High Strength Polyacrylamide/nmSiO₂ Composite Hydrogel for Well Killing

Abstract

Killing pills of high strength composite hydrogel were prepared by polyacrylamide, chromium acetate crosslinker and silica nanoparticles reinforcer. The killing performance of composite hydrogel depended on its viscoelasticity and compression strength, which were both influenced by polymer content, ratio of polymer to chromium acetate and nano silica content. In this work, the effect of these altering factors on strength of composite hydrogel were evaluated, results showed that elastic moduli (G′), viscous moduli (G″) and compression strength all increased as polymer content increased, ascribing to close entanglement among polymer chains and increasing crosslinking density. G′ was proportional to the ratio of polymer to chromium acetate, whereas G″ and compression strength experienced initial increase then decrease, indicating an optimal ratio existed to achieve the strength peak of composite hydrogel. Silica nanoparticles contributed significantly to viscoelasticity and compression strength of hydrogel. From SEM images, we can see silica nanoparticles attached onto network branches and filled into the network pores in aggregation, in this dispersion form to strengthen the microstructure further to enhance the strength of composite hydrogel. Moreover, the polymer/nmSiO₂ composite system is shear-thinning fluid, which promises its pumpability as killing fluid during killing operation.