Famous Maritime, Reference-Standard of Integrity, "Det Norske Veritas" has released the analysis report regarding the Macondo BOP.
The links to the report are shown in the P.S. section, below.
The numerous pictures in Volume 1 around page 60 show that the rams (the thick metal knife-wedges or blocks, that either cut off, or go around the pipe inside a BlowOut Preventer) don't look totally destroyed.
Looks to me, like they didn't have enough go-power to get through the casing and drill pipe all the way.
I haven't read these reports yet, but a summary I read today in an Oil & Gas Journal blurb, said that DNVeritas claims high rate fluid flow caused the drill pipe to buckle between rams, and contact the side of the BOP at an odd angle or something, and that's the reason for the closure malfunctions.
However, that would basically explain, perhaps, why one or two sets wouldn't close, not all of them. And if the pipe was merely at an angle, and the flowrate was high, pushing back because of the angled deflection, then, when enough ram force was used to sever the pipe metal itself (which is what is supposed to happen with some of the ram sets), then how-much the pipe is resisting (before it is pinned against the opposing jaws, and its compressive & shear strength exceeded at the ram cutter edges) shouldn't matter too much. Maybe what they say, is that the internal buckled pipe bridged against other-than-the-cutter tips on all shearing rams, and the annulars were blown out by abrasive fines flow within the effluent.
Back when this happened, the Government released a reading of the various BOP stage pressures ( image attached - Whoops ! ! - must have had that one on the Laptop that was stolen this summer - image not attached ). These pressure readings, showed about 400 to 700 psi in pressure drop across each ram / preventer stage.
No matter what, I still think the malfunction cause might be, that the rams merely didn't power-through the tubulars as they were mis??-designed to do, with the available source-of-force - Sandy-Blasting flow or not. Whatever happened, the BOP activation didn't blow the rams right through both the casing and drill pipe, and nearly out the other side of the preventer - that's for sure. (Good thing these guys don't make aircraft ejection seats!!!)
What would be a better source of force, and a lot of it? Like an airbag expander - only with more power? ? ? Hydraulics are used now, but they didn't look too impressive here.
This couldn't conceivably be that somebody didn't take into account the operating temperatures for the hydraulic accumulator's gas blanket(s) could it? ? ? ? That sounds WAY TOO obvious, since most that are skilled-in-the-art know that roughly for the expanding air/gas inside the hydraulic accumulators: p1 V1 / T1 = p2 V2 / T2 which, at a lot colder temperatures, makes the available pressures a lot less, if the volumes are the same.
If they really wanted to get way serious about cutting through impossible stuff, they would have probably used something like the dreaded "burning bar" safe-cracking method. Maybe they didn't think that "more-extreme-tech" was needed.
Thank you. Regards, rjf
Volume 1: http://www.deepwaterinvestigation.com/external/content/document/3043/1047291/1/DNV%20Report%20EP030842%20for%20BOEMRE%20Volume%20I.pdf
Volume 2: http://www.deepwaterinvestigation.com/external/content/document/3043/1047295/1/DNV%20BOP%20report%20-%20Vol%202%20(2).pdf
Thank you so much for sharing those PDF files with me as i was really looking for them :)
ReplyDelete