Numerical simulation of gas hydrate dissociation in lab-scale depressurization experiment

  • 楊 嘉勝

Student thesis: Master's Thesis


Natural gas hydrates are clean and vast unconventional resources that exist around the world Depressurization is one of their production mechanisms and is considered an effective way to produce natural gas from hydrates To date some experiments have been conducted in other laboratories to investigate the mechanism of hydrate dissociation However it is worth having the comparative results from a simulation study The purpose of this study is to develop a two-dimensional axisymmetric numerical model to simulate the behavior of hydrate dissociation in a lab-scale depressurization experiment This work also investigates the effects of the flow characteristics hydrate reaction parameters and basic properties of hydrate In this study the CMG-STARS numerical model is set up to simulate a lab-scale depressurization experiment chosen from the literature The numerical grids are discretized based on the vessel size used in the laboratory To understand which parameters are likely to seriously affect the dissociation behavior we perform a sensitive analysis of the flow properties hydrate reaction parameters and thermal properties The numerical simulation runs were done to match the experimental data by adjusting the sensitive parameters Furthermore the simulation results from CMG-STARS and from TOUGH+HTDRATE which has been used in other studies are compared Finally the verified module is applied to an experiment conducted by a research team from National Taiwan University of Science and Technology (NTUST) The major findings from this study are: (1) The numerical model is developed for simulating a depressurization experiment from the literature and it is verified by matching the experimental data (2) Hydrate reaction parameters such as activation energy and intrinsic rate constant have a significant effect on the dissociation rate Moreover the flow parameters e g relative permeability and irreducible gas saturation are crucial for gas production (3) The numerical results are compared with the results of another numerical simulation from the literature Both works have a minor experimental data difference in the temperature profile but our study shows smoother results (4) Although the hydrate formation and dissociation are done in a hollow vessel without porous media filled in the numerical results still can model the behavior on the assumption that methane water and hydrate are distributed uniformly in the vessel
Date of Award2016 Aug 31
Original languageEnglish
SupervisorBieng-Zih Hsieh (Supervisor)

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