14 to 20 trillion standard m3 of natural gas is trapped as icelike solid natural gas hydrate deposits in northern Alaska. The commercial production of natural gas from this significantly large unconventional resource is feasible through detailed reservoir characterization and by energy-efficient in-situ decomposition of hydrates to natural gas. This paper provides a review of the characteristics of naturally occurring gas hydrates, the factors which control their distribution and stability, and describes their resource potential, geologic characteristics and origin in the North Slope, Alaska. Various novel techniques for decomposing in-situ hydrates are described and experimental results on the decomposition characteristics of hydrates during these techniques are discussed.
Gas hydrates are clathrate, non-stoichiometric. crystalline. Icelike solid compounds. Extensive deposits of naturally occurring gas hydrates have been found In many regions of the world In principally three different environments, where thermodynamically favorable conditions for formation of hydrates existed for millions of years and still exist. These Include:
shallow. arctic onshore sediments overlain by a continuous thick permafrost, e g., Prudhoe Bay and Kuparuk River regions of the Alaskan North Slope, huge Messoyakha field in Western Siberia (Makogon, 1965), Timan-Pechora and Kamchatka regions of U.S S R (Cherskiy et ai, 1985), Mackenzie-Delta regions of Canada and arctic Islands (Bily and DiCk, 1974, Judge, 1988);
deep oceanic sediments of tropical regions, e.g., Gulf of Mexico, Blake Bahama Outer Ridge, offshore regions of California, Guatemala, Panama, Nicaragua, Costa Rica, New Zealand, Australia, Columbia, Peru, Japan, West Norway, Gulf of Oman, Black Sea, Caspian Sea (Sloan. 1990), and
sediments underneath arctic and subarctic offshore waters, e.g., Beaufort Sea shelf and slope, Bering Sea slope (Navarln basin, Aleutian basin), North Pacific Ocean and Gulf of Alaska (Malone, 1987).