关键词: 页岩油, 孔隙网络模型, 孔隙结构, 两相流动, 采出程度, 剩余油

Abstract: In order to understand the flow characteristics of shale oil and the formation mechanism of microscopic remaining oil, the shale reservoir of the Shahejie Formation in Jiyang Depression was taken intuitively and accurately as the research object, and the focused ion beam scanning electron microscope system was used for scanning imaging. A three-dimensional digital core was constructed and a pore network model was extracted. The pore structure parameters were analyzed, and then the physical properties of the three-dimensional pore network model were compared with the laboratory experimental physical data to verify the accuracy of the model. On the basis of the pore network model, the pore throat structure characteristics of the samples were analyzed, and a mathematical model of oil-water two-phase seepage flow was established in combination with the Navier-Stokes equation. The finite element method was used to solve model, and the oil-water two-phase microscopic flow simulation was carried out. The results show that the shale samples have the characteristics of complex pore structure, low pore coordination number and poor connectivity. The reservoir space and flow space of shale oil are mainly nano-scale pores. The fluid flow in the pore network model is complex, and the recovery degree increases with the increase of displacement pressure. The higher the pressure is, the easier the fingering phenomenon occurs, and the local remaining oil will be formed. The size of local narrow throat is the key factor to limit the flow of fluid. When the wettability of the wall is water wet, the displacement effect is the best, while the model is oil wet, the displacement effect is the worst, and the remaining oil is not easy to form when the neutral wetting is in. The results of this study are of great significance for the study of oil-water two-phase flow of shale oil under micro conditions. The size of the locally narrowed throat is a key factor restricting fluid flow. When the wall wettability is water-wet, the oil displacement effect is the best, while the model wall is oil-wet, the oil displacement effect is the worst, and the remaining oil is not easy to form When the wall is neutrally wet. The research results have guiding significance for the study of oil-water two-phase flow of shale oil under microscopic conditions.

Key words: shale oil, pore network model, pore structure, two-phase flow, recovery degree, remaining oil