A new method for physical simulation of flow characteristics of fluids in shale oil reservoirs

Based on CT scanning of cores in shale oil reservoirs, focused ion beam-scanning electron microscope (FIB-SEM)and analysis of the microscopic pore structure characteristics of the reservoir using mercury intrusion data, the authors conduct physical simulation experiments of flow in cores generating shale oil with various physical properties using the self-developed enclosed high-precision evaluation system of shale oil flow, analyze the changing characteristics of microscopic pore structure during the flow process by means of nuclear magnetic resonance (NMR), and determine the flow laws of fluids in shale oil reservoirs. The research results show that compared with tight sandstone reservoirs, shale oil reservoirs have complex flow characteristics, mainly showing three flow characteristics:convex type (Kg>2.0 mD)and linear type (0.1 mD<Kg<2.0 mD)and concave type (Kg<0.1 mD), of which only typical concave-type and part of linear-type flow characteristics can determine the (pseudo)threshold pressure gradient. The flow characteristics of shale oil reservoirs are mainly determined by the coupling effect of boundary layer and stress sensitivity, and the relative strength of the both determines the different patterns of flow in shale oil reservoirs. The strongly stress sensitivity of shale oil reservoirs will cause the flow characteristics to change with the increasing of the producing pressure drop. Therefore, the numerical simulation of shale reservoirs must consider the influence of changes in pore structure on the flow characteristics. © 2021, Editorial Office of ACTA PETROLEI SINICA. All right reserved.