Comments about technological history, system fractures, and human resilience from James R. Chiles, the author of Inviting Disaster: Lessons from the Edge of Technology (HarperBusiness 2001; paperback 2002) and The God Machine: From Boomerangs to Black Hawks, the Story of the Helicopter (Random House, 2007, paperback 2008)

Wednesday, September 8, 2010

BP's Story

BP is distributing its version of events: full PDF is here.

It's a mix of lawyerly conclusions (BP's errors are characterized as forgivable ones of inadequate communications across work teams and faulty analysis of test results), some rather blurry diagrams, and many pages of extremely technical material about well control and design. A subsea engineer could follow it but the rest of us struggle.

Even BP execs would be hard pressed to say that it's a complete and convincing picture. For one thing, the report predates the recent recovery of the BOP -- and the BOP hasn't been taken apart and studied yet -- so a disaster report from BP is premature.

But rather than get into a book review, let me suggest that detail-hounds check out some descriptions of key hardware (such as the MUX reels to control the BOP and how they may have been damaged in the blast, accumulators to energize the rams and how they're normally recharged, the twin control pods, and how fault reporting on the BOP alarm board didn't alert the subsea engineer to weak batteries), fault trees, and new detail about events not previously reported.

On pp 163-166 is a description of pipe anomalies in the BOP, which includes a mention of the "drift-off" that must have occurred after the explosion, before the rig sank, and what it likely did in bending the riser above the blowout preventer.

Drift-off is when a floating rig loses power and ocean currents or winds try to drag it off station, while it is still connected via the riser to the BOP and wellhead. Since dynamically positioned deepwater rigs like the DH have no anchor lines to keep them on station, a loss of power to the thrusters puts a strain on the drill string, even in calm weather. As I read the report, the DH's drift-off began to drag drill string up and out of the wellhead. Has that ever happened before?

Also there's a photo of a section of deeply striated tool joint, apparently eroded by the enormous flow of sand, gas and fluids up the wellbore.

Also catching my eye was mention of ROV operations, undertaken before the rig sunk, in hopes of forcing the rams to close off the blowout. It didn't work but that must have been a time of high drama, and high frustration.

No comments:

Post a Comment