Enhanced Heavy Oil Recovery Using TiO2 Nanoparticles: Investigation of Deposition during Transport in Core Plug

Although application of nanoparticles in enhanced oil recovery has been reported, understanding the transport and retention of nanoparticles in the oilfield reservoir is still a crucial issue. In this research, behavior of low concentration of TiO2 nanoparticles in core plug porous media and the mechanism of increasing oil recovery were investigated. Flooding test with a concentration of 0.01% TiO2 nanoparticles showed improvement in sweeping heavy oil from 41% to 55%. Inductively coupled plasma results on the exiting effluent of the flooding test with a concentration of 0.05% TiO2 nanoparticles showed the presence of only 0.5% of injected nanoparticles, which indicates high affinity of the nanoparticles for deposition in porous media. The total amount of deposited TiO2 extracted from different cross sections of the core plug was consistent with the difference of injected and exited TiO2 material. At the entrance side, the amount of deposited TiO2 was high but decreased significantly in 0.1 cm depth, and reduces linearly versus distance. On the basis of surface area estimation of the core plug, only about 1% of the internal surface was deposited by nanoparticles. The viscosity, interfacial tension, and contact angle measurements showed that the main mechanism for increasing oil sweeping is changing the wettability of the rock surface from oil-wet to water-wet due to deposition of TiO2 nanoparticles. The role of the low concentration nanofluid in rapidly displacing crude oil from the rock surface may be described by gradient pressure of nanoparticles in the three-phase contact wedge of oil, nanofluid, and rock surface.