Temperature/salt tolerance and oil recovery of xanthan gum solution enhanced by surface-modified nanosilicas

Amide- and alkyl-modified nanosilicas (AANPs) were synthesized and introduced into Xanthan gum (XG) solution, aiming to improve the temperature/salt tolerance and oil recovery. The rheological behaviors of XG/AANP hybrid dispersions were systematically studied at different concentrations, temperatures and inorganic salts. At high temperature (75 °C) and high salinity (10,000 mg⋅L−1 NaCl), AANPs increase the apparent viscosity and dynamic modulus of the XG solution, and XG/AANP hybrid dispersion exhibits elastic-dominant properties. The most effective concentrations of XG and AANP interacting with each other are 1750 mg⋅L−1 and 0.74 wt%, respectively. The temperature tolerance of XG solution is not satisfactory, and high temperature further weakens the salt tolerance of XG. However, the AANPs significantly enhance the viscoelasticity the XG solution through hydrogen bonds and hydrophobic effect. Under reservoir conditions, XG/AANP hybrid recovers approximately 18.5% more OOIP (original oil in place) than AANP and 11.3% more OOIP than XG. The enhanced oil recovery mechanism of the XG/AANP hybrid is mainly increasing the sweep coefficient, the contribution from the reduction of oil-water interfacial tension is less.