Preparation and investigation of the physical and chemical properties of clay-based polyacrylamide/Cr (III) hydrogels as a water shut-off agent in oil reservoirs

The effects of clay (montmorillonite and kaolinite) in the hydrogels were investigated on various properties such as syneresis and strength of thermal and salinity situations in one of the southern Iranian oil reservoirs. The X-ray diffraction (XRD) patterns exhibited a significant increase in interplanar spacing between the montmorillonite clay layers, varying from the initial value of 12.43 A degrees A to 19.45 A degrees A, which evidences the intercalation formation. It was revealed that even increasing of the interlayer spacing due to kaolinite modification had no effect on the clay compositions. Formation water was used to study the strength of the hydrogel in the presence of ions. The results indicated that 15 wt% increase of kaolinite clay (modified and non-modified) leads to 20% decrease of the hydrogels' syneresis. The diffusion of polymer chains between the clay layers increased the elastic modulus (G') of the prepared hydrogels with modified kaolinite and montmorillonite, where the maximum value of G' was observed in 3 wt% of montmorillonite. Finally, the thermogravimetric analysis (TGA) indicated an increase in the thermal stability of the mentioned hydrogels.