Stability of Silica Nanofluids at High Salinity and High Temperature

Abstract

Nanoparticles have shown great potential in many sectors of the oil and gas industry, including enhanced oil recovery (EOR). They can be used to improve water flooding by altering the wettability of the porous medium, reducing the interfacial tension, blocking pores, or preventing asphaltene precipitation. Ensuring the stability of nanofluids injected into reservoirs is essential and a great challenge. However, high temperature favors particle collisions and high salinity (ionic strength) decreases electrostatic repulsion between particles. Therefore, nanofluids are extremely unstable at reservoir conditions. In this paper, we investigated the effects of electrolytes (brine and seawater) and temperature (up to 80 °C) on the stability of silica nanofluids. The nanofluids are characterized by dynamic light scattering (size), turbidity (stability), and zeta potential (electrostatic repulsions). One solution to increase the stability is to compensate for the loss of repulsive forces due to salts in the solution through increased electrostatic and/or steric repulsions by changing the pH of the base fluid. At high ionic strength (42 g/L NaCl and seawater), the stability of 0.1 and 0.5 wt% silica nanofluids at basic pH is about one day, regardless of temperature. In contrast, at pH 1.5, the nanofluids have a stability of at least three weeks at 80 °C. The results obtained with base fluids containing divalent cations confirmed their more destabilizing effect. This study confirmed that it is possible to stabilize silica nanofluids beyond one month at reservoir conditions just by lowering the pH near the isoelectric point.

Capturing Rare-Earth Elements by Synthetic Aluminosilicate MCM-22: Mechanistic Understanding of Yb(III) Capture

“…The fact that both materials exhibit a similar pH-dependent adsorption trend suggests that Al-bridged siloxanes play a role in the capture in both materials by making the surface negatively charged. Hutin et al reported that the negative charge on the silica surface is compensated by hydronium ions in an aqueous solution with a low pH and that exchange of the hydronium ions and cations occurs at around pH ≥ 5 . This mechanism explains that all our samples showed an increase in Yb adsorption around pH ∼ 5.…”

“…Hutin et al reported that the negative charge on the silica surface is compensated by hydronium ions in an aqueous solution with a low pH and that exchange of the hydronium ions and cations occurs at around pH ≥ 5. 56 This mechanism explains that all our samples showed an increase in Yb adsorption around pH ∼ 5. But the fact that despite having significantly low hydroxyl content in MCM-22 materials compared to kaolinite, the materials show comparable adsorption capacities which suggests that the BAS might play a role in REE capture for MCM-22.…”

Nanoparticle-Assisted Surfactant/Polymer Formulations for Enhanced Oil Recovery in Sandstone Reservoirs: From Molecular Interaction to Field Application

“…A higher formation temperature causes faster NP agglomeration, resulting in weakened stability of NPs. High temperatures lead to higher kinetic energies and collision frequencies of nanoparticles, which contribute to the aggregation of nanoparticles and adversely affect their stability . A study by Zhou et al investigated the stability of nanoparticles under different temperatures.…”

“…It is due to the formation of a monolayer of surfactant that the surface charges of the NPs cannot interact with each other, and the interactions between all NPs will be determined by the surfactant adsorbed on them. In H + protection, Hutin et al 40 investigated the stability of silica nanofluid at different pH values to evaluate its influence. It was concluded that silica nanofluids at a high ionic strength (42 000 ppm of NaCl and seawater) are stable for 1 day at basic pH and 3 weeks at pH 1.5, respectively.…”

“…High temperatures lead to higher kinetic energies and collision frequencies of nanoparticles, which contribute to the aggregation of nanoparticles and adversely affect their stability. 40 A study by Zhou et al 57 investigated the stability of nanoparticles under different temperatures. Nanofluid thermal stability was evaluated on the basis of particle size measurements at high temperatures (50−100 °C) to determine its thermal stability.…”