[QUOTE=bigmoose;35259]Deciphering the one fish/two fish condition in the riser.
PLCguy shared this pix of the shear cut made above the riser fold over crimp caused by DWH heading to the bottom. It showed one DP in the riser:
[ATTACH=CONFIG]934[/ATTACH]
Below the riser fold over and above the flex joint, two drill pipes appear to have been found in the riser: (also from PLCguy)
[ATTACH=CONFIG]935[/ATTACH]
I blew up and scaled this picture off of the GE Oil and Gas Division VetcoGray web site specification for Vetco HMF-Class H riser as specified in the TransOcean specifications for the Riser system on DWH (shown below) and scaled the left DP to 5.5" diameter, and the right one to 6.0" diameter. (Pix in a previous post of mine.)
Key parameters for Vetco HMF-Classs H Riser System:
OD 43"; ID 19.375 for 1" wall riser tube
Made up length 33.19" (not sure what this is as it is inches, I would have thought it was riser length, but thought that was ~90ft)
Weight 3901 lbs
6 Bolts, 3.87 inches in diameter
Choke/Kill lines are 6.5 inches diameter, 4.5 inch diameter boost line, and 3.5 inch diameter hydraulic line
A plausible scenario that would result in this evidence was that there was only one DP up through the flex joint when the DWH went down. That DP was captured in the fold over crimp. Subsequent cycling of the BOP could have allowed reservoir pressure to force a stub of the BOP successful sheared DP up alongside DP 1 and wedged against the foldover crimp. The reservoir pressure would be communicating through the second DP. The first DP, that was “easily” capped on the seabed would only be communicating the pressure in the riser above the flex joint and below the fold over crimp.
Diamond saw cutting DP 1 would have been according to estimate. Diamond saw cutting DP 2 would have produced a surprise of higher than anticipated flow and pressure.
I still wonder if the diamond saw cut was terminated and a crimp shear cut preferred so as to close off DP 2 as much as possible.
I sure wish I had an engineering drawing of the Vetco HMF-Class H riser and the connection to the flex joint. Then we could do some real engineering on an adapter.
Is what you oil guys call an overshot tool, what we land engineers would call a sealing expanding mandrel? I have been pulling some patents on “overshot tool” and that is the impression I get. The brochure I pulled on the Vetco riser implies that there just might be a gap where the male stub of the riser fits into the female socket in the flex joint. It may be possible to design an expanding mandrel to grab on that gap if the male stub does not bottom out. If an expanding mandrel could be designed to capture that groove and locked within the current 19.375 in diameter riser stub, and have a male H-4 stub machined on the surface end, this thing could be hardline hooked up to a H4 connector on the bottom of a new LMRP and riser system.
I’m probably thinking too much… I had 7 hours driving home yesterday from Wash, DC to ruminate on this and think…[/QUOTE]
I hate to bust everyone’s bubble. You guys are great & have been doing a lot of good thinking, but there was only one joint of pipe in the riser cut by the shears. In an earlier post I explained that a shear cut would badly deform a piece of pipe. The surest way to settle this in your minds that what you saw is not what you think you are looking at is this.
The circumference of a 21" riser is 21 X3.14 = 65.94" divide by 2 since the riser was smashed in two halves. 65.94/2 = 32.97" or 33" the work string was 6 5/8" diameter 6.625 x 3.14 = 20.8"/2 = 10.4".
33 /10.5 =3.14 the larger riser when smashed into two halves is 3 times as wide as the drill pipe. Looking at the picture the riser is 3 times as wide as the object in it. The upper riser shows evidence that the work string washed out during the time it was laid over due to the high flow rate. that is why it only looks like half of it is there. That provides a somewhat plausible explanation for the continuing expande flow rates.
You guys know I’m not a BP apologist & had they been frothright from the beginning, they would have gotten help from guys like me, but there is no mystery here. The two pipes are actually one deformed piece of pipe. I called my buddy with the shears this afternoon & he is on Toledo Bend. When he gets in Monday, he will see about emailing some pics of sheared pipe. He confirmed to me that there was only one joint in the riser & since he has sheared thousands of joints of pipe I will take his word until I get further confirmation to post. It is interesting & enlightening to hear everyone’s opinion & see the tremendous amount of thought & care you all have for this situation. Thank you very much.