Pore sweep efficiency quantitative investigation and fracture flow regulation mechanism of self-growing hydrogel particles in low-permeability fractured reservoirs

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Low-permeability fractured reservoirs exhibit pronounced fracture–matrix heterogeneity, where injected fluids preferentially channel through fractures, resulting in poor oil recovery from the matrix. To address this challenge, self-growing hydrogel particles were developed to achieve effective fracture flow regulation and improve matrix sweep efficiency. Catechol-functionalized polyacrylamide (CFPAM) was first crosslinked with a phenolic resin crosslinking agent to form a bulk gel, which was subsequently processed into hydrogel particles with self-growing aggregation and shear recovery capabilities through mechanical shearing and grinding. The particles were systematically characterized, and computed tomography (CT) was employed to quantitatively evaluate pore-scale sweep efficiency before and after treatment. The results show that the particles exhibit pronounced self-growing aggregation, with a 23-fold increase in size after 30 d of aging and a shear recovery rate of 91.62%. During fracture flow regulation, the irregular aggregates effectively block fractures and redirect subsequent fluids into the matrix. As a result, the pore-scale sweep efficiency of waterflooding increased from 43.63% to 77.46%. This work proposes a practical hydrogel particle-based strategy for fracture blocking and provides experimental evidence and mechanistic insights to guide field applications in low-permeability fractured reservoirs.