SEALING MATERIAL FOR ANNULAR BARRIERS

Abstract

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, the annular barrier comprising a tubular part and an expandable element made of metal surrounding the tubular part, and the annular barrier having a circumference, a longitudinal extension and an outer face and further comprising an annular seal comprising a sealing material, the sealing material extending around the outer face of the annular barrier and having a bundle of strands wherein at least one strand comprises graphite and/or carbon.

Description

FIELD OF THE INVENTION

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. The invention furthermore relates to a downhole system and a method.

BACKGROUND ART

Annular barriers or packers downhole often comprise an 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 a casing or borehole.

When expanding annular barriers or packers, the sealing material is expanded accordingly, thereby decreasing the sealing ability. Furthermore, the sealing ability of the elastomeric material is decreased when subjected to the harsh environment downhole, such as high temperatures and pressure and different kinds of acid.

Annular barriers may be part of a 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. This means that when the annular barrier is eventually expanded, the sealing ability of the elastomeric material may be lost.

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 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.

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, the annular barrier comprising a tubular part and an expandable element made of metal surrounding the tubular part, and the annular barrier having a circumference, an longitudinal extension and an outer face and further comprising an annular seal comprising a sealing material, the sealing material extending around the outer face of the annular barrier and having a bundle of strands wherein at least one strand comprises graphite and/or carbon.

In one embodiment, the expandable element may be an expandable sleeve surrounding a tubular part and may be connected with the tubular part.

Furthermore, the expandable element may be one or more expandable tubes extending around the tubular part.

Moreover, the strands may comprise at least 30% graphite and/or carbon, preferably at least 50% graphite and/or carbon, more preferably at least 75% graphite and/or carbon, and even more preferably at least 90% graphite and/or carbon.

In addition, each strand may comprise graphite and/or carbon.

In an 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.

Also, the annular seal may extend around the outer face of the annular barrier.

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.

Further, the sealing material may be wound around the outer face of the annular barrier with x windings, where x>1.0.

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.

Additionally, the annular seal may have an elongated shape and two ends.

In one embodiment, the ends may overlap when seen in the longitudinal extension.

Furthermore, the annular seal may be arranged side by side around the outer face as windings.

Moreover, the windings may be arranged side by side around the outer face without any material between the windings.

Furthermore, the annular barrier may comprise several annular seals.

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.

Moreover, the strands may abut each other.

In addition, the bundle and/or the strands may be coated with a second material selected from the group of metal, polymers, teflon and rubber, or a combination thereof.

Further, the strands may be twisted around each other, braided or may form a yarn.

Also, the strands may enclose a core.

The present invention further relates to an annular barrier as described above, wherein the tubular part for mounting as part of the well tubular structure has a longitudinal axis, and the expandable sleeve surrounding the tubular part defines 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, wherein the annular barrier further comprises an aperture for letting fluid into the space to expand the sleeve.

In an embodiment, the expandable sleeve may be made of metal.

In another embodiment, the aperture may be arranged in the tubular part.

In yet another embodiment, the annular barrier may be a packer arranged to seal against an inner surface of a well tubular structure.

The annular barrier as described above may further comprise an adhesive between the outer face and the annular seal.

The present invention further relates to a downhole annular seal comprising:

• • a sealing material having at least one strand comprising graphite and/or carbon.

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.

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.

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.

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, and
  • fastening the sealing material by providing an adhesive between the sealing material and outer face of the annular barrier.

The present invention further 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, and
  • expanding the annular barrier so that the annular barrier has y windings of sealing material around the outer face, wherein y<x.

In an embodiment of the application method, x may be >1.5 and y may be >1.0.

When expanding the annular barrier, the winded sealing material unwinds itself, and as a result, the unwinded sealing material has y windings.

In another embodiment, the annular barrier may be expanded from a first diameter to a second diameter, the second diameter being larger than the first diameter.

Finally, the sealing material may have substantially the same length before and after expansion of the annular barrier.

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 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 show different embodiments of the annular seal seen in a cross-sectional view and in a side view, and

FIG. 12 shows a downhole system.

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

FIGS. 1 and 2 show an annular barrier 1 for providing zone isolation between a first zone 2 and a second zone 3 in a borehole 20. The annular barrier 1 may also be set to provide 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 an outer face 5 and a circumference varying from a first, unexpanded diameter to a second, expanded diameter. The annular barrier 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. Each strand comprises at least 30% graphite and/or carbon, preferably at least 50% graphite and/or carbon, more preferably at least 75% graphite and/or carbon, and even more preferably at least 90% 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 not capable of withstanding such harsh downhole conditions over a longer period of time, such as over a time span of 10 to 20 years, before they disintegrate, dissolve or crack.

The annular barrier of FIG. 1 comprises a tubular part 9 for mounting as part of the well tubular structure 10, the tubular part having a longitudinal axis 11 and being mounted as part of a well tubular structure 10 for e.g. production casing. The annular barrier 1 has an expandable element which in FIG. 1 is 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 barrier will be disclosed as an annular barrier having the expandable sleeve and the tubular just described, but the annular barrier may also be a packer set arranged between a first tubular 22 and second tubular 23, as shown in FIG. 3, where projections 24 press the annular seal 4 against an inner face 25 of the second tubular 23.

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 opposite 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 opposite the other end 28 of the annular seal 4 and lies in two layers at least partly around the outer face. In FIG. 1, the annular barrier is in its unexpanded position, and x is between 1.0 and 2.0, and may preferably be between 1.1 and 1.7 and more preferably between 1.2 and 1.5. When the annular barrier is in its 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 extent of the overlap depends on how much the outer diameter of the annular barrier is to be increased during the expansion, and thus on the differences in the circumference before and after expansion.

When expanding the annular barrier 1, the sleeve 12 presses against the inner face 26 of the borehole 20, as shown in FIG. 2, thus pressing the annular seals against the inner face 26 and thereby 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 (shown in FIG. 1) of the annular seal 4 no longer overlap, as shown in FIG. 2.

In order to hold the sealing material in place during insertion of the annular barrier down through the well, the annular barrier further comprises an adhesive between the outer face and the sealing material of the annular seal. The overlapping end arranged opposite the innermost end may also be adhered to the other end. After expansion, the annular seal no longer needs to be adhered to the outer face as it is squeezed in between the sleeve and the inner face 26. In FIGS. 1 and 2, the sealing material covers less than 40% of the outer face, and in FIG. 4, it covers preferably less than 30% of the outer face, and more preferably less than 20% of the outer face.

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 is shown in its expanded condition, and FIG. 5 shows an enlarged view of one of the external safety sleeves 37 of the annular barrier, the annular barrier being in its unexpanded condition. Five annular seals are arranged on the outer face of the annular barrier, i.e. on the outer face of the external safety sleeve 37. In the unexpanded condition of the annular barrier, 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, meaning that the ends of the annular seals 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 26 of the borehole 20.

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.

In FIGS. 7a-11b, the different embodiments of the annular seal are shown. In FIGS. 7a, 8a, 9a, 10a and 11a, cross-sections of the annular seal are shown, and FIGS. 7b, 8b, 9b, 10b and 11b show the annular seal from a side. In FIGS. 7a and 7b, the 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, braided strands 8 in a bundle 7 themselves form the yarn-like pattern shown in FIGS. 8a and 8b. In FIGS. 9a and 9b, the bundled 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 FIGS. 10a and 10b, the bundled strands 8 are wound or braided around a core 42 of another material. In FIGS. 11a and 11b, the bundled strands 8 are twisted forming a coiling pattern 43, and the strands abut each other.

In FIGS. 7a and 9a, the other material 40 may be a material selected from the group of metal, polymers, teflon and rubber, or a combination thereof. The bundle of strands 8 may be coated with a second material selected from the group of metal, polymers, teflon, an elastomeric material, silicone, natural or synthetic rubber or a combination thereof. In this way, the sealing ability of the annular seal is substantially increased.

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 an isolation means isolating an isolated part of the inside 14 of the tubular part opposite the aperture 18 to pressurise the isolated part of the inside 14 and the space 13 to expand the expandable sleeve. 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.

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 an 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. The sealing material extends around the outer face of the annular barrier so that the ends overlap when seen along in the longitudinal extension of the tool. The number of windings x before the annular barrier is expanded is typically between 3 and 100, depending on the length of the barrier. The number of windings y after expansion of the annular barrier is most often at least 1.0, preferably at least 1.5.

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 wound, some kind of flexibility is built into the annular seal 4. 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 between the strands of the other end 28 of the annular seal, and the annular seal in that section is thus wider than annular seals in other sections.

An annular barrier may also be called a packer or a 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.

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.

The expandable sleeve may be an expandable tubular metal sleeve which is a cold-drawn or hot-drawn tubular structure.

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, and more preferably an at least 30% larger diameter than that of an unexpanded sleeve.

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.

The expandable sleeve 12 of the annular barrier 1 may be made of metal, polymers, an elastomeric material, silicone or natural or synthetic rubber.

In order to increase the thickness of the sleeve 12, an additional material may be applied (not shown) onto the expandable sleeve, e.g. by adding welded material onto the outer face.

In another embodiment, the thickness of the sleeve 12 may be increased by fastening a ring-shaped part onto the sleeve (not shown).

In yet another embodiment, the increased thickness of the sleeve 12 may be facilitated by 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.

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.

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 oil-containing fluid, etc. Gas, oil, and water fluids may thus all comprise other elements or substances than gas, oil, and/or water, respectively.

By a casing is meant any kind of pipe, tubing, tubular, liner, string etc. used downhole in relation to oil or natural gas production.

In the event that the tool is not submergible all the way into the casing, a downhole tractor can be used to push the tool all the way into position in the well. The downhole tractor may have projectable arms having wheels, wherein the wheels contact the inner surface of the casing for propelling the tractor and the tool forward in the casing. A downhole tractor is any kind of driving tool capable of pushing or pulling tools in a well downhole, such as a Well Tractor®.

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

1-23. (canceled)

24. An annular barrier for providing zone isolation between a first zone and a second zone in a borehole or a casing downhole, the annular barrier comprising a tubular part and an expandable element made of metal surrounding the tubular part, and the annular barrier having a circumference, a longitudinal extension and an outer face and further comprising an annular seal comprising a sealing material, the sealing material extending around the outer face of the annular barrier and having a bundle of strands wherein at least one strand comprises graphite and/or carbon.

25. An annular barrier according to claim 24, wherein the strands comprise at least 30% graphite and/or carbon, preferably at least 50% graphite and/or carbon, more preferably at least 75% graphite and/or carbon, and even more preferably at least 90% graphite and/or carbon.

26. An annular barrier according to claim 24, wherein each strand comprises graphite and/or carbon.

27. An annular barrier according to claim 24, wherein the sealing material is wound around the outer face of the annular barrier with x windings, where x>1.0.

28. An annular barrier according to claim 24, wherein the annular seal has an elongated shape and two ends.

29. An annular barrier according to claim 28, wherein the ends overlap when seen in the longitudinal extension.

30. An annular barrier according to 28, wherein the annular seal is arranged side by side around the outer face as windings.

31. An annular barrier according to claim 30, 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.

32. An annular barrier according to claim 24, wherein the sealing material may cover less than 60% of the outer face, preferably less than 40% of the outer face, and more preferably less than 30% of the outer face.

33. An annular barrier according to claim 24, wherein 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.

34. An annular barrier according to claim 24, wherein the strands abut each other.

35. An annular barrier according to 24, wherein the strands are twisted around each other, braided or forms a yarn.

36. An annular barrier according to claim 24, wherein

the tubular part for mounting as part of the well tubular structure has a longitudinal axis, and

the expandable sleeve surrounding the tubular part defines 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, wherein the annular barrier further comprises an aperture for letting fluid into the space to expand the sleeve.

37. An annular barrier according to claim 24, wherein the aperture is arranged in the tubular part.

38. An annular barrier according to claim 24, further comprising an adhesive between the outer face and the annular seal.

39. A downhole system comprising a well tubular structure and at least one annular barrier according to claim 24, wherein the annular barrier comprises a tubular structure mounted as part of the well tubular structure.

40. A manufacturing method for manufacturing a annular barrier according to claim 24, comprising the steps of:

winding the sealing material around the outer face of the annular barrier to form the annular seal, and

fastening the sealing material by providing an adhesive between the sealing material and outer face of the annular barrier.

41. An application method of providing an annular barrier according to claim 24 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, and - expanding the annular barrier so that the annular barrier has y windings of sealing material around the outer face, wherein y<x.

42. An application method according to claim 41, wherein x>1.5 and y>1.0.

43. An application method according to claim 41, wherein the sealing material has substantially the same length before and after expansion of the annular barrier.