Hi all,
cmjeff’s 's point is well taken. W/respect to rate of material travel up to the rig (and as pointed out on a couple other boards) in this case the fluids almost certainly came up the drill pipe.
Rough math at 231 cu in/gallon * 42 gal/bbl = 9702 cu in fluid per barrel. If riser was 21 in as often stated, assume about 19 in. inside diameter and 6-1/2 in. for relatively large drill pipe, (area = radius squared * pi) 283 in sq for liner cross section minus 33 in sq for drill pipe = 250 sq in = 3000 cu in. fluid per foot of riser, times 5000 ft of riser get you about 15,000,000 cu in of fluid in riser. At 9702 cu in /bbl, that’s about 1546 bbl of fluid. If well leaked as much as 40,000 bbl/day that’s about 55 minutes to displace the riser fluid at a constant flow rate. Even with gas expansion you’d think that would mean a good 10-15 minutes of excess fluid return up the riser which would have been ** noticed **.
Drill pipe would have held more like 190 bbl of fluid and with gas expansion this beast would be in your face in no time. With sea water rather than mud in the tubing this would have been a very rapid event, So based on lack of alarms etc. we can safely assume this came up the DP which is consistent with “rumor” of negative flow (draw down) test after bumping plug (which would have happened only after a successful high pressure test).
As pointed out above, human error is often a part of such incidents. But bad stuff often happens real fast and if you’re not at the top of your game you can get caught in a real mess.