Type of Document Dissertation Author Lin, Fang Author's Email Address email@example.com URN etd-10062005-222419 Title Experimental Study of the PVTX Properties of the System H2O-CH4 Degree PhD Department Geosciences Advisory Committee
Advisor Name Title Bodnar, Robert J. Committee Chair Dove, Patricia M. Committee Member Read, James Fredrick Committee Member Schreiber, Madeline E. Committee Member Sum, Amadeu K. Committee Member Keywords
- synthetic fluid inclusions
- Raman spectroscopy
- methane hydrate
- H2O-CH4 system
- PVTX properties
- phase equilibria
Date of Defense 2005-09-23 Availability unrestricted AbstractThe system H2O-CH4 is found in a variety of geological environments in the earth's crust,
from sedimentary basins to low grade metamorphic terrains. Knowledge of the Pressure-
Volume-Temperature-Composition (PVTX) properties of the H2O-CH4 system is
necessary to understand the role that these fluids play in different geological
environments. In this study the properties of the H2O-CH4 fluid system at elevated
temperatures and pressures has been investigated experimentally to determine the PVTX
properties of H2O-CH4 fluids in the P-T range equivalent to late diagenetic to low grade
metamorphic environments, and CH4 mole fraction less than and equal to 4mol%. A study has also been conducted to
determine methane hydrate stability over the temperature range of -40~20 degree Celsius. Synthetic
fluid inclusions were employed in both studies as miniature autoclaves.
Experimental data for the PVTX properties of H2O-CH4 fluids under late
diagenetic to low grade metamorphic conditions was used to calculate the slopes of iso-
Th lines (the line connecting the P-T conditions of the inclusions at formation and at
homogenization) at different PTX conditions. An empirical equation to describe the slope
of iso-Th line as a function of homogenization temperature and fluid composition was
developed. The equation is applicable to natural H2O-CH4 fluid inclusions up to 500 degree Celsius
and 3 kilobars, for fluid compositions less than and equal to 4 mol% CH4.
The Raman peak position of CH4 gas is a function of the pressure and temperature.
This relationship was used to determine the pressure along the methane hydrate stability
curve in the H2O-CH4 system. The combined synthetic fluid inclusion, microthermometry
and Raman spectroscopy method is a novel experimental approach to determine the P-T
stability conditions of methane hydrates. The method is fast compared to conventional
methods, and has the potential to be applied to study other gas hydrate systems.
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