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Theoretical model of hydrate formation in natural environments

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Title: Theoretical model of hydrate formation in natural environments
Author: Zatsepina, Olga
Degree Master of Science - MSc
Program Earth and Ocean Sciences
Copyright Date: 1997
Abstract: The solubility of two hydrate-forming gases, C02 and CH4 , is calculated over a range of pressure and temperature. The solubility of gas is shown to be significantly altered by the presence or absence of hydrate. In particular, gas solubility changes abruptly in hydrate presence, allowing it to crytallize from the aqueous solution without the need of any free gas. To test this prediction a set of experiments was performed. In the experiments, an aqueous solution of CO2 was cooled at a pressure of 2 MPa. A variety of methods were examined to detect the growth of hydrate. With cooling and hydrate formation, the physical characteristics of the porous medium (temperature, porosity, gas concentration) change. On the basis of known governing equations and conductivity of an aqueous solution in porous medium, the conductivity change due to hydrate formation was predicted. Conductivity was found to be particularly sensitive to hydrate formation, so electrical potential measurements were used to monitor hydrate growth. These electrical measurements indicated a pronounced resistance increase due to a change of gas concentration in the solution, corresponding to the amount of hydrate produced. Hydrate growth in the system was also detected in temperature data, which indicated a release of latent heat. The calculated phase diagram at typical pressure and temperature conditions in marine environments is applied to establish the gas concentration needed to stabilize hydrate. This information is used in simple methods of hydrate formation to estimate the vertical distribution of hydrate in marine sediments and the rate of accumulation.
URI: http://hdl.handle.net/2429/5803
Series/Report no. UBC Retrospective Theses Digitization Project [http://www.library.ubc.ca/archives/retro_theses/]

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