Sol–Gel Tailored Synthesized Nanosilica for Enhanced Oil Recovery in Water-Wet and Oil-Wet Benthemier Sandstone

In this work, nanosilica fluid flooding for tertiary oil recovery was investigated for Bentheimer sandstone. With use of a core flooding setup, brine imbibition was followed by nanosilica fluid flooding. Throughout this experimental work, four sizes of synthesized nanosilica were prepared using sol–gel method. The resulting particle sizes of 10, 20, 30, and 40 nm were characterized using transmission electron microscopy and dynamic light scattering. Core flooding experiments were conducted using water-wet and oil-wet Bentheimer-type sandstone. The Bentheimer sandstone core plug was aged in heavy oil to alter its wettability to oil-wet; the degree of wettability alteration was studied by Amott Harvey method. The effect of synthesized nanosilica concentration and particle size on the recovery factor for both water-wet and oil-wet Bentheimer core plugs were investigated. The displacement efficiency was calculated and compared to that achieved by commercial silica nanoparticles. At optimum concentration of 0.1 wt %, synthesized nanosilica achieved maximum cumulative oil recovery of 68% and 58% in water-wet and oil-wet Benthemier, respectively. This means that a 20% increase in the amount of recovered oil was achieved when using synthesized nanosilica as a tertiary recovery fluid compared to brine imbibition alone. On the other hand, only 13% increase in the amount of recovered oil was reached in the case of commercial nanosilica. In general, synthesized nanosilica achieved better recovery when compared to commercial nanosilica of the same concentration as a tertiary recovery technique. Moreover, it was found that oil recovery increases with the increase in synthesized nanosilica particles sizes until an optimum size of 30 nm was reached.