DESCRIPTION

[0001] The present invention relates to an arrangement and installation method of data communication and electrical energy transmission lines on off shore double catenary risers, particularly steel lazy wave risers (SLWR).

[0002] In a typical configuration of deep-sea oil and gas production system, an assembly of valves and fittings used to regulate the inflow and outflow of products from and to a well, so called trees, are positioned on the seabed and floating units, so-called Floating Production Storage Offloading (“FPSO”) facilities, are positioned at sea level. The trees are fluidically connected with the Floating Production Storage Offloading (“FPSO”) facilities by rigid or flexible oil or gas conveying pipes, the so-called risers, which extend from the seabed up to sea level.

[0003] The movements of the FPSO are linked to those of the riser and movements and stresses are transmitted between these two structural sub-systems.

[0004] To withstand the dynamic mechanical loads, the internal fluid loads and the corrosive and chemical attack, the risers are usually made of carefully selected materials or material combinations, such as e.g. metallic materials for rigid risers, multiple composite material layers for flexible risers, so-called umbilical duct structures with dedicated ducting tubes (umbilical) inside an external protection tube, or composite polymeric material in pipes that are used in particularly challenging projects.

[0005] Among the known possible shape and boundary conditions of the risers, there are to be listed the multiple and compound catenary shapes, such as e.g. the so-called steel lazy wave catenary riser (SLWR) or the dormant riser, in which the tension of the upper portion of the riser is reduced at the expense of an increased length.

[0006] The steel lazy wave catenary riser shape is defined by:

[0007] - an upper catenary section extending from an upper hang off location at the FPSO (or generic vessel) with an upper hang off angle (usually measured with respect to a vertical reference axis) downwards and then transitioning in a sag bend having a lowest sag bend point,

[0008] - a buoyant section extending from the sag bend further upward and forming a hog bend of opposite curvature with respect to the sag bend and defining a highest hog bend point, so that the sag bend and the hog bend define a double curvature section having a vertical arch height (the height difference between the lowest sag bend point and the highest hog bend point) and an inflection location between the sag bend and the hog bend,

[0009] - a lower catenary section extending from a downward oriented end of the buoyant section further downward and then transitioning into a horizontal direction at a touch down location on the sea bed.

[0010] In order to accomplish monitoring functions and operational functions at the riser, along the riser, and at the well on the sea bed, electrical energy and data communication must be provided, both along the extension of the riser and at the seabed. For this purpose it is known to extend so-called umbilicals along the riser itself. The umbelical comprises data signal transmission cables (e.g. copper cables or fibre optical conductors) and/or electrical power cables (e.g. copper cables) protected by an external armature and typically extended and fixed along the riser during its assembly and laying procedure.

[0011] For deep waters, the design of such light dynamic umbilicals represents a significant challenge due to the great external pressure and the high bending and traction loads acting on the umbelical and subjecting copper cables and optical fibers to considerable stresses and deformations.

[0012] The only previously known way to reduce the stresses acting on the umbilical was to increase the mechanical strength and the dimension of the umbilical, especially of the external armature layer, which however causes installation problems (assembly, fixation, laying) and operational problems due to the increased space requirement near the riser structure. To reduce stresses on the umbilical, it is also thinkable to install the umbilical itself in a lazy wave configuration, at the cost of expensive additional buoyancy and a large clearance from other structures.

[0013] The aim of the present invention is therefore to propose a new and improved arrangement and a method for the installation of data communication and electrical energy transmission lines on double bend offshore risers, particularly steel lazy wave catenary risers (SLWR), in which the stresses acting on the data/energy transmission umbilical can be reduced without over dimensioning the external armature layer of the umbilical.

[0014] A further aim of the invention is to propose a new and improved arrangement and method for the installation of data communication and electrical energy transmission lines, in which the data/energy transmission umbilical does not interfere with the assembly and laying process of the riser and the data/energy transmission umbilical installation does not need to be coordinated or synchronized with the assembly and laying of the riser.

[0015] A further aim of the invention is to propose a new and improved arrangement and method for the installation of data communication and electrical energy transmission lines, in which the data/energy transmission umbilical is not required to follow the entire path and the entire dynamic deformations of the riser.

[0016] A further aim of the invention is to propose a new and improved arrangement and method for the installation of data communication and electrical energy transmission lines, in which the data/energy transmission umbilical is intended to be used independently from monitoring of the SLWR riser, for example for cost-effectively providing a power/communications umbilical to any subsea facility for the purpose of energizing, operating and communicating with functional modules of the subsea facility.

[0017] A further aim of the invention is to propose a new and improved arrangement and method for the installation of data communication and electrical energy transmission lines, in which the data/energy transmission umbilical has different longitudinal traction and pre tension along different sections thereof.

[0018] The aim of the invention is achieved by an arrangement of an umbilical, containing data communication and electrical energy transmission lines, at a steel lazy wave catenary riser, according to claim 1 .

[0019] The aim of the invention is also achieved by a method of installation of an umbilical, containing data communication and electrical energy transmission lines, at a steel lazy wave catenary riser, according to claim 10.

[0020] Advantageous and preferred embodiments are the subject of the dependent claims. [0021] In accordance with an aspect of the invention, an arrangement of an umbilical of data communication lines and/or electrical energy transmission lines mounted on a steel lazy wave catenary riser (SLWR) comprises:

A) the steel lazy wave catenary riser having:

[0022] - an upper catenary section extending from an upper hang off location (intended to be fixed at an FPSO or generic vessel) downwards and transitioning in a sag bend having a lowest sag bend point and an upward oriented end section,

[0023] - a buoyant section having buoyant devices attached to the riser and extending from the upward oriented end section of the sag bend further upward and forming a hog bend of opposite curvature with respect to the sag bend and defining a highest hog bend point and a downward oriented end section, so that the sag bend and the hog bend define a double curvature section and an inflection location between the sag bend and the hog bend,

[0024] - a lower catenary section extending from the downward oriented end section of the hog bend further downward and then converging towards a horizontal orientation at a touch down location on the sea bed,

[0025] wherein the riser extension has, in addition to the vertical component, a continuously growing horizontal component in a horizontal riser direction starting from the upper hang off location towards the touch down location,

B) the umbilical having:

[0026] - a first umbilical section extending from the upper hang off location continuously downward to a first installation point at the riser,

[0027] - a second umbilical section extending from a second installation point at the riser continuously downward to the sea bed near the touch down location,

[0028] wherein:

- the first installation point is positioned in an installation region of the riser between the lowest sag bend point and the highest hog bend point, and

[0029] - the first umbilical section is tensioned to have a flatter catenary shape than the catenary shape of the riser between the upper hang off location and the first installation point, so that between the upper hang off location and the first installation point the first umbilical section extends at a distance from the riser and is preferably not connected to the riser. [0030] With further advantage,

- also the second installation point is positioned in the installation region of the riser between the lowest sag bend point and the highest hog bend point, and

- the second umbilical section has a catenary shape with an opposite curvature to the curvature of the buoyant section, so that between the second installation point and the touch down location the second umbilical section extends at a distance from the riser and is preferably not connected to the riser.

[0031] Advantageously, the first umbilical section extends at a distance above and in the horizontal riser direction with respect to the riser between the upper hang off location and the first installation point, whereas the second umbilical section extends at a distance below and opposite the horizontal riser direction with respect to the riser between the second installation point and the touch down location.

[0032] To obtain this configuration, advantageously, the first and second umbilical sections have different (longitudinal) pretension forces, particularly the first umbilical section has a higher pretension force than the second umbilical section.

[0033] The arrangement according to the invention makes the umbilical partially independent from the riser deformations and movements. Thanks to the division and end-fixation of at least two independent umbilical sections, the dynamic loads and movements on the umbilical are reduced and the individual umbilical sections can be configured differently and prestressed differently. The mechanical connection and force transmission between the umbilical and the riser in the installation points can be made by means of dedicated riser clamping bodies, independently from the riser laying process, which simplifies the installation of the umbilical and reduces the overall cost of the riser-umbilical arrangement.

[0034] The first (upper) umbilical section can be conveniently and easily individually tensioned to sit above the riser and avoid any space violation. The only mild motions of the SLWR riser at the hog-bend, particularly near the inflection point between the hog bend and the sag bend, provide a very convenient anchor point for the umbilical sections.

[0035] The arrangement is very simple, easy to install, equally applicable to new riser installations and as a retrofit to already existing SLWR risers, at significantly reduced costs with respect to conventional riser-umbilical arrangements and installation methods.

[0036] These and other features and advantages of the present invention shall be made apparent from the accompanying drawings which illustrate embodiments of the invention, and, together with the general description of the invention given above, and the detailed description of the embodiments given below, serve to explain the principles of the present invention.

[0037] Brief description of the figures

[0038] Fig. 1 shows a steel lazy wave catenary riser (SLWR) extending from a Floating Production Storage Offloading (“FPSO”) facility to the seabed, and an initial phase of installation of a first section of a data/energy transmission umbilical (in the following “umbilical) from a deploy vessel,

[0039] Figs. 2 to 5 show a step of extending and installing the first (upper) section of umbilical at a SLWR riser between the FPSO vessel or an upper hang off location of the riser and a first installation point at the SLWR riser,

[0040] Fig. 6 shows the steel lazy wave catenary riser (SLWR) extending from the Floating Production Storage Offloading (“FPSO”) facility to the seabed, with the already installed first (upper) section of umbilical, and an initial phase of installation of a second section of the umbilical from the deploy vessel,

[0041] Figs. 7 to 9 show a step of extending and installing the second (lower) section of umbilical at the SLWR riser between the sea bed and a second installation point at the SLWR riser,

[0042] Figs. 10 and 11 show a step of extending and connecting a third (intermediate) section, a so-called jumper section, of umbilical at the SLWR riser between the first umbilical section at the first installation point and the second umbilical section at the second installation point,

[0043] Fig. 12 shows a step of extending and installing a branch line, or so-called flying lead, of umbilical at the SLWR riser from the jumper section or second umbilical section at the second installation point to a monitored location at the hog bend,

[0044] Fig. 13 shows a step of extending and installing a further branch line, or so-called flying lead, of umbilical at the SLWR riser from the first umbilical section at the first installation point to a further monitored location at the sag bend,

[0045] Fig. 14 shows a portion of the steel lazy wave catenary riser (SLWR) and a final situation of installation of the data/energy transmission umbilical,

[0046] Figures 15, 16 are perspective and cross-section views of an exemplary armored umbilical,

[0047] Fig. 17 is a lateral view of a portion of umbilical with an external bending restrictor sheath,

[0048] Figures 18 and 19 are prospective and partially broken away views of an exemplary Clevis type umbilical cable termination with support swivel and cable connector,

[0049] Figures 20A, 20B, 20C, 20D are perspective views and front views of a ROV (remotely operated vehicle) - applicable riser clamping body with a jaw actuator, multiple umbilical connector sockets and a jaw actuation interface,

[0050] Figures 21 A, 21 B are perspective views of a mud mat with umbilical connection sockets intended to pe placed on the sea bed,

[0051] Figures 22, 23 are perspective views of exemplary umbilical optical/electrical connector plugs,

[0052] Fig. 24 shows a steel lazy wave catenary riser geometry,

[0053] Fig. 25 illustrates an alternative embodiment to the embodiment shown in figure 13, in which only one installation structure (clamping body) is provided and the third (intermediate) section, the so-called jumper section, of the umbilical can be obviated.

[0054] Detailed description of embodiments

[0055] With reference to the figures, an arrangement 1 of an umbilical 19 of data communication lines and/or electrical energy transmission lines mounted on a steel lazy wave catenary riser 2 comprises A) the steel lazy wave catenary riser 2 having:

[0056] - an upper catenary section 3 extending from an upper hang off location 4 (intended to be fixed at an FPSO 5 or generic vessel 5) downwards and transitioning in a sag bend 6 having a lowest sag bend point 7 and an upward oriented end section 8, [0057] - a buoyant section 9 having buoyant devices 10 attached to the riser 2 and extending from the upward oriented end section 8 of the sag bend 6 further upward and forming a hog bend 11 of opposite curvature with respect to the sag bend 6 and defining a highest hog bend point 12 and a downward oriented end section 13, so that the sag bend 6 and the hog bend 11 define a double curvature section and an inflection location 14 between the sag bend 6 and the hog bend 11 ,

[0058] - a lower catenary section 15 extending from the downward oriented end section 13 of the hog bend 11 further downward and then converging towards a horizontal orientation at a touch down location 16 on the sea bed 17,

[0059] wherein the course (shape) of the riser has, in addition to the vertical component, a continuously growing horizontal component in a horizontal riser direction 18 starting from the upper hang off location 4 towards the touch down location 16.

[0060] The arrangement 1 further comprises B) the umbilical 19 having:

[0061 ] - a first umbilical section 20 extending from the upper hang off location 4 continuously downward to a first installation point 21 at the riser 2,

[0062] - a second umbilical section 22 extending from a second installation point 23 at the riser 2 continuously downward to the sea bed 17 near the touch down location 16.

[0063] In accordance with an aspect of the invention, the first installation point 21 is positioned in an installation region 24 of the riser 2 between the lowest sag bend point 7 and the highest hog bend point 12, and the first umbilical section 20 is tensioned to have a flatter catenary shape than the catenary shape of the riser 2 between the upper hang off location 4 and the first installation point 21 , so that between the upper hang off location 4 and the first installation point 21 the first umbilical section 20 extends at a distance from the riser 2 and is preferably not connected to the riser 2.

[0064] In accordance with an embodiment, also the second installation point 23 is positioned in the installation region 24 of the riser 2 between the lowest sag bend point 7 and the highest hog bend point 12, and the second umbilical section 22 has a catenary shape with an opposite curvature to the curvature of the buoyant section 9, so that between the second installation point 23 and the touch down location 16 or sea bed 17 the second umbilical section 22 extends at a distance from the riser 2 and is preferably not connected to the riser 2.

[0065] According to one embodiment, the first umbilical section 20 is mechanically connected to the riser 2 at the first installation point 21 and, possibly, also at the upper hang off location 4 (either directly or both are mechanically connected to the FPSO 5 or vessel 5). Similarly, the second umbilical section 22 is mechanically connected to the riser 2 at the second installation point 23 and, possibly also at the touch down location 16 (either directly or both are mechanically connected to a mud mat 44 or similar sea bed installation structure.

[0066] According to an alternative embodiment, the first umbilical section 20 is not mechanically connected to the riser 2 at the upper hang off location 4, but only at the first installation point 21 . In this embodiment, an upper end of the first umbilical section 20 can be mechanically anchored at the FPSO 5 or vessel 5 which in this case shall be interpreted as a whole as the upper hang off location 4.

[0067] Similarly, the second umbilical section 22 may be not mechanically connected to the riser 2 at the touch down location 16, but only at the second installation point 23. In this embodiment, a lower end of the second umbilical section 22 can be mechanically anchored at an anchoring structure at the seabed which in this case shall be interpreted as a whole as the touch down location 16.

[0068] Advantageously, the first umbilical section 20 extends at a distance above and in the horizontal riser direction 18 with respect to the riser 2 between the upper hang off location 4 and the first installation point 21 , whereas the second umbilical section 22 extends at a distance below and opposite the horizontal riser direction 18 with respect to the riser 2 between the second installation point 23 and the touch down location 16.

[0069] To obtain this configuration, advantageously, the first and second umbilical sections have different (longitudinal) pretension forces, particularly the first umbilical section 20 has a higher pretension force than the second umbilical section 22.

[0070] The arrangement according to the invention makes the umbilical 19 partially independent from the riser 2 deformations and movements. Thanks to the division and end- only-fixation of at least two structurally independent umbilical sections 20, 22, the dynamic loads and movements on the umbilical 19 are reduced and the individual umbilical sections 20, 22 can be configured differently and prestressed differently.

[0071] According to an embodiment (figures 2 to 5, 8 to 10) the mechanical connection and force transmission between the umbilical 19 and the riser 2 in the installation points 21 , 23 can be made by means of dedicated riser installation structures 34, 35, 36, such as clamping bodies, independently from the riser laying process, which simplifies the installation of the umbilical 19 and reduces the overall cost of the riser-umbilical arrangement 1.

[0072] The first (upper) umbilical section 20 can be conveniently and easily individually tensioned to sit above the riser 2 and avoid any space violation. The only mild motions of the SLWR riser 2 at the hog-bend 11 , particularly near the inflection point 14 between the hog bend 11 and the sag bend 6, provide a very convenient anchor point for the umbilical sections

20, 22.

[0073] The arrangement 1 is very simple, easy to install, equally applicable to new riser installations and as a retrofit to already existing SLWR risers, at significantly reduced costs with respect to conventional riser-umbilical arrangements and installation methods.

[0074] Advantageously, the installation region 24 is confined within a distance from the inflection location 14 smaller than 2%, preferably smaller than 1% of the riser 2 length. [0075] Ideally, the installation region 24 is at the inflection location 14. That means for practical applications, that the first installation point 21 and the second installation point 23 are preferably within an exemplary distance of max. 25 meters, preferably 15 meters, from the inflection location 14. The third umbilical section 26 (jumper) may have e.g. an exemplary length of less than 50 meters or of about 20m.

[0076] Detailed description of the electrical and data transmission line configuration

[0077] In accordance with an embodiment (figures 11 to 14), the umbilical 19 comprises a third (intermediate) umbilical section 26, a so-called jumper section, extended between the first installation point 21 and the second installation point 23 and making an electrical and/or data communication connection between the first umbilical section 20 and the second umbilical section 22.

[0078] Preferably, the third umbilical section 26 has a length greater than a straight distance between the first installation point 21 and the second installation point 23, in order prevent undesired tensioning of the third umbilical section 26 and to facilitate the manipulation of the ends of the third umbilical section 26 for the purpose of a, e.g. plug-in, data/electrical connection with the first umbilical section 20 at the first installation point 21 and with the second umbilical section 22 at the second installation point 23.

[0079] In accordance with an embodiment (figures 12, 13), the arrangement 1 comprises at least one or more branch lines 27, 28, 30, 32 comprising one or more of data transmission cables 47 and electricity cables 46, branched off from the umbilical 19 and extending to monitoring locations 29, 30 at the riser 2, e.g:

[0080] - a sag bend branch line 27 branched off the umbilical 19, e.g. at the first installation point 21 , and extending to a sag bend monitoring location 29 at the sag bend 6 of the riser 2, and/or

[0081] - a hog bend branch line 28 branched off the umbilical 19, e.g. at the second installation point 23, and extending to a hog bend monitoring location 30 at the hog bend 11 of the riser 2, and/or [0082] - an upper branch line 31 branched off the umbilical 19, e.g. at the upper hang off location 4, and extending to an upper monitoring location 32 along a portion of the upper catenary section 3 of the riser 2, and/or

[0083] - a lower branch line 25 branched off the umbilical 19, e.g. at the touch down location 16 or sea bed 17, and extending to a lower monitoring location 33 along a portion of the lower catenary section 15 of the riser 2.

[0084] In accordance with a further embodiment, the arrangement 1 comprises no branch lines at all along the length of the riser 2.

[0085] Detailed description of the installation points

[0086] The first installation point 21 and/or the second installation point 23 can be formed by one or more installation structures 34, 35, 36 having each a (reversable) mechanical riser coupler 37 for a (reversable) mechanical connection of the installation structure with the riser 2, and one or more (preferably detachable) mechanical pull resistant umbilical couplers 38 for a (preferably detachable) mechanical connection of the installation structure with the umbilical 19, i.e. the first umbilical section 20 and/or second umbilical section 22 and/or possibly third umbilical section 26.

[0087] For the purpose of making an electrical and/or data communication connection between the first and second and possibly third umbilical sections 20, 22, 26, as well as possible branch lines 27, 28, 30, 32, cable end connectors 39 of the umbilical sections 20, 22, 26, and possible branch lines 27, 28, 30, 32, e.g. plug-in connectors, are (preferably detachably) connectable directly with each other or with corresponding connecting sockets 40 of an electrical and data distribution device 41 onboard the installation structures 34, 35, 36. The electrical and data distribution device 41 comprises multiple communicating connecting sockets 40 to allow for multiple connections between the umbilical sections 20, 22, 26, and/or branch lines 27, 28, 30, 32.

[0088] In accordance with an embodiment (figures 2, 3, 13, 20A-20D) the first installation point 21 is formed by a first installation structure 34 having:

[0089] - a mechanical riser coupler 37 and

[0090] - a mechanical umbilical coupler 38 to which the first umbilical section 20 is mechanically pull-resisting coupled, and

[0091] - a first electrical and data distribution device 41 to which cable end connectors 39 of the first umbilical section 20, of the third umbilical section 23, and (only if provided) of at least a sag bend branch line 27 are or may be connected.

[0092] In accordance with a further embodiment (figures 8, 9, 13, 20A-20D) the second installation point 23 is formed by a second installation structure 35 having:

[0093] - a mechanical riser coupler 37 and

[0094] - a mechanical umbilical coupler 38 to which the second umbilical section 22 is mechanically pull-resisting coupled, and

[0095] - a second electrical and data distribution device 41 ’ to which cable end connectors 39 of the second umbilical section 22, of the third umbilical section 23, and (only if provided) a hog bend branch line 28 are or may be connected.

[0096] In accordance with an alternative embodiment (figure 25), the first installation point 21 and the second installation point 22 are formed both by one single installation structure 36 having:

[0097] - a mechanical riser coupler 37 and

[0098] - a mechanical umbilical coupler 38 to which the first umbilical section 20 and the second umbilical section 22 are mechanically pull-resisting coupled, and [0099] - a data distribution device 41 to which cable end connectors 39 of the first umbilical section 20, of the second umbilical section 22, (only if provided) of a hog bend branch line 28 and/or of a sag bend branch line 27 are or may be connected.

[00100] According to an embodiment (figures 4, 20A-20D), each of the installation structures 34, 35, 36 is configured as a self-supporting clamping body having further: [00101] - a crane rigging attachment interface 42 to allow the installation structure 34, 35, 36 to be lifted, lowered and positioned by a crane,

[00102] - a coupling actuation interface 43 adapted to be engaged and operated by a remotely operated subsea vehicle (ROV) for engaging and releasing the mechanical riser coupler 37.

[00103] The mechanical riser coupler 37 comprises advantageously hydraulically or mechanically actuatable opposing jaws.

[00104] In accordance with an embodiment (figures 6, 7, 21 A, 21 B) at the touch down location, the umbilical 19, especially the lower end of the second umbilical section 22, is mechanically connected with a mud mat 44 placed on the sea bed 17. Similar to the installation structure 41 , the mud mat 44 may also have a mechanical umbilical coupler 38 and an electrical and data distribution device 41 with multiple connecting sockets 40 for the electrical and data transmission connection of the (second umbilical section 22 of) umbilical 19 and of possible branch lines, e.g. the lower branch line 25.

[00105] In accordance with an embodiment, the arrangement 1 comprises riser monitoring instrumentation 45 comprising e.g. pressure sensor/s, temperature sensor/s, accelerometer/s, strain gauge/s, optical sensor/s, telecamera/s, etc., connected to the umbilical 19 and/or branch line/s 27, 28, 31 , 32.

[00106] In accordance with an embodiment (figures 15, 16), the umbilical 19 comprises one or more electrical conductors 46, e.g. copper cables, and/or one or more data transmission lines 47, e.g. electrical signal cables or optical signal cables, protected and wrapped by an external armature sheath 48.

[00107] In accordance with an embodiment (figures 18, 19), for the mechanical pull resisting coupling of the first umbilical section 20 and second umbilical section 22 in the first and second installation points 21 , 23, the first umbilical section 20 and second umbilical section 22 may comprise a reinforced (e.g. steel) mechanical coupling end portion 49, e.g. a tubular clevis body, having:

[00108] - a lateral aperture 50 through which a flexible cable end portion exits to the outside of the mechanical coupling end portion 49, and

[00109] - a hinge connecting portion 52 at an end of the mechanical coupling end portion 49.

[00110] In accordance with an embodiment, the arrangement 1 is used for riser 2 integrity monitoring.

[00111] As already mentioned above, the umbilical 19 may be provided for the purpose of energizing, operating, and communicating with, functional modules of the subsea facility. In this case the provision and connection of branch off lines at the riser 2 is not mandatory. Accordingly, the described embodiments of the arrangement 1 and of the installation structures 34, 35, 36 are to be alternatively understood as having been also described separate and independently from the branch off lines.

[00112] Detailed description of the installation method

[00113] In accordance with an embodiment, a method for installing an umbilical 19 of data communication lines and/or electrical energy transmission lines on a steel lazy wave catenary riser 2 for obtaining the arrangement 1 , comprises the step of A) installing the first umbilical section 20 (figures 1 to 6) by:

[00114] positioning a deploy vessel 53, different from the FPSO vessel 5 which defines the upper hang off location 4, above the installation region 24 of the riser and paying out and lowering the first umbilical section 20 from the deploy vessel 53 until a lower end of the first umbilical section 20 reaches the first installation point 21 in the installation region 24,

[00115] while the deploy vessel 53 holds an upper end of the first umbilical section 20, mechanically coupling the lower end of the first umbilical section 20 with the riser 2 in the first installation point 21 , preferably by using a remotely operated subsea vehicle 54,

[00116] moving the deploy vessel 53 to the FPSO vessel 5 and contemporaneously paying out an additional length of the first umbilical section 20 from the deploy vessel 53,

[00117] transferring the upper end of the first umbilical section 20 from the deploy vessel 53 to the FPSO vessel 5 and fixating the upper end of the first umbilical section 20 in the upper hang of location 4 of the riser 2 at the FPSO vessel 5,

[00118] tensioning the first umbilical section 20 to a flatter catenary shape than the catenary shape of the riser 2 between the upper hang off location 4 and the first installation point 21 , so that between the upper hang off location 4 and the first installation point 21 the first umbilical section 20 extends at a distance from the riser 2.

[00119] In accordance with an embodiment, the method comprises the step of B) installing the second umbilical section 22 (figures 6 to 9) by:

[00120] positioning the deploy vessel 53, different from the FPSO vessel 5 which defines the upper hang off location 4, above the touch down location 16 of the riser and paying out and lowering the second umbilical section 22 from the deploy vessel 53 until a lower end of the second umbilical section 22 reaches the touch down location 16,

[00121] while the deploy vessel 53 holds an upper end of the second umbilical 22, mechanically coupling the lower end of the first umbilical section 20 in the touch down location 16, preferably by using a remotely operated subsea vehicle 54,

[00122] moving the deploy vessel 53 to a location above the installation region 24 of the riser 2 and contemporaneously lowering the upper end of the second umbilical section 22 from the deploy vessel 53,

[00123] mechanically coupling the upper end of the second umbilical section 22 with the riser 2 in the second installation point 23, preferably by using a remotely operated subsea vehicle 54.

[00124] In accordance with an embodiment, the method comprises the step of C) making an electrical and/or data transmission connection between the first umbilical section 20 and the second umbilical section 22 in the installation region 24, e.g. by installing the third umbilical section 26 (figures 10 to 12) by:

[00125] mechanically coupling and electrically and/or data transmission connecting a first end of the third umbilical section 26 in the first installation point 21 , preferably by using a remotely operated subsea vehicle 54,

[00126] mechanically coupling and electrically and/or data transmission connecting a second end of the third umbilical section 26 in the second installation point 21 , preferably by using a remotely operated subsea vehicle 54.

[00127] In accordance with an embodiment, the method comprises the step of D) connecting to the umbilical 19 one or more branch lines 27, 28, 30, 32 comprising one or more of data transmission cables 47 and electricity cables 46, preferably using a remotely operated subsea vehicle 54, and extending the branch lines 27, 28, 30, 32 to monitoring locations 29, 30 at the riser 2 (figures 12 to 14).

[00128] In accordance with an embodiment, the step A) comprises the step of coupling the lower end of the first umbilical section 20 to the first installation structure 34 or to the single installation structure 36 prior to lowering the first umbilical section 20 from the deploy vessel 53 and coupling the lower end of the first umbilical section 20 to the riser 2 by clamping the first installation structure 34 on the riser 2.

[00129] Similarly, in accordance with an embodiment, the step B) comprises the step of coupling the upper end of the second umbilical section 22 to the second installation structure 35 prior to lowering the upper end of the second umbilical section 22 from the deploy vessel 53 and coupling the upper end of the second umbilical section 22 to the riser 2 by clamping the second installation structure 34 on the riser 2.

[00130] In accordance with an embodiment, the step A) comprises:

[00131] - moving the deploy vessel 53 in a position above the installation region 24,

[00132] - preparing the deploy vessel 53 to spool out the first umbilical section 20 from an umbilical reel 55 onboard the deploy vessel 53,

[00133] - connecting the first installation structure 34 to a crane rigging 56 of the deploy vessel 53,

[00134] - connecting a coupling end portion 49 (initiation head) of the lower end of the first umbilical section 20 to the first installation structure 34,

[00135] - lifting the first installation structure 34 and placing the first umbilical section 20 into a VLS (vertical lay system) tensioner 57 onboard the deploy vessel 53,

[00136] - lowering the first installation structure 34 to the installation region 24, and contemporaneously paying out the first umbilical section 20 from the umbilical reel 55, [00137] - installing the first installation structure 34 on the riser 2 in the first installation point 21 by ROV 54,

[00138] - disconnecting the crane rigging 56 from the first installation structure 34,

[00139] - moving the deploy vessel 53 to the FPSO 5 and contemporaneously paying out the first umbilical section 20 from the umbilical reel 55,

[00140] - connecting a coupling end portion 49 (termination head) of the upper end of the first umbilical section 20 to the crane rigging 56 of the deploy vessel 53,

[00141] - using a crane of the deploy vessel 53 to hang-off the coupling end portion 49 (termination head) of the upper end of the first umbilical section 20 in the upper hang off location 4 at the FPSO 5.

[00142] In accordance with an embodiment, the step B) comprises:

[00143] - moving the deploy vessel 53 in a position above the touch down location 16, [00144] - preparing the deploy vessel 53 to spool out the second umbilical section 22 from an umbilical reel 55 onboard the deploy vessel 53,

[00145] - connecting the mud mat 44 to a crane rigging 56 of the deploy vessel 53,

[00146] - connecting a coupling end portion 49 (initiation head) of the lower end of the second umbilical section 22 to the mud mat 44,

[00147] - lifting the mud mat 44 and placing the second umbilical section 22 into a VLS (vertical lay system) tensioner 57 onboard the deploy vessel 53,

[00148] - lowering the mud mat 44 to (a touch down template in the) the touch down location 16, and contemporaneously paying out the second umbilical section 22 from the umbilical reel 55,

[00149] - positioning and placing or fixating the mud mat 44 in the touch down location 16, possibly by means of a ROV 54,

[00150] - laying the second umbilical section 22 by moving the deploy vessel 53 to a position above the installation region 24 and contemporaneously lowering the second umbilical section 22, possibly by means of an auxiliary support line or by a crane onboard the deploy vessel 53, from the deploy vessel 53,

[00151] EITHER:

[00152] - connecting a coupling end portion 49 (termination head) of the upper end of the second umbilical section 22 to a second installation structure 35,

[00153] - connecting the second installation structure 35 to the crane rigging 56 of the deploy vessel 53 and lowering the second installation structure 35 from the deploy vessel down toward the second installation point 23,

[00154] - installing the second installation structure 35 on the riser 2 in the second installation point 23 by a ROV 54,

[00155] - disconnecting the crane rigging 56 from the second installation structure 35, [00156] OR:

[00157] - connecting a coupling end portion 49 (termination head) of the upper end of the second umbilical section 22 to the crane rigging 56 of the deploy vessel 53 and lowering the coupling end portion 49 of the upper end of the second umbilical section 22 from the deploy vessel down toward the second installation point 23,

[00158] - installing the coupling end portion 49 of the upper end of the second umbilical section 22 on the first (and single) installation structure 34 (figure 25) by a ROV 54,

[00159] - disconnecting the crane rigging 56 from the upper end of the second umbilical section 22.

[00160] Further details of the method have already been specified within the detailed description of the arrangement 1 and, even though these details have been described as functional features, they are to be understood also as method features and equally disclosed in relation to the installation method, and therefore not repeated here for the sake of conciseness.

[00161] The arrangement 1 is adavantageously used to:

[00162] - provide power and communication umbilical/s to the seabed, and/or

[00163] - provide power and communication transmission for a riser monitoring system, and/or

[00164] - retrofit an electrical energy transmission link and/or fiber optic signal transmission link between an existing FPSO 5 and a shore location or a sea bed location,

[00165] - provide power and communication transmission for resident AUVs (autonomous underwater vehicle) and a subsea IOT (Internet of things) infrastructure and data processing and transmission equipment.

[00166] The lazy wave catenary riser has been described as a steel riser for the purpose of example only. The riser 2 can be made of a different material or material combination. [00167] While the present invention has been illustrated by description of several embodiments and while the illustrative embodiments have been described in considerable detail, it is not the intention to restrict or in any way limit the scope of the appended claims to such detail. Additional advantages and modifications may readily appear to those skilled in the art.

Reference numerals

1 arrangement

2 riser

3 upper catenary section

4 upper hang off location

5 FPSO, vessel 6 sag bend

7 lowest sag bend point

8 upward oriented end section

9 buoyant section

10 buoyant devices

11 hog bend

12 highest hog bend point

13 downward oriented end section

14 inflection location

15 lower catenary section

16 touch down location

17 sea bed

18 horizontal riser direction

19 umbilical data/energy

20 first umbilical section

21 first installation point

22 second umbilical section

23 second installation point

24 installation region

25 lower branch line

26 third umbilical section

27 sag bend branch line

28 hog bend branch line

29 sag bend monitoring location

30 hog bend monitoring location

31 upper branch line

32 upper monitoring location

33 lower monitoring location

34 first installation structure

35 second installation structure

36 single installation structure

37 mechanical riser coupler

38 mechanical umbilical coupler

39 cable end connectors, 40 connecting sockets

41 , 41 ’ first and second electrical and data distribution device

42 crane rigging attachment interface

43 coupling actuation interface 44 mud mat

45 riser monitoring instrumentation

46 electrical conductor

47 data transmission lines

48 external armature sheath 49 coupling end portion (clevis)

50 lateral aperture

51 flexible cable end portion

52 hinge connecting portion

53 deploy vessel 54 ROV

55 umbilical reel

56 crane rigging

57 VLS (vertical lay system) tensioner