EE 350 RADIOSCIENCE SEMINAR

Professor Umran S. Inan

Winter 1997-98



Date: Wednesday, February 25, 1998

Time: 4:15 PM ‚ Refreshments at 4:00

Location: Gesb 124 (Green Earth Sciences Bldg.)

Gas Hydrates under Earthıs Oceans

Prof. Amos M. Nur

Geophysics

Stanford University

Abstract

Gas hydrates (GH) are naturally occurring ice like solids composed of cages of water that enclose molecules of natural gass. Natural gas hydrates occur worldwide in marine bottom sediments of the outer continental margins in many parts of the world seas and oceans. The total amount of carbon bound in methane hydrates on earth is estimated to be twice the total amount of carbon found in all recoverable and non recoverable oil, coal, and conventional natural gas on earth. In addition, huge quantities free methane gas may be trapped beneath the self sealing and impervious gas hydrate layers. GHs are detected seismically through anusual seismic reflections from the bottom of the hydrate zones. Because hydrates and the methane trapped underneath are usually too deep to sample by drilling, it is imperative to obtain from remote seismic measurements whatever information possible about the physical state and properties of the frozen gas hydrate bearing sediments in order to determine. In this talk I show how seismic interpretation and rock physics data and theory are being used to determine insitu hydrate concentration, permeability in the frozen region, and pore pressure of gas trapped underneath. There are 3 important implications of gas hydrates: a. Offshore methane hydrates and methane trapped under hydrates may become one of the worldıs future major source of hydrocarbon energy. This is of special interest to countries that are short on conventional hydrocarbons. b. The abundance and relative instability of sub ocean hydrates may influence global warming and cooling. c. GHs may provide important insight into the debate about the GAIA hypothesis.