Construction and Performance Study of Aqueous Two-Phase Fracturing Fluids Based on Zwitterionic Composite Biological Polysaccharides

Abstract To address the trade-off between friction reduction and proppant suspension in conventional fluids, an aqueous two-phase system comprising nanoparticle-reinforced biopolysaccharideand zwitterionic gel was developed for deep offshore reservoir stimulation. Specifically, xanthan gum (XG) serves as the dispersed phase, while a rehydratable sulfobetaine-type zwitterionic cross-linked gel (poly(sulfobetaine methacrylate)-co-poly(ethylene glycol) diacrylate, PSBMA–PEGDA) synthesized via UV-initiated free radical polymerization followed by lyophilization and ball milling acts as the continuous phase. Silica nanoparticles are subsequently incorporated as a physical cross-linking reinforcing phase to ultimately yield a stable aqueous two-phase system. Comprehensive rheological, ball-on-disk tribological, and static proppant suspension characterizations reveal that the optimized system achieves an interfacial friction reduction efficiency of 82%, outperforming its single-phase counterpart by 41.3%. Furthermore, it exhibits a static proppant suspension duration exceeding 36 h, substantially outperforming that of conventional single-phase XG system (∼5.8 h). The friction reduction mechanism is primarily governed by the synergistic effect between the elastic kinetic energy dissipation of the semirigid XG network and the zwitterionic hydration lubrication layer. This robust proppant suspension capacity is attributed to the high-yield-stress 3D hybrid network, which is formed through the spatial interpenetration of the XG double-helical scaffold and PSBMA–PEGDA microdomains, and further fortified by silica nanoparticles acting as physical cross-linking nodes. Consequently, this aqueous two-phase system emerges as a highly functional fracturing fluid material, integrating superior friction reduction and proppant suspension properties for the reservoir stimulation of deep offshore oilfields.