HR: 17:00h
AN: OS34B-05    [Abstracts]
TI: Investigations on Mixed Gas Hydrates: Unexpected Experimental Observation Versus Calculated Data
AU: * Schicks, J M
EM: schick@gfz-potsdam.de
AF: GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AU: Naumann, R
EM: rudolf@gfz-potsdam.de
AF: GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AU: Erzinger, J
EM: erz@gfz-potsdam.de
AF: GeoForschungsZentrum Potsdam, Telegrafenberg, Potsdam, 14473 Germany
AB: The knowledge of the conditions for gas hydrate formation and their stability fields are necessary for the prediction of their influence on climate changes or slope stability. In the past, the phase equilibria of gas hydrates composed of pure gases like methane, ethane or propane and water have been described in detail in phase diagrams, based on experimental and modelled data. However, natural gas mixtures are composed of methane, ethane and propane and other components. Hence, it is no longer acceptable to assume that the phase behaviour of natural gas hydrates is similar to that of pure methane gas hydrates. Investigations on pseudo-binary systems like methane+ethane+water indicates unusual phase behaviour like structural transitions (Subramanian et al., 2000). Therefore, Ballard and Sloan (2001) published phase diagrams for pseudo-binary and pseudo-ternary hydrocarbon mixture with water, which have been generated from modelled data at 277.6 K using a Gibbs free energy minimization flash routine. Since the phase behaviour of multicomponent gas hydrates are almost unpredictable, we present in this contribution the stability fields and phase transitions of mixed gas hydrates composed of methane, ethane, propane and water based on experimental data. The multicomponent systems have been investigated in a pressure range between 1 MPa and 6 MPa and a temperature range between 270 K and 290 K. Microscopic observations, Raman spectroscopy and X-Ray diffraction data provide information about the phase boundaries and transformation processes, the composition and the structure of the hydrate phase, respectively. The similarities and discrepancies between modelled and experimental data will be discussed. References: A. L. Ballard, E.D. Sloan, Chemical Engineering Science 56 (2001) 6883-6895 S. Subramanian, R.A. Kini, S.F. Dec, E.D. Sloan, Chemical Engineering Science
DE: 3022 Marine sediments--processes and transport
DE: 1030 Geochemical cycles (0330)
DE: 1600 GLOBAL CHANGE (New category)
DE: 0330 Geochemical cycles
DE: 1000 GEOCHEMISTRY (New field, replaces Rock Chemistry)
SC: Ocean Sciences [OS]
MN: 2004 AGU Fall Meeting