Field of the invention
[0001] The present invention relates to an annular barrier for providing zone isolation
between a first zone and a second zone in a borehole or a casing downhole.
Background art
[0002] Annular barriers or packers downhole often comprise external sealing material, such
as elastomeric circumferential rings, to improve the sealing ability of the annular
barrier when expanded to abut the inner wall of the casing or borehole.
[0003] When expanding the annular barriers or packers, the sealing material is expanded
accordingly and the sealing ability is decreased and the sealing ability of the elastomeric
material is furthermore decreased when subjected to the harsh environment downhole,
such as high temperatures and pressure, and also different kinds of acid.
[0004] Annular barriers may be part of the completion for many years without being expanded,
while the elastomeric seals are continuously subjected to the harsh environment and
disintegrates and thus deteriorates over that time so that when expanded, the sealing
ability of the elastomeric material may be lost.
Summary of the invention
[0005] 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 seal for annular barriers capable of withstanding the harsh environment downhole,
such as high temperatures, high pressure and acid, over a period of time of approximately
10 to 20 years.
[0006] 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 providing zone
isolation between a first zone and a second zone in a borehole or a casing downhole,
said annular barrier having a circumference and an outer face and comprising an annular
seal comprising a sealing material having a bundle of strands wherein at least one
strand comprises graphite and/or carbon.
[0007] In one embodiment, the sealing material may cover less than 60% of the outer face,
preferably less than 40% of the outer face, more preferably less than 30% of the outer
face.
[0008] Also, the sealing material of the annular seal may extend around the outer face of
the annular barrier.
[0009] Moreover, a cross-sectional shape of the annular seal may substantially be a triangle,
a square, a pentagon, a hexagon, or a shape having more sides.
[0010] Further, the sealing material may be wound around the outer face of the annular barrier
with x windings, where x > 1.0.
[0011] x may be between 1.0 and 2.0, preferably between 1.1 and 1.7 and more preferably
between 1.2 and 1.5.
[0012] Additionally,the annular seal may have an elongated shape and two ends and may extend
around the outer face of the annular barrier.
[0013] In one embodiment, the ends may overlap.
[0014] Furthermore, the annular barrier may comprise several annular seals.
[0015] Also, the overlap may extend over at least 10% of the circumference of the annular
barrier, preferably at least 15% of the circumference, more preferably at least 30%,
and even more preferably at least 40% of the circumference.
[0016] Moreover, the strands may abut each other.
[0017] In addition, the bundle and/or the strands may be coated with a second material selected
from the group of metal, polymers, teflon, rubber or a combination thereof.
[0018] Further, the strands may be twisted around each other, braided, or may form a yarn.
[0019] Also, the strands may enclose a core.
[0020] The annular barrier according to the present invention may furthermore comprise a
tubular part for mounting as part of the well tubular structure, said tubular part
having a longitudinal axis, an expandable sleeve surrounding the tubular part and
defining a space being in fluid communication with an inside of the tubular part,
each end of the expandable sleeve being connected with the tubular part, and an aperture
for letting fluid into the space to expand the sleeve.
[0021] In one embodiment, the annular barrier may be a packer arranged to seal against an
inner surface of a well tubular structure.
[0022] The annular barrier as described above may further comprise adhesive between the
outer face and the annular seal.
[0023] The present invention further relates to a downhole annular seal comprising:
- a sealing material having at least one strand comprising graphite and/or carbon.
[0024] Also, the present invention relates to a downhole system comprising a well tubular
structure and at least one annular barrier as described above, wherein the annular
barrier comprises a tubular structure mounted as part of the well tubular structure.
[0025] The downhole system as described above may further have a tool comprising isolation
means isolating an isolated part of the inside of the tubular part outside the aperture
to pressurise the isolated part of the inside and the space to expand the expandable
sleeve.
[0026] Said tool may further comprise a pumping device for pumping fluid from the inside
of the tubular part being outside the isolated part and into the isolated part to
expand the expandable sleeve.
[0027] Additionally, the present invention relates to a manufacturing method for manufacturing
a annular barrier as described above, comprising the steps of:
- winding the sealing material around the outer face of the annular barrier to form
the annular seal,
- fastening the sealing material by providing adhesive between the sealing material
and outer face of the annular barrier.
[0028] Finally, the present invention relates to an application method of providing an annular
barrier in a casing or borehole, comprising the steps of:
- inserting an annular barrier in the casing or borehole having x windings of sealing
material around the outer face, where x > 1.0,
- expanding the annular barrier so that the annular barrier has y windings of sealing
material around the outer face, wherein x > y.
[0029] Said sealing material may have substantially the same length before and after expansion
of the annular barrier.
Brief description of the drawings
[0030] 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 in its unexpanded condition,
Fig. 2 shows the annular barrier of Fig. 1 in its expanded condition,
Fig. 3 shows another embodiment of the annular barrier,
Fig. 4 shows yet another embodiment of the annular barrier,
Fig. 5 shows en expanded view of part of Fig. 4 in which the annular barrier is unexpanded,
Fig. 6 shows en expanded view of part of Fig. 4 in which the annular barrier is expanded,
Figs. 7a-11b shows different embodiments of the annular seal seen in a cross-sectional
view and in a side view, and
Fig. 12 shows a downhole system.
[0031] 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
[0032] Fig. 1 shows an annular barrier 1 for providing zone isolation between a first zone
2 and a second zone 3 in a borehole 20 as illustrated in Fig. 2. The annular barrier
may also be set for providing zone isolation between a first zone 2 and a second zone
3 in a casing downhole, e.g. when arranging a production casing within an intermediate
casing. The annular barrier 1 has a circumference and an outer face 5 and comprises
several annular seals 4, each made of a sealing material 6 having a bundle 7 of strands
8 wherein at least one strand comprises graphite and/or carbon. In this way, the seals
of the annular barrier can withstand very high temperatures such as up to 650°C and
a high pressure such as up to 450 bar downhole. Seals of graphite or carbon are also
capable of withstanding hot steam, or other gasses, lyes, and acid, such as sulphur
and nitride. Known elastomeric seals are capable of withstanding such harsh downhole
conditions over a longer period of time, such over a time span of 10 to 20 years as
they dissolve or crack.
[0033] The annular barrier of Fig. 1 comprises a tubular part 9 for mounting as part of
the well tubular structure 10 having a longitudinal axis 11 and mounted as part of
a well tubular structure 10 for e.g. the production casing. The annular barrier 1
has an expandable sleeve 12 surrounding the tubular part and defining a space 13 being
in fluid communication with an inside 14 of the tubular part. Each end 15, 16 of the
expandable sleeve is connected with the tubular part in connection parts 17, and the
tubular part has an aperture 18 for letting fluid into the space 13 to expand the
sleeve. One end 15 is slidably connected with the tubular part 9 and seals 19 are
arranged in grooves 21 of the connection part 17 and the other end 16 is fixedly connected
with the tubular part 9. In the following,the annular barriers will be disclosed as
an annular barrier having the expandable sleeve and the tubular as just described,
but the annular barrier may also be a packer set between a first tubular 22 and second
tubular 23 as shown in Fig. 3, where projections 24 presses the annular seal 4 against
an inner face 25 of the second tubular 23.
[0034] As can be seen in Fig. 1, the sealing material of the annular seal extends around
the outer face of the annular barrier for one annular seal 4. The annular seal has
an elongated shape and two ends 27, 28 and the ends overlap so that one end 27 is
arranged outside the other end 28 of the annular seal 4. The sealing material is wound
around the outer face of the annular barrier with x windings, where x > 1.0. x is
1.0 if the ends 27, 28 face each other and x > 1.0 if one end 27 is arranged outside
the other end 28 of the annular seal 4 and lies in two layers at least partly around
the outer face. x is between 1.0 and 2.0 in Fig. 1 illustrating the annular barrier
in its unexpanded position, x is preferably between 1.1 and 1.7 and more preferably
between 1.2 and 1.5. In the unexpanded condition, the overlap extends over at least
10% of the circumference of the annular barrier, preferably at least 15% of the circumference,
more preferably at least 30%, and even more preferably at least 40% of the circumference.
The overlap depends on how much the outer diameter of the annular barrier is to be
increased during the expansion and thus depends on the differences in the circumference
before and after expansion.
[0035] When expanding the annular barrier 1, the sleeve 12 presses against the inner face
26 of the borehole 20 as shown in Fig. 2, pressing the annular seals against the inner
face 26 and thus squeezing the annular seals in between the sleeve and the inner face.
As the sleeve expands, the sealing material unwinds so that the ends 27, 28 of the
annular seal 4 no longer overlap as shown in Fig. 2.
[0036] In order to hold the sealing material in place during insertion of the annular barrier
down through the well, the annular barrier further comprises adhesive between the
outer face and the sealing material of the annular seal. The overlapping end 27 arranged
outside the innermost end 28 may also be adhered to the other end. After expansion,
the annular seal needs no longer to be adhered to the outer face as it is squeezed
in between the sleeve and the inner face 25.
[0037] In Figs. 1 and 2, the sealing material covers less than 40% of the outer face, and
covers, in Fig. 4, preferably less than 30% of the outer face, more preferably less
than 20% of the outer face.
[0038] In Fig. 4, the annular seals 4 are arranged in external safety sleeves 37 fastened
to the expandable sleeve 12 by a first connection 38 and a second connection 39. In
Fig. 4, the annular barrier 1 is shown in its expanded condition and in Fig. 5, an
expanded view of one of the external safety sleeves 37 of the annular barrier is shown
in an unexpanded condition of the annular barrier. Five annular seals are arranged
on the outer face of the annular barrier being on the outer face of the external safety
sleeve 37. In the unexpanded condition, the ends 27, 28 of the annular seals 4 overlap
as shown in Fig. 5. The external sleeve has a trapezoidal cross-sectional shape holding
the annular seals 4 closely together. In Fig. 6, the annular barrier has been expanded
and the annular seals 4 have been unwound so that the ends 27, 28 thereof no longer
overlap. In Fig. 6, fluid from one isolation zone has entered an opening 30 in the
external safety sleeve 37 and presses the annular seals even further against the inner
face 25 of the borehole 20.
[0039] As can be seen in Figs. 1-6, the cross-sectional shape of the annular seal is substantially
square, but may, in another embodiment, have another shape such as a triangular shape,
a pentagonal shape, a hexagonal shape, or a shape having more sides.
[0040] In Figs. 7a-11b,the different embodiments of the annular seal are shown. In Figs.
7a, 8a, 9a, 10a and 11a,the cross-section of the annular seal is shown, and Figs.
7b, 8b, 9b, 10b and 11b show the annular seal from a side. In Figs. 7a and 7b, bundle
7 of strands 8 is wound or braided together by means of another material 40 into a
yarn in which the four strands lie straight along the longitudinal extension of the
yarn so that they are substantially unbent. In Fig. 8a, the bundle 7 of strands 8
in which the strands 8 are braided itself forms the yarn-like pattern shown in Figs.
8a and 8b. In Fig. 9a, the bundle 7 of strands 8 are wound or braided together by
means of another material 40 into a yarn pattern 41 and the strands form a core 42.
In Fig. 10a, the bundle 7 of strands 8 are wound or braided around a core 42 of another
material. In Fig. 11a, the bundle 7 of strands 8 are twisted forming a coiling pattern
43 and the strands abut each other.
[0041] In Figs. 7a and 9a, the other material 40 may be a material selected from the group
of metal, polymers, teflon, rubber or a combination thereof. The bundle 7 of strands
8 may be coated with a second material selected from the group of metal, polymers,
teflon, an elastomeric material, silicone, or natural or synthetic rubber or a combination
thereof. In this way, the sealing ability of the annular seal is substantially increased.
[0042] Fig. 12 shows a downhole system 100 comprising a well tubular structure 10 and two
annular barriers having a tubular part 9 mounted as part of the well tubular structure
10. The downhole system 100 may further have a tool comprising isolation means isolating
an isolated part of the inside 14 of the tubular part outside the aperture 18 to pressurise
the isolated part of the inside 14 and the space 13 to expand the expandable sleeve
12. The tool may further comprise a pumping device for pumping fluid from the inside
of the tubular part being outside the isolated part and into the isolated part to
expand the expandable sleeve.
[0043] When manufacturing an annular barrier 1, the expandable sleeve 12 is fastened in
the connection parts 17 and the sealing material is wound around the outer face of
the annular barrier to form the annular seal. The sealing material is fastened to
the outer face by providing adhesive between the sealing material and the outer face
of the annular barrier. The annular barrier is then inserted into the casing or borehole
having x windings of sealing material around the outer face, where x > 1.0, and when
the annular barrier is subsequently expanded, the annular barrier has y windings of
sealing material around the outer face, wherein x>y.
[0044] The sealing material of each annular seal has substantially the same length before
and after expansion of the annular barrier and in this way, the strands are not broken
into several pieces which would ruin the sealing ability of the annular seal. Graphite
and carbon are not very bendable materials, but when they are being wound, some kind
of flexibility is then built into the annular seal 4.
[0045] When one end 27 of the annular seal overlaps the other end 28 and the expandable
sleeve 12 is expanded, the strands 8 may unwind themselves slightly so that the strands
of one end 27 lie in between the strands of the other end 28 of the annular seal,
and the annular seal in that section is thus wider than in other sections of the annular
seal.
[0046] An annular barrier may also be called a packer or similar expandable means. The well
tubular structure can be the production tubing or casing or a similar kind of tubing
downhole in a well or a borehole. The annular barrier can be used both in between
the inner production tubing and an outer tubing in the borehole or between a tubing
and the inner wall of the borehole. A well may have several kinds of tubing and the
annular barrier of the present invention can be mounted for use in all of them.
[0047] A valve may be arranged in the aperture 18 and the valve 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 aperture
may be arranged opposite a connection part and the connection part may have a fluid
channel fluidly connecting the aperture and the space 13.
[0048] The expandable sleeve may be an expandable tubular metal sleeve that is a cold-drawn
or hot-drawn tubular structure.
[0049] When the expandable sleeve 12 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 12 has an outside diameter 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.
[0050] Furthermore, the expandable sleeve 12 has a wall thickness which is thinner than
a length 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.
[0051] The expandable sleeve 12 of the annular barrier 1 may be made of metal, polymers,
an elastomeric material, silicone,or natural or synthetic rubber.
[0052] In order to increase the thickness of the sleeve 12, additional material may be applied
(not shown) onto the expandable sleeve, e.g. by adding welded material onto the outer
face.
[0053] In another embodiment, the thickness of the sleeve 12 is increased by fastening a
ring-shaped part onto the sleeve (not shown).
[0054] In yet another embodiment, the increased thickness of the sleeve 12 is facilitated
using a varying thickness sleeve 12 (not shown). To obtain a sleeve of varying thickness,
techniques such as rolling,extrusion or die-casting may be used.
[0055] The fluid used for expanding the expandable sleeve may be any kind of well fluid
present in the borehole surrounding the tool and/or the well tubular structure 3.
Also, the fluid may be cement, gas, water, polymers, or a two-component 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 between
the tubular part and the expandable sleeve before injecting a subsequent fluid into
the cavity.
[0056] By fluid or well fluid is meant any kind of fluid that may be present in oil or gas
wells downhole, such as natural gas, oil, oil mud, crude oil, water, etc. By gas is
meant any kind of gas composition present in a well, completion, or open hole, and
by oil is meant any kind of oil composition, such as crude oil, an oilcontaining fluid,
etc. Gas, oil, and water fluids may thus all comprise other elements or substances
than gas, oil, and/or water, respectively.
[0057] By a casing is meant any kind of pipe, tubing, tubular, liner, string etc. used downhole
in relation to oil or natural gas production.
[0058] In the event that the tool is not submergible all the way into the casing, a downhole
tractor can be used to push the tools all the way into position in the well. A downhole
tractor is any kind of driving tool capable of pushing or pulling tools in a well
downhole, such as a Well Tractor®. A downhole tractor may have wheels on arms projecting
from a tool housing of the tractor, or driving belts for moving the tractor forward
in the well.
[0059] 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.
1. An annular barrier (1) for providing zone isolation between a first zone (2) and a
second zone (3) in a borehole (20) or a casing downhole, said annular barrier having
a circumference and an outer face (5) and comprising an annular seal (4) comprising
a sealing material (6) having a bundle (7) of strands (8) wherein at least one strand
comprises graphite and/or carbon.
2. An annular barrier according to claim 1, wherein the sealing material is wound around
the outer face of the annular barrier with x windings, where x > 1.0.
3. An annular barrier according to claim 1 or 2, wherein the annular seal has an elongated
shape and two ends (27, 28) and extends around the outer face of the annular barrier.
4. An annular barrier according to claim 3, wherein the ends overlap.
5. An annular barrier according to claim 4, wherein the overlap extends over at least
10% of the circumference of the annular barrier, preferably at least 15% of the circumference,
more preferably at least 30%, and even more preferably at least 40% of the circumference.
6. An annular barrier according to any of the preceding claims, wherein the bundle and/or
the strands are coated with a second material selected from the group of metal, polymers,
teflon, rubber or a combination thereof.
7. An annular barrier according to any of the preceding claims, wherein the strands are
twisted around each other, braided, or forms a yarn.
8. An annular barrier according to any of the preceding claims, wherein the strands enclose
a core.
9. An annular barrier according to any of the preceding claims, wherein the annular barrier
comprises a tubular part (9) for mounting as part of the well tubular structure (10),
said tubular part having a longitudinal axis (11), an expandable sleeve (12) surrounding
the tubular part and defining a space (13) being in fluid communication with an inside
(14) of the tubular part, each end (15, 16) of the expandable sleeve being connected
with the tubular part, and an aperture (18) for letting fluid into the space to expand
the sleeve.
10. An annular barrier according to any of the preceding claims, further comprising adhesive
between the outer face and the annular seal.
11. A downhole annular seal comprising:
- a sealing material having at least one strand comprising graphite and/or carbon.
12. A downhole system comprising a well tubular structure and at least one annular barrier
according to any of claims 1-10, wherein the annular barrier comprises a tubular structure
mounted as part of the well tubular structure.
13. A manufacturing method for manufacturing a annular barrier according to any of the
claims 1-10, comprising the steps of:
- winding the sealing material around the outer face of the annular barrier to form
the annular seal,
- fastening the sealing material by providing adhesive between the sealing material
and outer face of the annular barrier.
14. An application method of providing an annular barrier in a casing or borehole, comprising
the steps of:
- inserting an annular barrier in the casing or borehole having x windings of sealing
material around the outer face, where x > 1.0,
- expanding the annular barrier so that the annular barrier has y windings of sealing
material around the outer face, wherein x > y.
15. An application method according to claim 14, wherein the sealing material has substantially
the same length before and after expansion of the annular barrier.