Direct visualization of fluid behaviors at the nanoscale for shale gas/oil fundamentals, challenges and applications

Hydrocarbon recovery from shale provides an increasing share of energy. These resources are multi-component fluid mixtures within multi-scale geometries, and understanding their fluid behaviors presents an array of challenges for experimentalists, theorists and operators. Here, we present our recent progress in visually quantifying fluid behaviors down to a few nanometers scale through nanofluidic device. During the gas production, we find the fluid phase behavior is highly governed by the gas flow in nanoconfinement, a case beyond bulk understanding. The vapor flow at a Knudsen number between 0.01 to 1 is of shale relevance. We also quantify the multiphase flow and interactions in nanoconfinement. An important application of this fundamental issue is the enhanced oil recovery strategies for tight oil reservoirs. With nanofluidic device, we have directly visualized and studied factors affecting immiscible gas fingering and miscible gas filming into liquid oil in nanoporous media, indicating fundamental challenges as well as potentials of gas-based enhanced oil recovery strategies in nanoporous shale. The nanofluidic approach presented here is not limited to probing oil-gas relevant features, but also a platform for studying fluid behaviors in nanoporous material.