Nanoparticle modified polyacrylamide for enhanced oil recovery at harsh conditions

Silicon dioxide (SiO2) nanoparticles (NPs) have been recently proposed to increase the performance of polyacrylamide (PAM) for enhanced oil recovery (EOR) applications. However, SiO2/PAM nanocomposites tend to agglomerate or even desposit under harsh conditions such as high temperature-high salinity (HT-HS), which greatly decreases the potential for future field applications. In this work, SiO2 NPs were modified by (3-aminopropyl) triethoxysilane (M_SiO2) to create positively charged active groups that enabled strong interaction with PAM functional groups, leading to high dispersion stability. Three samples including M_SiO2/PAM, SiO2/PAM and NP-free PAM were synthesised in-situ via free radical polymerisation, and their thermal stability, rheological properties and the effect of aging time were studied. It was found that M_SiO2 could reduce the thermal degradation of the polymer and safeguard its backbone, resulting in much better thermal stability of PAM in harsh environments. After 90 days of aging, SiO2/PAM and NP-free PAM had 45 and 78% viscosity reduction; whereas only 10% reduction was observed for M_SiO2/PAM. In addition, core-flooding experiments showed that M_SiO2/PAM solutions produced more oil recovery than those from SiO2/PAM and NP-free PAM solutions at HT-HS condition.