The instability of foams under high-temperature conditions presents a significant challenge for subsurface applications like enhanced oil recovery (EOR). This study introduces a novel, environmentally benign nanocomposite (KCl/SiO₂/Xanthan/Origanum vulgare, NCs) that synergistically stabilizes methane foams at elevated temperatures (30–90°C). Systematic evaluation of interfacial tension, contact angle, and zeta potential across a 10-60 ppm concentration range identified an optimal NCs concentration of ppm. At this dosage, the foam half-life was dramatically extended. Bubble-scale morphological analysis revealed the physical basis for this enhanced stability: the NCs promoted the formation of a fine-textured foam structure characterized by a minimal average bubble size of approximately 114 μm and thickened Plateau borders around 18 µm, which retard liquid drainage and thereby delay foam collapse. Interfacial analyses confirmed that the NCs effectively lower gas-liquid interfacial tension and shift rock wettability toward a hydrophilic state, thereby facilitating foam generation and strengthening liquid films. The core novelty of this work is the comprehensive multiscale investigation of methane foam stabilization—a system critically relevant to gas recovery but less studied than N₂ or CO₂ foams. It demonstrates that 25 a single, cost-effective green nanocomposite can achieve performance comparable to more complex chemical systems. The practical efficacy was validated through core flooding experiments, where the "NCs-Foam" system achieved an ultimate oil recovery of 69.0%, a substantial 21.5 percentage-point increase over pure gas injection (47.5%). These findings underscore the strong economic potential of this nanotechnology as a robust and efficient alternative to traditional surfactant-based foams for high-temperature reservoir applications
