Development of novel hydrate management technology for subsea petroleum production system

Abstract

Flow assurance is an engineering control successful and economical flow of hydrocarbon stream from reservoir to the point of sale. Among them, the control of hydrate formation is one of the most critical issues. Natural gas hydrates are crystalline compounds formed by the physical combination of water molecules and small hydrocarbon molecules. Hydrates are easily formed when the hydrocarbon gas contains water at high pressure and relatively low temperature. There are several ways to prevent hydrate plugging. Among them, mono-ethylene glycol (MEG) has been a robust choice for hydrate inhibition. Currently, the industry has been relying on the injection of considerable amount of MEG which is used to be over-estimated based on the worst operation conditions: shut-in pressure, sea water temperature, and maximum water cut. To reduce the operating cost for the injection of large amount of MEG, an under-inhibition system where an insufficient amounts of thermodynamic hydrate inhibitor is present might be possible to avoid hydrate blockage issues. In this study, the evaluation of under-inhibited system with synergistic effect is carried out to identify the possibility of hydrate blockage formation using simulation study and hydrate kinetics experiments. Virtual field is constructed and required MEG injection rate is calculated. Then, induction time using both of MEG and PVCap (kinetic hydrate inhibitor) is analyzed via experiments. Finally, the residence time and induction time is compared to decide optimized concentration of MEG and PVCap. Additionally, the reducible amounts of MEG and cost saving is calculated based on simulation and experimental results.