Upgrading of Extra-Heavy Crude Oils by Dispersed Injection of NiO-PdO/CeO_2±δ Nanocatalyst-Based Nanofluids in the Steam

The main objective of this study is to evaluate the injection of a dispersed nanocatalyst-based nanofluid in a steam stream for in situ upgrading and oil recovery during a steam injection process. The nanocatalyst was selected through adsorption and thermogravimetric experiments. Two nanoparticles were proposed, ceria nanoparticles (CeO_2±δ), with and without functionalization with nickel, and palladium oxides (CeNi0.89Pd1.1). Each one was employed for static tests of adsorption and subsequent decomposition using a model solution composed of n-C₇ asphaltenes (A) and resins II (R) separately and for different R:A ratios of 2:8, 1:1, and 8:2. Then, a displacement test consisting of three main stages was successfully developed. At the beginning, steam was injected into the porous media at a temperature of 210 °C, the pore and overburden pressure were fixed at 150 and 800 psi, respectively, and the steam quality was 70%. This was followed by CeNi0.89Pd1.1 dispersed injection in the steam stream. Finally, the treatment was allowed to soak for 12 h, and the steam flooding was carried out again until no more oil production was observed. Among the most relevant results, functionalized nanoparticles achieved higher adsorption of both fractions as well as a lower decomposition temperature. The presence of resins did not affect the amount of asphaltene adsorption over the evaluated materials. The catalytic activity suggests that the increase in resin content promotes a higher conversion in a shorter period of time. Also, for the different steps of the dynamic test, increases of 25% and 42% in oil recovery were obtained for the dispersed injection of the nanofluid in the steam stream and after a soaking time of 12 h, compared with the base curve with only steam injection, respectively. The upgraded crude oil reached an API gravity level of 15.9°, i.e., an increase in 9.0° units in comparison with the untreated extra-heavy crude oil, which represents an increase of 130%. Also, reductions of up to 71% and 85% in the asphaltene content and viscosity were observed.