15 May 2010

Stalwart Blowout Preventer Reducing Oil Flow Into Gulf

The much-derided Cameron blowout preventer (BOP) at the Deepwater Horizon well is significantly impeding the out-gushing of oil. The incoming pressure from below the BOP has been measured at between 8,000 and 9,000 psi, while the outflow pressure into the Gulf is only 2650 psi. If not for the BOP, the flow rates would be much higher.
He [Admiral Thad Allen] said an X-ray type analysis of the failed blow out preventer indicated that it had worked partially and was limiting flow from the well to some degree. He said officials had been able to measure the pressure, learning that oil was flowing into the device at 8,000 to 9,000 pounds per square inch and flowing out into the Gulf at around 2,650 pounds per square inch.

As Allen briefed reporters Friday at Dauphin Island, there were dozens of workers nearby, clad in white suits and brown boots, scouring the public beach for trash and debris.

Allen, the Coast Guard's commandant, characterized attempts by BP PLC to cap the well as a mitigation effort, not a permanent fix.

The long-term answer, Allen said, is a relief well that BP is working on - a solution that is likely at least two months away.

Allen described BP's response to the Deepwater Horizon rig explosion as relentless, "and we have been relentless in our oversight."

When asked whether an estimate of 5,000 barrels of oil leaking every day is still accurate, Allen stressed that any number reported is simply a best guess.

"We are operating in an environment where there is no human access," Allen said of the well 5,000 feet down on the seafloor. "I think it has the potential to be catastrophic. I am going to act as if it is. We all should." _al.com
Meanwhile, deep sea remotely operated vehicles (ROVs) have been trying to limit the oil leaking from the damaged riser pipe, by inserting a 6 inch stoppered suction tube inside the 21 inch riser, to divert the leaking oil to a storage vessel on the surface. This effort is taking place beyond the leaking BOP, so there is no risk of making the leak worse -- only a possibility that a portion of the leaking oil will be retrieved, and kept out of the Gulf. That is why this effort has been described on this blog as "ultra-cautious."
BP engineers say the current effort involves placing a tube inside a broken oil pipe that has been leaking oil for the past four weeks. Engineers hope the tube, which is fitted with a rubber cap, will enable them to pump most of the oil to a surface ship.

Coast Guard Commander Thad Allen said the tube is one of several techniques that BP is developing to stop the leak.

"I would caution everyone that this is a leak mitigation effort," said Admiral Allen. "It is not intended to completely capture all the oil that is leaking from there. But it should substantially reduce it, if it is successful."

BP representatives say a permanent fix for the leak is to drill a new well, which could take three months.

Earlier this week, BP released video from a remote controlled submarine, which showed oil spewing from a gash in the undersea pipe. Some scientists and oil experts say the video shows that far more oil is leaking than official estimates of 5,000 barrels a day. BP representatives say that number is hard to determine, because the leak is 1.5 kilometers below the surface.

Commander Allen says the debate over leak estimates has not affected the response from the U.S. Coast Guard.

"Whether it was one, five, 10 or 15 [thousand barrels of oil], our mobilization of resources has been for something far beyond that, because we are always prepared for a catastrophic event," he said. _VOANews
Knowing that the BOP is reducing well head pressures by 75%, explains much of the caution being exhibited by engineers on the site. They do not want to do anything to increase the oil gush into the seawater.

On the other hand, the relief wells are still several weeks from being in position to secure the original well, so the situation is still urgent. The Gulf coast has been very lucky so far. It is up to the engineers to make sure not to push that luck too far.

The U.S. Coast Guard and U.S. Environmental Protection Agency (EPA) today announced they have authorized BP to use dispersants underwater, at the source of the Deepwater Horizon leak. Oil spill dispersants are chemicals that attempt to break down the oil into small drops and prevent it from reaching the surface or the U.S. shoreline. Dispersants are generally less harmful than the highly toxic oil leaking from the source and they biodegrade in a much shorter time span.

The use of the dispersant at the source of the leak represents a novel approach to addressing the significant environmental threat posed by the spill. Preliminary testing results indicate that subsea use of the dispersant is effective at reducing the amount of oil from reaching the surface – and can do so with the use of less dispersant than is needed when the oil does reach the surface. This is an important step to reduce the potential for damage from oil reaching fragile wetlands and coastal areas.

“We will continue our relentless efforts to secure the source of the spill. In the meantime, we will employ every available technique we can to minimize the environmental impact on coastal habitats, communities and the marine ecosystem. This requires a responsible assessment of the risks and benefits of specific tactics,” said Coast Guard Admiral Thad W. Allen, the national incident commander for the spill.

“Based on the scientific analysis of the EPA and NOAA and review by the National Response Team, it has been determined that the use of dispersants at the subsea source is the prudent and responsible action to take along with other tactics including surface dispersant, skimming and controlled burns."

"We believe that the underwater use of dispersants could lessen the overall impact of the spill,” said EPA Administrator Lisa P. Jackson. “Dispersants are not the silver bullet. They are used to move us towards the lesser of two difficult environmental outcomes. Until the flow of oil is stemmed, we must continue to take any responsible action that will reduce the impact of the spill, and that is what we are doing.”

This course of action was decided upon with thorough evaluation and consideration of many factors as well as consultation with stakeholders. Because subsea use of dispersants is a novel approach, several tests were done to determine if the dispersant would be effective in breaking up the oil and helping to control the leaks. _DeepHorizonResponse
The use of dispersants has been criticised by "environmental" spokespersons as being untested and unproven. Of course, the same "environmental" spokespersons have declared that the effect of the oil itself will be apocalyptic on and below the surface, and on shore. It is clear that the only problem-solvers here are the engineers and the military personnel. The media, academics, faux environmentalists, lawyers, politicians, and bureaucrats all tend to exacerbate the problem, rather than helping to solve it.


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Blogger Allan Folz said...

The thing I've wondered, and not seen addressed anywhere, is once a siphon (of whatever design) is placed to capture the oil coming from the riser and route it directly to surface tankers, how are they going to deal with the natural gas coming up the siphon in an unrestrained fashion?

Is it possible the various siphons that are being debated and built but not really installed are theatrics to look like they are doing something, instead of simply sitting tight while waiting for the relief wells to complete?

Also, out of curiousness are the well psi's absolute or gage pressures? I understand water pressure is ~150 atm's or 2200psi at that depth. That seems to be a big difference for hoping the riser can be stopped up with junk rubber and so forth. Thanks.

Saturday, 15 May, 2010  
Blogger al fin said...

Good points.

As fast as public hysteria is building, BP cannot afford to wait until the relief wells secure the main well.

Working at extreme depth is tough. I don't know how they are measuring the pressures -- only that they had to rebuild the BOP's "brain" before they could get accurate readings.

The plan for the "junk shot" is to inject large quantities of rubber junk and matting into the blowout preventer itself. If this stopped the gusher, then concrete would be injected to seal the wellhead.

Oil drilling technology is just good enough to get us into this type of mess, but not yet good enough to deal with anything that might happen.

We can hope they learn some lessons from this, because humans definitely need the hydrocarbons that are down there.

Sunday, 16 May, 2010  
Blogger astrodominant said...

The rig (and all production ships and platforms) have an oil/gas/water separator on them. Horizontal or vertical tanks that separate gas from the top, oil from the middle and water from the bottom. They have been around since the beginning of the oil industry and are pretty basic pieces of equipment.

Sunday, 16 May, 2010  

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