You may have heard the news in the last two days about the Deepwater Horizon drilling rig which caught fire, burned for two days, thensank 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 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 ofdrilling 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.
Nautilus, being transported on a Heavy-Lift vessel
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 isnot moored; It does not use anchors because it would be too costly and too heavy to suspend this mooring load from the floatingstructure. 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 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.
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 ‘BOP’s” as they’re 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 aparently 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.
發布信息
