Preparation of in situ physicochemical interpenetrating hydrogels with polysaccharide polymers/polyacrylamide and rheology, plugging, and reservoir damage properties

Acrylamide (AM) monomers are frequently used to prepare temporary plugging materials. The contradiction between efficient plugging and degradability in high-temperature environments limits the application of acrylamide-based temporary plugging agents. This study reports the use of unstable cross-linkers, polyethylene glycol diacrylate, and acrylamide, to construct a polyacrylamide (PAM) temporary plugging hydrogel. The influence of the physical cross-linking networks of polysaccharide-based polymers of polyvinyl alcohol (PVA)/branched starch (ST), hydroxyethyl cellulose (HEC)/ST, and sodium alginate (SA)/ST on the rheological properties, plugging performance, and shale damage mechanisms of PAM temporary plugging hydrogels were also investigated. Physical interpenetrating cross-linked networks have negligible effects on the gelation and degradation times of PAM hydrogels. The rheology of the PAM hydrogel reaction solution modified by physical cross-linking was consistent with that of a shear-thinning fluid, which dramatically improved the ability of the solution to reside while safeguarding pumping performance. The mechanical properties of the PVA-ST and SA-ST modified PAM hydrogels were substantially enhanced, and the breakthrough pressure gradients at 0.5 ml/min were 4.86 and 5.26 MPa/m, respectively. The large number of hydroxyl groups in the physically cross-linked network formed hydrogen bonds with AM, which inhibited the permeability of the AM monomer in the shale matrix and reduced the damage performance of the PAM temporary plugging hydrogel. The polysaccharide-based physical cross-linking network can substantially improve the pumpability and plugging performance and inhibit damage to the shale matrix of the temporary plugging gel while safeguarding the degradability of the PAM temporary plugging hydrogel.