HYDROCARBONS OF EXPERIMENTAL AND NATURAL-GAS HYDRATES, GULF-OF-MEXICOCONTINENTAL-SLOPE

Gas hydrate was experimentally precipitated for the first time in the deep sea using natural starting materials. The experiments were perfor med using a research submarine on the Gulf of Mexico continental slope at a water depth of 540 m at 9.0-9.2 degrees C. Starting materials we re thermogenic hydrocarbon gases similar in composition to gases in un derlying subsurface reservoirs. These gases vented to the water column in association with sea-floor mounds of natural yellow-orange gas hyd rate (structure II). The vent gases were captured in transparent Lexan tubes at ambient conditions, and precipitation of white to yellow gas -hydrate dendrites and coatings was seen to occur within minutes. Expe rimental hydrates show delta(13)C of methane and C-1-C-5 hydrocarbon c ompositions that are similar to the vent eases from which they precipi tated. (C) 1997 Elsevier Science Ltd.