A Framework to Improve Gas Hydrate Management Strategies in Transient Operations of Subsea Production Systems

Gas hydrates are a major issue during transient operations such as shut-in and start-up of subsea oil and gas production systems. In this context, the Cool-Down Time (CDT), the time that the production system takes to reach the hydrate formation region, is the most important parameter for decision-making. This work presents a systematic new method to assess one-dimensional transient multiphase flow simulations for hydrate management. This advanced method integrates the analysis of the system’s phase distribution, thermal, and pressure history, enabling an accurate determination of CDT and capturing the evolution of subcooling, the driving force for hydrate formation. The technique is also discussed in light of hydrate formation mechanisms that involve metastability and limited hydrate growth during shut-in. The concepts of different shut-in modes, CDT extension by depressurization, warming, and recovery times are described in detail. Finally, the method was applied to two typical subsea satellite production tiebacks, providing insights into potential risks and gas hydrate management strategy optimizations. The impact of this work is to offer a systematic and accurate framework for optimizing production system shutdown and start-up procedures. This approach aims to increase the reliability of gas hydrate analysis and eliminate potential conservatism, increasing the flow assurance efficiency of an oil and gas production asset.