--> ABSTRACT: Thermogenic Gas Venting and Gas Hydrate in the Gulf of Mexico: Potential Significance to Climate Change, by Roger Sassen, Stephen T. Sweet, Alexei V. Milkov, Debra A. DeFreitas, and Harry Roberts; #90906(2001)

Datapages, Inc.Print this page

Roger Sassen1, Stephen T. Sweet1, Alexei V. Milkov1, Debra A. DeFreitas1, Harry Roberts2

(1) Texas A & M University, College Station, TX
(2) Louisiana State University, Baton Rouge, LA

ABSTRACT: Thermogenic Gas Venting and Gas Hydrate in the Gulf of Mexico: Potential Significance to Climate Change

Thermogenic gas hydrate is abundant on the Gulf of Mexico continental slope because hydrocarbon gases from a deep, hot subsurface petroleum system vent prolifically to the sea floor in regions of the gas hydrate stability zone. The distribution of gas hydrate is controlled by geologic structure. Gas hydrate is transiently unstable near the sea floor, but the larger volume of gas hydrate is buried and insulated in sediment. Molecular distributions of gases venting from thick hydrate-bearing sediments show that gas hydrate decomposition is not significant in comparison to flux of free gas from the subsurface petroleum system. Structure II gas hydrate is commonly encountered, and contains thermogenic hydrocarbons that crystallize from relatively unaltered vent gas. Most structure II gas hydrate studied from relatively unaltered vent gas. Most structure II gas hydrate studied from the 540-1930 m water depth range appears stable, and gas hydrate is thought to be accumulating to considerable depth in sediment because of the prolific, ongoing, venting of gas. The rate at which thermogenic gas is venting to the ocean and atmosphere appears to have been underestimated in the Gulf of Mexico. A leaky petroleum system could be the main contributor of thermogenic greenhouse gases to the ocean and atmosphere from the Gulf of Mexico, not gas hydrate decomposition. Gas hydrate crystallization in the Gulf of Mexico sequesters large volumes of greenhouse gases in sediments, deforming soft sediments, and is proposed as an agent that could stabilize or dampen climatic change under the present climatic regime.

AAPG Search and Discovery Article #90906©2001 AAPG Annual Convention, Denver, Colorado