文献名：Tuning the Electrical Properties of Nanoparticles and Application in the EOR Process of Ultra-low Permeability Reservoirs 

作者： Hongda Zhou, Rui Cheng, Caili Dai, Yuyang Li, Mingwei Zhao and Wenjiao Lv

School of Petroleum Engineering, State Key Laboratory of Heavy Oil, China University of Petroleum (East China), Qingdao, Shandong 266580, China

摘要：In this study, electronegative silica nanofluid and electropositive alumina nanofluid were prepared to enhance oil recovery of ultra-low permeability cores. Transmission electron microscopy and dynamic light scattering were employed to characterize their morphology and size. Nanofluids with different concentrations, ranging from 0.001wt% to 0.2 wt%, were used for spontaneous imbibition tests of sandstone cores to evaluate the performance of these nanofluids for EOR. The wettability alteration experiment and zeta potential measurements were employed to investigate the mechanism of nanofluids for EOR. As the concentration of alumina nanofluid increases, the adsorption of alumina nanoparticles could cause pore blocking. On the contrary, electronegative silica nanofluid could improve displacement efficiency and oil recovery as the increase of concentration of silica nanofluid. Electronegative silica nanofluid has great potential for EOR in ultra-low permeability reservoir.