Advanced Shut-Down / Start-Up Analysis for Gas Hydrate Prevention in Subsea Production Systems

Abstract

This study introduces an advanced method for enhancing the post-processing of transient multiphase flow simulations, explicitly addressing the determination of Cool-Down Time (CDT), the time that the production system takes to reach the hydrate region, which is crucial for managing gas hydrate flow assurance issues in offshore production systems. The post-processing functions that have been developed analyze the subcooling independently for gas, oil, and water phases, estimating the subcooling evolution over time for each phase. The effect of different shut-in types on the CDT and subcooling evolution is also discussed. Finally, the method was applied to two typical subsea satellite production tiebacks, providing several insights into gas hydrate potential risks in the system during transient operations. A reliable and detailed analysis of the subcooling evolution and cool-down time enables the design of hydrate-safe operations of subsea production systems.