Study on mechanisms of novel nano-composite polymer gels with silica and alpha-alumina nanoparticles for water shut-off in hydrocarbon reservoirs

• Optimal conditions for nano-composite polymer gel system were determined via bottle test, swelling test, rheological analysis, and morphology evaluation. • Synthesis of SiO2 and ∝ − A l 2 O 3 nanoparticles was performed via the sol-gel method and the effect of combination of these nano-particles on gel strength was investigated. • Investigating impacts of SiO 2 and ∝ − A l 2 O 3 nanoparticles at different concentrations on hydrogel performance. SiO 2 and ∝ − A l 2 O 3 nanoparticles had a positive and negative effect, respectively, on the swelling of polymer gels. Polymer gels can be employed as an effective strategy to reduce water flow in oil and gas wells, however, it suffers from some inefficiency. The addition of nanoparticles to polymer gels may enhance the efficiency and performance of them. This study aims to conduct a detailed investigation and comparative analysis of the effects of silica and alumina nanoparticles on the structural properties and performance of polymer gels. Silica and alpha-alumina nanoparticles were synthesized using the sol-gel method and characterized through XRD, FTIR, FESEM, and EDS analyses. Bottle tests and rheological analyses were conducted to evaluate the gel strength under reservoir conditions and, the effect of salinity on the behavior of polymer gels was investigated using high saline formation water. The results showed that the presence of silica nanoparticles in the polymer gel structure increased the gel strength from 370 Pa to 450 Pa, while alpha-alumina nanoparticles revealed a minimal impact on the rheological properties of the polymer gel. Moreover, swelling of polymer gels in formation water increased by up to 1.15% for samples containing silica nanoparticles. In contrast, polymer gels containing alpha-alumina nanoparticles experienced less swelling, with shrinkage levels reaching up to 3.1%. Based on these experimental results, the polymer gel samples containing 0.3 wt% silica nanoparticles showed superior structural strength and thermal stability at 85°C, making it a promising candidate for the field applications.