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WO2015033115A2 - Ensemble colonne montante et procédé - Google Patents

Ensemble colonne montante et procédé Download PDF

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Publication number
WO2015033115A2
WO2015033115A2 PCT/GB2014/052635 GB2014052635W WO2015033115A2 WO 2015033115 A2 WO2015033115 A2 WO 2015033115A2 GB 2014052635 W GB2014052635 W GB 2014052635W WO 2015033115 A2 WO2015033115 A2 WO 2015033115A2
Authority
WO
WIPO (PCT)
Prior art keywords
riser
point
assembly
buoyancy
riser assembly
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Ceased
Application number
PCT/GB2014/052635
Other languages
English (en)
Other versions
WO2015033115A3 (fr
Inventor
Yanqui Zhang
Zhimin Tan
Richard Alasdair Clements
Yucheng Hou
Jiabei YUAN
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Baker Hughes Energy Technology UK Ltd
Original Assignee
GE Oil and Gas UK Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by GE Oil and Gas UK Ltd filed Critical GE Oil and Gas UK Ltd
Publication of WO2015033115A2 publication Critical patent/WO2015033115A2/fr
Publication of WO2015033115A3 publication Critical patent/WO2015033115A3/fr
Anticipated expiration legal-status Critical
Ceased legal-status Critical Current

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Classifications

    • E—FIXED CONSTRUCTIONS
    • E21—EARTH OR ROCK DRILLING; MINING
    • E21B—EARTH OR ROCK DRILLING; OBTAINING OIL, GAS, WATER, SOLUBLE OR MELTABLE MATERIALS OR A SLURRY OF MINERALS FROM WELLS
    • E21B17/00—Drilling rods or pipes; Flexible drill strings; Kellies; Drill collars; Sucker rods; Cables; Casings; Tubings
    • E21B17/01—Risers
    • E21B17/015—Non-vertical risers, e.g. articulated or catenary-type

Definitions

  • the present invention relates to a riser assembly and method.
  • the present invention relates to a riser assembly suitable for use in the oil and gas industry, in which the configuration of the riser in the water is controlled.
  • Flexible pipe is utilised to transport production fluids, such as oil and/or gas and/or water, from one location to another.
  • Flexible pipe is particularly useful in connecting a sub-sea location (which may be deep underwater) to a sea level location.
  • the pipe may have an internal diameter of typically up to around 0.6 metres (e.g. diameters may range from 0.05 m up to 0.6 m).
  • Flexible pipe is generally formed as an assembly of a flexible pipe body and one or more end fittings.
  • the pipe body is typically formed as a combination of layered materials that form a pressure-containing conduit.
  • the pipe structure allows large deflections without causing bending stresses that impair the pipe's functionality over its lifetime.
  • the pipe body is generally built up as a combined structure including polymer and/or metallic, and/or composite layers.
  • a pipe body may include polymer and metal layers, or polymer and composite layers, or polymer, metal and composite layers.
  • the pipe body includes one or more tensile armour layers.
  • the primary loading on such a layer is tension.
  • the tensile armour layer may experience high tension loads from a combination of the internal pressure end cap load and the self-supported weight of the flexible pipe. This can cause failure in the flexible pipe since such conditions are experienced over prolonged periods of time.
  • buoyancy aids provide an upwards lift to counteract the weight of the riser, effectively taking a portion of the weight of the riser, at various points along its length. Employment of buoyancy aids involves a relatively lower installation cost compared to some other configurations, such as a mid-water arch structure, and also allows a relatively faster installation time. Examples of known riser configurations using buoyancy aids to support the riser's middle section are shown in Figs. 1a and 1 b, which show the 'steep wave' configuration and the 'lazy wave' configuration, respectively.
  • a riser assembly 200 suitable for transporting production fluid such as oil and/or gas and/or water from a subsea location to a floating facility 202 such as a platform or buoy or ship.
  • the riser may be provided as a flexible riser, i.e. including a flexible pipe, or as a composite riser, or a metallic riser, and includes discrete buoyancy modules 204 affixed thereto.
  • the positioning of the buoyancy modules and flexible pipe can be arranged to give a steep wave configuration 206 ! or a lazy wave configuration 206 2 .
  • Wave riser configurations as shown in Figs. 1a and 1 b may also be used in shallow water applications so as to allow for excursions of the vessel from the point where the riser contacts the sea bed.
  • a riser may be subject to dynamic loading due to conditions such as motion of a vessel or platform on the sea surface. Surge and heave motion of such surface vessel can cause curvature changes in a riser configuration. Strong currents may also have a similar effect. It is generally advantageous to prevent shape changes or control such changes within predetermined limits.
  • the attachment of buoyancy modules, for example in a wave configuration, is one technique for creating a pre-determined nominal shape without constraining the pipe, although the effects of surface motion or current motion are still significant in the upper section of the riser and in the areas of the sag and hog bends of the wave configuration.
  • a mid-water arch system has a comparatively higher degree of control and constraint on the pipe, as the pipe is typically clamped to a buoyancy module which has guides running across it for the pipe to lie in.
  • a buoyancy module which has guides running across it for the pipe to lie in.
  • the size and weight of such mid-water arches is such that the costs of design, manufacture and installation can be very high indeed.
  • WO2009/063163 discloses a flexible pipe including weight chains secured to a number of buoyancy modules on the pipe. The chains hang from the buoyancy modules, extending downwards to the sea bed and having an end portion lying on the sea bed.
  • Another known arrangement employs a mid-water arch structure (as briefly mentioned above), where a riser is laid over and attached to the mid-water arch, so that the weight of the riser in the water is partially taken by the mid-water arch, reducing tension loading and degrees of freedom of the pipe.
  • These structures tend to be difficult to install because they are secured to an anchor or gravity base on the seabed in a specific location, and also very expensive to install.
  • a riser assembly for transporting fluids from a sub-sea location, comprising:
  • buoyancy compensating element attached to the riser for providing positive, negative or neutral buoyancy to the riser
  • a tethering element connecting a first point of the riser with a further point of the riser so as to form a hog bend or a sag bend in the riser.
  • a method of supporting a flexible pipe comprising the steps of:
  • buoyancy compensating element attached to the riser for providing positive, negative or neutral buoyancy to the riser
  • a riser assembly can be provided with a predetermined and controlled shape in the water.
  • Certain embodiments provide the advantage that regions of a riser having the greatest curvature can be controlled to prevent overbending, which may otherwise damage the pipe structure and affect the lifetime of the pipe structure.
  • Certain embodiments provide the advantage that vertical movement of a riser can be controlled and/or reduced to prevent damage to the pipe structure.
  • Certain embodiments provide the advantage that a riser assembly and method of supporting a riser can be provided for use in water with relatively strong current and/or wave movement with reduced chance of damage to the flexible pipe structure, controlling the pipe configuration form but not constraining the pipe significantly.
  • Certain embodiments provide the advantage that a riser assembly can be provided at relatively low cost compared to some other known arrangements.
  • Fig. 1 a illustrates a known riser assembly
  • Fig. 1 b illustrates another known riser assembly
  • Fig. 2 illustrates a flexible pipe body
  • Fig. 3 illustrates another riser assembly
  • Fig. 4a illustrates a riser assembly
  • Fig. 4b illustrates an enlarged view of a portion of the riser assembly shown in Fig.
  • Fig. 5 illustrates another riser assembly
  • Fig. 6 illustrates another riser assembly
  • Fig. 7a and 7b illustrate another riser assembly
  • Figs. 8a and 8b illustrates another riser assembly
  • Fig. 9 illustrates a perspective view of a yet further riser assembly
  • Fig. 10 illustrates a plan view of an arrangement of riser assemblies
  • Fig. 11 illustrates another plan view of another arrangement of riser assemblies.
  • a flexible pipe is an assembly of a portion of a pipe body and one or more end fittings in each of which a respective end of the pipe body is terminated.
  • Fig. 2 illustrates how pipe body 100 is formed from a combination of layered materials that form a pressure- containing conduit. Although a number of particular layers are illustrated in Fig. 2, it is to be understood that the present invention is broadly applicable to coaxial pipe body structures including two or more layers manufactured from a variety of possible materials.
  • the pipe body may be formed from polymer layers, metallic layers, composite layers, or a combination of different materials. It is to be further noted that the layer thicknesses are shown for illustrative purposes only.
  • composite is used to broadly refer to a material that is formed from two or more different materials, for example a material formed from a matrix material and reinforcement fibres.
  • a pipe body includes an optional innermost carcass layer 101.
  • the carcass provides an interlocked construction that can be used as the innermost layer to prevent, totally or partially, collapse of an internal pressure sheath 102 due to pipe decompression, external pressure, and tensile armour pressure and mechanical crushing loads.
  • the carcass layer is often a metallic layer, formed from stainless steel, for example.
  • the carcass layer could also be formed from composite, polymer, or other material, or a combination of materials. It will be appreciated that certain embodiments are applicable to
  • the internal pressure sheath 102 acts as a fluid retaining layer and comprises a polymer layer that ensures internal fluid integrity. It is to be understood that this layer may itself comprise a number of sub-layers. It will be appreciated that when the optional carcass layer is utilised the internal pressure sheath is often referred to by those skilled in the art as a barrier layer. In operation without such a carcass (so-called smooth bore operation) the internal pressure sheath may be referred to as a liner.
  • An optional pressure armour layer 103 is a structural layer that increases the resistance of the flexible pipe to internal and external pressure and mechanical crushing loads.
  • the layer also structurally supports the internal pressure sheath, and typically may be formed from an interlocked construction of wires wound with a lay angle close to 90°.
  • the pressure armour layer is often a metallic layer, formed from carbon steel, for example.
  • the pressure armour layer could also be formed from composite, polymer, or other material, or a combination of materials.
  • the flexible pipe body also includes an optional first tensile armour layer 105 and optional second tensile armour layer 106.
  • Each tensile armour layer is used to sustain tensile loads and internal pressure.
  • the tensile armour layer is often formed from a plurality of wires (to impart strength to the layer) that are located over an inner layer and are helically wound along the length of the pipe at a lay angle typically between about 10° to 55°.
  • the tensile armour layers are often counter-wound in pairs.
  • the tensile armour layers are often metallic layers, formed from carbon steel, for example.
  • the tensile armour layers could also be formed from composite, polymer, or other material, or a combination of materials.
  • the flexible pipe body shown also includes optional layers of tape 104 which help contain underlying layers and to some extent prevent abrasion between adjacent layers, the tape layer may be a polymer or composite or a combination of materials.
  • the flexible pipe body also typically includes optional layers of insulation 107 and an outer sheath 108, which comprises a polymer layer used to protect the pipe against penetration of seawater and other external environments, corrosion, abrasion and mechanical damage.
  • Each flexible pipe comprises at least one portion, sometimes referred to as a segment or section of pipe body 100 together with an end fitting located at at least one end of the flexible pipe.
  • An end fitting provides a mechanical device which forms the transition between the flexible pipe body and a connector.
  • the different pipe layers as shown, for example, in Fig. 2 are terminated in the end fitting in such a way as to transfer the load between the flexible pipe and the connector.
  • Fig. 3 illustrates a riser assembly 300 suitable for transporting production fluid such as oil and/or gas and/or water from a sub-sea location 321 to a floating facility 322.
  • the sub-sea location 321 includes a sub-sea flow line.
  • the flexible flow line 325 comprises a flexible pipe, wholly or in part, resting on the sea floor 324 or buried below the sea floor and used in a static application.
  • the floating facility may be provided by a platform and/or buoy or, as illustrated in Fig. 3, a ship.
  • the riser assembly 300 is provided as a flexible riser, that is to say a flexible pipe 323 connecting the ship to the sea floor installation.
  • the flexible pipe may be in segments of flexible pipe body with connecting end fittings.
  • Fig. 3 also illustrates how portions of flexible pipe can be utilised as a flow line 325 or jumper 326.
  • Embodiments of the present invention may be used with any type of riser, such as a freely suspended (free, catenary riser), a riser restrained to some extent, totally restrained riser or enclosed in a tube (I or J tubes).
  • a freely suspended riser such as a freely suspended (free, catenary riser), a riser restrained to some extent, totally restrained riser or enclosed in a tube (I or J tubes).
  • Fig. 4 illustrates a riser assembly according to one embodiment.
  • the riser assembly 400 includes a riser 402, extending from a location at the seabed 406 to a floating vessel 404.
  • the riser itself may be a flexible pipe, for example as described above, and therefore for brevity will not be described in further detail.
  • the riser assembly 400 also includes at least one buoyancy compensating element 408 ⁇ attached to the riser for providing positive or negative buoyancy to the riser.
  • a buoyancy compensating element may either provide positive buoyancy to the riser (e.g. a buoyancy aid or buoyancy module), or provide negative buoyancy to the riser (e.g. a ballast weight).
  • the buoyancy compensating element is a buoyancy module providing upward lift to the riser, for supporting a section of the riser.
  • the buoyancy modules 408 the riser lies in the water in a 'wave' configuration.
  • five buoyancy modules 408 are shown in Fig. 4 as an example, it will be appreciated that any number of buoyancy modules, or buoyancy compensating elements, may be used depending on the specific requirements and circumstances of use.
  • the riser assembly 400 also includes a tethering element 410, which in this case is a length of metal chain 410.
  • the chain ties a first buoyancy module to a further buoyancy module, so as to urge the riser into a bend configuration.
  • the tethering element 410 has a length shorter than the length of flexible pipe between the points of tying, so as to create the formation of a hog bend.
  • the tethering element 410 has a length at least 5% shorter than the length of flexible pipe between the points of tying.
  • the chain connects a first point 416 of the riser (i.e. a first specific location along the riser) with a further point 418 of the riser (i.e. a further specific location along the riser) so as to form the hog bend 412 in the riser (as shown in Fig. 4b).
  • the chain connects the first and further points 416, 418 of the riser via buoyancy modules.
  • the chain may connect the first and further points of the riser via elements securing the buoyancy modules to the pipe.
  • formation of a hog bend 412 also leads to the formation of a sag bend 414.
  • a metal connector ring (not shown) is applied to each of the first buoyancy module and the further buoyancy module.
  • the connector ring (or alternatively two or more rings) acts to attach to the buoyancy module, and create an attachment point for the chain to be connected to.
  • the connector ring helps to achieve easy connection of tethering element to the riser, and thus easy installation of the riser assembly.
  • a clamp or other connecting device may be used, or the chain may be affixed directly to the buoyancy module or flexible pipe (without a connecting device).
  • a riser or flexible pipe may be supported in the water in a configuration such as that exemplified in Fig.
  • the at least one tethering element is generally in a taught configuration joining a first point of the riser to a further part of the riser so as to maintain the riser in a wave configuration.
  • the tethering element will generally be in tension.
  • adverse conditions for example rough seas or strong underwater currents, may cause the riser to adopt a wave configuration having a smaller radius of curvature. In this case the tethering element may become temporarily slackened. When normal conditions are resumed the tethering element will become taught again and will maintain the riser in the desired wave configuration.
  • the riser can be paid out from a vessel, with the at least one buoyancy compensating element being attached to the riser at a predetermined location as the riser is paid out.
  • the buoyancy compensating element(s) may have a connector ring also attached at the time of being attached to the riser.
  • the tethering element 410 can be attached to the buoyancy modules so as to achieve the final riser shape.
  • the necessary elements of the riser assembly may be provided in the factory at the stage of manufacture at the factory, or at the time of deployment of the riser, or a combination thereof.
  • the specific dimensions of the riser, the shape it assumes in the water, the buoyancy of the buoyancy modules, and the dimensions of the tethering element, etc. may be predetermined in accordance with the specific requirements for the particular use of the riser assembly.
  • the tethering element helps to control and support the shape of the riser in the water, to help prevent unwanted movement of the riser after installation.
  • the tethering element helps to prevent or reduce unwanted vertical movement of the riser caused by wave motion of the surface vessel or platform and/or motion from strong currents.
  • the tethering element may be made from chain, wire or fibre rope, strip(s) of tensionable material, bar or such like, suitable to apply the tension required between the first and further riser locations in order to create the desired shape in the flexible pipe.
  • the riser assembly may include a tethering element, e.g. a length of metal chain, to attach a first point on the riser to a further point on the riser, so as to urge the riser into a sag bend configuration.
  • a tethering element e.g. a length of metal chain
  • a chain may extend from a location on the riser 402 on the hog bend (e.g. at the buoyancy module 408 n ) to a position along the riser closer to the vessel, i.e. across the sag bend region 414.
  • Fig. 5 illustrates another riser assembly 500 according to a further embodiment.
  • the riser assembly 500 has several elements in common with the riser assembly 400 described above, which will not be described again for brevity. However, in this case the riser assembly 500 includes a tethering element 510 that is formed of a number of sub- elements.
  • the tethering element 510 includes a plurality of lengths of chain 5 ⁇ 6 ⁇ n .
  • the plurality of lengths of chain 516 -n are each connected at a common point and respectively extend to various points along the riser, in this embodiment via buoyancy modules.
  • each sub-element chain 516 1-n is predetermined so as to control the shape of the riser and urge the riser into a bend configuration.
  • each of the plurality of lengths of chain 516 ⁇ are generally in a taught configuration (i.e. in tension).
  • each length of chain will experience a different level of tension depending on where it is connected to the riser.
  • the chains extending approximately horizontally will experience greater tension than the chain extending approximately vertically.
  • Fig. 6 illustrates another riser assembly 600 according to a further embodiment.
  • the riser assembly 600 has various elements in common with the riser assembly 400 and 500 described above, which will not be described again for brevity.
  • a weight chain 618 is employed as a further sub-element of the tethering element 610.
  • the chain 618 is secured at one end to a position on the remainder of the tethering element, in this case to the common point where lengths of chain 616 1-n are connected (so as to spread any load relatively evenly).
  • the chain hangs down freely towards the sea bed 606. A remaining end of the chain 618 rests upon the sea bed 606. In this way a part of the weight chain rests on the seabed.
  • a top section of a weight chain may be replaced or provided by an alternative flexible filament such as a synthetic rope, wire, cable or the like.
  • a weight chain is secured at a lower end region of the filament so that again a portion of the weight chain rests upon the sea bed.
  • the weight chain itself may be trimmed at the sea bed during installation to ensure that a section of the chain remains on the sea bed at the lightest riser configuration.
  • the length of the chain on the sea bed will be determined for the largest potential change, for example in the riser contents.
  • a length of chain is attached to each selected buoyancy module or to the flexible pipe itself as it leaves an installation deck of an installation vessel and before it reaches the surface water.
  • the rest of the chain is then lowered into the water after it is attached to the flexible pipe or buoyancy module.
  • the riser is then paid out continually until the next buoyancy module reaches the installation deck for weight chain attachment.
  • weight chain in combination with the buoyancy modules and tethering element acts as a self-adjusting device for automatically maintaining a flexible pipe configuration. Also, the weight chain acts to increase the support and control the shape of the riser in the water to help prevent unwanted movement of the riser after installation. Particularly, the weight chain helps to restrict unwanted vertical movement of the riser after installation.
  • the upper portion of the tethering element i.e. chains 616 ⁇
  • a fixed structure which may for example be a gravity base (anchor weight) located on the seabed.
  • anchor weight anchor weight
  • a tether of rope or chain for example may be used to tie the upper portion directly to the fixed structure.
  • a weighting element such as a ballast weight hanging freely in the water (but not necessarily extending fully to the seabed or other structure), or to a buoyancy tank or element above a section of the riser, to which suitable lengths of chain are attached and which in turn attach at selected locations to the pipe, either directly or indirectly, to create the desired riser shape.
  • a ballast weight or buoyancy tank or element may help ensure the tethering elements retain the required configuration.
  • Fig. 7a illustrates another riser assembly 700 according to a further embodiment.
  • the riser assembly 700 is provided in a 'double wave' configuration.
  • the riser assembly 700 includes a tethering element 710 3 .
  • the tethering element 710 3 in this case includes a number of chains of predetermined length.
  • the chain 716 3 is secured at one end to a position on the flexible pipe, in this case to the riser 702.
  • the chain hangs down freely towards the sea bed 706. A remaining end of the chain 716 3 rests upon the sea bed 706.
  • the chains 716 ! and 716 2 attach to the chain 716 3 at a common point.
  • the chains each have a predetermined length, and the point of attachment is determined, so that the tethering element 710 3 is configured such that the central chain, 716 3 , extends to a lower overall height than the outer chains 716 1 2 .
  • the tethering element is therefore arranged to create the formation of a sag bend. It will be appreciated that other arrangements may be possible, with other numbers of chains or other sub elements, to form a sag bend in a riser.
  • fig. 7b illustrates another riser assembly, including a hog bend and a sag bend.
  • the additional tethering element 720 connects a first point of the riser to a second point of the riser so as to form a sag bend.
  • the additional tethering element 720 helps to maintain the sag bend configuration in the riser, along with the tethering element 710.
  • the tethering element 710 hangs from the riser to maintain the vertical position of the riser and maintain the lower portion of the sag bend in the desired position, as described above.
  • the optional additional tethering element 720 generally remains in tension (taught) and provides extra support to the riser, helping to keep the relevant portion of the riser in a sag bend shape, particularly during adverse sea conditions.
  • a buoyancy element may be attached (either directly or through suitable tethering means) to a central portion of the additional tethering element 720.
  • the chains connect first and further points of the riser directly.
  • the chains may connect to the riser via clamps or buoyancy modules or other intermediate feature, or directly onto at least one end fitting of a mid-line connection between two lengths of pipe, for example.
  • a weighting element such as a ballast weight hanging freely in the water (Fig. 8a or 8b).
  • a ballast weight would perform the task of ensuring the upper portion of the tethering element remains in the required configuration.
  • This configuration may also be inverted to use a buoyancy tank / element attached at multiple locations to the pipe, so also creating a hog bend or optionally a sag bend.
  • Fig. 8a illustrates another riser assembly 800 according to a further embodiment.
  • the tethering element 810 includes various sub elements including chains 8 ⁇ 6 ⁇ i _ n and a connector element 820, which in this case is a cylinder beam (spreader beam).
  • Each chain 816 -n is connected at one end to a respective buoyancy module 808 ⁇ and at its other end to the cylinder beam 820.
  • Figure 8b shows a similar arrangement from a perspective view.
  • At least one connector ring (not shown) is applied to each of the buoyancy modules.
  • the at least one connector ring acts to attach to the buoyancy module, and create an attachment point for the chain to be connected to.
  • a clamp or other connecting device may be used, or the chains may be affixed directly to the buoyancy module or flexible pipe (without a connecting device).
  • the cylinder beam 820 in this case is negatively buoyant, i.e. acting as a ballast weight.
  • the cylinder beam 820 therefore acts as a weighting element so as to ensure the chains ⁇ remain taught in the water.
  • the cylinder beam may alternatively be neutrally or positively buoyant.
  • the cylinder beam acts as a frame such that the remaining sub elements can be affixed thereto.
  • the cylinder beam may itself be constructed of suitable materials such as will provide the desired size shape and buoyancy. This may be determined as a fabricated steel or alloy tank filled with air (or another gas), water (or another liquid), or dense solid particles (for example sand or lead shot). Alternatively the cylinder beam may include a hollow polyurethane or polypropylene chamber; alternatively a steel or alloy sub-frame with a light, thin balloon or envelope attached at various locations to secure it to the sub-frame. It will be understood that other construction materials can also be envisaged.
  • the shape of the cylinder beam may be that of a cylinder, or barrel, or section of material of a suitable shape in order to provide sufficient stiffness through either material properties, design (second moment) or a combination of the two.
  • the effect of different shapes of the cylinder beam would likely require a change to the lengths of the chains 8 ⁇ 6 ⁇ n , minimising the risk of connecting chains to the incorrect positions on the pipe or the cylinder beam.
  • the chains 8 ⁇ 6 ⁇ i _ n each have a predetermined length, which has been calculated so that the shape formed by the riser assembly is a hog bend in the water. As shown in Fig. 8, the central chain has a length longer than the chains either side.
  • the specific dimensions of the chains and number of chains can be predetermined to suit the particular application of use, including the environmental conditions and the riser shape required.
  • the chains 816 ⁇ control the vertical movement of the riser pipe and to a lesser degree the lateral movement of the pipe, although the system as a whole is allowed to move together, within the limitations applied by the fixed ends of the pipe.
  • the chains 816 will be in tension due to the weight of the cylinder beam acting downwards towards the sea bed.
  • the tension in the chains helps to urge the riser into a hog bend configuration.
  • a sag bend can also be created using a cylinder beam and a number of chains.
  • the length of the chains can be adjusted accordingly to create the desired wave configuration. For example, for a weighted (negatively buoyant) cylinder beam, chains connected to the outer edges of the cylinder beam will need to be of longer length than those connected closer to the centre of the cylinder beam in order to create a sag bend.
  • the chains connected to the outer edges of the cylinder beam will need to be shorter than those connected closer to the centre of the cylinder beam in order to form a sag bend.
  • the buoyancy of the cylinder beam will provide an upward force acting on the chains, keeping them in tension during use and urging the riser into a sag bend configuration.
  • Fig. 9 illustrates another riser assembly 900 according to a further embodiment.
  • the riser assembly 900 has chains 916 1-n and a cylinder beam 920 in common with the riser assembly 800 described above, which will not be described again in detail for brevity.
  • the cylinder beam 920 is itself tethered to a fixed structure, in this case a heavy, concrete base 922 located on the seabed. The concrete base acts as an anchoring element.
  • the cylinder beam 920 is tethered at two points via four ropes 924 ⁇ to four points on the concrete base 922, respectively.
  • This embodiment requires that the tethering element is tied to a fixed location in the water. This helps to not only control the shape of the riser's hog bend but also control the accuracy of the position of the riser overall with respect to other fixed structures, e.g. the seabed, or other relatively fixed structures, e.g. a vessel or other risers in the water.
  • the cylinder beam 920 is positively buoyant, though it may alternatively be negatively buoyant or neutrally buoyant.
  • the buoyancy of the cylinder beam may be predetermined in relation to the buoyancy of the riser and in relation to the contents of the riser in service (gas risers can be more positively buoyant than, for instance, a water injection riser).
  • the arrangement of Fig. 9 may be assembled, for example, as follows.
  • the concrete base 922 may be positioned on the seabed and tied to the cylinder beam 920, which has a positive buoyancy.
  • the buoyancy modules 908 ⁇ may be mounted to the riser whilst the riser is held on a laying vessel.
  • the riser is installed into the water, if necessary (i.e. if the pipe is itself not sufficiently negatively buoyant either un-filled or filled with water), with temporary ballast material to counteract the buoyancy modules during installation.
  • some or all of the buoyancy modules may be connected to the cylinder beam using chains 916 by divers or using a ROV (remotely operated underwater vehicle).
  • Figs. 10 and 11 show a plan view of other variations to the embodiment of Fig. 9.
  • Fig. 10 illustrates risers 1002 1 _ 3 with buoyancy modules ⁇ ⁇ extending from a vessel 1004 comprising a turret, to which the risers are connected.
  • each riser may be equipped with its own chain and cylinder beam 1020 configuration, but the cylinder beams are tied at different angles to two anchoring elements 1022 1 2 .
  • the cross-tethering of the cylinder beams may help to strengthen the structure of the overall arrangement.
  • rigid cross connecting elements may be used directly between cylinder beams, or even directly between the risers themselves using additional or common connection points on buoyancy or clamps.
  • the rigid connecting elements may be bars or tubes of metal or other suitable material but may also possess significant degrees of freedom of movement with respect to the risers at the respective connection points through the use or flexible or universal jointing systems, but be able to maintain a desired separation between adjacent risers due to their rigidity.
  • cross tethers or cross connecting elements it may be possible to reduce the number or size of the cylinder beams or anchoring elements 1022!, 2 .
  • Fig. 11 is similar to Fig. 10, showing three risers with buoyancy modules 1108 ⁇ and corresponding cylinder beams 1120 ⁇ with cross-tethering of cylinder beams to anchoring elements 1 122 1 2 via ropes 1124 ⁇ .
  • the risers are installed almost parallel as if hanging from the side of a platform or vessel.
  • the cylinder beam configurations may alternatively include a more complex framework of connecting elements for forming more complex structures to hold flexible pipes in a desired configuration.
  • the tethering element may be a rope or filament or cord, or cable, or the like, or a combination thereof.
  • the tethering element may also include other parts in addition to the chain, rope, filament, cord, cable, etc.
  • the tethering element is at least partly flexible. This may help the tethering element to react to various surrounding conditions, e.g. changes in the riser or movement of the surrounding water.
  • the tethering element 410 has a length (L te ) extending from the first point to the second point of the riser, and the riser has a length extending from the first point to the second point (L r ), and the length of the tethering element 410 (L te ) is shorter than the length of the riser between the first point and the second point (L r ).
  • buoyancy compensating elements described above have been usually described as positively buoyant, they could also be negatively buoyant, e.g. ballast weight, for use in risers that require the addition of negative buoyancy. Alternatively a combination of both buoyancy modules and ballast modules may be used.
  • buoyancy compensating elements could be any number, depending on the specific requirements of the particular use.
  • the buoyancy compensating elements may be attached to or integrated with the flexible pipe or riser.
  • riser extending between a floating facility (vessel) and the sea bed
  • riser could alternatively extend between fixed or floating platforms or other structures at different heights above or below sea level.
  • a riser assembly may be provided with a predetermined and controlled shape in the water. Also, regions of a riser having a relatively high curvature can have the shape controlled to prevent overbending of the riser. Enhanced support may be provided to the riser assembly, which leads to improved riser performance.
  • the riser assembly may provide the same precision shaping and control to a pipe as a known mid-water arch structure, but without the associated high costs.
  • a riser assembly may be provided for use in water with relatively strong current and/or wave movement with reduced chance of damage to the flexible pipe structure. For example, where two or more risers are positioned in relatively close proximity, wave action and/or currents may otherwise cause the risers to clash together. This is often possible, particularly in shallower waters or even deep waters. This may be particularly so because, in these types of waters, a hog bend/sag bend combination is frequently used to give the riser the flexibility to adapt to movement of the surface vessel (because the sag bend effectively allows some slack or a margin of error in the position of the riser relative to the vessel).
  • the corresponding hog bend may then induce a relatively large lateral drag force, particularly with a large number, or a large cross sectional area, of buoyancy compensating elements.
  • the riser assemblies described herein help to prevent such movement, and clashing with adjacent structures and the related damage, because of the superior control over the shape of the riser and position in the water.
  • tethering elements that extend to a fixed location, e.g. the seabed (or platform or other fixed structure)
  • a more precise control over the riser shape and location in the water can be achieved compared to known arrangements.

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  • Engineering & Computer Science (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Geology (AREA)
  • Mining & Mineral Resources (AREA)
  • Mechanical Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Environmental & Geological Engineering (AREA)
  • Fluid Mechanics (AREA)
  • General Life Sciences & Earth Sciences (AREA)
  • Geochemistry & Mineralogy (AREA)
  • Earth Drilling (AREA)
  • Sink And Installation For Waste Water (AREA)

Abstract

L'invention concerne un ensemble colonne montante et un procédé de support d'un tuyau flexible. L'ensemble comprend une colonne montante; au moins un élément de stabilisation fixé à la colonne montante pour fournir une flottabilité positive, négative ou neutre à la colonne montante; et un élément d'attache raccordant un premier point de la colonne montante à un autre point de la colonne montante de manière à former une courbure en arc ou en creux dans la colonne montante.
PCT/GB2014/052635 2013-09-04 2014-08-29 Ensemble colonne montante et procédé Ceased WO2015033115A2 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US14/018,313 US20150060079A1 (en) 2013-09-04 2013-09-04 Riser assembly and method
US14/018,313 2013-09-04

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WO2015033115A2 true WO2015033115A2 (fr) 2015-03-12
WO2015033115A3 WO2015033115A3 (fr) 2015-06-11

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US (1) US20150060079A1 (fr)
WO (1) WO2015033115A2 (fr)

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US10184589B2 (en) * 2015-03-04 2019-01-22 Ge Oil & Gas Uk Limited Riser assembly and method
US9797526B2 (en) * 2015-09-16 2017-10-24 Ge Oil & Gas Uk Limited Riser assembly and method of installing a riser assembly
WO2020117793A1 (fr) * 2018-12-03 2020-06-11 Bp Corporation North America, Inc. Systèmes et procédés d'accès à des conduits sous-marins
US11506319B2 (en) 2019-07-23 2022-11-22 Bp Corporation North America Inc. Hot tap assembly and method
US11781395B2 (en) 2019-07-23 2023-10-10 Bp Corporation North America Inc. Systems and methods for identifying blockages in subsea conduits
CN114884004B (zh) * 2022-05-10 2023-10-31 中天科技海缆股份有限公司 一种动态缆保护系统及风电系统

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CN110872942A (zh) * 2019-10-24 2020-03-10 中国石油化工股份有限公司 油藏注采耦合方式下不同作用力对采收率贡献的研究方法

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US20150060079A1 (en) 2015-03-05

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