BP’s oil spill fight plagued by methane hydrates, a hazard of deep water

BP is turning to desperate measures in its battle to stop its oil spill in the Gulf of Mexico, proposing to fire bits of tyre and golf balls into the failed blow-out preventer on the sea bed, to plug the leaking pipe.

It has been forced to consider such extreme tactics by the failure of its attempt to use a “coffer dam” – a 100-tonne steel and concrete box – to trap the oil. As the attempt started, BP warned that coffer dams had never previously been used in such deep water, and its experience has shown that the conditions 5,000 feet down do indeed make things much more difficult.

The problem at those depths has been the formation of gas hydrates, ice crystals described as “jelly like” by one former drilling engineer, which filled the top of the container and made it impossible to use it to pump the oil up to the surface.

The problems have highlighted the issue of gas hydrates: strange substances that create a variety of hazards, but may also offer a huge opportunity.

Gas hydrates are formed when molecules of methane or other gases are trapped in water crystals. They are found at the sea bed and trapped in permafrost, created by high pressure and low temperature environments.

They are well-known hazards for pipelines, but many aspects of their behaviour are still not fully understood.

It has been suggested that they may have been responsible for the leakage of gas into the Deepwater Horizon’s drill riser that appears to have caused the last month’s explosion.

A presentation last year by an engineer at Halliburton, the oil services company that was responsible for cementing the well to secure it, highlighted the risks that could be presented by gas hydrates for deep-water cement jobs.

The presentation warned:

Gas flow may occur after a cement job in deepwater environments that contain major hydrate zones.

Destabilization of hydrates after the cement job is confirmed by downhole cameras.

The gas flow could slow down in hours to days if the de- stabilization is not severe.

However, the consequences could be more severe in worse cases

It is likely to take the conclusion of the full investigations into the accident to determine whether hydrates were an issue in this case.

On a global scale, hydrates are also one of the main issues that raise concerns about the possibility of catastrophic runaway global warming. Methane is a greenhouse gas, with about 25 times the warming impact of carbon dioxide. If huge quantities were released from the sea bed and permafrost by warming oceans and global temperatures, some experts believe the effects would be devastating.

As the environmentalist Mark Lynas says, the release of methane from hydrates was responsible for global warming during the Eocene era, 55 million years ago:

Fossils even show that breadfruit trees were growing on the coast of Greenland, while the Arctic Ocean saw water temperatures of 20C within 200km of the North Pole itself. There was no ice at either pole; forests were probably growing in central Antarctica

He adds:

As the oceans warm, [methane hydrates] could be released once more in a terrifying echo of that methane belch of 55 million years ago. In the process, moreover, the seafloor could slump as the gas is released, sparking massive tsunamis that would further devastate the coasts.

Meanwhile, however, the possible benefits of gas hydrates were highlighted in the the New Scientist last year, which suggested they could one day be an important source of fossil fuel supplies.

The article noted:

The US Department of Energy is now working with the oil company ConocoPhillips on a field trial in Alaska (pdf), to test whether the technique can be scaled up

In Alaska’s North Slope alone, recoverable reserves of hydrates are estimated by the US Geological Survey to hold about 2,400bn cubic metres of gas: equivalent to four years of total US gas production. Worldwide, there are estimated to be at least ten quadrillion – that is, ten billion billion – cubic metres of gas in hydrates: enough to meet global demand for four thousand years!

If those trials pay off, the deep water may be more useful as a source of hydrates than a source of oil.

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