Enhanced oil recovery (EOR) in the last several years has become an important factor in oil production due to the shortfall in high quality crude oil. Heavy oil as one of the unconventional hydrocarbons is still vastly abundant in nature and is hence frequently explored with EOR. The viscous characteristic of heavy oil necessitates further in-situ upgrading processes to be executed before extraction. An interesting upgrading method is through aquathermolysis under the addition of catalyst. This review focuses on presenting nanoparticle catalysts, such as nickel-, iron-and cobalt-based nanocatalyst. The explanation covers topics from synthesis methods and characterization up to the effect of reducing the viscosity of heavy oil. Lastly, concluding remarks and future perspectives are highlighted regarding the visibility and available approaches of developing nanofluids for EOR.

Catalytic aquathermolysis is proposed as one of the potential methods which functions to reduce the viscosity of heavy oil for ease of extraction. In this research, we have developed a solution dispersed catalyst of Fe3O4 nanoparticles through a co-precipitation method. FeCl3·6H2O and FeCl2·4H2O were used to serve as an Fe source, with NaOH as a co-precipitator. The as-synthesized nanoparticles were characterized by X-ray diffraction (XRD) to verify materials. In order to be able to be used in the reservoir, the prepared powder was further dispersed into a base fluid with the addition of a dispersant by an ultrasonication for 2 hours. The stable nanofluid was achieved using the ratio of ethylene glycol/water mixture of 20%:80%. Dynamic light scattering (DLS) characterization results showed that the average size of the particle was about 309 nm, which is small enough to ensure its ability to pass through rock pores. Catalytic aquathermolysis of heavy oil in laboratory scale was employed under the addition of stable nanofluid at 200°C for 6 hours. The viscosity of heavy oil after the reaction could be reduced up to 71.3%.