Hydrates arrive on the scene

Methane hydrates were first encountered in the 1930s by operators of gas pipelines laid in cold climates. The white crystalline substance would build up in the pipes and block the gas flow.

In the 1960s, hydrates found in Siberian gas wells were widely reported. In the 1970s, ocean researchers announced the first reports of hydrates in deep submarine sediments. The avalanche of information grew – geochemical traces of hydrates were found in cold oceans, in the Arctic permafrost, but also on the tropical shelf, on the floor of the Gulf of Mexico, and in the Black Sea. However, there was still no material for study; the hydrates disintegrated too quickly. Only in 1981 did the Glomar Challenger drilling ship recover the first hydrate sample from the ocean floor near Guatemala. The drill core, impregnated with hydrates over a 1-meter section, became the scientific sensation of the year. In 1996, the crew of the German research vessel FS Senne managed to extract 50 kg of hydrates from the Pacific Ocean floor near Oregon using a deep-sea scoop.

Today, large government organizations and oil companies are exploring hydrates. The stakes are high: according to conservative estimates, hydrate deposits could provide at least as much energy as all fossil fuels combined—coal, oil, natural gas, peat, etc.

For a hydrate deposit to form, three conditions are necessary: there must be sufficient water and methane, the mixture must freeze at the appropriate temperature and pressure, and the methane ice must be covered with impermeable sediments.

Water is present almost everywhere. Methane is produced by bacteria during the anaerobic decomposition of organic matter. Today, this process can be observed in marshes – the gas bubbles that rise to the surface are methane, once called marsh gas. If such a marsh were covered with a layer of impermeable clay, the gas, accumulating under the cover, would form a deposit, currently composed of water and gas. For hydrates to form, the mixture must freeze, and do so under high pressure – only then does ice crystallize in a regular pattern, creating symmetrical cages in which methane molecules can be trapped. The fate of the deposit depends on external conditions – as long as high pressure and low temperature persist, the deposit will exist. If one of these parameters changes, the deposit will disappear. The stability and conditions for deposit formation are determined by the methane clathrate stabilization curve, obtained from laboratory experiments. The stabilization curve explains why hydrates occur in marine sediments below a depth of 300 m - only at this depth is there sufficient pressure to form ice in a regular, cage-like pattern.