Institute of Petroleum Engineering

Centre for Gas Hydrate Research Publications

Abstract 164

Experimental and Thermodynamic Modelling of Systems Containing Water and Ethylene-Glycol: Application to Flow Assurance and Gas Processing

Haghighi, H., Chapoy, A., and Tohidi, B.
Fluid Phase Equilibria, 276, 24-30 (2009).

In petroleum exploration and production operations, gas hydrates remain a major challenge and a serious economic and safety concern. Thermodynamic inhibitors, such as ethylene glycol, are widely used to reduce the risks associated with gas hydrate formation. The current trend is towards gas and oil production from reserves located in deep water and consequently at high pressure. In many cases the flow assurance strategy is to rely upon injection of organic inhibitors and in order to inhibit hydrate formation at these conditions the concentrations required are likely to be relatively high. 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. In this communication, we report new experimental dissociation data for various systems consisting of methane/water/ethylene glycol and natural gas/water/ethylene glycol. A statistical thermodynamic approach, with the Cubic-Plus-Association equation of state, is employed to model the phase equilibria. The hydrate-forming conditions are modelled by the solid solution theory of van der Waals and Platteeuw. The thermodynamic model was used to predict the hydrate dissociation conditions of methane and natural gases in the presence of distilled water or ethylene glycol aqueous solutions. Predictions of the developed model are validated against independent experimental data and the data generated in this work. A good agreement between predictions and experimental data is observed, supporting the reliability of the developed model.

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