In this study, a set of advanced characterization techniques were used to evaluate the morphological, structural, and thermal properties of a novel molecular hybrid based on silica nanoparticles/hydrolyzed polyacrylamide (CSNH-PC1), which was efficiently obtained using a two-step synthetic pathway. The morphology of the nanohybrid CSNH-PC1 was determined using scanning electron microscopy (SEM), dynamic light scattering (DLS), and nanotracking analysis (NTA) techniques. The presence of C, N, O, and Si atoms in the nanohybrid structure was verified using electron dispersive scanning (EDS). Moreover, the corresponding structural analysis was complemented using powder X-ray diffraction (XRD) and attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FT-IR). The covalent bond between APTES-functionalized SiO2 nanoparticles (nSiO2-APTES), and the hydrolyzed polyacrylamide (HPAM) chain (MW ≈ 20.106 Da) was confirmed with high-resolution X-ray spectroscopy (XPS). Finally, the thermal properties of the nanohybrid were evaluated by using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The results showed that the CSNH-PC1 has a spherical morphology, with sizes between 420–480 nm and higher thermal resistance compared to HPAM polymers without modification, with a glass transition temperature of 360 °C. The integration of these advanced characterization techniques implemented here shows promising results for the study and evaluation of new nanomaterials with multiple applications.

In industry, silica nanoparticles (NPs) are obtained by the fuming and the precipitation method. Fumed silica NPs are commonly used in the preparation of nanocomposites because they have an extremely low bulk density (160–190 kg/m3), large surface area (50–600 m2/g), and nonporous surface, which promotes strong physical contact between the NPs and the organic phase. Fumed silica has fewer silanol groups (Si–OH) on its surface than the silica prepared by the Stöber method. However, the number of –OH groups on the fumed silica surface can be increased by pretreating them with sodium hydroxide (NaOH) before further surface modification. In this study, the effectiveness of the NaOH pretreatment was evaluated on commercial fumed silica NPs with a surface area of 200 m2/g. The number of surface –OH groups was estimated by potentiometric titration. The pretreated fumed NPs, and the precipitated NPs (prepared by the Stöber method) were modified with 3-aminopropyltriethoxysilane (APTES) to obtain A200S and nSiO2-APTES, respectively. The NPs were characterized using electron dispersive scanning (EDS), scanning electron microscopy (SEM), dynamic light scattering (DLS), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), X-ray diffraction (XRD), BET (Brunauer–Emmett–Teller) analysis, and ζ-potential. XRD confirmed the presence of the organo-functional group on the surface of both NPs. After the amino-functionalization, the ζ-potential values of the nSiO2 and A200 changed from −35.5 mV and −14.4 mV to +26.2 mV and +11.76 mV, respectively. Consequently, we have successfully synthesized functionalized NPs with interesting, specific surface area and porosity (pore volume and size), which can be attractive materials for chemical and energy industries.

In this study, the surface of silica nanoparticles (NPs) synthesized using the Stober method was modified with 3-aminopropyltriethoxysilane and hydrolyzed polyacrylamide (HPAM). The surface modification of the silica NPs was confirmed by Fourier transform infrared spectroscopy, field emission gun scanning electron microscopy, and thermogravimetric analysis. The characteristics of the nanopolymer sol were evaluated using rheology, viscosity retention ratio, interfacial tension, and contact angle measurements. The core flooding experiments were performed at 56 °C using Berea core plugs with Klinkenberg permeabilities of 450 and 478 mD and a porosity of ∼21%. The nanopolymer sol was prepared in injection brine (0.24 wt % TDS) with 550 ppm of the nanohybrid, while the polymer solution was prepared with 750 ppm of HPAM. The displaced fluid was dead oil with a viscosity of 60 cP (@56 °C and 7.3 s −1 ). The results show that the nanopolymer sol reduces the capillary forces and increases the viscous forces compared to the HPAM solution. These improved properties of the nanopolymer sol were suitable for increasing the cumulative oil recovery in 2.2% OOIP in comparison with the HPAM solution at a lower concentration.

Partially Hydrolyzed Polyacrylamide (HPAM) is the polymer most used in chemical enhanced oil recovery (cEOR) processes and it has been implemented in several field projects worldwide. Polymer injection has shown to be an effective EOR process. However, it has not been implemented massively due to HPAM polymer's limitations, mostly related to thermal and chemical degradation caused by exposure at high temperatures and salinities (HTHS). As an alternative, a new generation of chemically stable monomers to improve the properties of HPAM has been assessed at laboratory and field conditions. However, the use of enhanced polymers is limited due to its larger molecular size, large-scale production, and higher costs. One of the alternatives proposed in the last decade to improve polymer properties is the use of nanoparticles, which due to their ultra-small size, large surface area, and highly reactive capacity, can contribute to reduce or avoid the degrading processes of HPAM polymers. Nanoparticles (NPs) can be integrated with the polymer in several ways, it being worth to highlight mixing with the polymer in aqueous solution or inclusion by grafting or chemical functionalization on the nanoparticle surface. This review focuses on hybrid nanomaterials based on SiO2 NPs and synthetic polymers with great EOR potential. The synthesis process, characterization, and the main properties for application in EOR processes, were reviewed and analyzed. Nanohybrids based on polymers and silica nanoparticles show promising results in improving viscosity and thermal stability compared to the HPAM polymer precursor. Furthermore, based on recent findings, there are great opportunities to implement polymer nanofluids in cEOR projects. This approach could be of value to optimize the technical-economic feasibility of projects by reducing the polymer concentration of using reasonable amounts of nanoparticles. However, more significant efforts are required to understand the impact of nanoparticle concentrations and injection rates to support the upscaling of this cEOR technology.

One of the alternatives currently emerging as a solution to the problems presented by the HPAM in high temperature reservoirs is the use of nanotechnology as a tool to improve and potentiate the properties of the polymer. Nanoparticles have been used to improve the stability and viscosity of HPAM solutions and their properties could be an important tool to improve the thermal resistance of polymers. The scope of this work is the evaluation of new hybrid nanomaterial based on HPAM and nanoparticles of silica dioxide. The new prospective hybrid nanomaterials for oil and gas including Enhanced Oil Recovery (EOR) applications in were characterized including its thermal properties with applied advanced techniques such as Scanning Electron Microscopy (SEM - EDS), X-Ray Photoelectron Spectroscopy (XPS) and Thermogravimetric Analysis (TGA). These techniques contributed to demonstrate the formation of a covalent bond between the nanoparticle and the HPAM polymer, which allows having an inorganic - organic interaction that, according to its thermal properties, has a great potential in polymer flooding, among other applications. The results obtained with these techniques were compared with the synthesis precursors, which shows the morphological, structural and property changes of the new nanomaterial with respect to the synthetic polymer. The elemental analysis carried out by EDS demonstrate the presence of C, N, O and Si in the structure of the new nanomaterial based on silica nanoparticles. The high-resolution spectra obtained by the XPS technique show the functional groups corresponding to the covalent bond between the polymer and the nanoparticle, which provides a greater thermal resistance to the nanomaterial with respect to the conventional polymer. This thermal resistance is determined with the thermogravimetric analysis, in which the polymeric precursor and the new nanohybrid are subjected to a high resolution temperature ramp with a change of 10ºC / min from 25ºC to 700ºC. The results present a competitive advantage to the commercial polymer throughout the evaluation range, which will allow increasing the application ranges of the HPAM polymers and potentially inducing an increase in the recovery of oil.