Amphoteric polymerhave attracted immense research interest in hydraulic fracturing.However, current fracturing fluids prepared using conventional suspensions have poor stability and cannot be adapted to field applications in highly mineralized oilfield blocks, and they cannot reuse highly mineralized oilfield wastewater. To solve the above problems, a new concentrated suspension was prepared as a fracturing fluid thickener. The crystal layer spacing of SMB-2 exhibited an improved value of d = 13.564 nm. Experimental findings indicate that SRS-2 exhibited rapid thickening in saline water within a 5-minute timeframe. The viscosity of SRS-2 in high-salinity solutions demonstrated an impressive viscosity retention rate of 96.8 %, highlighting its excellent salt resistance properties. The zeta potential was measured at -62.13 mV. Notably, there was no significant settlement observed even after 30 days, with a settling velocity of 9.2592 × 10 −3 mm/s, underscoring its superior stability performance. Therefore, this new suspension thickener has good potential for applications as an alternative material in multiple fields, such as oil extraction and sewage treatment.
Graphical Nano-SiO₂ (0.02 wt%) extends gel stability to 95 days at 130 °C in seawater (versus 70 days control). SEM-confirmed H-bonding between Nano-SiO₂ silanols and AMPS groups reinforces network. Gelation activation energy (88.2 kJ/mol) derived via Arrhenius model. Nano-SiO₂-toughened polymer gels achieves 34.7 MPa/m breakthrough pressure (10 × base gel) in 1.4 Darcy cores. This study solves water shutoff gel syneresis/ degradation in high-salinity seawater (Ca 2 ⁺+Mg 2 ⁺ >1;500 mg/L) for South China Sea reservoirs. Reservoirs in the western South China Sea have entered a high-water-cut stage, exhibiting significant heterogeneity exacerbated by prolonged water flooding, necessitating urgent profile control measures to enhance oil recovery. Conventional polyacrylamide organic gels fail under the prevailing high-temperature (130 °C) and high-salinity conditions, characterized by divalent cation (Ca 2 ⁺ and Mg 2 ⁺) concentrations of 5650 mg/L. This study developed a robust gel profile control system specifically engineered for such challenging environments. Key parameters including polymer and crosslinker concentrations, gel pH, and temperature were systematically optimized to ensure stability under high temperature and salinity. The optimized formulation demonstrates exceptional stability in seawater at 130 °C, with a gelation activation energy of 88.2 kJ/mol. Incorporating nanosilica significantly enhanced the gel's thermal stability, salinity tolerance, and shear resistance. Scanning electron microscopy (SEM) revealed a strengthened network microstructure. The system exhibits favorable injectivity in 1.4 Darcy permeability cores. Nanosilica reinforcement dramatically increased the gel's breakthrough pressure gradient from 3.45 MPa/m to 34.7 MPa/m. Crucially, the addition of 0.02% nanosilica extended the polyacrylamide gel's functional stability from 70 days to 95 days. This nanosilica-reinforced system offers superior long-term stability and plugging performance, presenting a viable profile control and water-shutoff technology for offshore high-temperature, high-salinity seawater reservoirs.
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