Functionalized nano core-shell polystyrene spheres with polyionic liquids: An efficient shale stabilizer with both inhibit hydration and physical plugging

Abstract

Due to shale hydration and the development of nano and micropores, wellbore instability often occurs during shale drilling, and high-performance shale stabilizers are urgently needed. A novel nano spherical shale stabilizer (i.e., PSIL) was prepared by polymerizing vinyl imidazole ionic liquid with amino group and polystyrene seed. The electron microscopy experiments and particle size analysis indicated that PSIL had a core-shell spherical structure with a particle size distribution between 200 and 300 nm. The plugging performance of PSIL was analyzed using the microporous membrane filtration experiment and pressure transfer experiment. The final filtration loss volume of 3 wt% PSIL aqueous solution was only 20 mL, and the final pressure at the end of the core was 4.0 MPa, which demonstrated that PSIL could form a dense plugging layer in the nanopore gap, thus reducing filtration loss and pressure transfer. Moreover, when the solution contained 3 wt% PSIL, the linear expansion rates of the bentonite pellets decreased from 69.1% to 38.3%, and the rolling recovery rate of shale cuttings increased from 10.5% to 41.2%. The experimental results indicated that PSIL could effectively be adsorbed onto the clay surface through electrostatic interaction and hydrogen bonds, thus reducing the repulsive force between clay interlayers and inhibiting the hydration dispersion of shales. Therefore, PSIL could play a dual role in physical plugging and inhibiting hydration, providing a new direction for developing high-performance shale inhibitors, thereby enhancing wellbore stability during drilling.