Use of a Modification of the Patel-Teja Equation of State + van der Waals-Platteeuw Theory Based Model for Predicting Hydrate Phase Boundary of Methane - Ethylene Glycol - Water System from Ice Point Data of Aqueous Solution

• Published in: Oil & gas science and technology 2007-09, Vol.62 (5), p.695-700
• Main Authors: Mohammadi, A. H., Richon, D.
• Format: Article
• Language: English
• Subjects: Applied sciences; Crude oil, natural gas and petroleum products; Energy; Exact sciences and technology; Fuels; Physics
• ISSN: 1294-4475; 1953-8189
• DOI: 10.2516/ogst:2007065

A major concern with the oil/gas pipelines and production/processing facilities is the possibility of flow restriction and blockage due to gas hydrate formation, which can lead to serious operational, economic and safety problems. Organic inhibitors such as methanol and ethylene glycol are normally used for preventing gas hydrate formation. Accurate knowledge of hydrate phase equilibrium in the presence of inhibitors is therefore crucial to avoid gas hydrate formation problems and to design/optimize production, transportation and processing facilities. Experimental data are needed for developing models capable of predicting hydrate phase behavior. In general, measuring hydrate phase equilibrium in the presence of inhibitor is more difficult than measuring ice point of inhibitor aqueous solution, particularly at high concentrations of inhibitor. This is partly due to the fact that the presence of inhibitor shifts hydrate phase boundaries to high pressures, which leads to difficulties in hydrate phase equilibria measurements. In this work, we examine the need for hydrate phase equilibrium data in the presence of inhibitor (ethylene glycol) aqueous solutions for tuning parameters of a thermodynamic model based on a modification of the Patel-Teja equation of state + van der Waals-Platteeuw theory. We consider two cases for tuning: use of ice point data or, using hydrate phase equilibrium data. The results show that using only ice point data of inhibitor aqueous solution for tuning thermodynamic model can lead to acceptable predictions of hydrate phase equilibrium in the presence of inhibitor and therefore experimental hydrate phase equilibrium data are not strictly indispensable. Un souci important avec les canalisations de pétrole/gaz et la production/les unités de traitement est la possibilité de restriction et de colmatage des écoulement dus à la formation d'hydrate de gaz. En effet le résultat étant de sérieux problèmes opérationnels, économiques et de sécurité. Des inhibiteurs organiques tels que le méthanol et l'éthylène-glycol sont couramment employés pour prévenir la formation d'hydrates de gaz. La connaissance précise des équilibres de phases de solutions comprenant des hydrates en présence d'inhibiteurs est donc cruciale afin d'être en mesure d'éviter tout problème de formation d'hydrate de gaz et pour concevoir et optimiser la production, le transport et les équipements de traitement. Des données expérimentales sont nécessaires pour développer les m