Abstract: In order to further clarify the microscopic oil-water occurrence law during the water flooding process in high-permeability sandstone reservoirs,a microfluidic model of high-permeability sandstone in the Bohai Sea was established by scanning the core of the reservoir; based on the microscopic parameters such as the shape factor and Euler number, the computational program code was prepared to finely identify and extract the microscopic characterization of the remaining oil of five types, such as film, drop and column; and the experimental scheme was designed for the different fluid properties and development modes, so as to clarify the microscopic oil-water occurrence law and the evolution characteristic of the typical high-permeability sandstone of the Bohai Sea in the context of the different crude oil properties and the development regimes. The results show that With the increase of remaining oil discontinuous phase, it is difficult to produce the flow-around zone and stagnant zone within the water flooding range, and the porous and clustered remaining oil has become the main remaining oil occurrence pattern; high-speed displacement of water flooding has a larger sweep range, but the injected water flow-around is easy to lead to the water visible at the extraction end in advance, and the reach is no longer significantly increased; in low-viscosity reservoirs, the sweep efficiency of high-velocity displacement is increased by 0.154 compared to that of low-velocity displacement; in high-viscosity reservoirs, the sweep efficiency at the end of water flooding is increased by 0.137 after the liquid flow redirection and adjustment. For the typical reservoir properties of Bohai Oilfield and the conditions of high water content development stage, low-viscosity reservoirs are more suitable for increasing the displacement rate for potential tapping, and high-viscosity reservoirs are suitable for liquid flow redirection to further produce the remaining oil. The research results provide a reference for the efficient development through water flooding in Bohai Oilfield.

Key words: occurrence law, microfluidic modeling, microscopic characteristic parameters, remaining oil, sweep range, high-permeability sandstone reservoir, Bohai Sea Oilfield