Polyacrylamide and polyethylenimine mixed hydrogels tailored with crude glycerol for conformance fluids: Gelation performance and thermal stability

Abstract

Minimization of water output is key to prolong oil field production. Although hydrogels are an effective alternative to sealing preferable water pathways in highly permeable reservoirs, their thermal and viscoelastic properties must be tuned to withstand harsh reservoir conditions and avoid damage to the formation. To that end, herein we tested a novel solid-free gel system containing crude glycerol (CG) to control fluid loss in overbalanced operations. Analytical grade glycerol (AGG) was also studied for comparison. Polyacrylamide (PAM) crosslinked with polyethyleneimine (PEI) embedded with CG produced hydrogels thermically resistant and capable to prevent filtration in reservoir conditions (65 °C/90 °C and 300 psi). CG significantly lengthened the gelation time and stability of hydrogels in comparison to AGG, a behavior related to the presence of chloride ions in CG. Noteworthy, glycerol-based hydrogels displayed robust viscoelastic properties, similar to those of systems with solid particles and nanomaterials. Glycerol also enhanced PAM-PEI hydrogels thermal stability, retaining most of gel fraction up to 250 °C. The composition of CG associated with PAM-PEI resulted in a complex combination of ionic and hydrogen bonds that boosted hydrogel network conferring greater stability. The possibility of incorporating CG in conformance fluids is quite advantageous to mitigate the ecological shortcoming posed by the accumulation of biodiesel-derived glycerol.