Institute of Petroleum Engineering

Centre for Gas Hydrate Research Publications



Abstract 085
Gas Hydrates in the Caspian Sea: Their Potential Importance to Iran's Exploration Activities
Tohidi, B.
12th International Oil, Gas and Petrochemical Congress, Tehran, Iran, February 24-26 (2003).

Gas hydrates (or clathrates) are crystalline compounds which can form when water or ice and suitably sized molecules are brought together under favourable conditions, usually at a low temperature and moderate to high pressure. The pressure-temperature conditions for their formation depends on several factors, most importantly the composition of the gas and the water-rich phase. In the natural environment, suitable conditions for gas hydrate formation can be found in some marine sediments, in deep lakes, and in the subsurface of arctic permafrost regions. Most natural gas hydrates are methane hydrates produced from anaerobic bacterial breakdown of organic materials. Methane hydrates could be found at water depths of greater than 500m, depending on the presence of a suitable gas source. In the Caspian Sea, the presence of deep-seated hydrocarbon reservoirs and their seepage provides the suitable conditions for the formation of thermogenic gas hydrates. As these seepages contain significant quantities of intermediate compounds, their formation can occur at much lower pressures (depths) compared to well-documented methane hydrates. Some researches report on the presence of gas hydrates at water depths less than 150 metres and maximum thickness of 1300 metres. These together with higher seabed temperature and active mud volcanoes give some interesting peculiarities to the gas hydrates in the Caspian Sea. Little research on gas hydrates in the Caspian Sea has been conducted/reported in Iran, despite considerable research in the neighbouring countries, in particular Russia and Azerbaijan. In this communication we give a summary of the previous findings and their potential importance to Iran's exploration and production activities both in Iran and abroad.