Abstract：

Water flooding is the most important development mode of conventional sandstone reservoirs in China. Studying the flow dynamics of the microscopic residual oil is of great significance to guide the development of water flooding reservoirs in the high water cut stage. In this paper, on the basis of flooding experiments conducted on microscopic glass models, a method that uses the parameters including the number of pores occupied by the microscopic residual oil, the Euler number, the contact ratio of oil and rock and shape factor was established to quantify the microscopic remaining oil. The remaining oil was classified into 5 five kinds based on its occupancy characteristics: cluster, multi-porous, columnar, droplet and membranous. Then the identifi cation and quantitative statistics of the microscopic residual oil were carried out, and the occupancy characteristics and dynamic variation characteristics of micro residual oil in the process of water flooding were studied. Moreover, the average pore radius, the average pore-throat ratio and the average coordination number of the pores occupied by the residual oil was used to analyze the flow dynamics of the residual oil. The results show that the pore radius is the main controlling factor of the occurrence of the clustered residual oil, and the pore-throat ratio is the main controlling factor for forming porous residual oil, while the poreradius, the pore-throat ratio and the coordination number of the droplet residual oil distribution are widely distributed, and the pore-throat ratio and the coordination number of the columnar and membranous residual oil distribution are also widespread. In the heterogeneous model, inhomogeneity plays a leading role in the flow of the cluster and the multi-porous micro-residual oil, and the micro-residual oil mainly exists in low-permeability areas with small pore throat radius, and the effect of pore-throat ratio and coordination number is not large, while the remaining three types of non-continuous-phase residual oil are formed in the water-drive process, especially the high-water-cut stage, and they are mostly in the area where water flooding has spread, and heterogeneity has little effect on the flow dynamics of this microscopic residual oil. The methods proposed by this paper may also be useful for other researchers in the EOR area.    

Key words：microfluidic model; micro remaining oil; occurrence state; oil field development; characteristics of flow path variation

Received： 2019-09-02

Corresponding Authors： lijunjian@foxmail.com

Cite this article：WANG Chuan, JIANG Hanqiao, XU Fei1, YU Fuwei, ZHAO Yuyun, LI Junjian. Study of the variation of pore-scale residual oil flow based on a microfluidic model. Petroleum Science Bulletin, 2020, 03: 376-391.

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