“What is being released from the platform is methane gas plus low molecular weight ‘condensates’ (these are relatively volatile organic chemicals which are liquids when cool and gases when warm). Total estimate the release rate to be2kg/sec or 200 000 m3 gas/day. The condensates have formed a slick on the cool sea surface that extends for several kilometres. However the quantities of hydrocarbons in the slick are relatively small compared to, for example, the 2010 Gulf of Mexico accident and, in my view, there is little current danger of significant effects on sea birds and marine plants and animals.
“Contrary to earlier reports, the North Sea gas release does apparently not contain the toxic gas hydrogen sulphide that was of concern originally. This is because the gas is not coming from the main reservoir but from a second, adjacent but shallower gas reservoir that was not being exploited but which is somehow finding its way into a well that Total had closed off over a year ago. From this incursion point above the well sealing plug, the gas is rising to deck level on the platform. There are no current indications that any gas is leaking from the sea floor or seabed structures.
“Total have indicated that they are pursuing a twofold strategy to try and get the situation under control. The first is described as ‘well kill operations using a floating support’. More specific details are not yet available but this would seem to be a strategy of tackling the problem by a top-kill approach whilst avoiding the risk of reintroducing personnel to the gas-rich environment on the platform itself. Well kill operations normally involve pumping heavy mud into the well. This effectively acts as a plug to stop the flow. The second strategy is to drill a relief well or wells. These intercept the original well allowing gas to be drawn off in a controlled manner and the problem well to be sealed. Relief wells are slow and expensive to construct and, in this case, estimates are of the order of 6 months because of the depth of the holes that need to be drilled.
“If things continue as they are, I do not think that the marine pollution risks are high. The condensate slick is reported to be slight and diminishing. The absence of hydrogen sulphide in the gas greatly reduces its toxicity and the fact that it is escaping to air and not to seawater also diminishes the risks to marine life. Although the hazard level has reduced now that the flare has gone out the freely escaping gas is still hazardous and great care will need to be taken in future operations to prevent accidental ignition.
“Wider concerns about resource extraction in ever more hostile environments are not going to be diminished by these events. In my opinion the advances in technology in oil and gas extraction techniques are not being matched by similar improvements in accident remediation techniques. Difficult environments lead to more complex system failures and therefore more unpredictable and expensive accidents.”
Read the latest BBC coverage: http://www.bbc.co.uk/news/uk-scotland-north-east-orkney-shetland-17581994