Gas Hydrate Prospecting and Characterization

Data acquired from major gas hydrate field programs over the past 20 years has led to much better understanding of the distribution of gas hydrate on the continental margins and how to detect them. Gas hydrate systems are extensions of the conventional hydrocarbon system but are much more closely related to biogenic gas systems. The temperatures at which most biogenic gas is generated is mostly below the base of gas hydrate stability which means that most biogenic gas has to migrate into the gas hydrate stability zone and has to be at levels in excess of solubility for gas hydrates to form. Gas hydrates had been considered ‘self-sealing’ but evidence from pressure cores and laboratory experiments indicate that gas hydrate deposits may need local seals. Detection of gas hydrates though seismic and other remote sensing methods has been demonstrated through drilling and coring programs. The GC955 site in the Gulf of Mexico is used as an example to demonstrate exploration concepts, through basin models, seismic detection, and drilling and coring results. Data from other locations are also discussed. A review of remote sensing data that could be used to delineate and quantify gas hydrate deposits is presented with an emphasis on low frequency exploration 3D seismic for imaging gas hydrate deposits at the base of gas hydrate stability.