Hydrate Secondary Formation and Blockage Prediction Model in Wellbore During Depressurization-Based Hydrate Production

During depressurization-based natural gas hydrate production, low-temperature and high-pressure wellbore conditions can induce secondary hydrate formation and deposition, risking flow channel blockage and production safety compromise. This study develops a predictive kinetic model for secondary hydrate formation and blockage in annular and mist flows, the flow patterns most susceptible to hydrate hazards. The model integrates multiphase flow, heat and mass transfer, hydrate phase change, and particle transport and deposition, coupling conservation equations with hydrate phase equilibrium and flow regime transition criteria to quantitatively predict the hydrate formation rate, deposition rate, and wall blockage severity. Validation against published experimental loop data shows that model-predicted pressure drop increases fall within 5.3% of measurements. Simulations based on a production well in the South China Sea’s Shenhu area provide quantitative predictions of three key operational controls: enlarging the tubing diameter compresses the hydrate stability zone; increasing the gas–liquid ratio suppresses hydrate formation by limiting free water; and the liquid production rate exerts stronger control over formation and deposition than the gas rate. The model serves as a practical quantitative tool for wellbore blockage risk assessment and operational decision support during hydrate trial production.