LOW TEMPERATURE X-RAY DIFFRACTION STUDIES OF NATURAL GAS HYDRATE SAMPLES FROM THE GULF OF MEXICO

• Main Authors: Claudia J. Rawn, Roger Sassen, Shannon M. Ulrich, Tommy J. Phelps, Bryan C. Chakoumakos, E. Andrew Payzant
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Arctic; Ice; permafrost
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.164.6297; http://www.netl.doe.gov/technologies/oil-gas/publications/2008_ICGH/ICGH_5801_FEAB111.pdf

Clathrate hydrates of methane and other small alkanes occur widespread terrestrially in marine sediments of the continental margins and in permafrost sediments of the arctic. Quantitative study of natural clathrate hydrates is hampered by the difficulty in obtaining pristine samples, particularly from submarine environments. Bringing samples of clathrate hydrate from the seafloor at depths without compromising their integrity is not trivial. Most physical property measurements are based on studies of laboratory-synthesized samples. Here we report X-ray powder diffraction measurements of a natural gas hydrate sample from the Green Canyon, Gulf of Mexico. The first data were collected in 2002 and revealed ice and structure II gas hydrate. In the subsequent time the sample has been stored in liquid nitrogen. More recent X-ray powder diffraction data have been collected as functions of temperature and time. This new data indicates that the larger sample is heterogeneous in ice content and shows that the amount of sII hydrate decreases with increasing temperature and time as expected. However, the dissociation rate is higher at lower temperatures and earlier in the experiment. Keywords: natural gas hydrates, X-ray powder diffraction, thermal expansion _________________________