Regulation of Fluid Flow Behavior in Porous Media Based on Particle Migration

The particle migration phenomenon in porous media exhibits dual effects: it can both impede fluid flow and regulate the flow field. The temporary plugging effect induced by particle migration can delay the formation of preferential flow paths in waterflooding and enhance recovery efficiency. However, research on actively controlling the flow field through particle migration to improve recovery efficiency is still limited. This study aims to investigate the generation of a temporary plugging effect within the pores by controlling the particle size and concentration in the injected water, thereby regulating the distribution of the flow field and enhancing oil recovery. The research combines numerical simulation techniques with core flooding experiments, constructing numerical models with different micro-pore structure characteristics, such as moldic pores and intrafossil pores, and physical models with varying permeability gradients. Experimental results show that after the formation of preferential flow paths in waterflooding, continued water injection can no longer effectively displace the remaining oil in the porous media. At this point, the addition of suspended particles (median particle size: 5 μm, concentration: 200 mg L⁻¹) to the injected water further enhances displacement. The particles migrate with the water flow and preferentially accumulate in high-connectivity pores and throats, forming a temporary plugging effect. This alters the local flow path, expanding the sweep volume of waterflooding and effectively mobilizing oil in low-permeability pores.

When the particle size exceeds 10 μm or the concentration exceeds 400 mg L⁻¹, bridging or sealing effects are likely to occur at pore entrances, severely obstructing fluid flow. Conversely, when the particle size is too small (<2 μm) or the concentration too low (<10 mg L⁻¹), the particles fail to effectively retain and do not form a significant temporary plugging effect. After the particle-based flow regulation treatment, the final oil recovery efficiency of the model can be increased by approximately 10% to 20%.