Fire in the Ice – Methane Hydrates
Methane Hydrates – The fuel of the future
In the last three decades of the twentieth century the scientists made surprising discoveries on the ocean floor: chemosynthetic communities drawing their energy from sulfur vents, methane or ammonia, gas hydrates, etc.. Methane hydrates, among others, constitute an enormous reserve of energy. It is clear that we will try to exploit this reserve. But will he do so without damaging the environment ?
The fuel of the future - Methane Hydrates - Source: USGS
Methane Hydrate, also called methane clathrate or methane ice, is a solid form of water that contains a large amount of methane within its crystal structure (a clathrate hydrate). Originally thought to occur only in the outer regions of the Solar System where temperatures are low and water ice is common, significant deposits of methane clathrate have been found under sediments on the ocean floors of Earth. Can be found also in the sediments of deep lakes, e.g. the freshwater Lake Baikal, Siberia. Continental deposits have been located in Siberia and Alaska in sandstone and siltstone beds at less than 800 m depth.
It is estimated that the ocean floor contain twice methane hydrates that all the deposits of natural gas, oil and coal mondialememt known. Only the south-east coast of the USA, an area of 26 000 square km contains 35 Gt (gigatons = billion tons) of methane hydrates, or 105 times the natural gas consumption in the USA in 1996!
The map below shows the distribution of known deposits of methane hydrate in the world.
Gas Hydrates - Global Map
Laboratory Investigation of Hydrate Production through CO2-CH4 Exchange
Early in 2002 researchers at the University of Bergen and ConocoPhillips Reservoir Engineering lab ran an experiment to determine whether carbon dioxide could be successfully sequestered within hydrate by replacing the methane. While there was some earlier experimental evidence supporting this exchange mechanism in bulkhydrates, the question of how well it would work for hydrates found in nature was uncertain.
The University of Bergen’s experience with thermodynamic calculations on hydrate phase transitions indicated a good likelihood that this process would proceed “relatively rapidly,” under conditions found in nature. ConocoPhillips had significant experience in designing and running flow in porous media experiments within a MRI-compatible sample holder that could generate important 3-D information within the sample on the progress of an experiment.
Despite the inevitable problems that accompany first experiments and a shortage of available time, the results from the hydrate formation as viewed by 3-D MRI images were satisfying. As cooling began, the initial state showed the water-saturated core with methane in the spacer and in the end pieces . The constant-pore pressure system allowed for the addition of methane as it was consumed during hydrate formation.
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