Micro-nano scale confined flow characteristics and mechanism in tight reservoir: Insights from experimental and molecular simulation studies

Understanding and controlling the confined flow in micro-nano pores and throats are of great significance for the efficient development of tight reservoirs. This paper covers the experimental and molecular simulation studies available on flow in confined spaces in the literature. The former provides fundamental and intuitive results, while the latter expands the scope of research and analyzes the internal mechanism. When the channel scale is reduced to several microns, the flow velocity begins to deviate from the prediction and the classical Hagen-Poiseuille equation is no longer applicable. Both flow enhancement and flow suppression phenomena may exist under different wall conditions at micro-nano scale channels. Influenced by the property of fluid and wall (wettability, channel shape, material, etc.), the relative interaction strength between solid-wall and liquid-liquid molecules is in a dynamic alteration. Fluid molecules form an ordered stacking structure near the wall, resulting in differences in fluid properties compared to the bulk phase. It is essential to consider the relevant flow parameters (viscosity, thickness, slip length, etc.) of the boundary region and their influence on overall flow in confined space. Finally, aiming to better apply the research results to enhanced oil recovery in tight oil, it is critical and necessary to consider the actual reservoir environment and form a suitable theoretical model.