The influence of 3D digital core pore-throat characteristics and displacement parameters on seepage displacement ability

Abstract: It is of great significance to clarify the microscopic pore throat, microscopic seepage characteristics and influencing factors of tight reservoirs for guiding the oil and gas development of tight reservoirs. In this paper, the tight reservoir of Chang 8 group in Fuxian area of Ordos Basin is taken as the research object. 3D digital core and pore model are established based on CT scanning. The pore model is converted into grid model and insert into the seepage simulation platform. The single-phase and oil-water two-phase seepage simulation is further carried out, and the influence of microscopic pore structure and displacement parameters on displacement seepage is discussed. The results show that: 1) The seepage flow velocity and pressure difference are the largest at the throat, forming a high flow velocity and stress concentration area, and the change is small in the pore area; the seepage displacement characteristics of the model with large pore and small throat and strong heterogeneity are relatively more complex, and it needs more driving pressure to reach the same residual oil saturation. 2) The stress concentration area formed by small throat and complex pore throat structure will lead to displacement stop and plugging. Throat parameters and heterogeneity affect the process and range of seepage displacement. Connected pore parameters affect the size of the driving space, which in turn affects the displacement efficiency. 3) In addition to the mainstream, When the proportion of throat with a radius less than 8μm is relatively high, increasing the driving pressure has a significant effect on improving the displacement efficiency, while the influence is small when the proportion of larger throat is relatively high. In addition to the mainstream, When the proportion of pores with a radius larger than 18μm is high, reducing the viscosity ratio has effect on improving the displacement efficiency, while when the proportion of smaller pores is high, the displacement efficiency will be reduced. This paper discusses the combined effect of microscopic pore throat characteristics and displacement parameters on the effect of seepage displacement, which provides new ideas and theoretical guidance for the study of microscopic seepage and efficient displacement development of tight reservoirs.