Review of Micro/Nanofluidic Insights on Fluid Transport Controls in Tight Rocks

Microfluidics and nanofluidics have been used in the oil and gas industry for pore-scale research experiments and as application-specific tools (such as lab-on-a-chip PVT analyzers). The former technology constructs pore and pore-network proxies on compact lab-on-a-chip devices. Such proxies are then used to investigate the impact of specifically tuned geometric and/or material variable(s) on fluid transport via direct observation with microscopy. This paper reviews micro/nanofluidics findings by the authors and other geoscience and general porous-media researchers. Findings are related to the impacts of pore size, surface chemistry (wettability), fluid type and composition, and surface texture (roughness) on fluid transport variables, such as effective viscosity, imbibition, capillary trapping, adsorption, and diffusive processes. For example, the authors' microfluidic findings include a critical surface roughness value beyond which capillary trapping during drainage increases drastically due to changes in subpore-scale flow regimes. The authors' nanofluidic findings include that the fluid polarity and surface chemistry of a silica nanoconfinement can lead to additional contact line friction that causes significant deviations from the continuum Washburn equation for imbibition; these effects can potentially be incorporated in the quantitative analysis through an increased effective viscosity. Finally, this review highlights practical approaches for using lab on-a-chip devices and their associated pore-scale findings as diagnostic tools to augment petrophysical laboratory measurements and guide field-scale pilot operations.