Development and Characterization of CO 2 -Responsive Surfactants for Coalbed Methane Fracturing

To address issues of traditional coalbed methane (CBM) fracturing fluids (high displacement, weak sand-carrying, poor stability, severe coal seam damage), this study synthesized CO 2 -responsive erucamide propyl dimethylamine surfactant (C 22 ZEA, yield 99%), with molecular structure verified by 1 H NMR (400 MHz, CDCl 3 ) matching the target. Molecular simulation showed CO 2 protonates C 22 ZEA into EA + : 1 wt% forms a simple micelle network, while 3 wt% enhances entanglement into a dense 3D network. Experiments indicated: 3 wt% solution reaches 160 mPa·s viscosity in 200 s under CO 2 (0.2 L·min −1 ); 1.5–4.5 wt% solutions are pseudoplastic ( n = 0.14–0.18), with G′ > G″ when concentration > 2 wt%; viscosity recovery rate > 95% after alternating shear (170 s −1 /10 s −1 ); viscosity remains > 160 mPa·s after 1 h shear (170 s −1 ) at 70 °C; gel breaks to 0.01–0.02 Pa·s in 15 min with N 2 at 45 °C; 1.0–3.0 wt% solutions meet non-toxic standards via EC 50 /96 h LC 50 . This study supports high-efficiency low-damage smart fracturing fluids, boosting CBM extraction efficiency.