Editor’s note:

Background information: The ‘Deepwater Horizon’ was a semi-submersible offshore drilling rig operating in the US Gulf of Mexico, which exploded on April 20. The rig sank two days later. Measuring 121 metres long and 78 metres wide, ‘Deepwater Horizon’ was built in 2001 by Hyundai Heavy Industries, South Korea. There were 126 crewmembers on board, 115 of whom were recovered. Eleven remain missing.

The rig belongs to Transocean, the world’s biggest offshore drilling contractor.  The rig was originally contracted through the year 2013 to BP and was working on BP’s Macondo exploration well when the fire broke out. The rig costs about $500,000 per day to contract. The photos show the progression of events over the 36 hours from catching fire to sinking.

The full drilling spread, with helicopters and support vessels and other services, will cost closer to $1 million per day to operate in the course of drilling for oil and gas.  The rig cost about $350 million to build in 2001 and would cost at least double that to replace today.

The rig represents the cutting edge of drilling technology. It is a floating rig, capable of working in up to 3,040 metres water depth. The rig is not moored; it does not use anchors because it would be too costly and too heavy to suspend this mooring load from the floating structure.  

Rather, a triply-redundant computer system uses satellite positioning to control powerful thrusters that keep the rig on station within a few feet of its intended location, at all times.  This is called Dynamic Positioning.

The rig had apparently just finished cementing steel casing in place at depths exceeding 5,485 metres. The next operation was to suspend the well so that the rig could move to its next drilling location, the idea being that a rig would return to this well later in order to complete the work necessary to bring the well into production.

It is thought that somehow formation fluids – oil /gas – got into the wellbore and were undetected until it was too late to take action.  

With a floating drilling rig setup, because it moves with the waves, currents, and winds, all of the main pressure control equipment sits on the seabed – the uppermost unmoving point in the well.  This pressure control equipment – the blowout preventers, or “BOPs” as they are called, are controlled with redundant systems from the rig.  

In the event of a serious emergency, there are multiple panic buttons to hit, and even fail-safe deadman systems that should be automatically engaged when something of this proportion breaks out.  

None of them were apparently activated, suggesting that the blowout was especially swift to escalate at the surface. The flames were visible up to about over 55km away. Not the glow; the flames were 60 to 90 metres high.

All of this will be investigated and it will be some months before all of the particulars are known. For now, it is enough to say that this marvel of modern technology, which had been operating with an excellent safety record, has burned up and sunk taking eleven souls with it.

The well still is apparently flowing oil, which is appearing at the surface as a slick.  They have been working with remotely operated vehicles, or ROVs which are essentially tethered miniature submarines with manipulator arms and other equipment that can perform work underwater while the operator sits on a vessel. These are what were used to explore the ‘Titanic’, among other things.  

Every floating rig has one on board and they are in constant use. In this case, they are deploying ROVs from dedicated service vessels. They have been trying to close the well in using a specialised port on the BOPs and a pumping arrangement on their ROVs. They have been unsuccessful so far.  

Specialised pollution control vessels have been scrambled to start working the spill, skimming the oil up. In the coming weeks they will move in at least one other rig to drill a fresh well that will intersect the blowing one at its pay zone. They will use technology that is capable of drilling from a floating rig, over 4.8km deep to an exact specific point in the earth – with a target radius of just a few metres plus or minus. Once they intersect their target, a heavy fluid will be pumped that exceeds the formation’s pressure, thus causing the flow to cease and rendering the well safe at last.  

It will take at least a couple of months to get this done, bringing all available technology to bear. It will be an ecological disaster if the well flows all of the while;  Optimistically, it could bridge off downhole.

It’s a sad day when something like this happens to any rig, but even more so when it happens to something on the cutting edge of our capabilities.  

Comments

Andrew Heaton

+1

 

 

Thank you for the above discussion – very interesting and informative.

I agree that it was a 'sad day' as stated in the discussion. But with respect, I cannot agree with the focus in this regard. It seems to me that the focus of the 'sadness' in this discussion places disproportionat e emphasis around the technological setbacks associated with the explosion – with insufficient weight being attached to the human, environmental and economic impact.

Based on the description above, this does seem to be a pretty significant setback from a technological point of view, and that point must rightfully be acknowledged (especially in blogs like this about the maritime industry).

But that should not be the primary focus of any regret about this- not when (according to Wikipedia) eleven people died, seventeen more were injured, more than four-hundred species were under threat and the fishing and tourism industry stand to lose .5 billion and billion respectively.

The technological setback is a pity, but the focus of any 'sadness' associated with this disaster should be on the human, environmental and economic impact - in that order.

Wednesday 19 May 2010, 09:07

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