Low Adsorption of Magnetite Nanoparticles with Uniform Polyelectrolyte Coatings in Concentrated Brine on Model Silica and Sandstone

Abstract

In subsurface imaging and oil recovery where temperatures and salinities are high, it is challenging to design polymer-coated nanoparticles with low retention (high mobility) in porous rock. Herein, the grafting of poly­(2-acrylamido-2-methyl-1-propanesulfonic acid-co-acrylic acid) (poly­(AMPS-co-AA)) on magnetic iron oxide nanoparticles was sufficiently uniform to achieve low adsorption on model colloidal silica and crushed Berea sandstone in highly concentrated API brine (8% NaCl and 2% CaCl2 by weight). The polymer shell was grafted via amide bonds to an aminosilica layer, which was grown on silica-coated magnetite nanoparticles. The particles were found to be stable against aggregation in American Petroleum Institute (API) brine at 90 °C for 24 h. For IO nanoparticles with ∼23% polymer content, Langmuir adsorption capacities on colloidal silica and crushed Berea Sandstone in batch experiments were extremely low at only 0.07 and 0.09 mg of IO/m2, respectively. Furthermore, upon injection of a 2.5 mg/mL IO suspension in API brine in a column packed with crushed Berea sandstone, the dynamic adsorption of IO nanoparticles was only 0.05 ± 0.01 mg/m2, which is consistent with the batch experiment results. The uniformity and high concentration of solvated poly­(AMPS-co-AA) chains on the IO surfaces provided electrosteric stabilization of the nanoparticle dispersions and also weakened the interactions of the nanoparticles with negatively charged silica and sandstone surfaces despite the very large salinities.

High temperature stability and low adsorption of sub-100 nm magnetite nanoparticles grafted with sulfonated copolymers on Berea sandstone in high salinity brine

“…Recently, our group has demonstrated electrosteric stabilization of IONPs in very high salinity American Petroleum Institute (API) brine (8% NaCl and 2% CaCl 2 by weight) at elevated temperatures up to 90 o C using a series of sulfonated random and block copolymers [5,6,[34][35][36]. Poly(AMPS-co-AA) random copolymers were found to be effective stabilizers for ~100 nm IONP dispersions at 90 °C for up to 30 days.…”

“…The high acidity of the AMPS moieties provided resistance against Ca 2+ specific binding while the reactive AA units afforded multiple reactive grafting points for robust attachment. To provide sites for grafting of poly(AMPS-co-AA) with a ratio of 3:1, the IONPs were amine functionalized with aminopropyltriethoxysilane (APTES), followed by (N-(3dimethylaminopropyl)-N′-ethylcarbodiimide hydrochloride) (EDC) catalyzed amidation [35] or thermal amidation as shown in Figure 1 [36]. The grafting was performed at high ionic strengths…”

“…fold, and demonstrating the polymer was still present by thermal gravimetric analysis. The IONPs, grafted with poly(AMPS-co-AA) either thermally [36] or EDC [35] catalysis, were stable in API brine at elevated temperature (90 °C) for 1 month and exhibited relatively low adsorption in dynamic flow experiments through Ottawa sand and crushed Berea sandstone packed columns [35,36]. Also, it was found that homopolymers including anionic PAMPS and zwitterionic sulfobetaine[3-(methancryloylamino)-propyl]-dimethyl(3-sulfopropyl)ammonium hydroxide (PMPDSA) could be tethered to IONPs via a "grafting through" approach.…”

“…Thermal grafting of IONPs may limit the complete covalent grafting thus limiting surface coverage [36]. Thus, catalyzed grafting of polymer chains under optimal conditions onto IONPs would be a method of choice to enhance the graft density.…”

“…Herein, we present an improved approach to synthesize and purify IONPs grafted with a random copolymer poly(AMPS-co-AA) that are colloidally stable in API brine at 120 °C and smaller than 100 nm, about two fold smaller than in our previous studies [34][35][36]. The polymer chains were grafted onto IONPs via an EDC catalyzed amidation reaction at room temperature at high ionic strength under sonication.…”