Interfacial and Bulk Stabilization Mechanisms of Thermally Stable anionic–zwitterionic Foam Fracturing Fluids for Unconventional-Reservoir Applications

Foam fracturing fluids can reduce water consumption and improve proppant transport compared with conventional water-based fracturing fluids, but maintaining foam stability as temperature increases remains challenging because of accelerated drainage, film thinning, and bubble coalescence. This study aimed to develop and mechanistically evaluate thermally stable foam systems based on α-olefin sulfonate (AOS), sodium dodecylbenzenesulfonate (SDBS), and lauryl sulfobetaine (LB), with cetyltrimethylammonium bromide (CTAB) included as a reference individual surfactant and AOS–LB and SDBS–LB investigated as binary mixtures. Interfacial and thermodynamic properties were characterized at 25 °C, while foam performance was evaluated at 30–70 °C. The mixed surfactant systems exhibited superior foam performance compared with the individual surfactants. AOS–LB showed a stronger tendency toward bulk micellization and drainage resistance, whereas SDBS–LB exhibited more favorable interfacial characteristics, bulk viscoelasticity, and the highest overall foam stability. At 70 °C, SDBS–LB maintained a foam half-life of 65 min and reduced proppant settling velocity by approximately 46% relative to AOS. The combined results revealed distinct but complementary stabilization pathways, with AOS–LB dominated by bulk structural organization and SDBS–LB benefiting from favorable interfacial characteristics and bulk viscoelasticity. The novelty of this work lies in establishing an integrated framework that relates interfacial characteristics, bulk rheology, drainage, bubble morphology, and proppant transport to the temperature-dependent stability of anionic–zwitterionic foam systems. These findings identify SDBS–LB as a promising formulation for further development of foam fracturing fluids for unconventional-reservoir applications.