Thermal insulation of flexible pipes

(54) Title: THERMAL INSULATION OF FLEXIBLE TUBES (30) Unionist Priority: 02/10/2007 gb 0719215.6 (73) Holder (s): Wellstream International Limited (72) Inventor (s): Peter Raoul Williams (57) Summary: thermal insulation of flexible tubes. A flexible pipe body and a method for making a flexible pipe body are described. The flexible tube body includes an internal pressure sheath, at least one insulating layer comprising a mesh layer comprising a plurality of pockets and an outer sheath.

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100 • 106 “THERMAL INSULATION OF FLEXIBLE TUBES”

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Field of the Invention

The present invention relates to flexible tube bodies that can be used to form flexible tubes of the type suitable for transporting mineral oil, crude oil or similar production fluids. In particular, but not exclusively, the present invention relates to flexible pipe bodies having a thermal insulation layer formed as an interstitial layer with pocket of the flexible pipe body.

Fundamentals of the Invention

Traditionally, flexible tubes are used to transport fluids, such as oil and / or gas and / or water, from one location to another. The flexible tube is particularly useful in connecting an underwater location to a location at sea level. The flexible tube is generally formed of a set of a tube body and one or more end fittings. The tube body is typically formed as a composite of layered materials that form a fluid and pressure-containing duct. The structure of the tube allows great deflections without causing bending stresses that damage the functionality of the tube during its useful life. The tube body is generally, but not necessarily, constructed as a composite structure including metallic and polymer layers.

In many known flexible tube designs, the tube includes one or more layers of tensile protection. The main charge in such a layer is tension. In high pressure applications, such as in deep and ultra deep water environments, the traction protection layer experiences high voltage loads from the load of the internal pressure end cap as well as weight. This can cause the hose to fail since such conditions are experienced for extended periods of time.

The non-welded flexible pipe has been a qualifier for developments in deep water (less than 3,300 feet (1,005.84 meters)) and in ultra deep water (more than 3,300 feet) for 15 years. The technology enabled the industry to initially produce in deep water in the early 1990s and then in ultra-deep water at around 6,500 feet (1,981.2 meters) in the late 1990s. Water depths greater than 6,500 feet push the envelope where typical configurations of free-suspension elevating ducts and flexible tubes in general can operate.

It is the growing demand for oil that is driving exploration to take place at ever greater depths where environmental factors are more extreme. In such deep and ultra deep water environments, the temperature of the ocean floor increases the risk of production fluids cooling to a temperature that can lead to blockage of the pipe. For example, when transporting crude oil, blockage of the internal orifice of the flexible tube may occur due to the formation of paraffin. As a method of overcoming such problems, it has been suggested in the past that a thermal insulation layer should be provided around the barrier layer of a flexible tube, that layer being the layer that forms the internal orifice through which the fluid is transported. . The thermal insulation was, in some way, effective in isolating the internal orifice of the tube from the low external temperature thus helping to prevent blockage. However, the effects of the insulation provided were limited.

An additional problem with known insulation techniques is that the formation of insulation layers can be a complex process that involves careful alignment, heating and cooling steps during manufacture. It will be appreciated that prior known insulation techniques have appreciably increased the cost and time to manufacture the flexible pipe body.

Summary of the Invention

It is an objective of the present invention to at least partially alleviate the problems mentioned above.

It is an object of embodiments of the present invention to provide flexible tube bodies which can be used in flexible tubes of a type capable of transporting production fluids and which include at least one thermal insulation layer between an internal pressure sheath, such as a layer or barrier coating, and an external protective layer of the flexible pipe body.

It is an object of embodiments of the present invention to provide flexible pipe bodies that include one or more layers of insulation that are simple and quick to manufacture and yet provide a highly effective thermal resistance to prevent the flow of hot energy in the radial direction through the body. flexible tube.

It is an objective of modalities of the present invention to provide an elevating duct assembly, locking, flow line and / or a flexible pipe manufacturing method capable of operating in deep and ultra deep water environments.

According to a first aspect of the present invention, a flexible tube body is provided for a flexible tube, said flexible tube body comprising:

an internal pressure sheath;

at least one insulation layer comprising a mesh layer comprising a plurality of pockets; and an outer sheath.

In accordance with a second aspect of the present invention, a method is provided for making flexible pipe bodies, comprising the steps of:

provide an internal tubular pressure sheath;

forming an insulating layer comprising a mesh layer comprising a plurality of pockets on the inner pressure sheath; and forming an outer sheath layer over the insulation layer.

The embodiments of the present invention provide a flexible tube body in which a thermal insulation layer is formed between a barrier layer or coating and an outer sheath. One or more layers of insulation can be formed, each having a layer of mesh comprising a plurality of pockets. The mesh layer can be a reinforcement of filaments interlaced with holes between the filaments forming the pockets or it can be a sheet of material in which the pockets are formed by a plurality of through holes or blind holes.

The embodiments of the present invention provide an insulating layer that has a number of pockets in which an insulating fluid, such as air or gas or some other insulating material, such as airgel material, can be located.

The embodiments of the present invention provide a coaxial tube with at least one low conductivity insulation layer between an inner and outer layer of the tube. The insulating layer, which may be an armature or blade that appears stamped or other such structure, serves as a means of increasing the thermal resistance of the pipe wall. The tubing thus interstitially insulated will decrease the thermal loss of flowing fluid, such as crude oil, by delaying the start of paraffin crystallization and by delaying or preventing the deposition of solid material on an inner surface of the tube. As a result, the need to 'clean' the pipe can be delayed or eliminated.

Brief Description of Drawings

The modalities of the present invention will now be described below, by way of example only, with respect to the attached drawings, in which:

Figure 1 illustrates a flexible tube body;

Figure 2 illustrates a catenary elevating duct, flow line and locking;

Figure 3 illustrates an insulation layer;

Figure 4 illustrates holes in a network;

Figure 5 illustrates an armature; and

Figure 6 illustrates interlaced threads.

In the drawings, the reference numbers refer to similar parts.

Detailed Description of the Invention

Throughout this specification, reference will be made to a flexible tube. It is understood that a flexible tube is an assembly of a tube body part and one or more end fittings in each of which an end of the tube body is terminated. Figure 1 illustrates how the tube body 100 is formed according to an embodiment of the present invention from a composite of layered materials that form a pressure-containing duct. Although a number of particular layers are illustrated in Figure 1, it is understood that the present invention is widely applicable to composite tube body structures including two or more layers. Note also that the thickness of the layer is shown for illustrative purposes only.

As illustrated in Figure 1, a tube body typically includes an inner shell layer 101. The shell provides an iriter-interlocked metal construction that can be used as the innermost layer to completely or partially prevent the contraction of an inner pressure sheath 102 due to the decompression of the tube, internal pressure, pressure of protection against traction and mechanical crushing loads. It is appreciated that the modalities of the present invention are applicable to 'smooth bore' as well as such 'coarse bore' applications.

The internal pressure sheath 102 acts as a fluid retention layer and typically comprises a polymer layer that ensures internal fluid integrity. It is understood that this layer can comprise a number of sub-layers. It is appreciated that when the optional shell layer is used, the internal pressure sheath is often referred to as a barrier layer. In operation without such a housing (so-called smooth bore operation), the internal pressure sheath can be referred to as a liner.

A pressure protection layer 103 is a structural layer with an offset angle close to 90 ° that increases the resistance of the flexible tube to internal and external pressure and mechanical crushing loads. The layer also structurally supports the internal pressure sheath and typically consists of an interlocking metal construction.

The flexible tube body may also include one or more layers of tape 104 and a first layer of tensile protection 105 and a second layer of tensile protection 106. Each layer of tensile protection is a structural layer with an offset angle typically between 20 ° and 55 °. Each layer is used to support tensile loads and internal pressure. The tensile protection layers are typically coiled in pairs.

The flexible tube body also typically includes an outer sheath 107 which comprises a polymer layer used to protect the tube from penetration of seawater and other external environments, corrosion, abrasion and mechanical damage.

Each flexible tube comprises at least one part, sometimes referred to as a pipe body segment or section 100 together with an end fitting located on at least one end of the flexible tube. An end fitting provides a mechanical device that forms the transition between the flexible pipe body and a connector. The different pipe layers as shown, for example, in Figure 1, are terminated in the end fitting in such a way as to transfer the load between the flexible pipe and the connector.

Figure 2 illustrates an elevating duct assembly 200 suitable for transporting production fluid such as oil and / or gas and / or water from an underwater location 201 to a floating installation 202. For example, in Figure 2, underwater location 201 is an underwater flow line. The flexible flow line 203 comprises a flexible tube, completely or in part, resting on the seabed 204 or buried in the seabed and used in a static application. The floating installation can be provided by a platform and / or buoy or, as illustrated in Figure 2, a ship. The elevating duct 200 is supplied as a flexible elevating duct, that is, a flexible tube connecting the ship to the installation on the seabed.

It is appreciated that there are different types of elevating duct, as is well known to those skilled in the art. The modalities of the present invention can be used with any type of elevating duct, such as a freely suspended elevating duct (catenary elevating duct) restricted to some extent (buoys, chains), elevating duct totally contained or closed in a tube (tubes I or J).

Figure 2 also illustrates how the flexible pipe body parts can be used as a flow line 205 or lock 206.

With reference again to Figure 1, an insulation layer 108 is provided under the outer sheath 107. As illustrated in Figure 1, the insulation layer can be formed from multiple layers or, according to the modalities of the present invention, it can be be a single layer structure. The insulation layer 108 provides an interstitial layer in the coaxial tube and increases the interstitial thermal resistance to heat flow radially externally through the tube. The thermal energy leaving a transport fluid, running along the central orifice, and entering the cold submarine environment is thus decreased. It is appreciated that the flexible tube body 100 may include one, two or more layers of insulation located between the selected layers of the flexible tube body.

Figure 3 illustrates an example of an insulation layer 108 according to an embodiment of the present invention. The insulation layer includes an adjacent extruded layer 300, a honeycomb layer 301 and an external extruded layer 302. By forming an insulation layer 108, a radially inward extruded layer is formed during the manufacture of the tube and while it remains soft, a preformed honeycomb layer is formed around the inner extruded layer. The extruded layer will then solidify by 'locking' the mesh layer and the extruded layer together. The mesh layer 301 can be added in the form of a foil or it can suitably be preformed like a ribbon which can be wrapped around the extruded layer. Because of the fact that the extruded layer is soft when the mesh layer is introduced, the radially internal margin regions 303 of the mesh layer will descend into the extruded layer. The mesh layer 301 and the adjacent extruded layer 300 thus effectively become an integral layer. An additional external extruded layer 302 is then extruded over the type of the mesh layer 301 effectively placing the mesh layer between the two extruded layers 300, 302. The external extruded layer 302 is extruded in such a way that the external extruded layer is soft when it finds the mesh layer. The radially outer margin regions 304 will thus become embedded in an adjacent surface of the outer extruded layer 302 prior to the configuration of the outer extruded layer such that the adjacent extruded layer 300, the mesh layer 301 and the extruded layer 302 effectively become a layer unitary insulator. A transverse contact area offered by the insulating layer or layer within the insulating layer is reduced in relation to that offered by adjacent layers.

The mesh layer 301 includes a multitude of hexagonal units 305 (the one highlighted in Figure 3) connected together. A central region 306 in each hexagonal unit defines a pocket in which air is captured when the outer extruded layer 302 is extruded over the intermediate mesh layer 301 and the lower extruded layer 300. This captures air or any other such fluid in each pocket 306.

Appropriately, before extruding the outer layer 302 over the mesh layer, a material having a particularly low thermal conductance U can be introduced into the pockets. The fluid may be air, an inert gas or airgel material or the like. Such airgel insulation products typically have thermal conductivities in the range of 0.009 to 0.022 w / mk.

The 301 mesh layer is preformed with conventional techniques and can be manufactured from a wide variety of candidate materials such as stainless steel, titanium, constantan, monel, inconel alloy or incoloy alloy or the like. While Figure 3 illustrates a honeycomb pattern, Figure 4 illustrates how alternatively a wide variety of preformed metal layers or expanded metal layers can be used. Figure 4a illustrates how a notched orifice configuration can be used with elongated slits 400 being preformed in a metal body 401. Figure 4b illustrates how round holes 402 can be formed and Figure 4c illustrates how square holes can be formed. It is appreciated that the modalities of the present invention are not restricted to any specific preformed shape.

When generating the mesh layer 301, a metal blade is drilled to produce the pocket regions illustrated in Figures 3 and 4. It is appreciated that instead of drilling a metal blade with through holes, blind holes can alternatively be formed. Also, instead of using a perforated blade or blade including blind holes, an expanded metal mesh of material having, for example, a decorative structure or flat pattern can be used. It is appreciated that if blind holes are formed, then one of the inner or outer extruded layer 300, 302 can be omitted since the mesh layer itself includes the structure necessary to close an open side of each pocket.

Figure 5 illustrates how an interlaced layer 500 can be used as a mesh layer to form an insulating layer on the flexible tube body 100 according to alternative embodiments of the present invention. The interlaced mesh layer 500 shown in Figure 5 is illustrated as a flat reinforcement shown more clearly in Figures 6a and 6b in which the thermal resistance offered by the mesh layer can, in many respects, be determined by controlling the physical geometric parameters of the armor during manufacturing. As shown in Figure 6a, each armature has 600 ^ 600 warp threads₂ and weft threads 601 _B 601₂. The thickness d of the warp threads 600 can be greater, less than or equal to the thickness x of the weft threads 601. The open spaces 602 are formed between interlaced threads that form the pockets for the mesh layer in use.

As per the material of the perforated or expanded mesh layer noted above with respect to Figures 3 and 4, the threads of the armature 500 can be formed of any material having a sufficiently low thermal conductivity value k such that the insulating layer 108 offers thermal resistance in the flexible tube body 100. The suitable material for the threads is thus a metal layer such as titanium, uranium, constantan, inconel, monel, stainless steel or nickel-chromium or the like. Also, instead of a metal armor, threads can be manufactured from other types of material such as plastic materials such as a polymer resistant to compressive loads in the operating environment. A nylon like PA11 or PA12 or the like can be appropriately used.

It is appreciated that while the modalities of the present invention have been described above with respect to an insulating layer 108 formed of a layer of intermediate mesh and extruded outer layers, the modalities of the present invention may make use merely of a layer of mesh located among other layers flexible tube body. That is, omitting the extruded layers described above. In such cases, a layer of mesh of interlaced material or blade completely or partially perforated around an adjacent layer of the flexible pipe body with the covering layer of the flexible pipe body being formed thereon. This formation of an outer layer captures air or other insulating fluid in pockets formed by the mesh layer.

Suitably, a mesh layer as described above can be formed over a flexible pipe body layer and a layer of metal tape wrapped around the mesh layer. This helps to disperse the load in the flexible tube body and prevents deformation. A layer of high thermal resistance gel such as airgel can optionally then be formed on an outer surface of the rolled ribbon layer with an additional layer of the flexible tube body being formed on the gel layer. In this modality, extruded layers such as those noted above are also optional.

It is appreciated that while the modalities of the present invention have been described with respect to the use of a layer of metal mesh, the modalities of the present invention can use a plastic or other non-metallic material for the mesh layer. Appropriately, the mesh / reinforcement is not compressible such that the adjacent layers touch.

Throughout the description and claims of this specification, the words "understand" and "contain" and variations thereof, for example, "comprising" and "understand", mean "including, but not limited to", and are not intended to (and not the do) exclude other portions, additives, components, integers or steps.

Throughout the description and claims of this specification, the singular encompasses the plural unless the context requires otherwise. In particular, where the indefinite article is used, the specification is understood to encompass plurality as well as singularity, unless the context requires otherwise.

Characteristics, integers, compounds, chemical moieties or chemical groups described together with a particular aspect, the modality or example of the invention is understood to be applicable to any other aspect, modality or example described here unless incompatible with it.