Where is methane hydrate

Challenges still exist to fully understand the potential for, and implications of, gas production from hydrates. The Program also works to confirm the scale and nature of the potentially recoverable resource through complex drilling and coring programs needs to be carried out. The Program will ultimately develop the technologies needed to safely and efficiently find, characterize, and recover methane from hydrates through field testing, numerical simulation, and laboratory experimentation.

The commercial viability of gas hydrate reservoirs is not yet known, but will depend on economic conditions in the future. Limited number of short production tests have been conducted to date. Now a new generation of sophisticated models are offering new insights into how they are deposited in nature.

A recent article in Reviews of Geophysics assesses two decades of methane hydrates research and suggests new avenues of research. Natural gas hydrates are an ice-like solid composed of water and gas, most commonly methane. They only form at high pressure and low temperatures, in places where both water and gas are plentiful. Small changes in temperature and pressure can cause gas hydrates to abruptly separate into water and gas, which means they are very difficult to study.

The most interesting gas hydrate deposits are those found within the pores of coarse-grained, sandy sediments or squeezed into rock fractures.

These deposits have the highest concentrations of gas hydrates and are of particular interest because of their energy potential. Why do we need to better understand the presence and behavior of gas hydrates in the environment?

Natural gas hydrates, which are derived from naturally occurring gas hydrocarbons, are an important part of the carbon cycle. Methane itself is a powerful greenhouse gas, with a warming effect nearly forty times that of carbon dioxide. Methane escaping from large natural gas hydrate deposits has been linked to periods of past climate change. Methane hydrate is energy-dense: at atmospheric pressure, each unit of frozen methane hydrate can produce units of natural gas.

Their abundance in nature means that methane hydrates represent one of the largest known unconventional energy sources — and a much cleaner alternative to crude oil or coal. We do not fully understand how gas hydrates are distributed in nature and how these deposits evolve. Methane hydrate deposits in the Gulf of Mexico alone have the potential to power the United States with natural gas for hundreds of years.

Important questions remain , however, because we do not fully understand how gas hydrates are distributed in nature and how these deposits evolve. What is the best way to categorize the many different types of gas hydrate deposits? Natural gas hydrate deposits can be categorized into several types depending on where they are found, how they form, and their physical properties. Low concentrations are found almost ubiquitously throughout the first few hundred meters beneath the seafloor around continental margins.

If you were to dig into these muddy sediments you would find tiny pockets of methane hydrates in the microscopic pores between sediment grains or within thin, vein-like fractures in the rock. Large fractures connecting the deep subsurface with the seafloor can also be rich in gas hydrates. At vent sites on the seafloor, methane gas escapes these fractures and seeps into the ocean, typically as a visible stream of bubbles.

Great efforts are presently being made to develop hydrate deposits, particularly in the territorial waters of Japan, China, India, South Korea and Taiwan. Methane hydrates occur worldwide. The basic idea is very simple: the methane CH 4 is harvested from the hydrates by replacing it with CO 2. Laboratory studies show that this is possible in theory because liquid carbon dioxide reacts spontaneously with methane hydrate.

If this concept could become economically viable, it would be a win-win situation, because the gas exchange in the hydrates would be attractive both from a financial and a climate perspective. Natural gas is a relatively clean fossil fuel. CO 2 emissions from gas-fired power plants are about 50 per cent lower than from conventional coal-fired plants. But even the emissions from modern gas-fired systems can be reduced considerably when CCS technology carbon capture and storage is installed.

By this method the CO 2 is isolated directly at the power plant and is stored in underground geological formations. Another option would be to inject the CO 2 into the marine methane hydrates; by this method, not only would methane gas be obtained, but the carbon dioxide would also be securely captured. Onshore, CO 2 is stored as a supercritical fluid that is mobile and chemically very aggressive. Some experts are concerned that underground storage reservoirs could therefore start to leak after a time.

If, instead, carbon dioxide is stored as a hydrate within the cold deep sea floor, it would be much safer, because CO 2 hydrates are considerably more thermally stable than methane hydrates. Even warming of the sea floor would not destabilize them. But this approach also involves ecological risk.

During hydrate excavation the methane could escape unchecked into the seawater. To eliminate this risk, only the very deep hydrate occurrences that are covered by fine-grained sediment layers at least metres thick should be developed. This is the only way to enable the methane gas to be retrieved safely through a borehole without the possibility of its escaping into the environment. In addition, care must be taken to ensure that the formation pressure is not increased by more than 10 bar during retrieval of the gas, as the sediment layers could otherwise break open and allow large amounts of methane to escape.

The amount of carbon stored in methane hydrates at the sea floor C in gigatonnes far exceeds that stored in oil, gas and coal. So far the necessary mining technology has only been tested under laboratory conditions.

Many years of development work are still needed to be able to reliably evaluate the potentials and risks and to realize mining on an industrial scale. The extraction of natural gas from methane hydrates onshore was successfully tested for the first time in by Japanese and Canadian scientists. In northern regions, methane hydrates lie hundreds of metres beneath the permafrost sediments.

It is cold enough and the pressure is sufficient for hydrates to form there too. In contrast to the deposits in the sea floor, however, these hydrate occurrences are easy to access and therefore suitable for production tests.