Synthesis and characterization of natural rosin-modified silica nanocomposite and its green multifunctional applications for drilling fluid

The increasing energy demand and environmental pressure require the utilization of high-performance and eco-friendly drilling fluid materials for oil/gas exploration. Herein, a green nanocomposite involving the core structure of silica (SiO2), the resin shell structure of rosin dehydroabietic acid (DHAA) derivative [poly(DHAA-co-styrene) (PDS)], and the crown structure of hydrophilic layer [crosslinked poly(2-acrylamido-2-methyl-1-propanesulfonic acid-co-N, N-dimethylacrylamide) (CAD)] was prepared through semi-continuous emulsion polymerization and utilized as a high-performance and multifunctional additive for drilling fluid. The optimal composition of core, shell and crown was determined to be 0.3: 10: 2 in mass, and the DHAA component accounted for 50 wt% in the shell structure and the molar ratio of 2-acrylamido-2-methyl-1-propanesulfonic acid and N, N-dimethylacrylamide in the crown was 3:7. The core-shell-crown nanocomposite (SiO2-PDS-CAD) exhibited a well-organized multi-layered nanostructure with an effective encapsulation of PDS on nano-SiO2 and CAD on PDS, facilitating a uniform nano-dispersion of SiO2-PDS-CAD. The bulky copolymerized rosin-based segments coupled with nano-SiO2 resulted in high thermal stability of SiO2-PDS-CAD and broadened the softening point of raw rosin from 87°C to 141°C. Meanwhile, the environmental assessments of acute toxicity and biodegradability showed that SiO2-PDS-CAD was nontoxic and readily biodegradable, and the higher incorporation of rosin components enabled SiO2-PDS-CAD more biodegradable in contrast to the non-biodegradability of the analog without rosin. Moreover, SiO2-PDS-CAD showed versatile functions in bentonite-based drilling fluid by maintaining high yield points, lowering fluid loss and enhancing nano-porous plugging capacity (100–400 nm), especially at elevated temperatures (140–180°C). A maximum increment of 1200 % on yield point occurred after aging 170°C, and the highest improvement of approximately 72 %-75 % on fluid loss occurred at 150–180°C. It also could effectively inhibit clay swelling and decrease the lubrication coefficient. The enhancement mechanism was revealed to be the core-shell-crown synergistic effects, in which the hydrophilic crown contributed to the dispersion stability of SiO2-PDS-CAD and affinity with bentonite clay, and the rigid bridging of core and flexible deformation of rosin shell strengthened the interparticle interactions. The study highlighted a novel strategy for preparing high-value-added rosin-based biomass material for green multifunctional applications in water-based drilling fluids.