, where the liquid imbibition process is entirely under surface tension-dominant. The tested capillary number decreased to 8.49 × 10 −6 , and the thinnest observed liquid film was reduced to 2 μm. The comparison results in two gas groups (nitrogen and carbon dioxide) show that CO 2 gas fluid in microscopic porous media would have more tendency to snap off and leave fewer residual bubbles blocked between the constrictions. However, the N 2 gas fluid forms smaller isolated gas bubbles after snap-off. By combining the experimental data and numerical output with the theoretical evolution equation by Beresnev and Deng and by Quevedo Tiznado et al., the results of interface radius, temporal capillary pressure, and velocity profiles for axisymmetric and continuously tapering models are presented and validated. Those findings create a paradigm for future studies of the evolution of microscopic multiphase fluid and enhance a deeper understanding of geological underground fluid properties for greenhouse gas storage and utilization in low permeability formations.