Gas pressure

With global oil prices soaring and continued concerns over the security of gas supplies, the need to exploit alternative sources of fossil fuels has never been greater.

The US Geological Survey estimates that the amount of organic carbon stored as frozen natural gas under the Earth’s surface is greater than the world’s oil, coal and non-frozen, free gas reserves combined. Large reserves are thought to exist under the oceans off the coasts of Japan, China, India, Canada and Russia.

Like conventional natural gas, the methane held within these reserves was formed as a by-product by microbes feasting on organic matter trapped in sediment. In cold, high-pressure environments, water molecules form open solid lattices that trap methane molecules without chemical bonding — methane hydrates. It is thought that around 55 million years ago some event caused vast quantities of gas to be released from these structures, causing abrupt global warming.

Methane from hydrates is more environmentally friendly than normal natural gas as it produces less carbon dioxide when burned. However, accidental creation of a large uncontrollable leak could be catastrophic. Identifying and extracting methane from hydrates for commercial use thus presents an enormous technical challenge that has swallowed millions of research dollars in countries including Japan, Canada and the US.

Methane hydrate is the most abundant natural form of clathrate, a unique class of chemical substance in which molecules of one material (in this case, water) form an open solid lattice that encloses, without chemical bonding, appropriately-sized molecules of another material (in this case, methane).

The US National Energy Technology Laboratory’s National Methane Hydrate Programme, initiated in 1997, aims to develop technologies to allow the commercial production of gas from methane hydrates by 2015.

Last month researchers led by chemist Dr Devinder Mahajan of the Advanced Fuels Group at the US government’s Brookhaven National Laboratory on Long Island, New York, announced they had come up with a method to recreate the high-pressure, low temperature conditions found on the seabed. This will allow scientists to design better methods for finding and extracting the methane, as seismic probes used to detect oil and gas deposits find it hard to identify deposits.

But in the same month the US suffered a setback when the National Science Foundation announced estimates of hydrate reserves in the northern Gulf of Mexico should be slashed as sediments were too warm and salty to hold large amounts of gas. Future funding for the $10m (£5m) per year National Methane Hydrate Programme is also uncertain. It ends this September and no new budget has been agreed by Congress. Other agencies are still free to fund hydrate extraction programmes but their budget is only half that of NETL.

‘The official position is that, with high energy prices, industry will pick up the shortfall,’ said Edith Allison, exploration programme manager at NETL’s Office of Natural Gas and Petroleum Technology.

Now, another country is poised to join the quest. Though the Republic of Ireland may not have the spending power of larger nations, a group led by geologist Dr Padraic Mac Aodha of the National University of Ireland, Galway, hopes they can leap ahead of larger nations.

Partnered with Dublin-based oil and gas firm Providence Resources and UK firm Sosina Exploration, the group is investigating the possibility of extracting methane from hydrates deposited within the continental shelf off the coast of County Mayo in the west of Ireland. If the fields can be exploited, it would eliminate the expense of importing natural gas from elsewhere in Europe and increase security of supply for a country situated precariously at the far end of the gas importation route. If all goes well, the natural gas would be extracted and converted to a very low emission diesel-like fuel so it can be transported without the need for a pipeline network.

The hydrates off Ireland are believed to consist of a crystalline solid behind which is a reservoir of free gas. If the gas is removed, this reduces the pressure on the hydrate and gas starts to be released from its base. However, the reaction is endothermic, cooling the remaining hydrate body and making it hard to extract.

If water or steam is pumped into the well the hydrate can be warmed, a technology used by scientists from the US, Canada, Japan, India and Germany during a joint operation to drill three wells at a site in the north west of Canada.

In December 2003 the £12.5m project produced a five-day flow of natural gas from frozen deposits after pumping hot water into the ice to raise the temperature and banging it with drills to create fractures that lowered the pressure.

‘This process is messy and uses a lot of energy,’ warned Mac Aodha. He believes the most efficient method would be one based on technology used to extract oil tar whereby a small burner is dropped into the well. This burns a small amount of gas from the hydrate as it dissociates. The level of burning can be determined by controlling the oxygen supply. ‘This way, about 10 per cent of the gas is burned, but the other 90 per cent is recovered,’ Mac Aodha said.

Another technology involves the use of specific frequency microwaves that target and heat the hydrate. ‘This method is more efficient as it allows you to heat only the hydrate rather than the surrounding rock,’ said Mac Aodha.

Like Japan, Ireland’s geography and lack of other fossil resources means methane hydrate extraction is highly desirable, which may give it the edge over larger countries’ efforts.

‘In north America, gas hydrate development will have to be competitive with the large conventional natural gas accumulations that are often spatially near, or underlying, the gas hydrate accumulations, none of which have transportation to market currently,’ said Kirk Osadetz, manager of the Gas Hydrates Fuel of the Future programme at Geological Survey of Canada in Calgary. ‘Where issues of supply security override economic competitiveness, such as in Japan, it is possible force of will alone will motivate development.’

Compared with international methane hydrate extraction attempts, Ireland’s project is small yet ambitious. But given the combination of fewer participants and little alternative for the country’s future fuel security, it is possible it will be able to succeed where other nations have stalled.