Characterization of movable particle transport and plugging mechanism in fractured low-permeability reservoirs

During the development of fractured low-permeability reservoirs, the transportation and clogging of movable particles in the pores is a key issue that restricts the enhancement of recovery. In this paper, the transportation characteristics of movable particles in fractured low-permeability reservoirs and their clogging mechanism are systematically studied through high pore volume (PV) displacement experiments, combined with laser particle size analysis, scanning electron microscopy (SEM), X-ray diffraction (XRD) and CT scanning technology. The experimental results show that the dynamic change of the displacement pressure shows a staged character, the initial stage is caused by the capillary resistance and viscous resistance leading to a sudden rise in pressure, and the subsequent pressure fluctuation is closely related to the dynamic balance of the transport, plugging and scouring of the clay particles. The particle size analysis of the extracted liquid shows that the particle size distribution varies significantly in different stages of displacement, and the particle size gradually increases with displacement. Scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) analysis showed that the filtrate of the extracted fluid was mainly composed of clay minerals such as montmorillonite and illite, accompanied by quartz particles, and CT scanning revealed that the porosity and connectivity of the reservoir were increased but the uniformity of the pore-throat distribution was reduced after the displacement. This study provides a theoretical basis for particle transport control and reservoir protection in fractured low-permeability reservoir development.