Experimental and molecular dynamics studies of physicochemical properties of highly thickening and active nanofluids based on acrylamide modified silica

Abstract

Binary compound flooding is an important technology that continuously promotes stable oil reservoir production. By comparing with traditional binary compound flooding, the binary system with nanoparticles has higher application value in enhanced oil recovery (EOR). In this work, we prepared a flexible polymeric brushes hybrid nano-silica star-like hydrophobically associative polyacrylamide (SHPAM). Subsequently, a surfactant named alkyl alcohol polyoxyethylene ether sulfonate (CEOS) was selected to study physicochemical properties of nanofluids through a combination of experiments and simulations. The results indicated that the prepared nanofluids had good dispersion stability in strong brine. When the concentration of monomer SHPAM reached 2000 mg/l, its thickening performance was the best. Significantly, even if the concentration of SHPAM was reduced (750 mg/l), the thickening performance of nanofluids (107.2 mPa s) was better than that of monomer SHPAM. Interestingly, the nanofluids ensured the same degree of reduction in interfacial tension as the alone CEOS (the order of 10−2 mN/m). The molecular simulation showed that the nanofluids could stably adsorb on the oil–water interface and form a layer of interfacial film to increase the viscosity and reduce the interfacial tension. The prepared nanofluids could significantly change the wettability of the core and improve producing degree in the pore throat above 1.0–10 μm about 40%. We envisage that this nanofluidic material can apply in EOR with high efficiency and low cost.