AN ANNULAR BARRIER
Field of the Invention
The present invention relates to an annular barrier for being expanded in an
annulus between a well tubular structure and an inside wall of a borehole
downhole. The annular barrier comprises a tubular part for mounting as part of
the well tubular structure; an expandable sleeve made of a first metal,
surrounding the tubular part and defining a space being in fluid communication
with an inside of the tubular part, the expandable sleeve having a longitudinal
extension, an inner face facing the tubular part and two ends.
Background art
In wellbores, annular barriers are used for different purposes, such as for
providing a barrier for flow between an inner and an outer tubular structure or
between an inner tubular structure and the inner wall of a borehole. The annular
barriers are mounted as part of the well tubular structure. An annular barrier has
an inner wall surrounded by an annular expandable sleeve. The expandable
sleeve is typically made of an elastomeric material, but may also be made of
metal. The sleeve is fastened at its ends to the inner wall of the annular barrier.
In order to seal off a zone between an inner and an outer tubular structure or a
well tubular structure and the borehole, a second annular barrier is used. The
first annular barrier is expanded on one side of the zone to be sealed off, and the
second annular barrier is expanded on the other side of that zone, and in this
way, the entire zone is sealed off.
The pressure envelope of a well is governed by the burst rating of the tubular
and the well hardware etc. used within the well construction. In some
circumstances, the expandable sleeve of an annular barrier may be expanded by
increasing the pressure in the well, which is the most cost efficient way of
expanding the sleeve. The burst rating of a well defines the maximum pressure
that can be applied to the well for expansion of the sleeve, and it is desirable to
minimise the expansion pressure required for expanding the sleeve to minimise
the exposure of the well to the expansion pressure.
When expanded, annular barriers may be subjected to a continuous pressure or a
periodic high pressure from the outside, either in the form of hydraulic pressure
within the well environment or in the form of formation pressure. In some
circumstances, such pressure may cause the annular barrier to collapse, which
may have severe consequences for the area which the barrier is to seal off, as
the sealing properties are lost due to the collapse.
The ability of the expanded sleeve of an annular barrier to withstand the collapse
pressure is thus affected by many variables, such as strength of material, wall
thickness, profile of the expanded sleeve, surface area exposed to the collapse
pressure, temperature, well fluids, etc.
A collapse rating currently achievable of the expanded sleeve within certain well
environments is insufficient for all well applications. Thus, it is desirable to
increase the collapse rating to enable annular barriers to be used in all wells,
specifically in wells that experience a high drawdown pressure during production
and depletion. The collapse rating may be increased by increasing the wall
thickness or the strength of the material; however, this would increase the
expansion pressure, which, as mentioned, is not desirable.
It is thus desirable to provide a solution wherein the collapse rating of expanded
sleeves is increased.
Summary of the Invention
It is an object of the present invention to wholly or partly overcome the above
disadvantages and drawbacks of the prior art. More specifically, it is an object to
provide an improved annular barrier with an increased collapse rating of the
expandable sleeve.
A further object of the present invention is to provide an annular barrier having
an increased collapse rating without increasing the strength of the material
and/or wall thickness of the sleeve.
The above objects, together with numerous other objects, advantages, and
features, which will become evident from the below description, are accomplished
by a solution in accordance with the present invention by an annular barrier for
being expanded in an annulus between a well tubular structure and an inside wall
of a borehole downhole, comprising
- a tubular part for mounting as part of the well tubular structure,
- an expandable sleeve made of a first metal, surrounding the tubular part and
defining a space being in fluid communication with an inside of the tubular part,
the expandable sleeve having a longitudinal extension, an inner face facing the
tubular part and two ends,
- a connection part made of a second metal, connecting the expandable sleeve
with the tubular part,
- an opening for letting fluid into the space to expand the sleeve, and
- a transition area comprising a connection of the sleeve with the connection
part,
wherein the first metal is more flexible than the second metal.
The tubular part may have an inner unexpanded diameter being the same as an
inner diameter of the well tubular structure.
Hereby, the annular barrier does not hinder the passage of tools submerged into
the well tubular part for other operations further down the well. Annular barriers
may be activated several years after insertion to provide an isolation of a first
zone from a second zone, e.g. in order to optimise the production. In this time
span from insertion to activation, the annular barriers merely function as part of
the well tubular structure and cannot diminish the inner diameter of the well
tubular structure as this is unacceptable with regard to later operations.
Said tubular part may have an inner diameter being substantially the same
before and after expansion of the expandable sleeve.
By the first metal being more flexible than the second metal is meant that the
metal of the expandable sleeve has an elongation higher than the elongation of
the metal of the connection part.
By having a connection part and a sleeve of two different metals, it is possible to
machine the connection part so as to fit the tubular part perfectly without
changing the material of the sleeve and the expansion ability of the sleeve.
In an embodiment, the annular barrier may comprise a restriction element in the
transition area, restricting a free expansion of the sleeve in the area.
By having a connection part and a sleeve made of two different metals as well as
a restriction element, the collapse rating of the expandable sleeve is increased
without increasing the wall thickness of the expandable sleeve or the overall
diameter of the annular barrier. Furthermore, by the present invention, the
expansion pressure necessary to expand the expandable sleeve will not be
increased, or may even be lowered.
In an embodiment, the connection part and the sleeve may be welded together.
Furthermore, the transition area may extend along the longitudinal extension of
the expandable sleeve from a first point at the connection to a predetermined
second point on the expandable sleeve.
In addition, the second point may be arranged on an unrestricted part of the
expandable sleeve.
The expandable sleeve may be more restricted in expanding at the first point
than at the second point.
Also, the restriction element may be a projecting part of the connection part.
Moreover, the expandable sleeve may be restricted in expanding in the transition
area by the projecting part of the connection part.
Additionally, the projecting part may taper towards the expandable sleeve.
Furthermore, each end of the expandable sleeve may have a tapering shape
corresponding to the shape of the projecting part.
Moreover, the restriction element may be an additional ring surrounding the
expandable sleeve, the additional ring being connected with the connection part
and tapering from the connection part towards the expandable sleeve.
Also, the expandable sleeve may be restricted in expanding in the transition area
by an additional ring surrounding the expandable sleeve, the additional ring being
connected with the connection part and tapering from the connection part
towards the expandable sleeve.
Furthermore, the restriction element may be an increased thickness of the
expandable sleeve, provided by adding an additional material at least on its
outside, which material tapers from the connection part towards the sleeve.
In addition, the expandable sleeve may be restricted in expanding in the
transition area by an increased thickness of the expandable sleeve provided by
adding an additional material at least on its outside, which material tapers from
the connection part towards the sleeve.
Moreover, the additional material may be added by means of welding.
In an embodiment, the thickness of the expandable sleeve may decrease from a
thickness of the connection part to a thickness less than 95% of the thickness of
the connection part, preferably a thickness less than 90% of the thickness of the
connection part, and more preferably a thickness less than 80% of the thickness
of the connection part.
Furthermore, the first metal may have an elongation of 35-70%, at least 40%,
preferably 40-50%. The first metal may have a yield strength (soft annealed) of
200-400 MPa, preferably 200-300 MPa.
Also, the second metal may have an elongation of 10-35%, preferably 25-35%.
The second metal may have a yield strength (cold worked) of 500-1000 MPa,
preferably 500-700 MPa.
Furthermore, the metal of the expandable sleeve may have an elongation of at
least 5 percentage points, preferably at least 10 percentage points higher than
the elongation of the metal of the connection part.
In addition, sections of the expanded sleeve may have an increased wall
thickness, resulting in a corrugated expanded sleeve. The corrugations will be
annular and strengthen the expanded sleeve even further.
As a consequence, the annular barrier according to invention is capable of
withstanding a higher collapse pressure than prior art annular barriers and will
thus also have enhanced sealing capabilities.
Furthermore, the sleeve may be provided with sealing elements on its outside.
The sealing elements may have a tapering or triangular cross-sectional shape.
The expandable sleeve may be capable of expanding to an at least 10% larger
diameter, preferably an at least 15% larger diameter, more preferably an at least
30% larger diameter than that of an unexpanded sleeve and it may have a wall
thickness which is thinner than a length of the expandable sleeve, the thickness
preferably being less than 25% of its length, more preferably less than 15% of its
length, and even more preferably less than 10% of its length.
In one embodiment, the expandable sleeve may have a varying thickness along
the periphery and/or length.
In addition, at least one of the connection parts may be slidable in relation to the
tubular part of the annular barrier, and at least one sealing element, such as an
O-ring, may be arranged between the slidable connection part and the tubular
part. In one embodiment, more than one sealing element may be arranged
between the slidable fastening means and the tubular part.
At least one of the connection parts may be fixedly fastened to the tubular part
or be part of the tubular part.
The connection part may have a projecting edge part which projects outwards
from the tubular part.
Also, the tubular part may have two sections at opposing sides of an intermediate
part and at a distance from the opening in the tubular structure, the tubular part
having, in the sections, an increased outer diameter and an increased wall
thickness in relation to an outer diameter and a wall thickness of the
intermediate part of the tubular part.
Moreover, the connection parts may be arranged opposite the two sections.
Further, one of the connection parts may be arranged in a sliding manner in
relation to the section of the tubular part and the other connection part may be
fastened to the tubular part in a sealing connection.
Additionally, the sealing connection may seal the space together with sealing
means arranged in the slidable connection part.
Each connection part may have a projecting part overlapping the expandable
sleeve.
Said projecting part of the connection part may be welded together with the
expandable sleeve.
The invention further relates to an annular barrier system comprising an
expansion tool and an annular barrier as described above. The expansion tool
may comprise explosives, pressurised fluid, cement, or a combination thereof.
In one embodiment, the annular barrier system may comprise at least two
annular barriers positioned at a distance from each other along the well tubular
structure.
Moreover, the invention finally relates to a downhole system comprising a well
tubular structure and at least one annular barrier as described above.
In one embodiment of the downhole system, a plurality of annular barriers may
be positioned at a distance from each other along the well tubular structure.
Brief Description of the Drawings
The invention and its many advantages will be described in more detail below
with reference to the accompanying schematic drawings, which for the purpose of
illustration show some non-limiting embodiments and in which
Fig. 1 shows an annular barrier according to the invention,
Fig. 2 shows another embodiment of the annular barrier,
Fig. 3 shows yet another embodiment of the annular barrier,
Fig. 4 shows yet another embodiment of the annular barrier,
Fig. 5 shows a system according to the invention,
Fig. 6 shows yet another embodiment of the annular barrier,
Fig. 7 shows the annular barrier of Fig. 6 in its expanded state,
Fig. 8 shows an enlarged partial view of Fig. 6, and
Fig. 9 shows yet another embodiment of the annular barrier in its expanded
state.
All the figures are highly schematic and not necessarily to scale, and they show
only those parts which are necessary in order to elucidate the invention, other
parts being omitted or merely suggested.
Detailed description of the invention
Annular barriers 1 according to the present invention are typically mounted as
part of the well tubular structure string before the well tubular structure 3 is
lowered into the borehole 5 downhole. The well tubular structure 3 is constructed
by well tubular structure parts put together as a long well tubular structure
string. Often, the annular barriers 1 are mounted in between the well tubular
structure parts when the well tubular structure string is mounted.
The annular barrier 1 is used for a variety of purposes, all of which require that
an expandable sleeve 7 of the annular barrier 1 is expanded so that the sleeve
abuts the inside wall 4 of the borehole 5. The annular barrier 1 comprises a
tubular part 6 which is connected to the well tubular structure 3, as shown in Fig.
1, e.g. by means of a thread connection 38.
In Fig. 1, the annular barrier 1 is shown in a cross-section along the longitudinal
extension of the annular barrier. The annular barrier 1 is shown in its
unexpanded state, i.e. in a relaxed position, from which it is to be expanded in an
annulus 2 between a well tubular structure 3 and an inside wall 4 of a borehole 5
downhole. The annular barrier 1 comprises a tubular part 6 for mounting as part
of the well tubular structure 3 and an expandable sleeve 7. The expandable
sleeve 7 surrounds the tubular part 6 and has an inner face 8 facing the tubular
part 6. Each end 9, 10 of the expandable sleeve 7 is connected with a connection
part 12 which again is connected with the tubular part 6. The expandable sleeve
7 is made of a first metal alloy and the connection part 12 is made of a second
metal alloy which is less flexible than the first metal alloy. The connection part 12
has a projecting part 18 overlapping the expandable sleeve 7. The connection
part 12 is welded together with the expandable sleeve 7 in a connection 14. An
inner ring 24 is arranged between the expandable sleeve 7 and the tubular part 6
and is welded in the same connection 14. The projecting part 18 of the
connection part 12 increasingly tapers towards the expandable sleeve 7 until the
projecting part 18 does not overlap the expandable sleeve 7 anymore and the
expandable sleeve 7 is free to expand.
The projecting part 18 and the connection 14 form part of a transition area 11
extending along the longitudinal extension of the expandable sleeve 7 from a first
point 2 1 at the connection to a predetermined second point 22 on an unrestricted
part of the expandable sleeve 7. The projecting part 18 has the purpose of
restricting the expansion of the expandable sleeve 7 so that the curvature
(shown by a dotted line in Fig. 1) of the expandable sleeve 7 is more S-shaped.
It is hereby obtained that the expandable sleeve 7 does not fracture during
expansion and that the cross-sectional profile of the expandable sleeve 7 is
capable of withstanding a higher collapse pressure than a known annular barrier.
Thus, the expandable sleeve 7 is more restricted in expanding at the first point
than at the second point. Furthermore, due to the fact that the projecting part 18
is made of a less flexible metal alloy and tapers from the connection towards the
second point, the expandable sleeve 7 is less restricted in expanding along with
the decreasing thickness of the projecting part.
Fig. 2 shows a cross-sectional view of the annular barrier 1 in which the
connection part 12 is connected with an outer ring 29, the expandable sleeve 7
and the inner ring 24. The expandable sleeve 7 is made of a first metal alloy and
the connection part is made of a second metal alloy which is less flexible than the
first metal alloy. The connection 14 is a welded connection. The outer ring 29
forms part of the transition area 11 in which the expandable sleeve 7 is restricted
in expanding freely. The outer ring 29 has a decreasing thickness tapering from
the connection 14 towards the unrestricted part of the expandable sleeve 7. The
outer ring 29 is made of the second metal alloy which is less flexible than the
metal alloy of the sleeve, and the outer ring 29 has the purpose of restricting the
expansion of the expandable sleeve 7 so that the curvature (shown by a dotted
line in Fig. 1) of the expandable sleeve 7 is more S-shaped. It is hereby obtained
that the expandable sleeve 7 does not fracture during expansion, and the crosssectional
profile of the expandable sleeve 7 is capable of withstanding a higher
collapse pressure than a known annular barrier.
Fig. 3 shows a cross-sectional view of the annular barrier 1 in which the
expandable sleeve 7 tapers towards the connection part 12, and the connection
part has a corresponding shape. The tapering part 33 of the expandable sleeve 7
and the tapering part of the connection part 12 overlap and are welded together.
The welded connection 14 and the tapering part of the connection part 12
extending from the connection 12 in an overlapping relationship with the
expandable sleeve 7 form part of the transition area 11. The expandable sleeve 7
is made of a first metal alloy and the connection part is made of a second metal
alloy which is less flexible than the first metal alloy. The tapering part of the
connection part 12 overlapping the sleeve restricts the expandable sleeve 7 in
expanding freely so that the curvature (shown by a dotted line in Fig. 1) of the
expandable sleeve 7 is more S-shaped. It is hereby obtained that the expandable
sleeve 7 does not fracture during expansion, and the cross-sectional profile of the
expandable sleeve 7 is capable of withstanding a higher collapse pressure than a
known annular barrier.
Fig. 4 is a cross-sectional view of the annular barrier 1 in which the expandable
sleeve 7 is welded together with the connection part 12, forming the connection
14 there between. The expandable sleeve 7 is made of a first metal alloy and the
connection part 12 is made of a second metal alloy which is less flexible than the
first metal alloy. In addition, an additional material 30 is added in the transition
area 11 from the connection 14 along a first part of the expandable sleeve 7. The
additional material 30 decreases in thickness from the connection 14 along the
expandable sleeve 7. The additional material 30 is made of the same material as
the connection part 12 or of metal alloy which is even less flexible than the metal
alloy of the connection part 12. The connection 14 and the additional material 30
form part of the transition area 11, and the additional material 30 hinders the
expandable sleeve 7 in expanding too much in the transition area, and the sleeve
thus forms a more S-shaped cross-sectional profile after expansion. Hereby, the
collapse pressure is increased compared to known annular barriers.
When the expandable sleeve 7 is made of a first metal alloy and the connection
part is made of a second metal alloy which is less flexible than the first metal
alloy, the metal alloy of the connection part 12 can be a metal alloy which is
more machinable than the metal alloy of the sleeve 7. When making the
connection part 12, it is important that it can be machined so as to fit the tubular
part more perfectly, thus forming a tighter seal, and even a metal -to- metal seal.
As can be seen, a space or cavity 13 is formed between the inner face 8 of the
sleeve 7 and the tubular part 6. In order to expand the expandable sleeve 7,
pressurised fluid is injected into the cavity 13 through an expansion tool 15, such
as a hole 19 or a valve 19, until the expandable sleeve 7 abuts the inside wall 4
of the borehole 5. The cavity 13 may also be filled with cement or the like in
order to expand the sleeve 7. The expansion tool 15 may also be an explosive.
When annular barriers 1 are expanded, they are exposed to a certain pressure.
However, the pressure may vary during production. As the pressure may thus
increase, the annular barrier 1 must be capable of withstanding an increased
pressure, also called "the collapse pressure", also in its expanded state, when the
outer diameter of the annular barrier 1 is at its maximum and its wall thickness
thus at its minimum. In order to withstand such an increased pressure, the
expandable sleeve 7 may be provided with at least one element 14.
When the expandable sleeve 7 of the annular barrier 1 is expanded, the diameter
of the sleeve is expanded from its initial unexpanded diameter to a larger
diameter. The expandable sleeve 7 has an outside diameter D and is capable of
expanding to an at least 10% larger diameter, preferably an at least 15% larger
diameter, more preferably an at least 30% larger diameter than that of an
unexpanded sleeve 7.
Furthermore, the expandable sleeve 7 has a wall thickness t which is thinner than
a length L of the expandable sleeve, the thickness preferably being less than
25% of the length, more preferably less than 15% of the length, and even more
preferably less than 10% of the length.
The expandable sleeve 7 of the annular barrier 1 is made of a first metal having
an elongation of 35-70%, at least 40%, preferably 40-50%, and the connection
part is made of a second metal having an elongation of 10-35%, preferably 25-
35%. The metal of the connection part has an elongation of at least 5 percentage
points, preferably at least 10 percentage points higher than the elongation of the
metal of the expandable sleeve. The yield strength (soft annealed) of the metal
of the expandable sleeve is 200-400 MPa, preferably 200-300 MPa. The yield
strength (cold worked) of the metal of the connection part is 500-1000 MPa,
preferably 500-700 MPa. Thus, the first metal is more flexible than the second
metal.
Providing the annular barrier 1 with a valve 19 makes it possible to use other
fluids than cement, such as the fluid present in the well or sea water, for
expanding the expandable sleeve 7 of the annular barrier.
As can be seen, the expandable sleeve 7 is a thin-walled tubular structure, the
ends 9, 10 of which have been inserted into the connection part 12.
Subsequently, the connection part 12 has been embossed, changing the design
of the fastening means and the ends 9, 10 of the expandable sleeve and thereby
mechanically fastening them in relation to one another. In order to seal the
connection between the expandable sleeve 7 and the connection part 12, a
sealing element may be arranged between them.
In Fig. 6, another annular barrier 1 is shown, wherein the expandable sleeve 7 of
the annular barrier 1 has been laminated with an additional material 30 in
predetermined areas, i.e. in those areas where the expanded sleeve 7 is exposed
to maximum hydraulic pressure. Advantageously, this additional material 30 may
be stronger than the material of which the rest of the expandable sleeve is made.
Normally, a stronger material will be less ductile. When only laminating the
expandable sleeve 7 with the additional stronger material 30 in certain areas, an
increased collapse rating of the expandable sleeve may, however, be achieved
without affecting the expansion properties of sleeve.
Lamination of the expandable sleeve 7 may be performed in many different ways,
e.g. by laser welding of dissimilar metals, cladding, etc.
When a stronger but less ductile material 30 is laminated onto the expandable
sleeve 7, the material of which is not quite as strong but more ductile, the result
is an expandable sleeve which is still sufficiently ductile, but the collapse rating of
which is increased. In its expanded state, the sleeve 7 will thus be capable of
withstanding a higher pressure close to or at the point of lamination.
When the expandable sleeve 7 is laminated with an additional material 30 in
certain areas, the wall thickness of the sleeve is increased in these areas. This
increase in the wall thickness is more easily deduced from Fig. 8.
Fig. 7 shows a cross-sectional view of the annular barrier 1 of Fig. 6 in its
expanded state. In this embodiment, the additional material 30 with which the
sleeve 7 has been laminated provides an increased collapse rating of the
expandable sleeve and thus of the annular barrier 1.
In Fig. 9, the tubular part 6 has two sections 36 having an increased outer
diameter and thus the tubular part has an increased thickness at two sections 36
at opposing sides and at a distance from the opening in the tubular structure.
Between the sections, the tubular part has an intermediate section 37. The
connection parts 12 are arranged opposite the two sections 36 and one of the
connection parts 12 is arranged in a sliding manner in relation to the section 36
of the tubular part. The other connection part 12 is welded to the tubular part in
a connection 35 and is, in this way, fixedly arranged in relation to the tubular
part, and the welded connection 35 provides a sealing connection sealing the
space 13 together with sealing means 20 arranged in the slidable connection part
12.
The expandable sleeve 7 of Fig. 9 is made of a first metal alloy and the
connection part 12 is made of a second metal alloy which is less flexible than the
first metal alloy. The two sections may be material welded on the outside of the
tubular part 6 and then the sections are machined and polished to have a precise
outer diameter at the sections before mounting the connection parts 12. Hereby,
a very smooth surface is provided so that a very tight seal between the sealing
means 20 and the tubular part can be accomplished.
The connection part 12 has a projecting part 18 overlapping the expandable
sleeve 7. The connection part 12 is welded together with the expandable sleeve 7
in a connection 14. The projecting part 18 of the connection part 12 projects
overlapping part of the expandable sleeve 7. At the end of the projecting part 18,
it may be fastened to the expandable sleeve, e.g. by means of welding in a
welded connection 34. In another aspect, the projecting part is not fastened to
the expandable sleeve 7. However, as the projecting part overlaps the
expandable sleeve 7, the sleeve 7 is not totally free to expand.
Between the two sections, the expandable sleeve 7 and the tubular part 6 form
the space 13 into which fluid is injected through the opening to expand the
sleeve for the isolation of a first zone 40 from a second zone 4 1 in the borehole,
which zones 40, 4 1 are shown in Fig. 1.
In another aspect, the expandable sleeve 7 may comprise at least two different
materials, one having a higher strength and thereby lower ductility than the
other material having a lower strength but higher ductility. Hereby, the
expandable sleeve 7 may comprise the material having the higher strength in
areas of the sleeve which are subjected to high hydraulic collapse pressure, when
the sleeve is expanded, and comprise the material having a lower strength in the
remaining areas of the sleeve. When the expandable sleeve 7 comprises a
material of higher strength with low ductility in certain areas, having a material of
lower strength but high ductility in the remaining areas, the expandable sleeve
maintains sufficient ductility whilst the lower strength expandable sleeve material
gains in collapse resistance. Once expanded, the overall effect is an expandable
sleeve 7 with a higher collapse resistance close to or at the areas where the
sleeve comprises the material of higher strength.
In another aspect, both ends 9, 10 of the expandable sleeve 7 are fixed to the
well tubular structure 3. Normally, when the expandable sleeve 7 expands
diametrically outwards, the increase in diameter of the expandable sleeve will
cause the length of the sleeve to shrink and the thickness of the wall of the
sleeve to become somewhat decreased.
If two ends 9, 10 of the sleeve 7 are fixed and no other changes are made to the
design of prior art annular barriers, the degree to which the wall thickness would
have to be decreased to achieve high diametrical expansion would be increased,
leading to a lower collapse rating and a possible burst of material.
In an additional aspect, the expandable sleeve 7 is provided with a series of
circumferential corrugations along the length of the expandable sleeve. The
series of circumferential corrugations enables an increase in the length of the
expandable sleeve 7 between the two fixed ends 9, 10 without increasing the
distance between the two fixed ends.
After forming the above-mentioned corrugations, the expandable sleeve 7 may
be subjected to some kind of treatment, e.g. heat treatment, to return the
material of the sleeve 7 to its original metallurgical condition.
In the transition area, either the sleeve 7 itself or the additional material 30 may
be machined to obtain a somewhat smaller wall thickness on the inner face 8 of
the sleeve in order to control where the bending of the sleeve is initiated during
expansion of the sleeve.
During expansion of the expandable sleeve 7, the corrugations are straightened
out, providing the additional material 30 necessary for large diametrical
expansion (e.g. 40% in diameter) without overly decreasing the wall thickness
and while still keeping the two ends 9, 10 fixed. This is shown in Fig. 10.
Preventing excessive decrease in wall thickness will maintain the collapse rating
of the expandable sleeve 7, which will be appreciated by the skilled person.
Fixing the two ends 9, 10 while at the same time achieving a maximum
diametrical expansion capability (e.g. 40% in diameter) is particularly
advantageous in that it eliminates moving parts and thus the expensive and risky
high pressure seals required for these moving parts. This is of particular
importance in regard to high temperatures or corrosive well environments, e.g.
Acid, H2S, etc.
In another aspect, the wall thickness of the expandable sleeve 7 along the length
of the sleeve may be profiled, which will allow control of the expansion in relation
to where wall thinning of the expandable sleeve would occur. The profiling may
be made to the expandable sleeve 7 via lamination of the same or different
materials to the surface of the expansion sleeve or could be effected via
machining or rolling of the expandable sleeve to varying thicknesses.
When the expansion is controlled through varying the wall thickness, it is possible
to vary the collapse rating at certain points along the length of the expandable
sleeve 7.
In Fig. 1, one end of the annular barrier 1 is slidable, meaning that the
connection part 12 in which the sleeve 7 is fastened is slidably connected with
the tubular part 6. When the expandable sleeve 7 is expanded in a direction
transverse to the longitudinal direction of the annular barrier 1, the sleeve will, as
mentioned above, tend to shorten in its longitudinal direction, if possible. When
one end is slidable, the length of the sleeve 7 may be reduced, making it possible
to expand the sleeve even further since it is not stretched as much as when it is
fixedly connected with the tubular part 6.
However, having one slidable end increases the risk of the seals 20 becoming
leaky over time. A bellows may therefore be fastened to the slidable connection
part 12 and fixedly fastened in a third connection part. In this way, the first and
third connection parts can be fixedly connected to the tubular part 6. The
expandable sleeve 7 is firmly fixed to the first connection part 12 and to the
slidable connection part 12, and the bellows is firmly fixed to the slidable
connection part 12 and the third connection part. Accordingly, the connection
parts 12, the expandable sleeve 7 and the bellows together form a tight
connection preventing well fluid from entering the tubular structure 3.
The incorporation of two ends 9, 10 fixed with maximum diametrical expansion
capability is considered beneficial in that this would eliminate moving parts, and
no expensive and risky high pressure seals within these moving parts are
needed. This is of particular importance when considering high temperature or
corrosive well environments, e.g. Acid, H2S etc.
When the annular barrier 1 has a slidable connection part 12 between the sleeve
7 and the tubular part 6, the expansion capability of the sleeve is increased by up
to 100% compared to an annular barrier without such a slidable connection part
12.
In another embodiment, the sleeve 7 has an outer face having two sealing
elements opposite an increased thickness of the sleeve. When expanded, the
sealing elements fit into a groove created by the increased thickness and seal
against the inner wall of the borehole 5.
The sealing elements have an outer corrugated face for increasing the sealing
ability. The sealing elements have a triangular cross-sectional shape so as to fit
the groove occurring in the sleeve 7 during expansion. The sealing elements are
made of an elastomer or similar material having a sealing ability and being
flexible.
By collapse pressure is meant the pressure by which an outside pressure can
collapse an expanded sleeve 7. The higher the collapse pressure, the higher the
pressure from the formation and the annulus the expanded sleeve 7 is capable of
withstanding before collapsing.
The invention also relates to a downhole system 50 having a well tubular
structure 3 and an annular barrier 1 or a plurality of annular barriers, as shown in
Fig. 5. In another embodiment, the system has a double annular barrier. The
double annular barrier 1 has two end connection parts 12 and a middle
connection part. The two expandable sleeves 7 are fastened to one end
connection part and the middle part. The middle connection part is slidable as is
one of the end connection parts 12. The other end connection part 12 is firmly
fastened to the tubular part 6. The annular barrier 1 has two openings for
injection of pressured fluid for expansion of the sleeves 7.
In another embodiment of a double annular barrier 1, the barrier only has one
opening for injection of pressured fluid for expansion of the sleeves 7. The
annular barrier 1 has two cavities, and the middle connection part 12 has a
channel fluidly connecting the two cavities so that fluid for expanding the cavity
having the opening can flow through the channel to expand the other sleeve 7 as
well.
The present invention also relates to an annular barrier system 40, as shown in
Fig. 5, comprising an annular barrier 1 as described above. The annular barrier
system 40 moreover comprises an expansion tool 15 for expanding the
expandable sleeve 7 of the annular barrier 1. The tool 15 expands the
expandable sleeve 7 by applying pressurised fluid through a passage 19 in the
tubular part 6 into the space 13 between the expandable sleeve 7 and the tubular
part 6.
The expansion tool 15 may comprise an isolation device 17 for isolating a first
section outside the passage or valve 19 between an outside wall of the tool and
the inside wall of the well tubular structure 3. The pressurised fluid is obtained by
increasing the pressure of the fluid in the isolation device 17. When a section of
the well tubular structure 3 outside the passage 19 of the tubular part 6 is
isolated, it is not necessary to pressurise the fluid in the entire well tubular
structure 3, just as no additional plug is needed, as is the case in prior art
solutions. When the fluid has been injected into the cavity 13, the passage or
valve 19 is closed.
In the event that the tool 15 cannot move forward in the well tubular structure 3,
the tool may comprise a downhole tractor, such as a Well Tractor®.
The tool 15 may also use coiled tubing for expanding the expandable sleeve 7 of
an annular barrier 1 or of two annular barriers at the same time. A tool 15 with
coiled tubing can pressurise the fluid in the well tubular structure 3 without
having to isolate a section of the well tubular structure; however, the tool may
need to plug the well tubular structure 3 further down the borehole 5 from the
two annular barriers 1 to be operated. The annular barrier system 40 of the
present invention may also employ a drill pipe or a wireline tool for expanding the
sleeve 7.
In one embodiment, the tool 15 comprises a reservoir containing the pressurised
fluid, e.g. when the fluid used for expanding the sleeve 7 is cement, gas or a
two-component compound.
An annular barrier 1 may also be called a packer or similar expandable means.
The well tubular structure 3 can be the production tubing or casing or a similar
kind of tubing downhole in a well or a borehole. The annular barrier 1 can be
used both between the inner production tubing and an outer tubing in the
borehole or between a tubing and the inner wall of the borehole 5. A well may
have several kinds of tubing, and the annular barrier 1 of the present invention
can be mounted for use in all of them.
The valve 19 may be any kind of valve capable of controlling flow, such as a ball
valve, butterfly valve, choke valve, check valve or non-return valve, diaphragm
valve, expansion valve, gate valve, globe valve, knife valve, needle valve, piston
valve, pinch valve or plug valve.
The expandable tubular metal sleeve 7 may be a cold-drawn or hot-drawn
tubular structure.
The fluid used for expanding the expandable sleeve 7 may be any kind of well
fluid present in the borehole 5 surrounding the tool 15 and/or the well tubular
structure 3. Also, the fluid may be cement, gas, water, polymers, or a twocomponent
compound, such as powder or particles mixing or reacting with a
binding or hardening agent. Part of the fluid, such as the hardening agent, may
be present in the cavity 13 before injecting a subsequent fluid into the cavity.
Although the invention has been described in the above in connection with
preferred embodiments of the invention, it will be evident for a person skilled in
the art that several modifications are conceivable without departing from the
invention as defined by the following claims.
Claims
1. An annular barrier (1) for being expanded in an annulus (2) between a well
tubular structure (3) and an inside wall (4) of a borehole (5) downhole,
comprising
- a tubular part (6) for mounting as part of the well tubular structure,
- an expandable sleeve (7) made of a first metal, surrounding the tubular part
and defining a space (13) being in fluid communication with an inside (64) of the
tubular part, the expandable sleeve having a longitudinal extension, an inner face
(8) facing the tubular part and two ends (9, 10),
- a connection part (12) made of a second metal, connecting the expandable
sleeve with the tubular part,
- an opening for letting fluid into the space to expand the sleeve, and
- a transition area (11) comprising a connection (14) of the sleeve with the
connection part,
wherein the first metal is more flexible than the second metal.
2. An annular barrier according to claim 1, wherein the annular barrier
comprises a restriction element in the transition area, restricting a free expansion
of the sleeve in the area.
3. An annular barrier according to claim 1 or 2, wherein the transition area
extends along the longitudinal extension of the expandable sleeve from a first
point (21) at the connection to a predetermined second point (22) on the
expandable sleeve.
4. An annular barrier according to claim 3, wherein the expandable sleeve is
more restricted in expanding at the first point than at the second point.
5. An annular barrier according to claim 4, wherein the restriction element is a
projecting part (18) of the connection part.
6. An annular barrier according to claim 5, wherein the projecting part tapers
towards the expandable sleeve.
7. An annular barrier according to claim 6, wherein each end of the
expandable sleeve has a tapering shape corresponding to the shape of the
projecting part.
8. An annular barrier according to claim 2-4, wherein the restriction element is
an additional ring (24) surrounding the expandable sleeve, the additional ring
being connected with the connection part and tapering from the connection part
towards the expandable sleeve.
9. An annular barrier according to claim 2-4, wherein the restriction element is
an increased thickness of the expandable sleeve, provided by adding an
additional material (30) at least on its outside, which material tapers from the
connection part towards the sleeve.
10. An annular barrier according to claim 7, wherein the thickness of the
expandable sleeve decreases from a thickness of the connection part to a
thickness less than 95% of the thickness of the connection part, preferably a
thickness less than 90% of the thickness of the connection part, and more
preferably a thickness less than 80% of the thickness of the connection part.
11. An annular barrier according to any of the preceding claims, wherein the
first metal has an elongation of 35-70%, at least 40%, preferably 40-50%.
12. An annular barrier according to any of the preceding claims, wherein the
second metal has an elongation of 10-35%, preferably 25-35%.
13. An annular barrier according to any of the preceding claims, wherein the
tubular part has two sections (36) at opposing sides of an intermediate part (37)
and at a distance from the opening in the tubular structure, the tubular part
having, in the sections, an increased outer diameter and an increased wall
thickness in relation to an outer diameter and a wall thickness of the
intermediate part of the tubular part.
14. An annular barrier according to claim 13, wherein the connection parts are
arranged opposite the two sections.
15. An annular barrier according to claim 14, wherein one of the connection parts
is arranged in a sliding manner in relation to the section of the tubular part and
the other connection part is fastened to the tubular part in a sealing connection
(35).
16. An annular barrier according to claim 15, wherein the sealing connection (35)
seals the space together with sealing means (20) arranged in the slidable
connection part.
17. An annular barrier according to any of claims 13-16, wherein each connection
part has a projecting part 18 overlapping the expandable sleeve (7).
18. An annular barrier according to claim 17, wherein the projecting part (18) of
the connection part is welded together with the expandable sleeve.
19. An annular barrier system (40) comprising an expansion tool (15) and an
annular barrier according to any of the claims 1 to 12.
20. An annular barrier system according to claim 19, wherein the expansion
tool comprises explosives, pressurised fluid, cement, or a combination thereof.
21. A downhole system (50) comprising a well tubular structure and at least
one annular barrier according to any of the claims 1 to 18.