Kinetics of natural gas hydrate formation and bed thickness evolution in wax-containing systems under multiple operating conditions

Wax-containing multiphase systems can undergo concurrent wax precipitation and natural gas hydrate formation under high-pressure and low-temperature conditions, producing cohesive composite beds that increase flow assurance risk. However, the coupled effects of operating variables on hydrate formation kinetics and the subsequent evolution of interfacial bed thickness remain insufficiently quantified. In this study, wax-containing oil–water emulsions were investigated in a visual high-pressure reactor to determine the effects of water content (30–70 %), wax concentration (0–3 wt%), stirring speed (150–300 rpm), and pressure (3.5–5.5 MPa) on gas consumption, water-to-hydrate conversion (WTH), hydrate volume fraction (HVF), and bed thickness evolution. Increasing water content generally increased total hydrate formation but decreased conversion per unit amount of water. Wax exerted a non-monotonic dual effect: moderate wax contents promoted heterogeneous nucleation, whereas excessive wax enhanced interfacial blocking, viscosity, and mass transfer resistance. Increasing stirring speed strengthened mixing and interfacial renewal, although this benefit weakened at high wax concentration. At constant temperature and gas composition, increasing pressure increased the pressure-based thermodynamic driving force and promoted hydrate formation, with diminishing incremental gains at the highest pressures. A power-law kinetic model based on normalized thickness decay reproduced the temporal evolution of the gas–liquid interfacial wax-hydrate composite bed, with R 2 = 0.9928, RMSE = 0.0688 cm, and MAE = 0.0388 cm. The model is intended for the investigated laboratory-scale system and parameter ranges and provides a quantitative basis for interpreting hydrate-deposition tendencies in wax-containing systems.