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Comparison of hydrates formation modeling software performance

Ismail Ismail

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Year 2020
Type of Item Master Thesis
Bibliographic Citation Ismail Ismail, "Comparison of hydrates formation modeling software performance", Master Thesis, School of Mineral Resources Engineering, Technical University of Crete, Chania, Greece, 2020
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Predicting hydrate stability/formation conditions is crucial for the oil and gas industry mainly to avoid pipelines blockage during oil and gas transportation and supplying. Additionally, exploitation methods of the natural gas and CO2 storage in hydrates have started gaining attention recently. Thus, understanding under what conditions hydrates are stable or can be stabilized is very important. Based on that, accurate knowledge of hydrate modeling in the presence of salts, inhibitors and non-ideal components is a main key in all related sectors.In the first part of this work, various approaches/models available in the literature and in the industry to describe hydrates thermodynamic behavior are presented and studied in detail so that the differences in stability, solid solution theory of Van der Waals and Platteeuw and the specific thermodynamic models representing all phases that co-exist (ice, water, solid CO2) adopted in each approach are well understood.Subsequently, the accuracy of the approaches describing the phase equilibria of gas hydrates in the presence of CO2 components, high/low concentration of aqueous salt(s) and/or high/low concentration of inhibitor(s) is evaluated. The approaches studied and tested are implemented in four well known commercial software packages extensively used in the industry, that hold the following industrial/developing name and the corresponding (approach): HydraFlash/HydraFact (HF, HF72), MultiFlash/KBC (MF(CPA)/MF(RKSA), CSMGem (CSMGem), CSMHyd (CSMHyd).The accuracy comparison is run against a large database of experimentally measured hydrate dissociation conditions which has been collected from papers that appeared in the literature between 2015-2019. The collected experimental data has been reproduced using all six approaches and the obtained results have been utilized to evaluate the accuracy of each method as a function of the temperature and pressure of the system.The results obtained are analyzed in detail and the reasons explaining the accuracy/deviations of each approach are presented. It has been found that the accuracy of the six studied approaches are ordered as follows (from most to less accurate): HF > HF72 > MF CPA > MF RKSA> CSMGem > CSMHyd.

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