Note: Descriptions are shown in the official language in which they were submitted.
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Method for fighting an oilspill in the aftermath
of an underwater oil well blowout and
installation for carrying out the method
[0001] This invention concerns a method for fighting oil spills in the
aftermath of a
blowout, and also an installation for carrying out the method. A blowout is
the
uncontrolled release of crude oil or natural gas or a mixture of the two from
a well,
typically for petroleum production, after pressure control systems have
failed.
When such an incident occurs, formation fluids begin to flow into the wellbore
and
up the annulus and/or inside the drill pipe, and this is commonly called a
kick. If
the well is not shut in (common term for the closing of the blow-out preventer
valves), a kick can quickly escalate into a blowout when the formation fluids
reach
the surface, especially when the fluid is a gas which rapidly expands as it
flows up
the wellbore, further decreasing the effective weight of the fluid, and
accelerates
to near the speed of sound. The gas and other hydrocarbons commonly ignite
during a blow-out, creating explosions and vigorous fires which are difficult
to
extinguish. Blowouts can cause significant damage to drilling rigs, injuries
or
fatalities to rig personnel, and significant damage to the environment if
hydrocarbons are spilled. Prior to the development of blow-out preventers,
blowouts were common during drilling operations, and were referred to as
gushers. Sometimes, blowouts can be so forceful that they cannot be directly
brought under control from the surface, particularly if there is so much
energy in
the flowing zone that it does not deplete significantly over the course of a
blowout.
In such cases, other wells (called relief wells) may be drilled to intersect
the well
or pocket, in order to allow kill-weight fluids to be introduced at depth.
Contrary to
what might be inferred from the term, such wells generally are not used to
help
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relieve pressure using multiple outlets from the blowout zone.
[0002] An "underground blowout" is a special situation where fluids from high
pressure zones flow uncontrolled to lower pressure zones within the open-hole
portion of the wellbore. Usually they come up the wellbore to shallower
formations
(typically near the last casing shoe) that have been fractured from the
overall
effect of hydrostatic mud head plus casing pressure imposed at the time of the
initial kick. Underground blowouts can be very difficult to bring under
control
although there is no outward flow at the drill site itself. However, if left
unchecked,
in time the fluids may find their way to the surface elsewhere in the vicinity
(possibly "cratering" the rig), or may pressurize other zones, leading to
problems
when drilling subsequent wells.
[0003] A very major blowout occurred on April 20, 2010 approx. 135 sea miles
(250km) south east of New Orleans in the Mexican Gulf. And it was a very
special
case since the blowout occurred very deep in the sea, and oil leaked out of
the
hole in a depth of 5000 ft or approx. 1500 meters. It is estimated that up to
10
million litres or 10'000 m3 of oil per day were being spilled into the ocean
from
underground or from broken drill pipes near the hole, which caused a dramatic
disaster for the environment of an entire large region.
[0004] There are no experienced and demonstrated techniques available in order
to stop such an enormous spill of oil and the obstacles to stop such
uncontrolled
flow of oil are tremendous since the leaks are located 1500m below sea level
on
the hole. The oil formations from where the oil was taken out are located
approx.
18'000 ft or approx. 5'500m below sea level, that is some 13'000 ft or approx.
4'000m below hole in the underground. Relief borings from the side have been
brought down in order to reach the leaking oil well pipe, open it there and
pump
great amounts of mud at high pressure into it in order to block it by the
weight of
this pumped in material. However, to bring down such relief borings is time
consuming. And even if the mud would arrive at the leaking oil pipe, the mud
could not prevent a leaking that occurs through slits and cracks around the
pipe
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and up the annulus or through natural cracks in the formation which may have
occurred due to detonations in the underground.
[0005] Another proposal was to put a domelike shell made of steel or
reinforced
concrete on top of the leaking points and evacuate their content and thereby
creating a big pressure onto the outer side of the shell and keep it in place,
and
then continuously pump the inflowing oil to the surface. However, underground
streams and waves created heavy problems for this undertaking, and due to the
low temperatures, freezing of valves created severe problems.
[0006] The purpose of this invention is to present a method by which such a
leaking of oil from the hole and from well pipes can be fought successfully so
that
the oil spill into the water can be stopped and prevent devastating
consequences
for the environment. A further purpose is to teach an installation which
allows it to
carry out this method even at greath depths, that is deep in the sea on the
hole.
[0007] The method according to claim 1 and the installation according to claim
5
are being presented in the following, by the example of the recent heavy
blowout
in the Mexican gulf. The method comprises several steps and is promising for
successfully deal with that enormous problem and get the oil leaking into the
water eventually stopped completely.
[0008] 10'000m3 of oil per day equals to roughly 375 tons per hour, or 104 kg
per
second. This is the proximate mass flow that has to be dealt with. But this
method
has the potential to keep up with an even substantially greater flux of oil.
In the
accident in the Mexican gulf, the oil has an initial temperature of approx. 80
C and
originates from sea bottom at depths of approx. 18'000ft or 5500m below sea
level. At such depths there is an enormous hydrostatic pressure of approx.
550bar
or even more acting. Apparently, there were several leaks ¨ such ones in the
collapsed oil well pipes - and further leaks of oil in the hole where the oil
escapes
through several cracks.
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PCT/EP2011/060016
[0009] This present method is in essence a low tech method, and therefore
quickly to apply, at low cost, and it does prevent the further spilling of oil
into the
sea water. With the exception of some rare special cases, this method will
allow to
pump pure crude oil after an initial phase of executing the method. Although
the
method is not thought to be a permanent solution, it can be in operation
several
months in order to bridge the time it takes to bring down release borings and
put
them in operation.
[0010] The installation for execution of the method is suitable to serve as an
emergency equipment and may be built in advance for future incidents should
they ever occur. There are hundreds of deep sea borings in operation and
therefore, a situation as the one which occurred in the Gulf of Mexico might
occur
on other sites in the future.
[0011] The method can be carried out no matter whether the leaking of the oil
is
from a broken pipe over the hole or comes out of the sea bottom through open
cracks. The method will now be described and its operation explained by
reference to the accompanying drawings. These figures show:
Figure 1
=
The overall situation of a underwater oil spill with the
.
installation for executing the method;
Figure 2
=
The three-leg pyramid-like steel support;
.
Figure 3
=
A section view of the three-leg support structure and the
.
adjacent covering foil on the sea bottom, with the detail of its
attachment to the support;
Figure 4
=
The stabilization of the three-leg support and foil on the sea
.
bottom, seen from above;
Figure 5
=
The connection of the pumping pipe with the top of the
.
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support structure;
Figure 6 = A side view of several steps
to lowering down the foil and the
support structure to the sea bottom;
Figure 7 = A side view of an alternative
method for lowering down the
support structure and foil to the sea bottom.
[0012] This method is suitable for leaking pipes over the level of the sea
bottom
as well as for situations where the oil is leaking out of the sea bottom
through
cracks since a pipe did break below sea bottom or there was a bursting out of
oil
through natural channels. The method does make use of the hydrostatic pressure
difference between the static pressure at the sea bottom and the reduced
pressure in a hollow room created at the sea bottom of which liquid is pumped
out. If oil and water is being pumped out of such an artificially created
hollow room
over the sea bottom, at a pressure drop of merely 50kPa (0.5 bar), the
pressure
from outside will amount to 50 kN/m2.
[0013] For realizing this method, a support structure or bearing support
together
with a reinforced foil are the key elements of the installation. The entire
installation is shown in figure 1. The support structure 4 is a steel
construction in
the form of a three-leg pyramid-like steel structure which is covered and
completely enclosed by strong steel plates 17 and this support structure 4 or
support structure has three legs 2 so it always stands safely and in a
definite
position on any ground 10. The legs 2 are equipped each with a foot 3 that can
swivel in any direction around the leg 2 end so the feet 3 will adapt to any
underground surface and provide stability for the entire structure. The three
legs 2
keep the entire support structure in a stable position so it can carry much
load.
The size of this support structure 4 may vary according the situation on site,
e.g.
the legs 2 stand on a circle of several meters in diameter, at least large
enough in
order to completely enclose the leaking spot, that is e.g. a crack 19 in the
sea
bottom, or a pipe 26 that was broken. The height of this support structure 4
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measures anything between approx. 3 and 15 meters, in special cases the height
may be even higher, and the side length at the bottom will be approx. 10
meters.
In any case, the most important point is that this support structure 4 will
cover the
entire spot where oil is leaking out into the sea water.
[0014] On this support structure 4, a strong reinforced, water tight, oil and
sea-
water resistant foil 1 is being connected along the lower edge 33 of the
pyramid-
like structure 4. The foil 1 can be composed of a number of strips that are
being
welded or glued together along their edges. The foil 1 is reincored by a steel
fabric or by a carbon-fabric in its interior. This foil 1 is finally lying on
the sea
bottom around the support structure 4. The foil 1 has in its center a hole of
triangular shape which is being put over the neck of the support structure 4
so the
inner edge of said hole will fit to the lower edge 33 of steel plates 17 on
the
structure. The foil 1 is securely attached on the lower edge 33 of the steel
plates
17 that cover the structure and hence the foil 1 covers the entire
surroundings of
the structure. At its periphery or outer edge, a surrounding frame 5 made of
strong
steel tubes or profiles is being placed in order to keep the position of the
foil 1 on
the sea bottom 10 and to keep it stretched. This frame 5 can form a circle, a
square, a triangle or have a rectangular shape when seen from above.
Alternatively, blocks 34 of concrete can be placed, one after the other, in a
row
along the outer edge of the foil 1, as shown in figure 4.
[0015] A pipe 6,7 coming from a tanker ship 9 on the surface of the sea can be
connected with a pipe neck that is extending out of the top of the support
structure
4 and once the connection is established, liquid can be pumped from below the
structure 4 and foil 1 to the sea surface into tanks of a tanker ship 9. Since
the
depth at which the installation is being placed may be several hundred or even
thousand meters deep, several underwater pumps 8 will be used since sucking is
only possible over somewhat less than 10 meters height. The power of these
pumps 8 are regulated by their revolution per minute, according to the
difference
between the pressure inside and outside the support structure 4 and to keep
that
difference constant in a certain range. By using underwater pumps 8, the
liquid
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can be pressed with high pressures onto the surface of the sea. Several pumps
8
can be installed over the entire distance which even act parallel in order to
establish a redundancy. As soon as the pressure within that pipe 6,7 and hence
in
the room within the support structure 4 is dropped to a pressure lower than
the
pressure acting outside of the foil and structure, the foil 1 is being pressed
with
enormous forces to the sea bottom and also the support structure 4 is being
pressed onto the sea bottom since the hydrostatic pressure of the sea water
will
cause that pressing force. If the pressure within the support structure 4 and
underneath the foil 1 is merely lowered at around 0.5 bar, the pressure which
then
acts from outside is about 50 kN/m2 and this pressure causes the foil 1 to be
pressed to the sea bottom and the pressure also acts on the plates 17 which
enclose the entire support structure 4. This will keep the structure 4 and
adjacent
foil 1 in place no matter what happens. The foil 1 and support structure 4
will even
resist substantial underground streams. The foil 1 is likewise pressed onto
the sea
bottom 10 and hence follows the form and shape of its surface. Even if some
water is leaking from the outer edge underneath the foil 1 toward its center,
the
force which does press the foil 1 onto the sea bottom is substantial, although
it
does slightly decrease toward the outer edge of the foil 1. At all times the
pressure within the support structure 4 and underneath the foil 1 will be kept
lower
than the outside acting water pressure. This will cause the entire
installation to
rest absolutely stable on the sea bottom.
[0016] In Figure 2, the support structure 4 on the sea bottom 10 is shown in a
perspective view. Reinforcement struts 20 or bars are welded into the lower
side
of the bearing support 4 in order to strengthen its load capacity and in order
to
provide a support structure for the steel plates 17 to be fixed around the
support
structure 4 so they will completely enclose it and ultimately form the outer
side of
the structure. The lower edge of the steel plates 17 will be positioned
approx.
0.5m to 1.5m above sea ground 10 so it will not touch it even if the sea
bottom is
uneven. The foil 1 will be connected tightly to the lower edge of the steel
plates 17
and from there extend on to the surrounding sea bottom 10. On the top of the
structure, the neck 21 is shown which does communicate with the inner side of
the
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support structure 4.
[0017] In Figure 3, further details of the support structure 4 and foil 1 are
being
shown. The structure 4 may be equipped with an electrical heating installation
30
in order to keep the seawater which is mixing with the spilled oil warm enough
for
pumping. On the lower edge 33 of the steel plates 17, the foil 1 is tightly
attached.
This is shown here on the left side of the structure by way of example. As
shonw
in the respective enlarged view, a clamping device 35 holds a steel plate 32
which
is slightly bent upwards. Along the lower surface of this steel plate 32, the
foil 1
will smoothly adapt when the entire structure and attached foil will be
lowered
down onto the sea bottom as will be explained later. Underneath this bent
steel
plate 32, there is a flexible deflecting steel plate 31 which is bent toward
the sea
bottom. Between these two steel plates 31,32, the reinforced foil 1 is clamped
by
the clamping device 35 and thereby securely attached to the structure 4. When
the structure 4 is lowered from a ship down to the sea bottom, the surrounding
flexible steel plates 31 adapt to the uneven sea bottom and there outer edge
will
lay on the sea bottom. The outer edge of the foil 1 is attached to a frame 5
made
of strong steel pipes or profiles. This frame 5 forms a circle with a radius
of
approx. 10 meters, or a square, triangle or rectangle with a side length of
approx.
20 meters around the entire support structure 4 and the attached foil 1 and
keeps
the foil 1 stretched at all times.
[0018] In Figure 4, the support structure 4, foil 1 and the surrounding frame
5 are
shown from above, laying on the sea bottom. The corners of the frame 5 are
stabilized by cables 36 which are attached to concrete blocks 34 positioned on
the sea bottom. Further blocks 18 can be put onto the edge of the foil 1. In
Figure
5, the connection of the pumping pipe 6 with the top of the foil 1 on the
support
structure 4 or support structure is shown. The neck 21 comes through the steel
plate 17 on top of the structure 4. A conical connecting piece 16 is put over
the
neck 21 and will be sucked onto the steel plate 17 once the pressure within
the
support structure 4 is lower than the outside pressure of the seawater. The
connecting piece is followed by a pipe with a flange 14 at its end. To this
flange
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14, another one is fixed which is connected to a strong rubber bellow 15 which
provides a certain flexibility. This rubber bellow pipe 15 may have a steel
spring in
its interior in order to withstand the pressure difference between outside and
inside. The pumping pipe 6 is connected to the upper flange 13 of the rubber
bellow 15. The pumping pipe 6 can therefore move a certain distance in any
direction and also its direction may vary from the straight upward direction.
This
pumping pipe 6 may be equipped with electrical heating means, e.g. a heating
coil
surrounding the pipe 6 over the initial section in order to prevent a freezing
of the
pumped liquids due to the lowered pressure and the low temperature of the
surrounding sea water.
[0019] Figure 6 does show in a schematic view how the reinforced foil 1 with
the
support structure 4 being attached to it is brought down onto the sea bottom.
Typically, three or even four or more ships are being used which do cooperate
with each other. They are equipped with winches with long steel cables 22. The
ends of these steel cables 22 are fixed to the frame 5 with the reinforced
foil 1
attached to it and the entire installation will be lowered down within the sea
in a
generally horizontal position. Therefore the ships must pull their cables
radially
away from a definite center and contemporarily lowering their cables from
their
winches. A strong steel cable 24 may be used as a guiding cable so the
structure
4 hanging on the foil 1 will be directed to the spilling spot on the sea
bottom. The
cable 24 hangs on a swimmer 23 and the edge of the hole 25 in the structure 4
is
made of a strong steel ring in order to prevent the structure 4 to be damaged.
At
the lower end, the cable 24 is fixed on a concrete block that has been
positioned
in advance. Therefore, the structure 4 and foil 1 will be perfectly guided
with the
central hole 25 of the structure. Once, the structure 4 and foil 1 are
positioned on
the sea bottom, the pumping pipe will be directed with its conical connecting
piece
16 over the neck 21. Then, the pumping can start which will help cause the
foil 1
to be sucked tightly around the support structure 4 and onto the sea bottom.
The
pumping pipe 6 and its connecting piece may likewise be put over the neck 21
by
using guiding cables which are fixed on top of the support structure 4.
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[0020] Figure 7 shows an alternate way to bring down the support structure 4
and
the foil 1. Four or even more ships are being used which do cooperate with
each
other. They first lower down heavy weights 27 hanging on a loose roll 28. This
weights may be concrete blocks 27 of several tons of weight. These weights 27
are being positioned exactly around the spot where the support structure 4
needs
to be positioned on the sea bottom 10. They then have a definite distance from
that selected spot. Once the weights 27 are in position, the cables 29 going
around the loose rolls 28 on the weights 27 will serve as guiding cables for
lowering down the support structure 4 and the foil 1. E.g. for such weights
and
guiding strings can be used, or even more which are positioned overhead the
edge of the foil 1 when it is finally down on the bottom of the sea. The
support
structure 4 can fixed to the foil 1 so it will furtheron hang on the center of
the foil
1. The connection to the pumping pipe 6 is then already established. The foil
1
can then be lowered down, contemporarily with the support structure 4 hanging
on
it. One pipe piece of the pumping pipe after the other will be installed as
the
lowering down proceeds. The frame 5 around the foil 1 is attached via holding
elements which are fixed on the cables 29 of each guiding string. By this, the
foil 1
can be held almost horizontal and stretched and can be lowered down in
completely controlled manner. This also facilitates the task to bring the
support
structure 4 exactly over the leaking pipe on the sea bottom since the foil and
the
support structure 4 are precisely guided along the stretched vertical cables
29
going down do definite points. Once the support structure 4 is close to the
leaking
spot, e.g. several meters, the pumps are activated and start to pump liquid
from
the interior of the support structure. Once the support structure 4 is layed
onto the
sea bottom and finds a definite stand, the foil 1 is completely lowered down
on the
sea bottom as well and the pumping out of liquid through the top neck of the
support structure 4, the foil 1 will be tightly sucked to the outer surface of
the
support structure and also to the surrounding sea bottom.
[0021] Once the pumps are active, the pressure in the interior of the support
structure 4 and underneath the foil 1 will at all times be kept lower than the
outside water pressure. This will keep the structure and foil 1 in place and
the oil
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is being sucked out of the created hollow room and pumped to the surface. A
further spilling of oil into the sea water is prevented and time is gained for
bringing
release borings down and eventually shut down the well in a conventionally and
approved manner.
