Albite-anorthite synergistic effect on the performance of nanofluid enhanced oil recovery

Large volumes of oil sit within our reach primarily of the strong capillary forces, which themselves are subsequent to the attraction between the polar ends of the oil and the surface charges of bearing-matrix. Altering these interactions occurring within tiny pore throats or even more, unveiling the extent to which the geochemistry impacts these interactions can invariably improve the production. Therefore, we evaluated the performance of water-based nanofluid for oil production with the respect to the geochemistry. Alumina-silica nanocomposite (Al/Si-NP), synthesized by plasma-method, was used as primary material. Functionalized by dispersing 0.25 wt.% lyophilized NP into the formation water (TDS=4301 ppm) water under carbon dioxide bubbling. The nanofluid, NF, obtained therefrom, was then used for coreflooding tests, which aim at displacing a dead heavy oil (ρ =0.854 g/cm3) from a waterflooded Berea sandstone. The ionic composition of the effluent fluids was tracked and further used for modeling the geochemical interactions. The latter considered mineral precipitation and dissolution as well as ion adsorption and desorption. Model calculations were performed using the transport algorithm in PHREEQC. The experimental results from coreflood tests showed that Al/Si-NP, injected into a waterflooded sandstone, could displace up to 11% of the oil trapped, which was 10 times higher if no nanofluid as injected. Ionic tracking further revealed that the dissolution of albite along with anorthite weathering; both mechanisms concurred to the logjamming of Al/Si-NF. Furthermore, the geochemical modeling revealed weak and reversible cation exchange between sodium (Na+) and calcium (Ca2+). Also, we found that the pH of the preflush should be mildly basic with for controllable anorthite and albite precipitation plus silica cementation, from which derive Al-Si-NF aggregation. These points were further verified experimentally when the ionic composition was altered accordingly to the geochemical modeling, leading to the conclusion that albite, anorthite and silicate precipitation promotes high recovery, due to high Na+ and K+ ions. Silica cementation was proven to increase formation rock wettability.