The world’s oil demand is rising, and it is still presumed as one of the leading global energy sources for the next fifty years. Furthermore, unconventional methods such as enhanced oil recovery (EOR) must be considered to prove the future oil supply. Recently, nanoparticles (NPs) have shown promise to improve reservoir efficiency, but the utilization of NPs for EOR relies heavily on the production, stabilisation, and delivery of functional NPs to the reservoir.
A novel methodology to synthesise NPs in situ, i.e., under reservoir-like conditions, has been explored in this project, focusing on understanding the shape, size, and stability of NPs under harsh environmental conditions such as temperature, pressure, and salinity during the production of NPs and their formation kinetics. Therefore, the work performed in this study was divided into two key parts:
i. Stage 1: Microwave-assisted hydrothermal synthesis of nanoparticles (Ag, SiO2, CeO2, and Fe3O4) at a heating rate of 5, 10, and 15 ºC/min to reach a final temperature of 150 ºC, capping agent concentration of 1%, 2% and 4% and salinity levels of 0%, 2.5%, and 5%.
ii. Stage 2: High-pressure hydrothermal synthesis of selected nanoparticles (CeO2 and Fe3O4) at a temperature of up to 80 ºC and pressure of up to 250 bar with high salinity (10%).
In stage 1 experiments, the heating rate and capping agent concentration both played a crucial role in controlling the size and morphology of all NPs, giving the best performance at the heating rate of 15 ºC /min and capping agent concentration of 4% and no applied salinity. The greater the salinity, the greater the instability. All NPs formed were of spherical morphology and crystalline structure except silica which exhibited a slight sign of the amorphous structure. The performance of cerium oxide and iron oxide showed the best tolerance to added salinity and were taken forward to the second stage. In stage 2, more aggressive conditions mimicking reservoir conditions were simulated to synthesize cerium oxide and iron oxide NPs. Among both, iron oxide showed greater tolerance to added salinity which can be linked to the stronger attachment of the capping agent to the iron oxide surface. A novel methodology was proposed and showed promise for EOR applications.
It is recommended that cerium oxide and iron oxide NPs be considered potential candidates for EOR applications. This is because their size, shape, and stability can be precisely controlled by controlling the temperature, pressure, and salinity.
