Abstract

In offshore gas transmission pipeline systems, typically gas and water are produced under high pressure and low temperature conditions causing the formation of gas hydrates blocking pipelines. Thermodynamic modeling is necessary to understand the phase stability of hydrate in the presence of green solvents namely, ionic liquids (ILs). In this work, the thermodynamic models are based on the computation of fugacity of hydrate phase using Van der Waals and Platteeuw solid solution theory combined with Peng - Robinson equation of state (PR-EoS) for fugacity of hydrate former in the gas phase and the computation of fugacity of aqueous water phase using activity coefficient models such as the non - random two - liquid (NRTL) model and Pitzer - Mayorga model. The model results are compared with available experimental data from open literature and observed to be in good agreement with the reported literature. Finally, the hydrate suppression temperature due to ILs on methane hydrate is calculated to know the inhibition effectiveness of IL on methane hydrate formation in offshore pipeline system. The overall accuracy of Pitzer-Mayorga model is found to be 5.8 % while NRTL model's accuracy was 6.3 % for various ILs and methane hydrate system. Model results further indicated that ILs with shorter alkyl chain length exhibit better inhibition effect. The model developed in this work shows potential application in the determination of hydrate phase stability using green solvent for offshore oil field applications.

Keywords:
hydrate phase, flow assurance, hydrate dissociation temperature, hydrate inhibition, model parameter, chem, inhibition, thermodynamic model, upstream oil & gas, pitzer-mayorga model
Subjects:
Flow Assurance, Hydrates
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2014. International Society of Offshore and Polar Engineers
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