Castor Oil-Based Biopromoter Application for Long-Term Stabilization of Associated Petroleum Gas Hydrate Pellets

Gas hydrate-based technology represents a promising route for safe, compact, and energy-efficient natural gas storage; however, its industrial deployment is constrained by the need for rapid hydrate formation and long-term stability of hydrate pellets under moderate conditions. This study provides a comprehensive evaluation of methane and associated petroleum gas (APG) hydrate pellet formation, long-term stability, and decomposition behavior using a castor oil-derived biosurfactant (CS) in comparison with the conventional surfactant sodium dodecyl sulfate (SDS). Systematic pressure-dependent experiments (5–9 MPa) revealed that both promoters enhance formation efficiency, yet their effects on pellet morphology and stability differ fundamentally. While SDS ensures rapid kinetics, its foaming-induced porous pellet structure leads to reduced long-term stability and an inverse pressure–stability relationship. In contrast, CS forms denser pellets (0.920 g cm–3) with minimal foaming, resulting in superior self-preservation behavior and improved stability at higher formation pressures. Visual decomposition tests confirmed the operational advantage of CS, exhibiting rapid foam collapse relative to that of persistent SDS-stabilized foams. APG hydrate experiments performed at 6 MPa demonstrated similar conversion (∼74%) and storage capacity (∼140 v/v) for both promoters; however, CS-based pellets achieved a 36% lower decomposition pressure, indicating significantly enhanced gas retention. These findings establish bio-based CS as a promising promoter for industrial gas storage, offering high efficiency, improved stability, and enhanced operational performance.