Abstract: Concentrated Marine Gas Hydrate Deposits: Laboratory Simulations Seek Explanations of their Origin and Methods of Resource Analysis
James S. Booth, William J. Winters, William P. Dillon
Methane hydrates in continental margin sediments may comprise the most impressive remaining reservoir of fossil fuel. Although methane may be expensive to extract from hydrate reservoirs, some highly concentrated deposits of hydrates exist. Off the southeastern United States we estimated from seismic profiling data that a small area of the sea floor (3000 km2) on the Blake Ridge may hold up to 638 tcf of methane locked in hydrates, which is more than a 30-yr supply of natural gas for the United States at current rates of consumption. How and why was hydrate concentrated at this site? How can other sites that may become economically attractive for methane recovery be identified and their reserves accurately estimated?
To understand the processes by which gas hydrates may be concentrated and to develop tools (such as acoustic models) that aid recognition and resource analysis of offshore hydrate deposits, we have begun laboratory studies using a computer-controlled test system in which gas hydrates are formed and decomposed in sediment samples under simulated in-situ conditions. We also simulate possible mechanisms of natural concentration, which include (1) an accumulating sediment column, (2) cyclic eustatic change, (3) faulting and fluid migration, and (4) trapping free gas beneath a hydrate seal. In addition, the basic habits of formation and initial concentration of hydrates, whether of biogenic or thermogenic origin, are being investigated in different sediment types under different simulated ater depths and overburden pressures. For purposes of modeling and establishing baseline data sets, P- and S-wave velocities and electrical resistivities are monitored and recorded during all experiments.
AAPG Search and Discovery Article #90984©1994 AAPG Annual Convention, East Lansing, Michigan, September 18-20, 1994