Gas-Hydrates - A Synoptic View

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Abstract Large-scale occurrence of gas-hydrates in the marine sediments of outer continental margins is by now well-known. While the methods of tracing gas-hydrate enriched zones, like identifying markers such as bottom simulating reflectors and blanking zones on seismic reflection sections, are well-established, quantification and resource assessment of gas hydrates still remain hazy. Investigations over the classical gas-hydrate enriched Blake outer ridge on the U.S. Atlantic margin have provided new insights into the environs of gas-hydrate occurrences. Deep sea drilling results in this area indicate that the estimates of gas-hydrate from geophysical measurements could be less by an order of three in comparison with those obtained from drilling. Several factors like bathymetry, sediment thickness and sedimentation rates, sea bottom temperature and total organic carbon content, which control gas-hydrate formation, indicate that the shallow sediments in the offshore regions of India could be potentially enriched in gas hydrates. National agencies like the Oil & Natural Gas Corporation, Gas Authority of India Ltd., National Geophysical Research Institute, National Institute of Oceanography and others are now actively involved in assessing the true potential of this anticipated future energy resource. The environmental aspects of gas hydrates like large-scale release of methane gas into the air and slope instabilities and submarine landslides in the continental margins resulting in catastrophic events, however, need to be kept in mind.