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Distribution and Resources of Natural Gas Hydrates
Natural gas hydrate (NGH), also called gas hydrate, is an ice-like combination of water and natural gas molecules, resembling a slushy snow, which forms under a specific combination of pressure and temperature. As an important non-conventional natural gas resource, NGH has received much research attention in recent years. This paper aims to investigate the distribution and resources of NGH from a geological point of view.
The formation of natural gas hydrate requires three factors - a high pressure and low temperature environment, above 4°C and 100 bar. These conditions are mainly found in coastal continental margins and high latitude regions such as the Arctic. Worldwide, NGH has been found in permafrost regions, such as onshore Alaska, Northern Canada and Siberia, and in deep marine environments, such as the continental shelves of India and South Africa. Other potential locations of natural gas hydrate include the margins of the Bay of Bengal and the South China Sea.
In terms of resources, global estimates of NGH have been determined by a variety of methods. These include engineering calculations, computer simulations and geophysical modelling, as well as direct gas hydrate core samples. As a result of these different methods, the estimates of global NGH resources range from 10.8×10^12 to 10.04×10^15 m^3 of natural gas in place. In terms of potential rate of extraction, NGH may provide over 10% of the world’s current daily consumption of natural gas.
The estimation of NGH resources brings with it numerous technical challenges, mainly due to the hydrogeology of the region. As NGH is generally found in depths of up to 1000 m, it is difficult to collect direct samples and monitor its concentration changes in the subsurface. As such, most NGH resource estimation methods rely on indirect methods, such as seismic surveys, geophysical studies and core drilling.
Overall, it is evident that natural gas hydrate has great potential as an alternative energy source. Its global distribution, however, is still uncertain, and more research is needed to accurately identify and quantify NGH resources. Furthermore, the development of reliable exploration technology, coupled with advances in monitoring and extraction techniques, will be necessary to ensure its safe and effective use.
