New nanotechnology-based approaches are increasingly being investigated for enhanced oil recovery (EOR), with a particular focus on heavy oil reservoirs. Typically, the addition of a polymer to an injection fluid advances the sweep efficiency and mobility ratio of the fluid and leads to a higher crude oil recovery rate. However, harsh reservoir conditions, including high formation salinity and temperature, can limit the performance of such polymer fluids. Recently, nanofluids, that is, dispersions of nanoparticles (NPs) in a base fluid, have been recommended as EOR fluids; however, such nanofluids are unstable, even under ambient conditions. In this work, a combination of ZrO 2 NPs and the polyacrylamide (PAM) polymer (ZrO 2 NPs−PAM) was used to formulate a novel nanopolymer injection solution for EOR applications to overcome the limitations of simple PAM solutions by the in situ reservoir conditions including high temperature and salinity. A series of measurements were comprehended at controlled pH values to measure the stability and rheological properties of NPs−PAM combinations at different temperatures, salinities, NP concentrations, and shear rates. It is depicted from the results that a higher salinity decreased the viscosity of the polymer formulation. However, ZrO 2 NPs−PAM combinations reduced the effect of increased salinity on viscosity, which is essential for EOR applications. Furthermore, at low and medium shear rates, which are more relevant to the flow scenarios in oil reservoirs, ZrO 2 NPs−PAM exhibited a higher viscosity than the PAM solution at the same pH and salinity. In contrast, at higher shear rates, the viscosity of ZrO 2 NPs−PAM was less than that of the sole PAM solution. Mechanistically, an increased shear rate endorsed the adsorption of polymer molecules onto the surface of NPs, foremost to a lesser polymer concentration in the solution. Moreover, although ZrO 2 nanodispersion was unstable at all NPs and salt concentrations, ZrO 2 NPs−PAM was stable over an extensive range of salinities and temperatures. The results suggested that ZrO 2 NPs−PAM is more suitable than the sole polymer or NP solutions for EOR projects.

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Growth of an external filter cake with its final stabilization has been widely reported for waterflooding in oilfields, well drilling, fresh water storage, and industrial waste disposal in aquifers. We derive the mechanical equilibrium equation for stabilized cake accounting for electrostatic force and for varying permeate force factor. The main empirical parameter of the model, highly affecting the stabilized cake prediction, is the lever arm ratio for the particle on the cake surface. The lever arm ratio was calculated from laboratory cross-flow filtration experiments and from well injectivity data. It was also determined from Hertz's theory for the elastic particle deformation on the solid cake surface. Good agreement between the results validates the developed mechanical equilibrium model with the lever arm ratio determined from the elastic particle deformation theory.

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