In the present work, attempts have been made to prepare nanocomposite type of hydrogels (NC gels) by crosslinking the polyacrylamide/montmorillonite (Na-MMT) clay aqueous solutions with chromium (111). The Xray diffraction patterns of the NC gels exhibited a significant increase in d(001) spacing between the clay layers, indicating the formation of intercalated as well as exfoliated type of morphology. Exfoliation of the clay layers through Out the gel network was found to be predominated, which evidences the high interaction between the polyacrylamide segments and montmorillonite layers. Gelation time as well as variation of viscoelastic parameters such as storage modulus (G') of the gel network during gelation process at 75 degrees C was studied and followed by rheomechanical spectroscopy (RMS). The NC gels prepared with lower crosslinker concentration showed higher strength and elastic moduli-is compared with the similar but unfilled polyacrylamide gel. This distinct characteristic of the NC gels yields a gel network structure with high resistance towards syneresis at high temperature in the presence of the oil reservoir formation water. The effects of the composition, such as clay content, crosslinker concentration, and also water salinity upon the gelation rate, gel strength as well as rate of syneresis have been investigated. To optimize the injectivity of the intercalated polyacrylamide solution before the onset of gelation with the gel strength of the final developed gel, sodium lactate was employed as retarder. This was found to be effective to balance these two characteristics of the NC gels, which are aimed to be used for water shut-off and as profile modifier in enhanced oil recovery (EOR) process during water flooding process. The nanocomposite gels showed Much more elasticity and extensibility at low crosslinker concentration compared with the similar but unfilled gel, which makes the NC gels Suitable as an in-depth profile modifier, and also as an oil displacing agent in the heterogeneous oil reservoir in chemical EOR. Effects of the clay content on the thermal stability of the gel network have also been investigated by thermogravimetric analysis (TGA). Scanning electron microscopy (SEM) has been performed upon the NC-gel samples. (c) 2006 Wiley Periodicals, Inc.