Two types of polysilicon nanoparticles (PN) were used in oil fields to improve oil recovery and enhance water injection respectively in this work. The physical properties of the nanoparticles were studied experimentally, and pore characteristics of sandstone were investigated by mercury injection experiments. The adsorption experiments of lipophobic and hydrophilic polysilicon nanoparticles (LHPN) were conducted to testify wettability change (from oil wetting to water wetting) of sandstone surface, and the nanoparticles attached to pore walls were observed by a transmission electron microscope (TEM). A mathematical model to describe the nanoparticles transport carried by two-phase flow in random porous media was presented and a numerical simulator was developed to simulate two application examples of the nanoparticles in oilfields. An important discovery is that water-phase permeabilities of these sandstones increase from 1.6 to 2.1 times of their original values. However, there are decreases in their absolute permeabilities because of nanoparticle adsorption on pore surfaces and nanoparticle capture at pore throats. The important parameters such as the distributions of porosities and permeabilities. the changes in water injection capability and oil recovery are obtained successfully by numerical simulation approach. Furthermore, the permeabilities obtained from numerical simulation have a good match with experimental data. The conclusion that polysilicon nanoparticles are effective agents for enhancing water injection capability or improving oil recovery can be safely drawn. (C) 2009 Elsevier B.V. All rights reserved.