Temperature-sensitive amphiphilic nanohybrid as rheological modifier of water-in-oil emulsion drilling fluid: Preparation and performance analysis

In our previous study, as a rheological modifier for flat rheology water-based drilling fluid, binary composite temperature-sensitive SiO2 nanohybrid was successfully synthesized and characterized [J. Petrol. Sci. Eng. 219 (2022), 111,096]. The aim of this study was to investigate the flat rheological characteristics of emulsion drilling fluid, a temperature-sensitive amphiphilic ternary composite nanohybrid was prepared via the copolymerization of temperature sensitive polymer monomers N-isopropylacrylamide (NIPAM) and methylallyl alcohol (MAA) in the presence of nano-silica surface-capped by modifier containing double bond (denoted as SiO2-D). The as-prepared PNM/SiO2-D (PNM refers to polymerized NIPAM and MAA) nanohybrid was characterized by Fourier transform infrared spectroscopy and nuclear magnetic resonance spectroscopy and transmission electron microscopy. Findings indicate that PNM/SiO2-D nanohybrid has a three-dimensional network structure and a particle size of 20–30 nm. Rheological properties of PNM/SiO2-D nanohybrid in aqueous solution, water-in-oil (W/O) emulsion system and W/O emulsion drilling fluid system were investigated, respectively. And the results revealed that PNM/SiO2-D nanohybrid as a rheological modifier is more sensitive to temperature in the emulsion with a high water-oil ratio, and significantly increase the viscosity of the emulsion system at elevated temperatures. Furthermore, the W/O emulsion drilling fluid with a water-oil ratio of 4:6 exhibits higher modulus values than the one with a water-ratio of 1:9, due to the better suspending capacity of the former for drill cuttings under static conditions, which could ensure the application of emulsion drilling fluid in drilling process.