Direct disposal of liquid CO2 on the ocean floor is one of the approaches considered for sequestering CO2 in order to reduce its concentration in the atmosphere. At oceanic depths deeper than approximately 3000 m, liquid CO2 density is higher than the density of seawater and CO2 is expected to sink and form a pool at the ocean floor. In addition to chemical reactions between CO2 and seawater to...

The results of six high-precision constant energy molecular dynamics (MD) simulations initiated from methane-water systems equilibrated at 80 MPa and 250 K indicate that methane hydrates can nucleate via multiple pathways. Five trajectories nucleate to an amorphous solid. One trajectory nucleates to a structure-I hydrate template with long-range order which spans the simulation box across perio...

The structures and the guest-host distributions of iso-propylamine (i-PA) and n-propylamine (n-PA) hydrates with hydrogen as a secondary guest were identified by powder X-ray diffraction and Raman spectroscopic analysis. The structure of 11.1 mol% i-PA + H2 hydrate was identified to be hexagonal (space group P63/mmc) with a few unindexed diffraction peaks, while 5.6 mol% i-PA + H2 hydrate had a...

A Raman spectrometer extensively modified for deep ocean use was used to measure synthetic hydrates formed in an ocean environment. This was the first time hydrates formed in the ocean have been measured in situ using Raman spectroscopy. Gas hydrates were formed in situ in the Monterey Bay by pressurizing a Pyrex cell with various gas mixtures. Raman spectra were obtained for sI methane hydrate...

With the continuous growth in global energy demand, exploration and development of hydrates has been focus increasing attention, accurate evaluation mechanical properties hydrate layers become particularly important. In this study, using a self-developed sample preparation device triaxial seepage test platform, shear tests were carried out situ synthesis method for sediment laboratory, stress–s...

Fluid–fluid and fluid–solid phase equilibrium were experimentally determined under pressure on the system methane + heptadecane using a full isibility cell. Measurements were performed using the synthetic method on mixtures ranging from pure heptadecane to 99% of methane. The iquid–solid phase transitions were investigated up to 90 MPa and fluid phase boundary was studied in the temperature dom...

Initiation of phase transition was affected by the presence of hydrate H in the initial sample, but the presence of forms Z and M in the initial sample affected the middle interval of phase transition. The differences can be explained by accelerated nucleation of the stable polymorph A in the presence of water vapour released during the dehydration of hydrate H. However, in those cases when Z a...

Natural gas is projected to be the premium fuel of the 21st century because of availability, as well as economical and environmental considerations. Natural gas is coproduced with water from the subsurface forming gas hydrates. Hydrate formation may result in shutdown of onshore and offshore operations. Industry practice has been usage of alcohols--which have undesirable environmental impacts--...