Polyvinylpyrrolidone-resorcinol-formaldehyde hydrogel system reinforced with bio-synthesized zinc-oxide for water shut-off in heterogeneous reservoir: An experimental investigation

This work aims at evaluating advancement in water shut-off performance using nanocomposite hydrogel (PVP-ZnO:RF) prepared from PolyVinylPyrrolidone (PVP); used as polymer, Resorcinol-Formaldehyde (RF); used as a crosslinker and nano Zinc Oxide (ZnO); used as strength modifier and it was compared with conventional hydrogel (PVP:RF) i.e., hydrogel without ZnO nanofiller. The ZnO, used as a nanofiller in this work, was successfully bio-synthesized (i.e., green route synthesized) from plant extract (Moringa oleifera leaves) and the average size was found to be 10 nm. In this research work, the effect of ZnO nanofiller on gelation time, gel strength, thermal stability, rheological properties and water shut-off performance was systematically evaluated. On the incorporation of ZnO nanofiller, gelation time decreases but gel strength increases. The thermal stability of hydrogel was studied using a Differential Scanning Calorimeter (DSC) that depicts maximum tolerable temperature increases from 86 °C to 92 °C at 0.5 wt.% of ZnO concentration in nanocomposite hydrogel (PVP). The mechanical stability of the nanocomposite hydrogel (PVP-ZnO:RF) demonstrates that infusion of ZnO nanofiller has significantly enhanced the dynamic moduli (i.e., storage modulus (G′) and loss modulus (G″)). Moreover, the optimum results of storage modulus (G′) and loss modulus (G″) are found at 0.5 wt.% of ZnO nanofiller. The water shut-off performance in the high permeable streak, in terms of percentage reduction in permeability, was 97% and 92% for nanocomposite hydrogel (PVP-ZnO:RF) and conventional hydrogel (PVP:RF), respectively. Also, the residual resistance factor is found to be 31.31 and 12.71 for PVP-ZnO:RF and PVP:RF hydrogels. Thus, the developed nanocomposite hydrogel (PVP-ZnO:RF) may be a promising solution to excessive water production in mature oil fields.