Microwave-assisted synthesis of PAM preformed particle gels reinforced with carbon nanomaterials for conformance control in oil recovery

Enhanced oil recovery aims to increase the sweeping efficiency of a reservoir through the injection of displacing fluids. The use of preformed particle gels (PPG) has recently received great attention because it acts by blocking the high permeability channels, reducing water production and elevating the cost/benefit for production. Herein, an innovative microwave synthesis of polyacrylamide (PAM) hydrogels reinforced with graphene oxide (GO) and oxidized carbon nanotubes (CNT-ox), which were dried and grounded to obtain PPGs were prepared. Carbon nanomaterials were used to overcome the limitations of conventional PPG, improving blocking efficiency, and this is the first time that CNT-ox has been used for this purpose. Raman and X-ray photoelectron spectroscopy analyses were performed to confirm GO and CNT-ox incorporation on the PAM hydrogel and to identify an in situ acrylamide polymerization with unusual chemical cross-linkers. Rheological tests were conducted to evaluate the influence of the hydrogel formulation under relevant reservoir conditions and the injectivity of the system on the hydrogel strength. The results showed that the systems formed based on PAM cross-linked with carbon nanomaterials were able to form “strong gels” exhibiting pseudoplastic behavior (G”/G’ < 0.1). PAM-CNT-ox increased the resistance to deformation of the gel and swelling capacity with high ionic strength up to 57 % and 39 % for the systems stored at 25 °C and at 70 °C, respectively. The apparent viscosity results for PPGs showed that saline systems containing 0.5 wt%, 1.0 wt% and 2.0 wt% of PPG and R-PPG at 25 °C are suitable for injection to viscosity values < 30 mPa.s.