Suspension of surface-modified nano-SiO 2 in partially hydrolyzed aqueous solution of polyacrylamide for enhanced oil recovery

In high-temperature and high-salinity oil reservoirs, the poor thermal stability and salinity tolerance of partially hydrolyzed polyacrylamides (HPAM) solution hinder its efficiency in enhanced oil recovery (EOR). Therefore, a series of dispersible nano-SiO2 (denoted as DNS) separately surface-modified by silane coupling agents hexamethyldisilazane (denoted as HMDS) and hexadecyltrimethoxysilane (denoted as HDTS) are prepared by in-situ surface-modification technique. The two types of surface-modified hydrophobic nano-SiO2, i.e., DNS-HM (modified by HMDS) and DNS-HD (modified by HDTS), are separately added into HPAM solution to obtain the HPAM-based suspensions used for EOR. The effects of DNS-HM and DNS-HD on the thermal stability, apparent viscosity, and flooding performance of HPAM are investigated. The results indicate that the HPAM/DNS-HM8 and HPAM/DNS-HD16 (see Table 1) suspensions exhibit better apparent viscosity, storage stability and thermal stability than the HPAM/DNS-0 suspensions. Moreover, HPAM/DNS-HM8 suspension show better flooding performance and has a higher oil recovery factor (about 10.54%) than other HPAM-based suspensions.