Oil has been leaking from a ruptured pipeline at Royal Dutch Shell’s Gannet Alpha platform in the North Sea since last Wednesday at least, but even three days after the company confirmed that the spill had actually occurred, there is still no indication of how much crude has leaked into the ocean.
An oil spill in the North Sea is estimated to amount to several hundred tonnes, making it the biggest such leak in more than a decade, according to government figures.
The spill - far greater than annual totals dating back to 2001 - was described as "substantial" by the Department of Energy and Climate Change (DECC).
The total amount of oil discharged into the North Sea in 2009 was 50.93 tonnes.
Shell, which operates the Gannet Alpha platform about 112 miles east of Aberdeen, said the subsea well was shut on Wednesday, but it has not confirmed the quantity of the leak.
A DECC spokesman said the energy firm is still trying to "completely halt" any further leakage.
The spokesman said: "Although small in comparison to the Macondo, Gulf of Mexico, incident, in the context of the UK Continental Shelf (UKCS), the spill is substantial.
"But it is not anticipated that oil will reach the shore and indeed it is expected that it will be dispersed naturally.
"The UK Continental Shelf oil spill record is strong, which is why it is disappointing that this spill has happened.
"We take any spill very seriously and we will be investigating the causes of the spill and learning any lessons from the response to it."
The spokesman added: "Current estimates are that the spill could be several hundred tonnes.
"However, it is always very difficult and takes time to get an accurate assessment of the size of a spill and this is subject to ongoing revision."
It is important to note that it is unlikely to be very much. Production at Gannet Alpha is estimated to be between 4,500 to 6,000 barrels of oil a day and with the well that feeds the pipeline shut-in since Wednesday, the amount of oil that could have leaked out probably totals in the hundreds of barrels rather than the thousands.
The incident is very different from BP’s Gulf of Mexico spill last year, where oil spewed into the ocean directly from a wellhead that was thousands of feet underwater. The extreme depth and pressure complicated efforts to seal the well.
Gannet Alpha is a shallow rig, standing in water only 310 feet deep. However, rough seas and high winds are a complicating factor. But by not detailing the full extent of the spill days into the event, Shell runs the risk of allowing conjecture and skepticism to gain traction.
While Shell says it doesn’t expect the oil to reach British shores, that claim is undermined by its reluctance to say how much oil it’s actually dealing with.
Already environmental groups and politicians are criticizing the company for Shell’s secretive response, saying that even a minor spill can have a serious ecological impact. And the spill isn’t the first to have occurred on the platform. Data from the Health and Safety Executive show that 10 leak incidents happened at Gannet Alpha in 2009 and 2010. While only one of them was logged as serious–in that case, owing to a gas leak that could have ignited–it does raise the specter of ongoing safety and maintenance issues at the facility.
The HSE has in the past highlighted problems with ageing North Sea oil facilities, saying last December the industry “still has a long way to go in this.”
For now, Shell says that it has the leak under control and that the flow rate is slowing, suggesting that pressure inside and out the pipeline is equilibrating. This could mean the worst is over. But for now, we’re still dealing in hypotheticals. Until Shell comes out with some harder facts, that won’t change.