WO2020057869A1

WO2020057869A1 - An end-fitting and an unbonded flexible pipe

Info

Publication number: WO2020057869A1
Application number: PCT/EP2019/071813
Authority: WO
Inventors: Jonas Gudme; Jan Rytter
Original assignee: National Oilwell Varco Denmark I/S
Priority date: 2018-09-19
Filing date: 2019-08-14
Publication date: 2020-03-26

Abstract

The present invention relates to an assembly of an end-fitting and an unbonded flexible pipe for offshore transport of oil and gas, where the unbonded flexible pipe comprises from the inside and out an internal pressure sheath, at least one metallic armour layer and an outer sheath such that the internal pressure sheath and the outer sheath form an annulus in which the at least one metallic armour layer is located. The unbonded flexible pipe is terminated in the end-fitting, and the end-fitting comprises a channel connecting the annulus and a cavity, where the cavity comprises a specimen and a window allowing inspection of the cavity from ambient. The invention also relates to a method for detecting water in an annulus of an unbonded flexible pipe.

Description

AN END-FITTING AND AN UNBONDED FLEXIBLE PIPE

TECHNICAL FIELD

The present invention relates to an assembly of an end-fitting and an unbonded flexible pipe for offshore transport of oil and gas, where the flexible pipe comprises a plurality of layers and an annulus comprising at least one metallic armour layer.

BACKGROUND Unbonded flexible pipes as well as end-fitting therefore and assemblies thereof are well known in the art and are for example described in

"Recommended Practice for Flexible Pipe", ANSI/API 17 B, fifth Edition, May 2014 (hereafter API17B), and the standard "Specification for Unbonded Flexible Pipe", ANSI/API 17J, Fourth edition, May 2014 (hereafter API 17J). Such unbonded flexible pipes usually comprise an internal pressure sheath also often called an inner sealing sheath, an inner liner or an inner sheath, which is the innermost sealing sheath and which forms a barrier against the outflow of the fluid, which is conveyed in the bore of the pipe. The pipe further comprises one or more armour layers, and an outer sheath which provides mechanical protection of the armour layers and isolates the armor layers from ambient.

The unbonded flexible pipes may for example be applied for carrying fluids between a hydrocarbon reservoir located under the seabed to either a junction point between subsea structures or from the seabed to a floating structure. The fluid may be a hydrocarbon fluid, such as natural gas or oil. The fluids may comprise water, CO2, H2S or a mixture hereof depending upon the nature of the hydrocarbon reservoir. The fluid may also be an injection fluid such as water, supercritical CO2 or methanol. Unbonded flexible pipes are e.g. used for the transport of oil and gas at large or intermediate sea depths. The mentioned construction is particularly well suited for the transport of oil and gas from subsea sources to installations at sea level where the oil and gas are being treated or forwarded for further processing such as for example by compression, filtering, separation, distillation and/or further treatment.

In this text the term "unbonded" means that at least two of the layers including the armouring layers and polymer layers are not bonded to each other. In practice, the known pipe normally comprises at least two armouring layers located outside the internal pressure sheath and optionally an armour structure, a carcass, located inside the internal pressure sheath.

In general, flexible pipes are expected to have a lifetime of about 30 years in operation.

An unbonded flexible pipe thus, comprise several independent layers, including helical wound steel layers, and extruded polymeric layers formed around a central bore. A typical steel armoured flexible pipe comprises from the inside and outwards an inner carcass armouring layer, an internal pressure sheath surrounded by one or more wound armouring layers, such as pressure armouring and tensile armouring, and an outer sheath. The internal pressure sheath forms a bore in which the fluid to be transported is conveyed and thereby ensures internal fluid integrity and stability. In some unbonded flexible pipes the carcass may be omitted, such pipes are denoted "smooth bore" pipe, while pipes comprising a carcass are denoted "rough bore" pipe.

In some unbonded flexible pipes only the pressure armour is made from steel whereas the tensile armour is made from fibre reinforced polymer

composites. In some unbonded flexible pipes only the tensile armour is made from steel whereas the pressure armour is made from fibre reinforced polymer composites. The annular space or spaces outside the internal pressure sheath, which houses the steel armour layers, are usually referred to as the annulus or annuli. Generally, the annulus is the space between the internal pressure sheath and the outer sheath and normally the annulus houses one or more armour layers.

The armouring layers usually comprise or consist of one or more helically wound elongated armouring elements, where the individual armour layers are not bonded directly or indirectly to each other or via other layers along the pipe. When the armour layers are wound at an angle larger than 55° relative to the pipe center axis they are classified as pressure armour layers, whereas armour layers wound with an angle of less than 55° are classified as tensile armour layers. By using un-bonded wound elements, the pipe becomes bendable and sufficiently flexible to roll up for transportation. The unbonded flexible pipe may comprise a carcass which is an armour layer arranged on the inner side of the internal pressure sheath in the bore. The pipe may also comprise one or more pressure armours and/or one or more tensile armours arranged on the outer side of the internal pressure sheath.

In certain unbonded flexible pipes one or more intermediate layers may be arranged under, over or between the armour layers in the annulus.

The annulus furthermore contains voids. Some of these voids are small spacings intentionally left between winding of the armour layers. These voids are instrumental in making the flexible pipe bendable.

Usually the end parts of an unbonded flexible pipe are terminated in an end- fitting. The end-fitting is usually coupled to the unbonded flexible pipe to terminate at least an outermost armor layer. In most situations the end- fitting is coupled to the unbonded flexible pipe to terminate all layers of the unbonded flexible pipe. The end-fitting must be able to withstand both the internal pressure of the pipe and to transfer axial forces from the pipe into the attached structure via a bolted or clamped connection. This requires high strength from a component partly or fully made from steel or another metal. As a consequence, the end-fitting is very rigid relative to the flexible pipe.

The polymer layers constituting the internal pressure sheath and the outer sheath (and optionally intermediate layers) are normally terminated in the end-fitting by means of clamping.

When a carcass is present in the bore of the pipe, the carcass is normally fixed or terminated in the end-fitting by means of a carcass ring. When the unbonded flexible pipe comprises a pressure armour, such a pressure armour is conveniently fixed in the end-fitting by clamping means.

When the pipe comprises one or more tensile armours, these armours are normally terminated in a fixation zone located in a fixation chamber in the end-fitting. The fixation chamber is normally formed between an inner casing and an outer casing of the end-fitting and when the end-fitting is terminating one or more tensile armours the fixation chamber is filled with a solidifying solid such as a resin like epoxy or concrete. During normal operation of the pipe water molecules may diffuse from the bore of the pipe through the internal pressure sheath and condense as droplets in the voids of the annulus. Also gasses like CO₂ and H₂S may migrate from the bore of the pipe into the annulus. Furthermore, water may diffuse from ambient into the annulus or water may enter the annulus if the pipe is damaged e.g. by outer sheath breach or seal failures.

During operation other gasses like e.g. CO₂ and H₂S may diffuse from the bore of the pipe into the annulus or annuli of the pipe. Over time the diffused gasses may cause the pressure in the annulus to rise, which can lead to bust of the outer sheath. To prevent this, gas vent valves are normally mounted in the end-fittings of the pipes, such that the gas pressure in the pipe is relieved when the pressure in the annulus significantly exceeds ambient pressure, as. e.g. described in API 17B, 5.2.4. The gas vent valves are connected to the annulus or annuli of the pipe via one or more channels in the end-fitting.

Ingress of gas and water into the annulus may result in a corrosive annulus environment. This may cause corrosion of the steel armour elements located in the annulus, eventually leading to premature failure of the pipe. Thus, it is desirable to have a method for detecting water and gasses in the annulus of the pipe.

One known method to test the annulus of a submerged flexible pipe is to use a ROV (remote operated vehicle) to dock a test-vessel with an internal pressure lower than the pressure in the annulus over one of the pipe vent valves. After docking, a valve is opened, and fluid is sucked from the annulus to the test-vessel. Hereafter the test-vessel is undocked and brought to a test facility where the liquid is analyzed. Although simple and straightforward, this strategy for annulus analysis is quite laborious, since a ROV in general only can hold one test-vessel. Thus, inspection of multiple pipe ends will require multiple ROV operations.

United States patent application US 2012/0211233 A1 discloses a solution by which the armour layers in a flexible pipe can be manually inspected via an inspection window in a scuttle. The scuttle must be mounted on the flexible pipe and requires a rather large intervention in the layers of the pipe.

Moreover, the scuttle itself is also rather complicated to mount and requires ring-shaped means for affixing and sealing which shall fit to the surface of the pipe with substantially no play.

DISCLOSURE OF THE INVENTION

An object of the present invention is to provide an assembly of an end-fitting and an unbonded flexible pipe and a method by which the presence of water in the annulus of the flexible pipe can be easily detected. A further possible object of the invention is to provide a method for estimating the chemical property of said water present in the annulus of a flexible pipe.

The present invention also provides a method for uncomplicated and cost- effective determination of the conditions in the annulus of the flexible pipe.

Thus, in a first aspect the present invention relates to an assembly of an end- fitting and an unbonded flexible pipe for offshore transport of oil and gas, said unbonded flexible pipe comprising from the inside and out an internal pressure sheath, at least one metallic armour layer and an outer sheath such that the internal pressure sheath and the outer sheath form an annulus in which the at least one metallic armour layer is located, said unbonded flexible pipe being terminated in the end-fitting, said end-fitting comprises a channel connecting the annulus and a cavity, said cavity comprising a specimen and a window allowing inspection of the cavity from ambient and optionally the specimen from ambient.

The term "ambient" means the exterior environment surrounding the assembly of the end-fitting and the unbonded flexible pipe. Thus, ambient may e.g. be sea water or the atmosphere. The specimen is an object capable of storing an agent which can react with e.g. water and other fluids. The specimen may be paper or fabric, such as cotton. The specimen may also be based on ceramic or metallic material, such as porous ceramic or metallic material.

The internal pressure sheath and the outer sheath are made from polymer material, which is substantially fluid-tight. In the annulus between the two polymer layers one or more metallic armour layers are located. Typically, the metallic armour layers are made from helically wound metallic strips, and typically the armour layers are formed as one or more tensile armours and/or pressure armour. The unbonded flexible pipe may also, if required, comprise an armour in the bore of the pipe, making the pipe resilient to external pressure, such an armour is denoted "carcass".

If more than one metallic armour layers are present in the annulus, the layers may be separated by intermediate layers of e.g. polymer. The polymer layers may be substantially fluid tight and divide the annulus into "sub-annuli".

Preferably both the internal pressure sheath and the outer sheath and optionally intermediate polymer layers are made from a substantially fluid tight and temperature tolerant (i.e. capable of operating in a temperature range from about -5 °C up to about 150 °C) material and preferably the sheaths are made from polymer material. The polymer material is e.g.

selected from polyolefins, e.g. polyethylene (PE) or polypropylene (PP);

polyamide, e.g. poly amide-imide, polyamide-11 (PA-11), polyamide-12 (PA- 12) or polyamide-6 (PA-6)); polyimide (PI); polyurethanes; polyureas;

polyesters; polyacetals; polyethers, e.g. polyether sulphone (PES);

polyoxides; polysulfides, e.g. polyphenylene sulphide (PPS); polysulphones, e.g. polyarylsulphone (PAS); polyacrylates; polyethylene terephthalate (PET); polyether-ether-ketones (PEEK); polyvinyls; polyacrylonitrils;

polyetherketoneketone (PEKK); copolymers of the preceding; fluorous polymers e.g. polyvinylidene diflouride (PVDF), homopolymers or copolymers of vinylidene fluoride ("VF2 "), homopolymers or copolymers of

trifluoroethylene ("VF3 "), copolymers or terpolymers comprising two or more different members selected from VF2, VF3, chlorotrifluoroethylene,

tetrafluoroethylene, hexafluoropropene, or hexafluoroethylene; compounds comprising one or more of the above mentioned polymers, and composite materials, such as a polymer (e.g. one of the above mentioned) compounded or otherwise reinforced with fibers, such as glass-fibers, carbon-fibers and/or aramide fibers.

The internal pressure sheath and the outer sheath in the unbonded flexible pipe according to the invention can be made from the same or different polymer material. The flexible pipe is terminated in an end-fitting, and the end-fitting preferably manufactured from steel, such as carbon steel, which is optionally coated with a protective coating.

The end-fitting comprises a channel which connect the annulus of the flexible pipe to a cavity with a window allowing external inspection of said cavity.

The channel itself can also be connected to ambient and be used to vent water and other fluids from the annulus. The end-fitting may comprise more than one channel to vent the annulus, not all the channels need to be connected with a cavity. The cavity comprises a specimen comprising agents which may dissolve in water or react with water, or other fluids from the annulus. The cavity need not be very large and may have a volume in the range 1 to 1000 cm³, such as in the range 10 to 500 cm³.

The cavity has a window allowing the cavity, and optionally the specimen in the cavity, to be inspected from ambient, thus, it is required that the cavity is located such that the window is easily accessible using e.g. a ROV. In and embodiment the cavity is integrated in the end-fitting, which provides a compact design of the end-fitting assembly

In an embodiment the cavity is in a housing attached to the end-fitting. Thus, the cavity may be located in a housing which is not an integrated part of the end-fitting, and it is possible to attach the housing on existing end-fittings already in operation. In this case the housing is preferably mounted near the exit opening of a vent channel connected with the annulus and the annulus in the housing may be connected with the channel by means of either a drilled hole in the end-fitting or via the vent valve already present on the end-fitting. Regardless how the cavity is implemented, it might be beneficial to route the vent channel outlet through the cavity, such that the content of the cavity reflects current fluid composition in the pipe annulus. An intermediate piece for connecting e.g. two end-fittings may also comprise the cavity and constitute the housing for the cavity.

The channel may be used to vent water, vapor and other fluids from the annulus to ambient and in an embodiment the channel in the end-fitting forms a connection between the annulus and ambient.

To ensure proper function of the assembly the channel may comprise one or more valves, which can control the flow through the channel, such as a flow from the annulus to ambient.

The connection between the channel and the cavity may be controlled by a valve to obtain more control over the function. Thus, in an embodiment of the assembly according to the invention, the channel and the cavity are in fluid communication via a valve.

The specimen located in the cavity preferably comprises a reactive or dissolvable agent. The reactive agent provides the option a detecting a certain condition in the cavity which is connected with the annulus such that the condition in the cavity corresponds to the condition in the cavity.

Optionally the reactive agent is contained in a material which is wettable. Moreover, it is clear that the specimen may contain several different agents, such that several different conditions can be detected. One condition which it is desirable to detect is the humidity or presence of water, thus, in an embodiment the specimen comprises one agent which dissolves in water, making it easy to distinguish an empty cavity from a cavity partly or completely filled with water.

Another condition which it is desirable to detect is the pH of water in the cavity due to e.g. CO₂ and in an embodiment the specimen comprises one agent which is either directly reactive with CO₂ or indicates the pH of the water which is a strong indication of the CO₂ content. Yet another condition which it is desirable to detect is the presence of H₂S and in an embodiment the specimen comprises one agent which is reactive with H₂S.

A conveniently way to detect the presence of a substance in a fluid or liquid is to use a dye which react with the substance and change color which can easily be detected by a visual inspecting device.

In one embodiment the specimen is impregnated with zinc oxide which is white. Upon exposure to H₂S, the zinc oxide forms zinc sulfide which is bright purple - thus color shift indicates presence of H₂S in the gas. As the fluid from the annulus may contain water it is desirable that the agent is water soluble.

In an embodiment the specimen comprises at least one agent which is a dye dissolvable in water. Examples of suitable dyes are Bromocresol Green,

Methyl Orange, Methyl Red or Phenol Red. These dyes have the additional advantage that their color depends on the acidity of the dissolvable fluid. Thus, once dissolved in water, the colour will reveal the water acidity.

As previously mentioned the flexible pipe comprises at least one metallic armour layer and in an embodiment the metallic armour layer is at least one tensile armour, which serves to take up tensile forces in the pipe.

Preferably the tensile armour is made from metallic elongate members where the elongate members are wound around the pipe with a winding angle of 25 to 55 degrees in respect of the axis of the pipe.

In an embodiment the flexible pipe comprises at least one metallic pressure armour to absorb pressure forces in the pipe.

The pressure armour can be made from metallic elongate members and in an embodiment the pressure armor comprises elongate metallic members wound around the pipe with a winding angle of 55 to 89 degrees, such as up to 89.8 degrees in respect of the axis of the pipe.

The tensile armor and the pressure armor can e.g. be made from carbon steel or stainless steel. The present invention also relates to a method for detecting water in an annulus of an unbonded flexible pipe for offshore transport of oil and gas said unbonded flexible pipe comprising from the inside and out an internal pressure sheath, at least one metallic armor layer and an outer sheath such that the internal pressure sheath and the outer sheath form an annulus in which the at least one metallic armor layer are located, said unbonded flexible pipe being terminated in an end-fitting, said end-fitting comprises a channel with a cavity comprising a window allowing inspection from ambient. The method comprises the steps of: placing a specimen sensible to water in the cavity, inspecting the cavity through the window, based on inspection of the cavity determine if water is present in the cavity and if water is present how the specimen has reacted with water.

Thus, as the cavity is connected with the annulus, the invention provides a surprising simple and efficient method for determining if water is present in the annulus.

The cavity is inspected through the window, and the inspection can be performed using any suitable device for inspection, such as a camera or optical detector. The window is preferably made from transparent material, such as glass or plastic material. The window should have a sufficient thickness to be able to resist ambient pressure at the intended location of installation. In an embodiment the window is detachable attached, such that the cavity can be accessed from ambient, e.g. for replacement of the specimen. In an embodiment of the method the channel can vent the annulus to ambient. Thus, water, CO₂, H₂S and other substances can be vented efficiently from the annulus to ambient.

It is desirable that the method also is capable of detecting other substances besides water and in and embodiment the specimen can react with water, e.g. C0₂, Na, Cl, and/or H₂S. The reactions with water, C0₂, Cl, Na and/or H₂S can be achieved by incorporation of e.g. dyes into the specimen, which dyes when dissolved in water reacts with water, CO₂ Cl, Na and H₂S and/or change colour. The change in colour can subsequently be found by inspection of the cavity.

Consequently, in an embodiment of the method the presence of water and a substance chosen among CO₂ Cl, Na and/or H₂S in the cavity and the annulus of the pipe can be determined by the reaction of the specimen.

In an embodiment of the method the pH of fluid in the cavity can be determined by the reaction of the specimen. The specimen may contain a dye which color is an indicator for the pH in a substance. Thus, the method can be used to determine the acidity of the fluids in the annulus of the pipe.

Although the inspection of the cavity through the window can be performed with any suitable means, such as e.g. manual inspection, the method provides an embodiment where the cavity is inspected by a ROV. A ROV is a well-known tool within the offshore industry and very suitable for inspection of the cavity. The ROV can be equipped with a camera, optical detector or other suitable detectors.

Throughout the description or claims, the singular encompasses the plural unless otherwise specified or required by the context.

It should be emphasized that the term "comprises/comprising" when used herein is to be interpreted as an open term, i.e. it should be taken to specify the presence of specifically stated feature(s), such as element(s), unit(s), integer(s), step(s), component(s) and combination(s) thereof but does not preclude the presence or addition of one or more other stated features.

The term "substantially" should herein be taken to mean that ordinary product variances and tolerances are comprised.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be explained more fully below with reference to the drawings in which:

Figure 1 shows an assembly of an end-fitting and an unbonded flexible pipe according to the invention;

Figure 2 shows a cross section of an assembly of an end-fitting and an unbonded flexible pipe according to the invention;

Figure 3 shows a cross section of an alternative embodiment of an assembly of an end-fitting and an unbonded flexible pipe according to the invention; and

Figure 4 shows a cross section of yet an alternative embodiment of an assembly of an end-fitting and an unbonded flexible pipe according to the invention.

The figures are schematic and simplified for clarity, and they show only details which are essential to the understanding of the invention, while other details are left out. The same reference numerals may be used for identical or corresponding parts.

Figure 1 illustrates an assembly 1 comprising an unbonded flexible pipe 2 and an associated end-fitting 3. Such assemblies are well-known within the offshore industry. As seen in the figure, the unbonded flexible pipe 2 comprises, from the inside an out, a carcass 10, an internal pressure sheath 11, a pressure armour 12, a tensile armour 13 and an outer sheath 14.

The carcass 10 is made from elongate members of stainless steel wound with a winding angle of approximately 85 degrees in respect of the axis 15. The pressure armour 12 is made from an elongate member of carbon steel and wound around the internal pressure sheath 11 with a winding angle of approximately 88 degrees in respect of the axis 15. The tensile armour 13 is also made from an elongate member of carbon steel and wound around the pressure armour with a winding angle of approximately 35 degrees in respect of the axis 15.

In this embodiment, the internal pressure sheath 11 and the outer sheath 14 are both substantially fluid tight and the space between the two layers forms the annulus of the pipe. The internal pressure sheath 11 is made from extruded polyethylene and the outer sheath 14 is made from extruded polyamide.

The end-fitting 3 comprises a body part 4, a neck piece 5 and a flange 6 for connection to a connector or another end-fitting. The flange 6 comprises holes 7 for bolts which may be used for the connection. The material of the end-fitting is carbon steel.

The body part 4 of the end-fitting comprises a valve device 43 which is in fluid communication with the annulus of the pipe and allows fluids from the annulus to be vented to ambient. The body part 4 of the end-fitting also comprises a window 44 allowing inspection of a cavity in fluid communication with the annulus of the pipe.

Figure 2 shows a cross section of an assembly 1 according to the present invention. The flexible pipe 2 enters the end-fitting 3 at the front end and the layers of the pipe 2 are terminated in the end-fitting 3.

The pipe 2 comprises from the inside and outwards the following layers: A carcass 10, an internal pressure sheath 11, a pressure armor 12, a tensile armor 13 and an outer sheath 14. The bore 26 of the pipe is surrounded by the internal pressure sheath.

The layers of the flexible pipe are all terminated in the end-fitting 3. The end- fitting 3 comprises an outer casing 30 and an inner casing 31. In a void 32 between the outer casing 30 and the inner casing 31, a fixation zone 33 is for the tensile armour 13 is formed.

The tensile armour layer 13 of the flexible pipe 2 is terminated in the end- fitting 3 and anchored in the fixation zone 33. In this embodiment, the tensile armor layer 13 is fixed by means of an epoxy resin which fills the void 32 forming the fixation zone 33. The other layers of the flexible pipe 2 are also terminated in the end-fitting 3 in a known manner. The pressure armor 12 is terminated in the end-fitting 2 at termination point 35. The internal pressure sheath 11 is terminated and fixed in the end-fitting by pressure means 36. The carcass 10 is terminated by the carcass ring 37. The outer sheath 14 is terminated in the end-fitting at point 38 and fixed in the end-fitting by pressure means.

A channel 40 is formed in the outer casing 30 between the annulus 16 of the pipe and the valve device 43. This channel 40 allows venting of the annulus 16 to ambient via the valve device 43. The channel 40 is in fluid connection with a cavity 42 by means of opening 41. The cavity 42 is at one end in the outer surface part of the outer casing 30 closes with a window 44. The window 44 allows inspection of the cavity from ambient and the cavity 42 may comprise a not shown specimen. The window 44 is attached to the outer casing 30 by suitable attachment means which provide a strong and fluid- tight connection between the window 44 and the outer casing 30. Figure 3 shows a cross section of an alternative embodiment of and assembly according to the present invention.

The flexible pipe 2a enters the end-fitting 3a at the front end and the layers of the pipe 2a are terminated in the end-fitting 3a. The pipe 2a comprises from the inside and outwards the following layers: An internal pressure sheath 11, a pressure armor 12, a tensile armor 13 and an outer sheath 14. Thus, the flexible pipe 2a is a "smooth bore" pipe without a carcass.

The layers of the flexible pipe are all terminated in the end-fitting 3. The end- fitting 3a comprises an outer casing 30 and an inner casing 31. In a void 32 between the outer casing 30 and the inner casing 31, a fixation zone 33 is for the tensile armour 13 is formed.

The tensile armour layer 13 is terminated in a conventional and well-known fashionin the end-fitting 3a and anchored in the fixation zone 33 by means of an epoxy resin which fills the void 32 forming the fixation zone 33.

The other layers of the flexible pipe 2 are also terminated in the end-fitting 3 in a known manner. The pressure armor 12 is terminated in the end-fitting 2 at termination point 35. The internal pressure sheath 11 is terminated and fixed in the end-fitting by an annular shaped clamping ring 39. The outer sheath 14 is terminated in the end-fitting at point 38 and fixed in the end- fitting by pressure means.

A venting channel 40 is formed in the outer casing 30 between the annulus 16 of the pipe and the valve device 43 for venting of the annulus 16 to ambient. The channel 40 is in fluid connection with a cavity 52 by means of opening 51. The cavity 52 is located inside a housing 50 which is attached to the outer surface of the outer casing 30. A window 54 in the housing 50 allows inspection of the cavity 52 from ambient and the cavity 52 may comprise a not shown specimen. The window 54 is attached to the housing 50 by suitable attachment means which provide a strong and fluid-tight connection between the window 54 and the housing 50. The housing 50 itself is attached to outer casing 30 and an strong fluid-tight connection using packings and bolts. The opening 51 may be pre-shaped in the outer casing 30 or formed subsequently, e.g. by drilling. Thus, the embodiment is also suitable for application on existing assemblies and end-fittings.

Figure 4 also shows a cross section of an alternative embodiment of and assembly according to the present invention. The flexible pipe 2b enters the end-fitting 3b at the front end and the layers of the pipe 2b are terminated in the end-fitting 3b.

The pipe 2b comprises from the inside and outwards only the following layers: An internal pressure sheath 11, a tensile armor 13 and an outer sheath 14. Thus, the flexible pipe 2b is also a "smooth bore" pipe without a carcass. Moreover, the pipe has no pressure armour.

The layers of the flexible pipe 2b are all terminated in the end-fitting 3b. The end-fitting 3b comprises an outer casing 30 and an inner casing 31. The layer of the flexible pipe are terminated in the end-fitting in a manner substantially corresponding to the termination of the layers of the embodiment of figure 3 described above except from the pressure armour which is not present in this particular embodiment.

A venting channel 40 is formed in the outer casing 30 between the annulus 16 of the pipe and the valve device 43 for venting of the annulus 16 to ambient. In this particular embodiment the end-fitting 3b is connected with and intermediate piece 60 by means of the holes 7, 67 and nuts and bolts 68.

The intermediate piece 60 comprises a cavity 62 which can be inspected from ambient via the window 64. The cavity 62 is connected with the valve device 43 for venting the annulus 16 by means of a tube 65. The tube 65 runs from valve device 43 to the cavity 62 over the end-fitting 3a and the intermediate piece 60 and enters the cavity 62 via a hole or opening 61 in the intermediate piece. Thus, the valve device 43 may conduct fluid from the annulus 16 to cavity 62 instead of releasing the fluid to ambient. In the cavity 62 the fluid may react with agents present in a not shown specimen. The result of the reaction may be inspected from ambient through the window 64. Thus in this embodiment the intermediate piece 60 forms a housing for the cavity.

The cavity 62 can be connected with not shown venting means allowing venting of fluid from the cavity if required.

As previously mentioned, the figures are schematic and simplified for clarity, and they show only details which are relevant in respect of the present invention. For example, the end-fittings may comprise several other parts than shown in the figures, such as bolts and other connection means, Moreover, the dimensions of some of the illustrated parts may be

exaggerated or not exactly correct.

The unbonded flexible pipe may also comprise more layers than the layers indicated in the figures. The pipe may e.g. comprise two pressure armor layers and two tensile armor layers and optionally one or more intermediate layers such as anti-wear layers and insulating layers.

Claims

1. An assembly of an end-fitting and an unbonded flexible pipe for offshore transport of oil and gas, said unbonded flexible pipe comprising from the inside and out an internal pressure sheath, at least one metallic armour layer and an outer sheath such that the internal pressure sheath and the outer sheath form an annulus in which the at least one metallic armour layer is located, said unbonded flexible pipe being terminated in the end-fitting, said end-fitting comprises a channel connecting the annulus and a cavity, said cavity comprising a specimen and a window allowing inspection of the cavity from ambient.

2. An assembly according to claim 1, where said cavity is integrated in the end-fitting

3. An assembly according to claim 1, where said cavity is located in a housing attached to the end-fitting

4. An assembly according to any one of the preceding claims, wherein a channel in the end-fitting forms a connection between the annulus and ambient.

5. An assembly according to any one of the preceding claims, wherein the cavity is coupled to a one-way valve which allows venting to ambient.

6. An assembly according to any one of the preceding claims, wherein the channel comprises one or more valves.

7. An assembly according to any one of the preceding claims, wherein the channel and the cavity are in fluid communication via a valve.

8. An assembly according to any one of the preceding claims, wherein the specimen comprises a reactive agent, optionally the reactive agent is contained in wettable material.

9. An assembly according to any one of the preceding claims, wherein the agent is dissolvable in water

10. An assembly according to any one of the preceding claims, wherein the agent is reactive with water

11. An assembly according to any one of the preceding claims, wherein the color of the agent depends on pH.

12. An assembly according to any one of the preceding claims, wherein the agent is reactive to H2S.

13 An assembly according to any one of the preceding claims, wherein the color of the agent depends on the chloride concentration in the water.

14. An assembly according to any one of the preceding claims, wherein the color of the agent depends on the sodium concentration in the water.

15. An assembly according to, any one of the preceding claims wherein the agent is a dye.

16. method for detecting water in an annulus of an unbonded flexible pipe for offshore transport of oil and gas said unbonded flexible pipe comprising from the inside and out an internal pressure sheath, at least one metallic armor layer and an outer sheath such that the internal pressure sheath and the outer sheath form an annulus in which the at least one metallic armor layer are located, said unbonded flexible pipe being terminated in an end-fitting, said end-fitting comprises a channel with a cavity comprising a window allowing inspection from ambient, wherein the method comprises the steps of: placing a specimen sensible to water in the cavity, inspecting the cavity through the window, based on inspection of the cavity determine if water is present in the cavity and if water is present how the specimen has reacted with water.

17. A method according to claim 16, wherein the channel can vent the annulus to ambient.

18. A method according to claim 16 and 17, wherein the specimen can react with water, CO2 and H2S.

19. A method according to any one of the preceding claims 16-18, wherein the specimen comprises an agent which is water soluble.

20. A method according to any one of the preceding claims 16-19, wherein the pH of fluid in the cavity can be determined by the reaction of the specimen.

21. A method according to any one of the preceding claims 16-20, wherein the presence of water, CO2 and H2S in the cavity can be determined by the reaction of the specimen.

22. A method according to any one of the preceding claims 16-21, wherein the cavity is inspected by a ROV.