Patent Description:
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.

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

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.

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.

The steel lazy wave catenary riser shape is defined by:.

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 umbilical 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.

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.

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. Such prior art arrangements are know from for instance <CIT> which discloses a waved steel production riser, which in addition to a primary buoyancy section wherein the waved steel production riser is provided with a first set of external buoyancy modules and an upward buoyancy force in the body of water is greater than a downward gravity force, further comprises an auxiliary buoyancy section in the hanging section in which the waved steel production riser is provided with a second set of external buoyancy modules and wherein the upward buoyancy force in the body of water is smaller than the downward gravity force. The sag point is located within the auxiliary buoyancy section. The waved steel production riser may be used in a method for producing a hydrocarbon stream, whereby mineral hydrocarbon fluids produced from a subsea hydrocarbon reservoir are conveyed to a floating structure via the waved steel production riser.

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.

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.

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.

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.

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 pretension along different sections thereof.

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 <NUM>.

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 <NUM>.

Advantageous and preferred embodiments are the subject of the dependent claims.

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:.

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.

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.

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.

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.

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.

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.

With reference to the figures, an arrangement <NUM> of an umbilical <NUM> of data communication lines and/or electrical energy transmission lines mounted on a steel lazy wave catenary riser <NUM> comprises A) the steel lazy wave catenary riser <NUM> having:.

wherein the course (shape) of the riser has, in addition to the vertical component, a continuously growing horizontal component in a horizontal riser direction <NUM> starting from the upper hang off location <NUM> towards the touch down location <NUM>.

The arrangement <NUM> further comprises B) the umbilical <NUM> having:.

In accordance with an aspect of the invention, the first installation point <NUM> is positioned in an installation region <NUM> of the riser <NUM> between the lowest sag bend point <NUM> and the highest hog bend point <NUM>, and the first umbilical section <NUM> is tensioned to have a flatter catenary shape than the catenary shape of the riser <NUM> between the upper hang off location <NUM> and the first installation point <NUM>, so that between the upper hang off location <NUM> and the first installation point <NUM> the first umbilical section <NUM> extends at a distance from the riser <NUM> and is preferably not connected to the riser <NUM>.

In accordance with an embodiment, also the second installation point <NUM> is positioned in the installation region <NUM> of the riser <NUM> between the lowest sag bend point <NUM> and the highest hog bend point <NUM>, and the second umbilical section <NUM> has a catenary shape with an opposite curvature to the curvature of the buoyant section <NUM>, so that between the second installation point <NUM> and the touch down location <NUM> or sea bed <NUM> the second umbilical section <NUM> extends at a distance from the riser <NUM> and is preferably not connected to the riser <NUM>.

According to one embodiment, the first umbilical section <NUM> is mechanically connected to the riser <NUM> at the first installation point <NUM> and, possibly, also at the upper hang off location <NUM> (either directly or both are mechanically connected to the FPSO <NUM> or vessel <NUM>). Similarly, the second umbilical section <NUM> is mechanically connected to the riser <NUM> at the second installation point <NUM> and, possibly also at the touch down location <NUM> (either directly or both are mechanically connected to a mud mat <NUM> or similar sea bed installation structure.

According to an alternative embodiment, the first umbilical section <NUM> is not mechanically connected to the riser <NUM> at the upper hang off location <NUM>, but only at the first installation point <NUM>. In this embodiment, an upper end of the first umbilical section <NUM> can be mechanically anchored at the FPSO <NUM> or vessel <NUM> which in this case shall be interpreted as a whole as the upper hang off location <NUM>.

Similarly, the second umbilical section <NUM> may be not mechanically connected to the riser <NUM> at the touch down location <NUM>, but only at the second installation point <NUM>. In this embodiment, a lower end of the second umbilical section <NUM> 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 <NUM>.

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

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

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

According to an embodiment (<FIG>, <FIG>) the mechanical connection and force transmission between the umbilical <NUM> and the riser <NUM> in the installation points <NUM>, <NUM> can be made by means of dedicated riser installation structures <NUM>, <NUM>, <NUM>, such as clamping bodies, independently from the riser laying process, which simplifies the installation of the umbilical <NUM> and reduces the overall cost of the riser-umbilical arrangement <NUM>.

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

The arrangement <NUM> 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.

Advantageously, the installation region <NUM> is confined within a distance from the inflection location <NUM> smaller than <NUM>%, preferably smaller than <NUM>% of the riser <NUM> length.

Ideally, the installation region <NUM> is at the inflection location <NUM>. That means for practical applications, that the first installation point <NUM> and the second installation point <NUM> are preferably within an exemplary distance of max. <NUM> meters, preferably <NUM> meters, from the inflection location <NUM>. The third umbilical section <NUM> (jumper) may have e.g. an exemplary length of less than <NUM> meters or of about <NUM>.

In accordance with an embodiment (figures <NUM> to <NUM>), the umbilical <NUM> comprises a third (intermediate) umbilical section <NUM>, a so-called jumper section, extended between the first installation point <NUM> and the second installation point <NUM> and making an electrical and/or data communication connection between the first umbilical section <NUM> and the second umbilical section <NUM>.

Preferably, the third umbilical section <NUM> has a length greater than a straight distance between the first installation point <NUM> and the second installation point <NUM>, in order prevent undesired tensioning of the third umbilical section <NUM> and to facilitate the manipulation of the ends of the third umbilical section <NUM> for the purpose of a, e.g. plug-in, data/electrical connection with the first umbilical section <NUM> at the first installation point <NUM> and with the second umbilical section <NUM> at the second installation point <NUM>.

In accordance with an embodiment (<FIG>), the arrangement <NUM> comprises at least one or more branch lines <NUM>, <NUM>, <NUM>, <NUM> comprising one or more of data transmission cables <NUM> and electricity cables <NUM>, branched off from the umbilical <NUM> and extending to monitoring locations <NUM>, <NUM> at the riser <NUM>, e.

In accordance with a further embodiment, the arrangement <NUM> comprises no branch lines at all along the length of the riser <NUM>.

The first installation point <NUM> and/or the second installation point <NUM> can be formed by one or more installation structures <NUM>, <NUM>, <NUM> having each a (reversable) mechanical riser coupler <NUM> for a (reversable) mechanical connection of the installation structure with the riser <NUM>, and one or more (preferably detachable) mechanical pull resistant umbilical couplers <NUM> for a (preferably detachable) mechanical connection of the installation structure with the umbilical <NUM>, i.e. the first umbilical section <NUM> and/or second umbilical section <NUM> and/or possibly third umbilical section <NUM>.

For the purpose of making an electrical and/or data communication connection between the first and second and possibly third umbilical sections <NUM>, <NUM>, <NUM>, as well as possible branch lines <NUM>, <NUM>, <NUM>, <NUM>, cable end connectors <NUM> of the umbilical sections <NUM>, <NUM>, <NUM>, and possible branch lines <NUM>, <NUM>, <NUM>, <NUM>, e.g. plug-in connectors, are (preferably detachably) connectable directly with each other or with corresponding connecting sockets <NUM> of an electrical and data distribution device <NUM> onboard the installation structures <NUM>, <NUM>, <NUM>. The electrical and data distribution device <NUM> comprises multiple communicating connecting sockets <NUM> to allow for multiple connections between the umbilical sections <NUM>, <NUM>, <NUM>, and/or branch lines <NUM>, <NUM>, <NUM>, <NUM>.

In accordance with an embodiment (<FIG>, <FIG>, <FIG>) the first installation point <NUM> is formed by a first installation structure <NUM> having:.

In accordance with a further embodiment (<FIG>, <FIG>, <FIG>, <FIG>) the second installation point <NUM> is formed by a second installation structure <NUM> having:.

In accordance with an alternative embodiment (<FIG>), the first installation point <NUM> and the second installation point <NUM> are formed both by one single installation structure <NUM> having:.

According to an embodiment (<FIG>, <FIG>), each of the installation structures <NUM>, <NUM>, <NUM> is configured as a self-supporting clamping body having further:.

The mechanical riser coupler <NUM> comprises advantageously hydraulically or mechanically actuatable opposing jaws.

In accordance with an embodiment (<FIG>, <FIG>, <FIG>) at the touch down location, the umbilical <NUM>, especially the lower end of the second umbilical section <NUM>, is mechanically connected with a mud mat <NUM> placed on the sea bed <NUM>. Similar to the installation structure <NUM>, the mud mat <NUM> may also have a mechanical umbilical coupler <NUM> and an electrical and data distribution device <NUM> with multiple connecting sockets <NUM> for the electrical and data transmission connection of the (second umbilical section <NUM> of) umbilical <NUM> and of possible branch lines, e.g. the lower branch line <NUM>.

In accordance with an embodiment, the arrangement <NUM> comprises riser monitoring instrumentation <NUM> comprising e.g. pressure sensor/s, temperature sensor/s, accelerometer/s, strain gauge/s, optical sensor/s, telecamera/s, etc., connected to the umbilical <NUM> and/or branch line/s <NUM>, <NUM>, <NUM>, <NUM>.

In accordance with an embodiment (<FIG>), the umbilical <NUM> comprises one or more electrical conductors <NUM>, e.g. copper cables, and/or one or more data transmission lines <NUM>, e.g. electrical signal cables or optical signal cables, protected and wrapped by an external armature sheath <NUM>.

In accordance with an embodiment (<FIG>), for the mechanical pull resisting coupling of the first umbilical section <NUM> and second umbilical section <NUM> in the first and second installation points <NUM>, <NUM>, the first umbilical section <NUM> and second umbilical section <NUM> may comprise a reinforced (e.g. steel) mechanical coupling end portion <NUM>, e.g. a tubular clevis body, having:.

In accordance with an embodiment, the arrangement <NUM> is used for riser <NUM> integrity monitoring.

As already mentioned above, the umbilical <NUM> 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 <NUM> is not mandatory. Accordingly, the described embodiments of the arrangement <NUM> and of the installation structures <NUM>, <NUM>, <NUM> are to be alternatively understood as having been also described separate and independently from the branch off lines.

In accordance with an embodiment, a method for installing an umbilical <NUM> of data communication lines and/or electrical energy transmission lines on a steel lazy wave catenary riser <NUM> for obtaining the arrangement <NUM>, comprises the step of A) installing the first umbilical section <NUM> (<FIG>) by:.

In accordance with an embodiment, the method comprises the step of B) installing the second umbilical section <NUM> (<FIG>) by:.

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 <NUM> and the second umbilical section <NUM> in the installation region <NUM>, e.g. by installing the third umbilical section <NUM> (<FIG>) by:.

In accordance with an embodiment, the method comprises the step of D) connecting to the umbilical <NUM> one or more branch lines <NUM>, <NUM>, <NUM>, <NUM> comprising one or more of data transmission cables <NUM> and electricity cables <NUM>, preferably using a remotely operated subsea vehicle <NUM>, and extending the branch lines <NUM>, <NUM>, <NUM>, <NUM> to monitoring locations <NUM>, <NUM> at the riser <NUM> (<FIG>).

In accordance with an embodiment, the step A) comprises the step of coupling the lower end of the first umbilical section <NUM> to the first installation structure <NUM> or to the single installation structure <NUM> prior to lowering the first umbilical section <NUM> from the deploy vessel <NUM> and coupling the lower end of the first umbilical section <NUM> to the riser <NUM> by clamping the first installation structure <NUM> on the riser <NUM>.

Similarly, in accordance with an embodiment, the step B) comprises the step of coupling the upper end of the second umbilical section <NUM> to the second installation structure <NUM> prior to lowering the upper end of the second umbilical section <NUM> from the deploy vessel <NUM> and coupling the upper end of the second umbilical section <NUM> to the riser <NUM> by clamping the second installation structure <NUM> on the riser <NUM>.

In accordance with an embodiment, the step A) comprises:.

In accordance with an embodiment, the step B) comprises:.

Further details of the method have already been specified within the detailed description of the arrangement <NUM> 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.

The arrangement <NUM> is adavantageously used to:.

The lazy wave catenary riser has been described as a steel riser for the purpose of example only. The riser <NUM> can be made of a different material or material combination.

Claim 1:
Arrangement (<NUM>) of an umbilical (<NUM>) of data communication lines and/or electrical energy transmission lines mounted on a lazy wave catenary riser (<NUM>) comprising:
A) the lazy wave catenary riser (<NUM>) having:
- an upper catenary section (<NUM>) extending from an upper hang off location (<NUM>) at an FPSO (<NUM>) downwards and transitioning in a sag bend (<NUM>) having a lowest sag bend point (<NUM>) and an upward oriented end section (<NUM>),
- a buoyant section (<NUM>) having buoyant devices (<NUM>) attached to the riser (<NUM>) and extending from the upward oriented end section (<NUM>) of the sag bend (<NUM>) further upward and forming a hog bend (<NUM>) of opposite curvature with respect to the sag bend (<NUM>) and defining a highest hog bend point (<NUM>) and a downward oriented end section (<NUM>), so that the sag bend (<NUM>) and the hog bend (<NUM>) define a double curvature section and an inflection location (<NUM>) between the sag bend (<NUM>) and the hog bend (<NUM>),
- a lower catenary section (<NUM>) extending from the downward oriented end section (<NUM>) of the hog bend (<NUM>) further downward and then converging towards a horizontal orientation at a touch down location (<NUM>) on the sea bed (<NUM>),
wherein the course of the riser (<NUM>) has, in addition to a vertical component, a continuously growing horizontal component in a horizontal riser direction (<NUM>) starting from the upper hang off location (<NUM>) towards the touch down location (<NUM>),
B) the umbilical (<NUM>) having:
- a first umbilical section (<NUM>) extending from the upper hang off location (<NUM>) continuously downward to a first installation point (<NUM>) at the riser (<NUM>),
- a second umbilical section (<NUM>) extending from a second installation point (<NUM>) at the riser (<NUM>) continuously downward to the sea bed (<NUM>) at the touch down location (<NUM>),
wherein
the first installation point (<NUM>) is positioned in an installation region (<NUM>) of the riser (<NUM>) between the lowest sag bend point (<NUM>) and the highest hog bend point (<NUM>), and
the first umbilical section (<NUM>) is tensioned to a flatter catenary shape than the catenary shape of the riser (<NUM>) between the upper hang off location (<NUM>) and the first installation point (<NUM>), so that between the upper hang off location (<NUM>) and the first installation point (<NUM>) the first umbilical section (<NUM>) extends at a distance and detached from the riser (<NUM>).