Self-growing Hydrogel Particles with Applications for Reservoir Control: Growth Behaviors and Influencing Factors.

Abstract

Chemical profile control agents are the key for conducting effective reservoir control to enhance crude oil recovery. Self-growing hydrogel particles have emerged as highly competitive profile control agents as they can grow for control after migrating to deep fractures, exhibiting great potential in long-term adaptive reservoir control. In this work, self-growing hydrogel particles were prepared by mechanical shearing of self-repairing bulk gels constructed by catechol-functionalized partially hydrolyzed polyacrylamide p[AM-AANa-DOPA] and phenolic resin cross-linking agents. After aging for 15 days under the reservoir conditions, the median size of hydrogel particles increased from ∼3.5 to ∼18.0 μm, demonstrating apparent self-growing property and significantly enhanced resistant coefficient in waterflooding. Different factors affecting growth behaviors of hydrogel particles including cross-linking density, chemical re-cross-linking, hydrolysis degree, and molecular weight of the copolymer were studied. The results showed that the cross-linking density affected the strength and toughness of the bulk hydrogel, with appropriate polymer chain mobility facilitating the intermolecular interactions. Quantitative NMR results of the gelation process indicated that chemical re-cross-linking contributed little to the growth of hydrogel particles. Based on the rheological and nanomechanical results, bulk gels prepared by polymers with a lower hydrolysis degree and smaller molecular weight possessed a higher elastic modulus recovery rate, while the corresponding hydrogel particles exhibited stronger adhesion among each other. This work provides new insights into the growth behavior of hydrogel particles, which may help better understand and select a suitable hydrogel system and preparation technology and further promote efficient reservoir control.