Speaker
Description
Miscible CO2 injection in tight formations is crucial for carbon sequestration and enhanced hydrocarbon recovery, where the minimum miscibility pressure (MMP) between CO2 and hydrocarbons at the nanoscale is a key fluid property to be determined. Here, we developed a novel nanofluidic slim-tube method that enables direct visualization of CO2-hydrocarbon miscible behavior and in situ measurement of nanoscale MMP. This approach markedly reduces sample consumption (~0.59 μL) and shortens testing time (from six weeks to six hours), enabling rapid, high-throughput, and reliable MMP measurements. Using this method, we investigated CO2-hydrocarbon miscibility in nanoporous media (100 nm) and multiscale porous media spanning 100 nm to 10 μm. The results showed that molecular diffusion dominates mass transport at the nanoscale relative to convection. Under miscible conditions, CO2 fingering caused by mobility differences is substantially suppressed, yielding ~100% displacement efficiency. We further demonstrated that MMP in nanoporous media is reduced relative to bulk values. Multiscale features induce early CO2 breakthrough, whereas miscible displacement mitigates this tendency by suppressing fingering and stabilizing the advance of the CO2 front. Moreover, in multiscale porous media, distinct miscible stages arise from scale-dependent compositional variations and CO2 selective extraction. Notably, the MMP measured in multiscale porous media exceeds theoretical predictions for the largest pore size, highlighting the need for predictive frameworks that explicitly account for multiscale confinement effects. Overall, this work provides a nanofluidic strategy to elucidate confined miscibility and pore-structure impacts, offering a practical route to quantify fluid miscibility in complex porous media.
| Country | China |
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