RESEARCH ARTICLE


Gas Hydrate Formation Phase Boundary Behaviour of Synthetic Natural Gas System of the Keta Basin of Ghana



Eric Broni-Bediako1, *, Richard Amorin1, Cornelius B. Bavoh2
1Department of Petroleum Engineering, University of Mines and Technology, Tarkwa, Ghana
2 Chemical Engineering Department, Universiti Teknologi Petronas (UTP), Seri Iskandar, Perak, Malaysia


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© 2017 Broni-Bediako et al.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: https://creativecommons.org/licenses/by/4.0/legalcode. This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author the Department of Petroleum Engineering, University of Mines and Technology, Box 237, Tarkwa, Ghana, Tel: +233 243 052 455; E-mails: bronibediako2005@yahoo.com, ebroni-bediako@umat.edu.gh


Abstract

Background:

Gas hydrates are considered as a major threat to the oil and gas flow assurance industry. At high pressure and low temperature conditions, gas hydrates form in pipelines and production facilities leading to pipeline blockages, high removal cost, environmental hazards and loss of lives. For a successful prevention of gas hydrate formation, predicting the hydrate formation phase boundary of hydrocarbon fluid composition becomes very necessary.

Objective and Method:

In this study, computer simulation software called PVTSim was used to predict hydrate formation phase boundary of synthetic natural gas composition of the Keta basin of Ghana at pressure and temperature ranges of 43.09 bar - 350 bar and 12.87 °C - 27.29 °C respectively. The effect of changes in natural gas composition (N2 and H2S) and the presence of four commonly used thermodynamic gas hydrate inhibitors (methanol, ethanol, diethylene glycol and monoethylene glycol) on the hydrate formation phase boundary is also discussed. Prior to the study, the accuracy of PVTSim was validated with the hydrate formation phase data in literature.

Results and Conclusion:

Results suggested that the hydrate formation phase boundary decreased with increasing N2 composition and increased with increasing H2S composition, suggesting that, the presence of H2S increases the threat of hydrate formation. However, a reduction in hydrate formation threat was observed in the presence of all four commonly used gas hydrate thermodynamic inhibitors with methanol demonstrating the highest inhibition effect.

Keywords: Gas hydrate, PVTSim, Phase boundary, Natural gas, Thermodynamics.