<p>In order to develop and apply nanotechnology in oil industry, nanoparticles transport in porous media has been studied in the past few years. Theoretical modeling were carried out to evaluate nanoparticle mobility and investigate nanoparticle retention mechanism. In this study, a simulator based on Ju and Fan&rsquo;s mathematical model was used to study nanoparticles transport in porous media on a reservoir scale. The simulator was verified with two simulation software, Eclipse from Schlumberger and MNM1D (Micro- and Nanoparticle transport Model in porous media in 1D geometry) developed by Tosco et al. Different injection scenarios were simulated: continuous injection, slug injection, and postflush. The effect of injection time, injection rate, and slug size on oil recovery were studied. The result discovered that when nanofluids flooding is used after water flooding as tertiary recovery method, early nanofluids injection will lead to higher oil recovery, but with more nanoparticle loss. Higher injection rate of nanofluids could help improve the flooding efficiency, but not the ultimate oil recovery for field development. Also, it can cause more nanoparticle loss. Brine water postflush is recommended when doing nanoflooding. It can significantly improve the recovery of nanoparticles, and for a homogeneous or heterogeneous reservoir, oil recovery is better compared to water flooding. </p>

<p>A high-pressure CO2 foam was generated with silica nanoparticle dispersion and CO2 for fracturing applications. The effects of different ions and temperature on nanoparticle aggregation were studied. Nanoparticle dispersions were mixed with individual monovalent, divalent ions with varying concentrations, and two synthesized Permian connate water solutions. Samples of nanoparticle dispersions with the presence of NaCl were put into chambers with constant temperature for 14 hours. The peak size of aggregated nanoparticles in each sample was measured. It was found this silica nanoparticle dispersion had a high thermal stability up to 85?. The silica nanoparticle dispersion used in this study maintained a desired stability under an 18% reservoir salinity condition, yet it could be sensitive to high concentrations of Na2SO4 solutions. To investigate foam rheology and stability, high-pressure CO2 foams were generated in a beadpack with different CO2/NP ratios in NaCl solutions. The resulting foam was observed in a sapphire tube. The differential pressure across a capillary tube was recorded to calculate the apparent viscosity of foams. Nanoparticle-stabilized foams could remain stable for days and foam stability decreased with the increasing foam quality. Foam apparent viscosity was found to increase with foam quality and could be 3 times as high as that of the ambient phase. The high stability and fine texture of high-pressure CO2-in-water foams stabilized by silica nanoparticles have broadened the development of foam fracturing, offering a new opportunity for the effective development and stimulation of unconventional reservoirs.