We studied the phase behavior of silica nanoparticle suspensions as a function of silica and NaCl concentrations. Monodisperse 3M silica nanoparticles have a wider window of gelation with respect to salinity than polydisperse NexSil5 particles. The time to the onset of gelation depends strongly on silica and NaCl concentration and temperature. The gelation time decreases exponentially as a function of silica, NaCl concentration or temperature. The storage modulus, G', increases with particle concentration following a power law behavior. The critical strain appears to be constant as a function of silica concentration. The samples withstand minimum critical strain of 10% before the structure breaks. However, the critical strain does not have a clear dependency of salt concentration for both types of particles studied. Steady shear measurements show that silica nanoparticle gels exhibit non-Newtonian, shear thinning behavior which could be described by power law model or Carreau model depending on the particle and NaCl concentration. Silica nanoparticle gels are good candidates for conformance control in hydrocarbon reservoirs.
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