Ester-Bond-Cleavable Self-Degradable Gel Particles for Temporary Plugging and Controlled Deplugging in Multi-Fracture Reservoir Systems

Temporary plugging and flow diversion in multi-fracture reservoirs require gel particles that can provide stable plugging in dominant fractures while enabling low-residue deplugging after treatment. In this study, ester-bond-cleavable self-degradable gel particles were prepared by aqueous free-radical crosslinking using acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, N-vinyl-2-pyrrolidone, and polyethylene glycol diacrylate as a hydrolysable crosslinker. An MBAA-crosslinked particle was used as a nondegradable control. FTIR and SEM results confirmed the formation of ester-containing crosslinked networks with tunable morphology. Among the prepared samples, EGP-2 showed a balanced hydration and mechanical response, with an equilibrium swelling ratio of 7.12 g/g at 80 °C and 100,000 mg/L salinity, a storage modulus of 205 Pa at 1 Hz, a compressive stress of 54.2 kPa at 30% strain, and a height recovery ratio of 91.8%. In single-fracture tests, EGP-2 achieved plugging efficiencies of 98.6% and 97.4% in 0.5 and 1.0 mm fractures, respectively, with corresponding erosion retention ratios of 94.1% and 92.6%. In a three-parallel-fracture model, EGP-2 reduced the dominant-fracture flow split ratio from 78.4% to 32.8%, while increasing the combined flow split ratio of the medium and narrow fractures from 21.6% to 67.2%, corresponding to a flow diversion efficiency of 58.2%. After aging at 120 °C for 96 h, EGP-2 exhibited a mass loss ratio of 78.4% and a G′ retention ratio of 25.4%. Subsequent flowback tests showed a flowback ratio of 82.6%, a permeability recovery ratio of 88.7%, and a residue ratio of 10.9%. These results demonstrate that ester-bond-cleavable gel particles can integrate temporary plugging, flow diversion, and controlled deplugging, offering a low-residue strategy for multi-fracture reservoir conformance control.