Preparation and Characterization of Nanoclay-Based (Na-MMT and Bentonite) Polyacrylamide Hydrogels as Water Shut-Off Agent for Enhanced Oil Recovery

A novel poly(acrylamide)/ clay mineral composite was synthesized by controlled radical polymerization of acrylamide, clay minerals using potassium persulfate (KPS) and N, N '-methylenebisacrylamide (MBA) as redox initiator and cobalt acetylacetonate (Co(acac)(2)) as a catalyst in an aqueous solution. Synthesized nanocomposite copolymer was characterized by FTIR, XRD and DSC. XRD indicated intercalation formation by an inter-planar spacing increase between the clay layers. DSC showed an increase in the thermal stability of the mentioned hydrogels. Hydrogels with acceptable gel strengths, gelation time and gel stability were prepared by crosslinking of aqueous solutions of synthesized nanocomposite copolymer with Chromium (III) acetate for using in water shut-off operations in oil reservoirs. The effects of pH, salinity, Co(acac)(2), temperature, and clay minerals on the gelation time were investigated, and the activation energy was measured. By increasing temperature, gelation occurred more rapidly. The addition of Co(acac)(2) increased loss and storage modulus because of reversible activation-deactivation radical polymerization and decreased the gel swelling. Polymer chains can be diffused between the clay layers so the elastic modulus (G ') of the prepared hydrogels increased than hydrogels without nanoclays, and the reversible interaction between clay and acrylamide chains led to increased loss modulus (G '').