Vast quantities of natural gas are held in hydrate form in geologic reservoirs in sub-oceanic sediments and arctic permafrost zones (KVENVOLDEN, 1988; SLOAN, 1998), where conditions of high pressure and low temperature are within the hydrate stability region. In 1995, the U.S. Geological Survey (USGS) conducted a study to assess the quantity of natural gas hydrate resources in the United States...

Molecular dynamics simulations were performed for CO2 dissolved in water near silica surfaces to investigate how the hydrophilicity and crystallinity of solid surfaces modulate the local structure of adjacent molecules and the nucleation of CO2 hydrates. Our simulations reveal that the hydrophilicity of solid surfaces can change the local structure of water molecules and gas distribution near l...

INTRODUCXION Gas hydrates are crystalline molecular complexes formed from mixtures of water and suitably sized gas molecules. Based on hydrogen bonding, water molecules form unstable lattice structures with several interstitial cavities. The gas molecules can occupy the lattice cavities and, when a minimum number of cavities are occupied, the crystalline structure becomes stable and solid gas h...

Under ambient conditions, water freezes to either hexagonal ice or a hexagonal/cubic composite ice. The presence of hydrophobic guest molecules introduces a competing pathway: gas hydrate formation, with the guests in clathrate cages. Here, the pathways of the phase transitions are sought as sequences of states with coexisting phases, using a generalized replica exchange algorithm designed to s...

Ocean storage of CO2 was proposed by Marchetti as one of greenhouse gas control technologies, where CO2 is captured from flue gas of fossil fuels and injected into deep seafloor below the depth of 3500m to be sequestered from the atmosphere as shown in Fig. 1. In the last decade of the twenties century, there was a great progress in study on the ocean storage. Aya and his colleagues and Nishika...

Clathrate hydrates are crystalline compounds formed by a physically stable interaction between water and relatively small guest molecules. Under suitable conditions of guest pressure and temperature, water molecules, via hydrogen bonds, form into polyhedral cavities that connect to give space-filling frameworks. Because of partial cage filling, these crystalline compounds are nonstoichiometric....

Formation of hydrates is observed during drilling and construction of wells, more frequently in gas wells located offshore (deep sea water). Hydrates of natural gas can clog chokes and kill lines, and obstruct the opening or closure of blow out preventer (BOP), seal well override valve and immobilize well string. Because of that, this work was mainly focused in the selection and adaptation of a...

We present a model of the global methane inventory as hydrate and bubbles below the sea floor. The model predicts the inventory of CH(4) in the ocean today to be approximately 1600-2,000 Pg of C. Most of the hydrate in the model is in the Pacific, in large part because lower oxygen levels enhance the preservation of organic carbon. Because the oxygen concentration today may be different from th...