The DeepWater Explosion: How the Gulf Oil Spill Began
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Last week the Deepwater Horizon drilling rig caught fire, burned for two days, then sank in 5,000 ft of water in the Gulf of Mexico. There are still 11 men missing, and they are not expected to be found. The disaster led to a massive oil spill that could rival the Exxon Valdez spill. Here's what happened, courtesy of geologist Jimmy Haigh, and <a href="http://wattsupwiththat.com/2010/05/01/the-gulf-oil-rig-explosion-on-the-scene-photos/" target="_blank"><b>Watts Up With That</b></a>? (Watts Up With That?)
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 full drilling spread, with helicopters and support vessels and other services, will cost closer to $1,000,000 per day to operate in the course of drilling for oil and gas. The rig cost about $350,000,000 to build in 2001 and would cost at least double that to replace today. (Watts Up With That?)
The rig represents the cutting edge of drilling technology. It is a floating rig, capable of working in up to 10,000 ft 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. (Watts Up With That?)
The rig had apparently just finished cementing steel casing in place at depths exceeding 18,000 ft. 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. The drilling mast has toppled over here – they usually melt pretty fast when fire breaks out. (Watts Up With That?)
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. Here, support vessels use their fire fighting gear to cool the rig. (Watts Up With That?)
This pressure control equipment (the Blowout Preventers or BOPs) are controlled with redundant systems from the rig. In the event of an emergency, there are multiple panic buttons to hit, and even fail-safe systems that should automatically engage when something of this proportion breaks out. None were activated, suggesting that the blowout was especially swift to escalate at the surface. The flames were visible up to about 35 miles away. Not the glow – the flames. They were 200 - 300 ft high. Here, the view from about 10 miles away on the dawn of Day 1. (Watts Up With That?)
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 souls with it. Here, support vessels use their fire fighting gear to cool the rig – note the list developing. (Watts Up With That?)
The well is still flowing oil, which is appearing at the surface as a slick. They have been working with remotely operated vehicles, or ROV's -- 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. (Watts Up With That?)
ROV’s are being deployed from dedicated service vessels. They have been trying to close the well by using a specialized port on the BOP’s and a pumping arrangement on their ROV’s. They have been unsuccessful so far. Specialized pollution control vessels have been scrambled to start working the spill, skimming the oil up. Here, note the pronounced list in the platform. (Watts Up With That?)
In the coming weeks BP 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 capable of drilling from a floating rig, over 3 miles deep to an exact specific point in the earth – with a target radius of just a few feet. 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. Here, early morning on Day 2. Note the hole burned through the aluminum helideck (Watts Up With That?)
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. Here, the morning of day 2 and the rig is settling quite low in the water -- a fuel and oil slick is forming. (Watts Up With That?)
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