Mechanistic Model To Predict Hydrate Deposition under Stratified Flow Conditions

Gas hydrate formation in pipelines is considered as a serious flow assurance threat to oil and gas production. The severity can be realized from its rapid tendency to form plugs and impede production. The assessment to determine the process of hydrate formation and deposition becomes paramount for effective production planning and optimization. The flow pattern, thermodynamic conditions, and kinetics dictate the entire process of hydrate formation and deposition. This study proposes a mechanistic model for predicting the amount of deposit at a given time under stratified flow conditions of gas and liquid. This pseudo-steady-state model couples the material balances of the gas phase, aqueous phase, and the newly formed hydrate phase along with their momentum and energy balances to provide the axial distribution of the phase velocities and holdups at various times. A hydrate deposition simulator is developed with the proposed model for predicting the thickness of the deposit. Particulate deposition is considered as the driving mechanism for deposition. The particle size, temperature, and operating conditions determine the ratio of deposition to that of formation rates. The subsequent changes in the properties due to the drastic pressure and temperature drops along the pipeline stress the importance of accurate prediction in real-time conditions.