Pore-scale simulation of shale oil flow based on pore network model

摘要

The pore-grain characteristics of shale oil reservoir rocks are complex: nano-size pore throats, multi-scale of pore size and topology, and rich in organic matter. Generally, shale oil flow in nanoporous media is significantly affected by microscopic fluid slippage and adsorption on the pore surfaces, which give rise to variable slip length, viscosity ratio of adsorbed phase to bulk phase, and thickness of adsorption layer in organic & inorganic pore throats. In this study, a new pore network model is developed based on a modified shale oil flow equation to consider those combinational effects on shale oil permeability under different organic matter contents, and then is applied to provide an order analysis of those effects on the permeability of a representative shale model. Different flow patterns characterizing fluid-solid interaction are also discussed. Analysis results show that shale oil permeability is strongly influenced by the slip length. The effect of adsorption on permeability is negligible for cases considered. Shale oil flow is mainly controlled by inorganic pores when volumetric TOC is low. The influence of TOC on permeability depends on slippage and adsorption conditions in organic and inorganic matters, referred in this paper to as flow patterns. As the organic matter content increases, the connectivity of organic pores and throats improves, which further affects network permeability.