Saturday, May 01, 2010

On Using a Faulty Blowout Preventer in Overpressure

It wasn’t long ago that when an offshore oil rig reached overpressured sediments, that was the end of drilling. Pack it up.

Overpressure is produced when the rate of sedimentation is so great that fluids literally have no time to escape upward as overburden accumulates. Something that is quite common in the deepwater of the Gulf of Mexico. Especially at the mouth of the Mississippi River, which has been pouring sediments into the Gulf for millions of years.

But as time went on, we got the knack of drilling in overpressure. But you had to be careful, and you had to watch the well all the time, making sure your mud system balanced the fluid pressure at depth. If the mud is too heavy it goes into the formation and induces fracture. The formation “breaks down.” Too light and the pressure pushes the mud column up the well.

So a subsea blowout preventer is essential. One with lots of backup including some “blind rams” that can cut right through pipe if a blowout is imminent. That’s a system of last resort because you definitely lose the well if you cut the pipe at the BOP.

But as it turns out, as reported in the London Times, BP has known that this particular type of BOP has had some defects.

Knew about it 10 years ago.

From the Times Online:
“In June 2000, the oil giant issued a "notice of default" to Transocean, the operator of the rig that blew up last month. The dispute was over problems with a blowout preventer, a set of iron slabs that should close out-of-control wells. It failed on the Gulf of Mexico rig, triggering the explosion and oil spill.”

“Transocean acknowledged at the time that the preventer did "not work exactly right". The rig in question, the Discover Enterprise, was unable to operate for extended periods while the problem was fixed.“

“The preventer was made by Hydril, now owned by GE's oil and gas arm, and Cameron International, a Houston company. Cameron also made the preventer on the Deepwater Horizon, the rig that exploded. Its preventer was fitted at about the same time BP was complaining of problems with its sister vessel.”
Whether that had any bearing on the cause to the most recent blowout and looming ecological disaster, one can only speculate. I hope it is not the case that the BOP was substandard. I hope it is not the case that BP and Transocean were cutting costs. Cutting costs in light of $2.60 per gallon gasoline and $84 per barrel crude. Cutting costs during times of record profits in the petroleum industry.

I hope this is not the case, but like my masthead announces, I am not optimistic.

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