Hydrocarbons of experimental and natural gas hydrates, Gulf of Mexico continental slope

Gas hydrate was experimentally precipitated for the first time in the deep sea using natural starting materials. The experiments were performed using a research submarine on the Gulf of Mexico continental slope at a water depth of 540 m at 9.0–9.2°C. Starting materials were thermogenic hydrocarbon gases similar in composition to gases in underlying subsurface reservoirs. These gases vented to the water column in association with sea-floor mounds of natural yellow-orange gas hydrate (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. Experimental hydrates show δ13C of methane and C1–C5 hydrocarbon compositions that are similar to the vent gases from which they precipitated.