Gas hydrates are a naturally occurring "ice-like" combination of natural gas (usually methane) and water that have the potential to provide an immense resource of natural gas from the world’s oceans and polar regions. They occur where pressure, temperature, gas saturation, and local chemical conditions combine to make them stable. Gas Hydrates occurs in the pore spaces of sediments, and may form cements, nodes, veins, or layers.
Large scale power production from gas hydrates
Energy production from gas relies on the following technologies:
- Gas turbines
- Fuel cells (futuristic)
Gas hydrates are a source of methane and can be integrated with these technologies.
Recovery of Methane Gas from Gas Hydrates
Modifying the equilibrium conditions by
- Depressurization: At fixed temperature, operating at pressures below hydrate formation pressure.
- Inhibitor injection: Inhibition of the hydrate formation conditions by using chemicals such as methanol and salts.
- Thermal stimulation: At fixed pressure, operating at temperatures above the hydrate formation temperature. This can be achieved by insulation or heating of the equipment.
Reconnaissance surveys carried out by DGH in the East Coast and Andaman Deepwater areas in 1997 deciphered the most promising areas for Gas Hydrates. The surveys have indicated the presence of several Gas Hydrate leads/ prospects. The total prognosticated gas resource from the gas hydrates in the country is placed at 1894 TCM.
- K.G. and Mahanadi Basins in East Coast,
- Kerala-Konkan basin in the west coast
- Andaman offshore.
DGH has done pioneering work for initiating gas hydrate exploration in the country. Reconnaissance surveys carried out by DGH in the East Coast and Andaman Deepwater areas in 1997 deciphered the most promising areas for Gas Hydrates.
Government of India formulated a National Gas Hydrate Programme (NGHP) in 1997 for exploration and development of gas hydrates resources of the country.
The National Gas Hydrate Program (NGHP) is a consortium of National E&P companies (Oil and Natural Gas Corporation Ltd ‘ONGC’, GAIL India Ltd & Oil India Ltd ‘OIL’) and National Research Institutions (National Institute of Oceanography, National Geophysical Research Institute and National Institute of Ocean Technology). Steered by the Ministry of Petroleum & Natural Gas and technically coordinated by Directorate General of Hydrocarbons (DGH) NGHP is given the responsibility to explore the Gas Hydrates in India.
The NGHP efforts in Indian offshore for gas hydrate exploration led to the following:
• Conducted comprehensive analyses of gas-hydrate-bearing marine sediments in both passive continental margin and marine accretionary wedge settings;
• Discovered gas hydrate in numerous complex geologic settings and collected an unprecedented number of gas hydrate cores (more than 2800 m from 21 sites and 39 holes);
• Delineated and sampled one of the richest marine gas hydrate accumulations yet discovered in the world (Krishna-Godovari basin)
• Discovered one of the thickest and deepest gas hydrate occurrences yet known (Andaman Islands) which revealed gas-hydrate-bearing volcanic ash layers as deep as 600 meters below the seafloor;
• Established the existence of a fully developed gas hydrate system in the Mahanadi basin of the Bay of Bengal
- There are not many wells being drilled for extracting methane hydrate.
- As there are not many wells drilled for methane extraction, its extremely difficult to assess the true amount of methane hydrate deposits.
- Given the stability conditions of methane hydrate, it is clear that it is only present at depths of up to 280 m below the seafloor in water depth of 1,000 m, or at depths of up to 570 m below the seafloor in water depth of 4,000 m. This makes it very difficult to extract and develop methane hydrates close to seafloor.
- When temperature increases methane hydrates disassociates into methane and water. Though this reaction is very important in methane hydrate production this must be avoided during drilling as the gas might invade into the well.
Association of Petroleum Geologists
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