From the moment we began covering the blowout of BP's Mississippi Canyon Block 252 well, we have been calling for BP and Transocean to provide the public with detail about specific operations that were being conducted on the well in the hours leading up to the blowout. The companies have not done so, but individuals being debriefed in hearings by the joint taskforce and by congressional investigations have begun to reveal a number of issues with the rig, the BOPs (blowout preventers) the drilling mud, cement job and the well itself. Though details of specifics are changing, our early conclusion of a backside blowout caused by a failed packoff in the casing head remains the primary suspected culprit. It also remains likely that gas migrated to the casing hanger after an insufficient cement job or mud lighter than spec being used to circulate and condition just prior to cementing. If the cement and mud were too light, gas could have easily migrated up the backside of the casing to the hanger.
A few things we learned from testimony in the hearings and from industry sources that give us more pieces to the puzzle:
- We learned from a wellbore diagram provided to Congress by Tim Probert of Halliburton confirmed early reports that the final string of casing was a tapered string with 7" on bottom, crossing over to 9/78" to the casing head.
Halliburton pumped 51 barrels of cement, with 3 barrels left in the shoe joint, the remaining 47 barrels would have come up the backside about 1,000 to 1,200 ft from bottom, putting top of cement at 16,800 to 17,000. Gas could have easily channelled through the green cement and gasified mud. Since the packoff was sealed, that gas just built up pressure under the packoff as it expanded 20 Years Of Free Journalism
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Drilling records that we've seen are incomplete, ending at 3 pm the afternoon of the blowout. The record we saw describes the positive test on the hanger packoff, coming out of the hole, and running back in with a 3 1/2" tubing "stinger"on drillpipe, we assume to set the top cement plug. The report stops there.Testimony from Probert, McKay, Newman, and BP's James Dupree confirmed that the negative test run on the casing hanger packoff was "inconclusive" and that other tests were run, just as Henry Waxman had asserted during his earlier statement. Details about the specific sequence of events gets fuzzy after these documented events. BP and Transocean continue to stonewall, not releasing the data that we all know they have, holding back until their investigation is complete. They need to release everything they know, so the industry and the government can formulate plans to make sure this never happens again.
Clearly, BP/Transocean missed critical signs. The well was talking to them, but unfortunately nobody was listening, especially the ones who were ironically at the party celebrating their safety record. This tone deafness, coupled with sloppy or careless maintenance on the BOP stack, converged into the worst offshore accident in 40 years.
