surrounding sediments and undermine the foundation upon
which the 450-ton blowout preventer sits. If such leaks
aren't sealed off in time, the entire structure could
topple over. After that, it goes into the realm of the worst things you can think of, writes a commenter on the oil-and-energy-focused website The Oil Drum. It was this
commenter's post that has become the subject of wider
speculation. The well may come completely apart as the
inner liners fail. There is still a very long drill
string in the well that could literally come flying out
at the very least we are stuck with a wide open gusher
blowing out 150,000 barrels a day of raw oil or more.
This
comment has since spread online, causing widespread fear
and speculation. But not everyone is convinced that such
a scenario is probable, or even possible. The BOP is
rigidly connected to all the pipe below, says Roger
Anderson, an oil geophysicist at Columbia University. It
would be like knocking the top off a coke bottle, except
the bottle top has already been fully breached. Other
experts have agreed with him, but point out that the
pipe below may have been significantly compromised by
initial recovery efforts. The blowout preventer should
be well anchored, with about 2,900 feet of full string
casing and cement, says Don Van Nieuwenhuise, director
of geosciences at the University of Houston. However,
the well has received some exceptional pressure jolts or
kicks, and that has been a concern to BP from the very
start.
The
likelihood of a complete collapse is difficult to
assess, in part, engineers and legislators say, because
BP hasn't shared enough information to evaluate the
situation. But a handful of clues suggest that the
company is concerned. On Friday, BP spokesperson Toby
Odone acknowledged that the 45-ton stack of the blowout
preventer was tilting noticeably, but said the company
could not attribute it to down-hole leaks. We don't know
anything about the underground portion of the well, he
said. But, the stack is tilting and has been tilting
since the rig went down. We believe that it was caused
by the collapse of the riser. The company is monitoring
the degree of leaning but has not announced any plans to
run additional supports to the structure.
As many
have speculated, and as the New Orleans Times Picayune
reported Friday, concerns over structural integrity are
what led BP to halt top kill efforts late last month.
When it was digging this particular well, the company
ran out of casing the pipe that engineers send down the
hole and switched to a less durable material called
liner. This may have created several weak spots along
the well that would be particularly vulnerable to
excessive pressure or erosion. So instead of sealing the
well, the company has been focused on trying to capture
the oil as it flows out the top.
At this
point, some experts say, additional leaks wouldn't
matter much. Its very possible that there are subfloor
leaks, says Anderson. But that doesn't change the
strategy moving forward. The linchpin of that strategy
involves drilling relief wells that would absorb all
possible leaks, both at the top and the bottom of the
hulking, teetering structure. Relief wells are drilled
straight down into the sea bottom. After running
parallel to the existing well for a few thousand meters,
they cut in and intersect the original well bore. BP is
drilling two such wells, one on either side of the main
well. Once they are complete, the company will use them
to pump heavy fluid and cement into the main well,
stopping the oil at its source. The approach usually has
a 95 percent success rate.
But to
work, the well must be sealed as far down as possible if
its sealed too high, oil could still escape through any
leaks beneath the seal. In this case, relief wells will
have to drill down to 5,500 meters, and that takes time,
at least until August. The real question now is whether
the entire structure can hold out long enough.
Additional reporting by Ian Yarett.
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