As I have previously
noted, it is now clear that there is damage to BP's well beneath
the sea floor.
Recently-retired Shell Oil President John
Hofmeister told MSNBC yesterday:
The question is
whether there is enough mechanical structure left at the base of the
reservoir to hold the cement when they start pouring cement in [from
the relief well].
***
The more oil we some coming out,
the more it tells you that the whole casing system is
deteriorating. The fact that more oil would be coming
out rather than less oil, would suggest that the construction
within the pipe is offering no resistance whatsoever, and we’re
just getting a gusher.
Newsweek gives
a balanced view regarding the risk of a total structural failure of
the well:
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 ... 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. “It’s very
possible that there are subfloor leaks,” says [Roger Anderson - an oil
geophysicist at Columbia University]. “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 it’s 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.
One of the dangers which the relief wells are
racing to try to beat is that the blowout preventer (BOP) is leaning
and might fall over.
The well casing itself is attached to the
BOP. And - as discussed below - the BOP is very heavy. So if the BOP fell over, it would likely
severely damage the structural integrity of the casing.
As Think Progress points out:
In a press teleconference Monday, National Incident Commander Thad
Allen announced that the riser package is tilting “10 or
12 degrees off perpendicular,” twice the 5.5 degree tilt of the Leaning
Tower of Pisa:The entire arrangement is kind of listed a little bit. I
think it’s 10 or 12 degrees off perpendicular so it’s not quite
straight up.
As the
Times-Picayune notes:
The integrity of the well has become a major topic of
discussion among engineers and geologists.
'Everybody's worried
about all of this. That's all people are talking about,' said Don Van
Nieuwenhuise, director of geoscience programs at University of
Houston. He said the things that BP has being doing to try to stop the
oil or gain control of it have been tantamount to repeatedly hitting
the well with a hammer and sending shock waves down the pipe. 'I don't
think people realize how delicate it is.'
'There is a very
high level of concern for the integrity of the well,' said Bob Bea,
the University of California Berkeley engineering professor known to
New Orleanians for investigating the levee failures after Katrina, who
now has organized the Deepwater Horizon Study Group. Bea and other
engineers say that BP hasn't released enough information publicly for
people outside the company to evaluate the situation.
***
When
wells are drilled, engineers send links of telescoping pipe down the
hole, and those links are encased in cement. The telescoping pipe,
called casing, unfolds like a radio antenna, only upside down, so the
width of pipe gets smaller as the well gets deeper.
The cement
and layers of casing are normally quite strong, Van Nieuwenhuise said.
But with the BP well, there are several weak spots that the highly
pressurized oil could exploit. BP ran out of casing sections before it
hit the reservoir of oil, so it switched to using something called
liner for the remainder of the well, which isn't as strong. The joints
between two sections of liner pipe and the joint where the liner pipe
meets the casing could be weak, Van Nieuwenhuise said.
Bill
Gale, an engineer specializing in fires and explosions on oil rigs who
is part of Bea's Deepwater Horizon Study Group, said the 16-inch wide
casing contains disks that are designed to relieve pressure if
necessary. If any of those disks popped, it could create undesirable
new avenues for the oil to flow.
Bea said there are also
concerns about the casing at the seabed right under the blowout
preventer.
Van Nieuwenhuise said he's never actually heard of
oil from a blown out well rupturing the casing and bubbling up through
the ocean floor. He would consider that an unlikely, worst-case
scenario.
A more likely problem, he said, is that oil could find
its way into open spaces in the casing string, known as the annulus,
and travel up the well in areas where it isn't supposed to be. This
scenario could be one reason why more oil than expected is flowing at
the containment cap that BP installed earlier this month to collect the
oil.
Bea is more concerned about the worst-case scenario than
Van Nieuwnhuise. In an answer to a question, Bea said, 'Yes,' there is
reason to think that hydrocarbons are leaking from places in the well
other than the containment cap.
'The likelihood of failure is
extremely high,' Bea said. 'We could have multiple losses of
containment, and that's going to provide much more difficult time of
trying to capture this (oil).'
Meanwhile, observers monitoring
the video feeds from the robotic vehicles working on the sea floor have
noticed BP measuring a tilt in the
40-ton blowout preventer stack with a level and a device called an
inclinometer.
***
Bea said BP isn't sharing
enough information for others to know. If there is oil and gas
escaping from the sides of the well, it could erode the sediments
around the well and eat away at the support for all the heavy
equipment that sits above. Bea said
reports that BP is using an inclinometer is significant news. 'It
tells me that they are also concerned,' he said.
While
the BOP weighs 40 tons, the riser package as a whole weighs over 450 tons. If the BOP and
riser package fell over, it would inflict severe damage to the attached
well casing.
The Houston Chronicle reports:
Money-saving measures
BP took while designing the Macondo well in the Gulf of Mexico appear
to have dogged efforts to bring the massive oil spill under control.
Documents released
by congressional investigators show that modifications to the well
design BP made last year included a reduction in the thickness of a
section of the casing — steel piping in the wellbore
The modification
included a slight reduction in the specified thickness for the wall of a
16-inch-diameter section of pipe toward the bottom of the well,
according to a May 14, 2009, document.
***
The condition of the well also limits how much oil and
gas can flow into containment systems now being used successfully to
capture some of the flow. Even if a vessel could capture all the
hydrocarbons gushing from the well, some would have to be released to
keep well pressure under control.
Marvin Odum, president of Houston-based
Shell Oil, the U.S. arm of Royal Dutch Shell, told the Houston
Chronicle last week that the integrity of the well casing is a major
concern. Odum and others from the industry regularly sit in on
high-level meetings with BP and government officials about the spill.
If the well casing
burst it could send oil and gas streaming through the strata to appear
elsewhere on the sea floor, or create a crater underneath the wellhead -
a device placed at the top of the well where the casing meets the
seafloor - that would destabilize it and the blowout preventer.
The steel casing used
in oil wells is strong, said Gene Beck, petroleum engineering professor
at Texas A&M, but pressures deep in a well are powerful enough to
split strong steel pipe or "crush it like a beer can."
The strength and
thickness of casing walls are key decisions in well design, he said. If
the BP well's casing wasn't strong enough, it may already be split or
could split during a containment effort.
BP spokesman Toby Odone said the decision
to reduce the pipe thickness was made after careful review. The company
said it doesn't know the condition of the well casing and has no way
of inspecting it.
BP is drilling two relief wells to intercept the Macondo
well near the reservoir and plug it with cement. A rupture in the
Macondo well casing probably wouldn't affect that effort, said Donald
Van Nieuwenhuise, director of geoscience programs at the University of
Houston.
'When
they start the bottom kill the cement will try to follow oil wherever
it's escaping, so it would actually hide a lot of sins in the well
bore,' Van Nieuwenhuise said.So far there are no signs that the section of the pipe
below the sea floor is leaking.
The blowout preventer
has been listing slightly since the accident, but officials believe
that may have happened when the Deepwater Horizon sank while still
attached to the well via a pipe called a riser.
***
But the longer the well flows uncontrolled
the more likely it is that the well casing could be damaged or the
blowout preventer damaged further. Sand and other debris that
flows through the pipes at high velocity can wear through metal over
time, said Van Nieuwenhuise.
The chances of
the well eroding from underneath and
the blowout preventer tipping may seem unlikely.
"But everything about this well has been
unlikely," said David Pursell, an analyst with Tudor Pickering Holt
& Co
While the official line is that the BOP
tipped over during the initial explosion and sinking of the rig,
Alexander Higgings points
out that the blowout preventer appears to be tipping over more and more each week.
Indeed,
oil industry expert Rob Cavner says that he wouldn't be surprised if
the leaning and damaged BOP ended up falling over entirely:
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