Dynamic covalent hydrogel fabricated in porous media through dynamic acylhydrazone bond from reactive precursors for deep profile control

In this work, we proposed a novel hydrogel system for in-depth conformance control through the dynamic covalent bond. Diffluent ketone-bearing and acyl hydrazide-bearing reactive precursors with low molecular weight are injected into the formation simultaneously, then gels in situ through dynamic hydrazone bonds to divert the post-injected fluid to un-swept oil zones. Ketone-bearing and acyl hydrazide-bearing reactive precursors with different reactive group ratios were synthesized by simple radical polymerization and hydrazinolysis. Rheological measurement results proved the two reactive precursors formed dynamic covalent hydrogel (DCG) through dynamic hydrazone bonds in deionized water and mineralized water. The viscoelasticity, flow behavior, and profile control behavior in the porous media of the DCG were evaluated. When the flow behavior and profile control experiments were conducted with a 9 m core, the injection pressure of DCG-20% of which the molar ratio of the reactive group was 20% was low (0-0.22 MPa) throughout the injection process, and the resistance factor was 4.40. After fully gelation, the post-water injection pressure significantly increased (0.22-7.54 MPa). The residual resistance factor was 150.80, and the plugging efficiency was 99.34%. This work proved that the DCG consisting of ketone-bearing and acyl hydrazide-bearing reactive precursors not only had a strong injection capacity but also had a good profile control effect in porous media which meant the DCG fully met the need for deep profile control.