Integrated Hydrate Phase Behavior Modeling: Key to Hydrate Mitigation and Removing Pipeline Blockages

Gas hydrates, which are ice-like crystalline structures formed under low-temperature and high-pressure conditions, present significant flow assurance challenges in hydrocarbon transportation systems by causing pipeline blockages. This study underscores the critical importance of advanced thermodynamic modeling in predicting hydrate phase behavior and developing effective mitigation strategies, particularly in cold climates. By implementing sophisticated equations of state, particularly the Cubic-Plus-Association (CPA) model alongside the comprehensive van der Waals-Platteeuw (vdWP) model for predicting chemical potential and fluid-hydrate equilibrium, coupled with experimental data and field insights, the research offers a comprehensive framework for understanding hydrate formation, dissociation, and blockage mechanisms. The study highlights the necessity of accurately modeling hydrate phase boundaries to differentiate hydrate blockages from other solid deposits, such as ice or salt, and to optimize inhibitor dosing strategies for efficient flow assurance. A detailed case study of hydrate blockage in a buried gas pipeline illustrates the practical application of these modeling techniques. The analysis reveals that while depressurization can initially dissociate hydrates, it can lead to ice formation at low pressure/temperature conditions, exacerbating blockage issues (as ice does not respond to pressure). The study evaluates the effectiveness of various inhibitors, including methanol and monoethylene glycol (MEG), and proposes an innovative approach combining nitrogen (N₂) injection with atomized methanol to address existing or future hydrate, ice, and salt blockages. This method successfully resolved the pipeline blockage, demonstrating the value of integrating advanced modeling, experimental validation, and field data for mitigating hydrate blockage. The findings emphasize the indispensable role of robust thermodynamic modeling in predicting fluid/solid behavior under operational conditions, optimizing inhibitor use, and minimizing economic and environmental impacts.