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Title: Phase behaviour modelling of systems containing gas hydrates and asphaltenes
Author: Mohammadi, Amir Hossein
Awarding Body: Heriot-Watt University
Current Institution: Heriot-Watt University
Date of Award: 2006
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Gas hydrates are crystalline compounds formed from a combination of water molecules with suitably sized non-polar or slightly polar molecules under certain conditions of temperature and pressure. They are well known for their role in the blockage of subsea pipelines and oil and gas production / processing facilities, which is a major concern for the petroleum industry. On the other hand, asphaltenes are the toluene / benzene soluble fractions that precipitate from petroleum when an excess (25 to 40 times) of n-heptane / n-pentane is mixed with petroleum and waiting at least four hours before filtering. Asphaltene precipitation causes fouling in the reservoir, in the well, in the pipeline and in the oil production and processing facilities. In this study, predictive methods and thermodynamic models to predict the hydrate and asphalt free zone of hydrocarbon fluids were developed for field applications. The topics studied included estimation of water content of natural gases in equilibrium with the liquid water, ice and gas hydrates, prediction of hydrate inhibition effects of mixed salt and organic inhibitor and finally modelling asphaltene precipitation conditions. The results showed that the existing predictive methods show large deviations for predicting the water content of natural gases at low temperature conditions and therefore, new predictive tools were developed. Furthermore, the application of a thermodynamic model was extended to mixed salt and chemical inhibitor commonly used in petroleum production and transportation. This will provide a basis for the design of production and transportation facilities, particularly for deepwater applications. A new correlation for predicting the hydrate inhibition effect of single and mixed thermodynamicin hibitors was also developed. A theoretical study was conducted to investigate asphaltene precipitation from petroleum fluids during petroleum production and transportation. The results showed that it is possible to use a polymer model namely the Scott-Magat theory combined with an equation of state to predict asphaltene precipitation from reservoir fluids. b
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available