EP2997220A1

EP2997220A1 - Device for anchoring a raceway mounting of a seabed-to-surface facility

Info

Publication number: EP2997220A1
Application number: EP14729411.0A
Authority: EP
Inventors: François Régis PIONETTI
Original assignee: Saipem SA
Current assignee: Saipem SA
Priority date: 2013-05-13
Filing date: 2014-05-12
Publication date: 2016-03-23
Anticipated expiration: 2034-05-12
Also published as: BR112015028130A2; WO2014184480A1; AU2014267082A1; EP2997220B1; FR3005484A1; US20160115667A1; BR112015028130B1; US9702109B2; AU2014267082B2; FR3005484B1

Abstract

The present invention relates to a device including a rigid structure (5) which is kept submerged under the surface by floats (6) and anchored to the seabed by tendons (7), which can be used to support a plurality of raceways (4) in a facility of seabed-to-surface connections including a plurality of flexible lines (1, 1a, 1b) extending to the seabed, said flexible lines being supported respectively by said plurality of raceways, characterised in that said structure (5) for supporting raceways is connected to a base (8) resting on and/or anchored to the seabed by a plurality of n tendons under parallel tension, preferably vertically, by said floats, n being no lower than 6, a plurality of p said tendons (7) among the n tendons, p being no lower than (n-2) each being connected at one of the ends thereof to a distance-changing device (10) secured to said base (8) or to said supporting structure (5), said distance-changing device being suitable for changing the distance between said supporting structure (5) and said base (8).

Description

DEVICE FOR ANCHORING A CHUTE HOLDER OF A

FOUNDAL-SURFACE INSTALLATION

The present invention relates to a device for anchoring a rigid structure maintained immersed in the sub-surface by floats and anchored to the seabed by tendons, useful for supporting a plurality of support elements and guide-shaped arch called chutes in an installation of bottom-surface connections between the same floating support and the bottom of the sea.

More particularly, the present invention relates to an installation of flexible multi-surface-to-surface bonds between wellheads, equipment or the ends of submarine pipes resting at the bottom of the sea and a floating support surface, comprising a plurality of flexible lines including flexible pipes whose lower ends are connected to the ends of a plurality of submarine pipes lying at the bottom of the sea or directly to wellheads or equipment resting at the bottom of the sea.

In the present description, the term "flexible line", pipes or cables capable of accepting significant deformations without generating significant return forces, such as flexible pipes defined below, but also cables or transfer lines energy or information such as electrical cables, control cables or hydraulic fluid transfer lines supplying hydraulic equipment such as cylinders or pipes containing optical fibers; or a control umbilical comprising one or more hydraulic lines and / or electric cables for transmitting energy and / or information.

The technical field of the invention is more particularly the field of the manufacture and installation of bottom-surface connections for the underwater extraction of oil, gas or other material. soluble or fusible or a suspension of mineral material from wellhead immersed to a floating support, for the development of production fields installed in open sea off the coast. The main and immediate application of the invention being in the field of oil production.

The floating support generally comprises anchoring means to remain in position despite the effects of currents, winds and waves. It also generally comprises oil storage and processing means as well as means of unloading to removal tankers, the latter being present at regular intervals to carry out the removal of the production. The common name of these floating supports is the Anglo-Saxon term "Floating Production Storage Offloading" (meaning "floating medium of storage, production and unloading") which one uses the abbreviated term "FPSO" in the whole of the following description.

But it can also be semi-submersible floating platform temporarily installed for a few years, for example pending the construction and final installation of an FPSO floating support. Background-to-surface bonds of an underwater pipe resting at the bottom of the sea are known, a tour-hybrid link comprising:

a vertical riser whose lower end is anchored to the seabed by means of a flexible hinge, and connected to a said pipe resting at the bottom of the sea, and the upper end is stretched by a float immersed in sub-surface to which it is connected, and

a connecting pipe, generally a flexible connecting pipe, between the upper end of said riser and a floating support on the surface, said flexible connecting pipe taking, if appropriate, by its own weight in the form of a curve in plunging chain, that is to say, descending widely below the float to then go up to this floating support. Background-to-surface bonds are also known which are carried out continuously up to the sub-surface of the strong and rigid ducts constituted by tubular elements of thick steel welded or screwed together, in a chain configuration with a continuously variable curvature. throughout their length in suspension, commonly referred to as "Steel Catenary Riser" (SCR) meaning "chain-shaped steel riser" and also commonly referred to as "catenary type rigid pipe" or "SCR type riser". Such a catenary duct may go up to the floating support surface or only to a subsurface float that tensions its upper end, which upper end is then connected to a floating support by a plunger flexible connecting pipe.

Background-surface bonds are also known for connecting a floating support to pipes or installations at the bottom of the sea made entirely of flexible pipes, especially in the case where the depth of water is not very important, for example 300 at 750m, or even 1000m and where the well heads or the underwater equipment are not very far from said floating support.

It will be recalled here that "flexible pipe" refers to the pipes known under the name "flexible", well known to those skilled in the art and which have been described in the normative documents published by the American Petroleum Institute (API ), more particularly under the API 17J and API RP 17 B references. Such hoses are manufactured and marketed by TECHNIP-COFLEXIP France. These flexible pipes generally comprise internal sealing layers of thermoplastic materials associated with layers resistant to the pressure internal to the pipe, generally made of steel or composite materials made in the form of spiral strips, contiguous inside the thermoplastic pipe to withstand the bursting internal pressure and supplemented by external reinforcements above the thermoplastic tubular layer also in the form of contiguous spiral strips, but with a pitch longer, that is to say an angle of inclination of the lower helix, in particular from 15 ° to 55 °.

In certain field developments, several well heads are connected in parallel by virtue of a plurality of bottom-surface connections joining a same floating support. In this case, each of said bottom-surface connections must be kept apart from its immediate neighbors in order to avoid any interference. and any impact, not only at the level of the floats, but also at the level of flexible pipes and electrical cables and other flexible lines such as electrical cables or information signal transfer umbilicals providing connection with said floating support, when said Flexible pipes are subject to the effects of the current, and that said floating support is subject to more waves, wind and current.

In some field developments, each of the wellheads is individually connected to said floating support and is then left with a very large amount of bottom-surface connections that we no longer know how to install because the length of the plating of the support is limited and therefore accepts only a limited number of bottom-surface links.

We seek to implement a maximum of bottom-surface bonds from the same floating support to optimize the exploitation of oil fields. This is why different systems have been proposed that can combine several vertical risers together in order to reduce the size of the operating field and to be able to implement a greater number of bottom-surface links connected to the same floating support. Typically it is necessary to be able to install up to 30 or even 40 bottom-surface bonds from the same floating support.

In WO 02/66786, WO 02/103153 and WO 2011/061422 in the name of the applicant, we have described hybrid towers with risers and multiple flexible pipes arranged in fans for associating a large number of connections to a same support floating, despite the problem of the interference of the movements of said risers which are subject to the same movement as their tensioning float at the head under the effect of displacements of the floating support surface subjected to swell, wind and currents.

In these installations, it has been proposed to have two flexible pipes superimposed or arranged side by side between the floating support and the upper riser or SCR ends, the two flexible ducts being guided in subsurface by respectively two troughs fixed in a superposed or laterally offset manner. a float tensioning a third riser disposed closer to the floating support that the first 2 risers, each said trough thus delimiting 2 portions of flexible pipe double plunging chain on either side of the chute. This configuration has the advantage of being able to route the flexible pipe to the upper end of the riser relatively far from the floating support without the low point of said portions of double plunging chain pipe is too deep.

When implementing a multiplicity of bottom-surface connections consisting exclusively of flexible pipes, it is also necessary to separate the different connections with respect to each other for at least the following reasons. Firstly, the flexible pipes are fragile at their outer sheath and it is imperative to prevent them from colliding with each other.

On the other hand, the flexible pipes are implemented through guiding elements in the form of arches called chutes defining a rigid convex curved support surface explained below, to delimit two portions of flexible pipes comprising a first portion of flexible pipe in the configuration of a double plunging chain between floating support and said chute and a second portion of flexible pipe in simple chain configuration between said chute and the point of contact and tangency of said flexible pipe with the bottom of the sea. These guiding elements in the form of an arch called chutes are well known to those skilled in the art; they present :

a longitudinal section of curved shape in section in the axial vertical longitudinal plane of the chute, preferably a concavity-shaped circular section facing the seabed and a convex outer surface on which the pipe is disposed, and

a transverse section in the vertical plane perpendicular to the vertical axial longitudinal plane of the chute, having a shape with a curved bottom, preferably circular, concavity facing upwards, constituted by said upper external surface framed by longitudinal lateral flanges ensuring the maintenance and guiding the pipe in the longitudinal direction between said flanges.

In known manner, the radius of curvature of the downwardly concavity-oriented longitudinal curvature is greater than the minimum radius of curvature of the pipe passing through said chute.

Such a chute makes it possible to confer on the portion of flexible pipe that it supports a controlled curvature to avoid excessive curvature which would degrade irreparably said pipe.

The function of these ducts and flexible pipe arrangements is to create a double-plunging chain curve upstream of the chute between the floating support and the chute, to avoid or reduce as much as possible the stresses and displacements of the flexible pipes at level of their points of contact with the sea floor which destroy the sea floor by creating trenches and weaken the pipe due to alternating bending in the area of the contact point, forcing to reinforce its structure and / or to protect the seabed . The stresses and displacements of the point of contact of the flexible pipe with the sea floor are effectively reduced because the stresses and displacements of pipes are damped by the first portion of flexible pipe-shaped double plunging chain created by the passage of the pipe on said chute, this first portion being more stressed to absorb the horizontal displacements of the floating support than the second portion of flexible pipe in a simple chain.

A so-called flexible underwater line suspended at its two ends takes its own weight in the form of a so-called double plunging curve, known to those skilled in the art, that is to say descending in configuration of chain to a low point of horizontal tangent (see below) to then go up to said floating support, which plunger chain allows large displacements of its ends absorbed by the deformations of the flexible pipe, including the rise or descent of said low point of the plunging chain.

It is recalled that the portion of flexible pipe between an end to which it is suspended and the low point of horizontal tangency, namely in the case of said second flexible pipe portion the contact point at the bottom of the sea, adopts a geometric curve formed by a portion of pipe of uniform weight in suspension subjected to gravity, called "chain" is a mathematical function of hyperbolic cosine type Coshx = (e ^x + e ^"x ) / 2, connecting the abscissa and the ordinate of any point of the curve according to the following formulas: y = R ₀ (cosh (x / R ₀ ) ^_1 )

R = R _0. (Y / R ₀ + 1) ² in which: x represents the distance in the horizontal direction between said contact point and a point M of the curve;

y represents the altitude of the point M (x and y are therefore the abscissae and ordered from a point M of the curve with respect to an orthonormal coordinate system whose origin is at the point of contact), Ro represents the radius of curvature at said point of contact, ie at the point of horizontal tangency,

- R represents the radius of curvature at the point M (x, y).

Thus, the curvature varies along the chain from the upper end where its radius of curvature has a maximum value Rmax, to the point of contact with the ground where its radius of curvature has a minimum value Rmin (or R ₀ in the formula above). Under the effect of waves, wind and current, the surface support moves laterally and vertically, which has the effect of lifting or resting the chain-shaped pipe at the bottom of the sea.

In the case of a single chain-to-surface link, the most critical portion of the chain is in the near-end portion of the point of contact and most of the efforts in this lower part of the chain are in fact generated by the own movements of the floating support and by the excitations that occur in the upper part of the chain subjected to the current and the swell, all of these excitations then propagating mechanically all along the pipe to the foot of chain.

The essential function of the first portion of a double plunger chain of flexible pipe upstream of the chute is, more specifically, to absorb, at least in part, the movements of the pipe and / or the movements of the floating supports to which said flexible line is connected, mechanically decoupling the respective movements of said second flexible pipe portion into a simple chain and said floating support. But, another function is also to reduce the tensile forces exerted by said second portion of flexible pipe, the marine equipment and / or the end of the pipe resting on the bottom of the sea to which it is connected, if any . In the prior art, these intermediate support chutes of said flexible pipes are maintained in surface at a certain depth by floats supporting or to which are suspended each of the chutes. But, these floats are subject to significant movement which requires to provide a sufficient distance between the different floats to prevent them from colliding against each other.

These constraints involve a spreading of the operating area and a limitation of the number of flexible bottom-surface connections that can be connected on the same floating support, at the edges, to avoid interference between the various flexible links and the different floats. Therefore, it is sought to provide an installation capable of operating from the same floating support a plurality of bottom-surface connections of the flexible type of reduced space and movement and which is also easier to install and can be manufactured at sea for a long time. pipe laying ship.

In WO 00/31372 and EP 0 251 488, pluralities of bottom-surface connections are described in which flexible pipes extend from a floating support to the seabed via a rigid support structure supporting a plurality of trunks. all arranged at the same height side by side offset laterally, said chutes being supported by a said support structure resting at the bottom of the sea or by a said support structure suspended from floats and connected by no more than 2 tendons to a base anchored to the bottom of the sea. The upper and lower ends of the tendons are connected to the support structure at the points of attachment of the support structure and respectively to the base at the levels of hooked points thereof hereinafter referred to "Top hung points" and "bottom hung points".

In the prior art, it is sought to minimize the number of tendons between the trunking support structure and the base at the bottom of the sea, so as to be with no more than 2 upper hooked points aligned at the level of the trunk. support structure of chutes and therefore not more tendons aligned in the same plane, usually vertical, at the level from their upper ends to obtain an isostatic mechanical bond. Indeed, if one implements 3 tendons, the maintenance of an isostatic connection requires that the 3 points of upper hanging of said tendons parallel to each other and substantially vertical, are in triangular disposition, preferably an equilateral triangle, in a plane which is not a substantially vertical plane. The more the said flattened triangle, that is to say that its vertex tends towards an angle of 180 °, the closer one is to a configuration of three aligned points and the more one deviates from an isostatic configuration. Mechanically, a configuration is called "isostatic", when the distribution of the forces in said tendons is univocal and therefore calculable in a known manner. On the other hand, in the case of three tendons whose upper hook points are aligned, as well as in the case of more than three tendons, the system becomes mechanically "hyperstatic", that is to say that the distribution of the efforts in each of the tendons can no longer be calculated unambiguously. In this hyperstatic case, as in the case of a four-legged stool, the whole becomes possibly wobbly, some tendons may take up a larger part of the load, while others will be less loaded, or in some cases completely soft, that is to say they will not take any load.

In the prior art previously described, the rupture of a tendon leads either to the ruin of the installation in the case where the tendon is unique, or to a dangerous imbalance of the support structure of chutes in the case of two tendons or in the case of three tendons arranged in a triangle in a plane not substantially vertical. This generally results in a very important tilt, even complete, of the trunking support structure which may irreparably damage the flexible pipes or the electric cables they support and thus lead to the partial or total failure of the bottom-surface installation. In addition, such incidents are likely to cause major pollution, in the case of crude oil production lines. These ruptures are particularly feared in the case of installations where the water depth is not very important, that is to say a few tens or even a few hundred meters, because in these depths, the swell and the current act. over the entire water portion and are then particularly aggressive vis-à-vis the chute support structure equipped with its chutes and its buoyancy elements. In addition, the swell, the wind and the currents also destabilize the floating support and the movements created are reflected through the flexible pipes on the immersed support structure, so on the tendons and their upper and lower hook points. Thus, when the depth is not very important, that is to say up to 300m of water depth and when the ocean-weather conditions are severe, the hoses, the structure carrying the chutes and its connections with the foundation at the bottom of the sea are particularly subject to significant efforts, even extreme, creating wear and fatigue, mainly at the ends of the tendons and their attachment points. Such accidents have already occurred in the recent past.

A known but unsatisfactory solution for reducing the hyperstaticity of a multi-tendon system consists in designing a support structure for troughs that has great flexibility, that is to say that can be deformed substantially, which makes it possible to participate then, but within certain limits, all the tendons. The main disadvantage of this configuration is that tiredness and wear problems feared at the level of the tendons and their hanging points, are then transferred to the support structure and can thus lead, in the event of an incident, to worse damage. again.

Another problem is to provide a system for anchoring said support structure for which it is possible without difficulty to perform maintenance operations consisting of changing any of the tendons, without disturbing the operation of the device, so without the need to disconnect the conduct and / or stop oil production More particularly, the problem posed according to the present invention is therefore to provide an installation with a multiplicity of connections bottom-surface flexible pipe from the same support structure trunking anchored at the bottom of the sea by a plurality of tendons d at least 3 tendons in a mechanically quasi or pseudo isostatic manner on the one hand and on the other hand whose maintenance is as easy as possible.

Another problem is to be able to make a manufacturing and easy implementation by manufacturing and sequential laying of the various pipes from a laying ship on the surface, and to optimize the implementation of the means of buoyancy and tensioning and anchoring of the trunking support structure in the case of implementation spread over time over a long period of time between the establishment of the various flexible bottom-surface connections and without it being necessary to know at the beginning the number of connections to be made, their characteristics in terms of dimensions, and unit weight.

Indeed, during the engineering phase of the development of an oil field, the oil reservoir is known at this stage only incompletely, production at full speed then often requires reconsideration, after a few months. years, the initial production plans and the organization of associated equipment. Thus, during the installation of the initial system, the number of bottom-surface links and their organization is defined with respect to estimated needs, said needs being almost always systematically revised upward after the production of the field, either for the recovery of crude oil, or for the need to inject more water into the tank, or to recover or reinject more gas. As the reservoir is depleted, it is generally necessary to drill new wells to reinject water or gas, or to drill production wells in new areas of the field, so that increase the overall recovery rate, which complicates all the bottom-surface connections connected to the plating FPSO.

Another problem of the present invention is also to provide a facility of flexible bottom-surface connections of high strength and low cost, and whose manufacturing processes and implementation and maintenance of the various components are simplified and also low cost, and can be achieved at sea from a laying ship.

To do this, the present invention relates to a device comprising a rigid structure maintained submerged in sub-surface by floats and anchored to the bottom of the sea by tendons, useful for supporting a plurality of support elements and guide-shaped arch called chutes in a bottom-surface connection facility between the same floating support and the seabed, comprising a plurality of flexible lines including flexible pipes extending to the bottom of the sea where they are connected to heads subsea wells, equipment or pipe ends lying at the bottom of the sea, said flexible lines being supported respectively by said plurality of troughs.

Said chute support structure is connected to a base resting and / or anchored to the bottom of the sea by a plurality of n tendons tensioned substantially parallel, preferably substantially vertically, by said floats, n being at least equal to 3, a plurality p said tendons among the n tendons, p being at least equal to (n-2), being connected at one of their ends each to a distance variation device integral with said base or said support structure, said variation device distance being connected to said base or said support structure or integral with said base or said support structure, the other end of said tendon being fixed to a hooked point integral with said support structure or said base, said device variation of distance being able to be actuated to vary the distance between its hooked point said tendon and said base or said support structure to which it is attached or connected.

More particularly and preferably, the upper end of said tendon is attached to an upper hooked point integral with said support structure or said distance variation device respectively, the lower end of said tendon being fixed to a fixed lower hooking point. said distance variation device or respectively said base, said distance variation device being able to: - vary the distance between said upper hook point and said support structure, when said distance variation device is integral with said structure support, or

- vary the distance between a said lower hooked point and said base, when said distance variation device is integral with said base.

It is understood that, in all cases, the distance variation device according to the invention makes it possible to vary the distance between said support structure and said base.

It is also understood that said distance variation device when it is secured to said structure is fixed to said support structure at the underside thereof, and when it is secured to said base, said distance variation device is fixed on the upper surface of said base.

It is understood that the decrease or increase in the distance between said support structure and said base, due to the actuation of said distance variation device, causes an increase or decrease in tension of said tendon. On the other hand, the increase of the tension of said tendon can cause an elongation of said tendon with an increase proportional to the tension, of its length, in practice an elongation of less than 1%. It is understood that, in this case, the variation in distance between said support structure and said base is substantially identical to the variation in distance between said lower (or upper) hook point and said base (or respectively said support structure), the the difference resulting from the variation of tendon length when the tension in said tendon increases because the distance between said base and said support structure decreases. More specifically, in this case, the variation in distance between said base and said support structure is slightly greater than the variation in distance between said lower (or upper) hook point and said base (or respectively said support structure) due to elongation of the tendon.

Thus, it is possible to configure at will during operation the distribution of the loads taken by the various tendons as a function of the loads supported by said support structure at the different chutes by adjusting the tension of said tendons using said distance variation devices. The distance variation devices then make it possible to make the system virtually isostatic, and where appropriate makes it possible to distribute the load on each of the tendons in a controlled manner. On the other hand, the distance variation device makes it easier to maintain and replace a tendon as needed by reducing the tension as needed.

In practice for tendons from 10 to 150m, when the support structure is submerged from 200 to 3000m deep, the distance variation device makes it possible to adjust the distance between the upper and lower hook points between 0 and 3m, from preferably between 0 and 1.5m which is sufficient to adjust the voltages as a function of the rebalances required according to the loads created by said pipes or flexible lines at the chutes. It will be understood that said distance variation device may be integral with (i) said support structure, in which case said upper hook point is integral with the distance variation device. or (ii) preferably secured to said base at the bottom of the sea, in which case said bottom hooked point is integral with the distance variation device.

Preferably, said upper hooking points of said tendons are arranged at said support structure and said lower hooking points of said tendons are arranged at said distance variation devices, said distance variation devices being integral with said support structures. said base, preferably fixed on the upper surface of said base, and each said distance variation device makes it possible to vary the distance between said lower hook point and said base.

The intervention at a distance variation device, for its actuation or handling, is easier when it is fixed on the base because it is further clear, especially to allow handling with the help of an underwater robot as described below, that when it is positioned on the underside of the support structure taking into account the congestion associated with the multiplicity of pipes and flexible lines passing at the level of the troughs. In this case, the distance variation device is a device for varying the distance between said lower hook point and said base.

In known manner, a said tendon consists of a cable or a chain or a rigid bar articulated at its ends. Preferably, said tendon connected to a said distance variation device is a single cable or chain.

Where appropriate, the two tendons not connected to a said distance variation device, are located at the two opposite longitudinal ends of the support structure preferably with their two corresponding upper attachment points arranged diagonally. In the case of three tendons not connected to a said distance variation device, the upper hook points of the three said tendons are in a substantially horizontal plane and form a triangle, preferably the closest to an equilateral triangle.

Preferably, all the tendons are connected to a said distance variation device. In FR 2954966, there is described a device comprising a rigid support structure of a plurality of chutes of the type described above, said structure being anchored by a plurality of anchor lines whose upper hook points are arranged in pairs in four zones of the structure, the four zones being arranged in trapezium. If a pair of tendons in one of the corners of the trapezium is to give way, the other tendons are not certain to ensure the stability of the support structure in all circumstances in the manner of an unstable tripod, as explained below.

An object of the present invention is therefore to provide an improved installation of a large amount of flexible bottom-surface connections for connecting a floating support with a plurality of well heads and / or subsea installations installed at the bottom of the sea, comprising a submerged chute support structure anchored to the sea bottom by a plurality of tendons which overcomes the above-mentioned drawbacks.

To do this, the present invention provides a device comprising a rigid structure maintained immersed in the sub-surface by floats and anchored to the bottom of the sea by tendons, useful for supporting a plurality of support elements and guide-shaped arch called chutes in a bottom-surface connection facility between the same floating support and the seabed, comprising a plurality of flexible lines including flexible pipes extending to the bottom of the sea where they are connected to heads subsea wells, equipment or pipe ends lying at the bottom of the sea, said flexible lines being supported respectively by said plurality of troughs, device in which:

said chute support structure is connected to a base resting and / or anchored to the seabed by a plurality of n tendons tensioned substantially parallel, preferably substantially vertically, by said floats, n being at least equal to 6, plurality of said p tendons among the n tendons, p being at least equal to (n-2), being connected at one of their ends each to a distance variation device, said distance variation device being connected to said base or said support structure or integral with said base or said support structure, the other end of said tendon being fixed to a hooked point integral with said support structure or said base, said distance variation device being able to be actuated to vary the distance between its point of attachment to said tendon and said base or said support structure to which it is attached or connected, and

the upper end of said tendon is attached to an upper hooked point integral with said support structure or said distance variation device, respectively, the lower end of said tendon being fixed to a lower hooked point integral with said distance variation device or respectively of said base, said distance variation device being able to:

varying the distance between said upper hook point and said support structure, when said distance variation device is integral with said support structure, or varying the distance between a said lower hook point and said base, when said distance variation device is integral with said base, characterized in that said device comprises at least 6 upper hook points of which at least 3 first upper hook points are inscribed in a circle (C), the at least 3 other upper hook points being disposed on or within said circle (C). Preferably, said support structure has a longitudinal shape of substantially rectangular section in horizontal section, and the at least 3 said first upper hook points are disposed near each of the longitudinal ends of said support structure.

It is therefore understood that two of said hooking points are disposed near a first longitudinal end, the other said hooking point being disposed on the side of the opposite longitudinal end of said support structure. It will be understood that all of said upper hooking points are half distributed on one side of a diameter of said circle and for the other half on the other side of said diameter, so that preferably the resultant of the tensions exerted by said tendons at their so-called upper hook points on said rigid structure is applied near the center of gravity of said rigid structure substantially corresponding to the center of said circle.

Preferably, all said upper hooking points are distributed so as to be arranged symmetrically with respect to the center of said circle. More particularly, at least two said upper hooking points are diametrically opposed and disposed near respectively each of the opposite longitudinal ends of said support structure.

More particularly still, said upper hook points according to the present invention are arranged and spaced in a plane of horizontal section of said structure so that at least two upper hook points inscribed in said circle (C) are arranged to respectively close to each of the opposite longitudinal ends of said support structure and at least two said upper hooked points inscribed on the circle (C) are arranged close to each end respectively opposite transverse of said support structure, said transverse direction being the direction perpendicular to the longitudinal direction of said support structure in said horizontal section plane. More particularly, when there are only three upper hooked points inscribed on a said circle, they are preferably arranged to form an isosceles triangle.

More particularly, said support structure has a longitudinal shape of substantially rectangular section in horizontal section, preferably substantially symmetrical with respect to a median longitudinal vertical plane (YZ), the device comprising at least 6 tendons, each connected to a said device for variation of distance and said support structure comprises at least 6 said upper hook points 4 points of which hooked upper define the 4 angles of a rectangle, the other two points of upper hook being arranged inside a circle ( C) circumscribed in said rectangle, preferably at or near the two great lengths of the rectangle, preferably at the level of the transverse median axis (XX ') of said rectangle, the 4 corner hooking points being arranged in the vicinity longitudinal ends of said support structure.

This form of support structure is the most practical to support a plurality of chutes arranged in parallel juxtaposed laterally and successively in said longitudinal direction. For this configuration, even when a tendon breaks, the other 5 tendons arranged in trapezium ensure stabilization of the support structure during the replacement of said tendon to be replaced. On the other hand, with only 5 tendons in trapezius, one would not be certain to ensure the stability of the support structure in any circumstance in case of rupture of a tendon with only 4 tendons remaining tensioned, because in certain configurations, the trapezium is would turn into an unstable triangle. In one embodiment, said support structure comprises two parts articulated in rotation about an axis of rotation (XI ΧΊ), substantially horizontal, preferably median, adapted to allow relative rotation of each of said two articulated parts one relative to each other, at an angle of -10 ° to + 10 °, preferably -5 ° to + 5 °, said rotation being limited by upper stops and lower stops of each of said two articulated parts of support structure, the two said articulated portions of support structure being preferably symmetrical with respect to a median vertical plane passing through said axis of rotation (XI ΧΊ), each of said two hinged portions being connected to said base by at least three so-called tendons of which at least one, preferably all three, are (are) connected (s) to one of its (their) ends to a distance variation device.

More particularly, each said articulated portion of said support structure has a longitudinal shape of substantially rectangular section in horizontal section, preferably substantially symmetrical with respect to a median longitudinal vertical plane (YZ), the device comprising at least 6 tendons each connected to a said distance variation device, and said support structure comprises at least 6 upper attachment points, each said articulated part of said support structure comprising at least:

two upper hooking points arranged at the longitudinal ends of each said articulated part furthest from said axis of rotation (XI ΧΊ), and an upper hooking point disposed closer to said axis of rotation than a said longitudinal end. .

More particularly still, the upper hooking points of said first hinged portion of the support structure are arranged symmetrically, at the three upper hooking points of the second hinged portion of the support structure with respect to the substantially vertical plane passing through said axis of rotation. preferably in isosceles triangle. This embodiment in two articulated parts is particularly advantageous for very large support structures, because it reduces the overall rigidity and facilitates the adjustment of tendon tensions due to the relative independence of the tendons of each of the two half structures.

The distance variation device may be a cable system with a said point hooked at its end cooperating with and drums, pulleys and / or winches or preferably a device of the linear actuator type of variable length, preferably of the type cylinder, either a mechanical cylinder or a hydraulic cylinder.

In a preferred embodiment, the device according to the invention comprises at least one said distance variation device comprising a jack, preferably a mechanical jack or preferably hydraulic jack. The implementation of a hydraulic cylinder is advantageous because it makes it possible to correlate the tension of said tendon with the hydraulic pressure inside the cylinder body indicated by a pressure gauge or, preferably, a pressure sensor at an orifice of the cylinder body. More particularly, said lower hooked point is secured to the movable rod of a said hydraulic cylinder whose cylinder body is integral with the base.

It is understood that the retraction of the rod of the cylinder makes it possible to reduce the distance between the lower hook point and said base and thus to increase the tension of said tendon and the extension of the rod of the jack makes it possible to increase the distance between said lower hooked point and said base and thus reduce the tension of said tendon.

In a preferred embodiment, said jack comprises a manometer or preferably a pressure sensor at a port of the cylinder body and a locking device adapted to lock the rod in position, preferably by sealing the cylinder chamber.

More preferably, said hydraulic cylinder is connected or adapted to be connected to a pressurization fluid supply unit embedded in an underwater robot preferably driven from a second vessel on the surface.

More particularly, said support structure supports from 5 to 12 arches having an arch of 1.5 to 3 m radius of curvature, said support structure measuring from 3 to 5 m wide and 10 to 30 m long self weight in the air of 30 to 50 T and said support structure comprising an integrated buoyancy in the underside of the troughs so that each said tendon is subjected to a tension of 0.5 to 10 T, preferably 1 to 5T, said tendon being dimensioned to be able to withstand a voltage of a multiple of 2 to 4 of said voltage to which it is subjected.

More particularly, said support structure is a metal lattice structure extending longitudinally horizontally.

More particularly, said rigid support structure is suspended from a submerged upper float to which it is connected by flexible connecting elements such as slings, and / or preferably said support structure is supported by at least one integrated lower float on which it is fixed.

More particularly, said support structure supports a plurality of chutes, preferably at least 5 troughs, offset laterally parallel in a direction (ΥΥ ') of said support structure, said chutes being arch-shaped preferably arranged symmetrically by relative to a vertical longitudinal axial plane (YZ) of said support structure. According to other advantageous characteristics: - A said flexible pipe is maintained in a said chute by retaining means and / or hooking means; and

- Chutes supported by the same rigid support structure are arranged at different heights; and the ends of the troughs that it supports comprise a deflector whose profile is able to avoid damaging the portion of flexible pipe that can come into contact with said deflector during laying of the pipe on a said trough.

The present invention also provides a bottom-surface connection facility between the same floating support and the seabed, comprising a plurality of flexible lines including flexible lines extending from said floating support to the bottom of the sea where they are connected to wellheads, equipment or ends of submarine pipes resting at the bottom of the sea, said flexible lines being supported by respectively one of said plurality of troughs delimiting each two pipe portions comprising a first portion of flexible line configuration double plunger chain link between the floating support and said chute and a second portion of flexible line in simple chain configuration between said chute and the point of contact of the flexible pipe at the bottom of the sea, said troughs being supported by a support device chutes according to the invention.

The present invention also provides a method for modifying the tensions to which the various tendons of a support device according to the invention are subjected, characterized in that at least one said distance variation device is actuated so as to adjust the tension of said tendon to which it is connected to a desired controlled value.

The present invention also provides a method according to the invention characterized in that the voltage of a said tendon by operating a said distance variation device to which it is connected and then performs the replacement of the tendon.

The present invention also provides a method according to the invention characterized in that the mechanical connection of the different tendons at said support structure is rendered mechanically quasi-isostatic by actuating at least one said distance variation device.

Here is meant by "quasi isostatic", in a known manner, the fact that the tension in each of the tendons is known and that during the movements of the trunking support structure under the effects of the swell, the current and the displacements of the floating support , said chute support structure moving substantially in a horizontal plane, the tension in each of said tendons varies in known manner and within a limit set by the overall geometry of said tendons, preferably parallel to each other.

Other features and advantages of the present invention will become apparent in the light of the detailed description which follows, with reference to the following figures in which:

- Figure 1 is a side view of a bottom-surface connection installation according to the invention between an anchored floating support 2 2b and a metal support structure 5 supporting a plurality of arches-shaped chutes 4, anchored on a base 8 resting on the bottom of the sea 3, by means of a plurality of tendons 7,

FIG. 2A is a side view of a prior art installation in the case of a single flexible pipe 1 resting on a single arched chute 4, anchored by a single tendon 7 ending at its upper end. by a crow's foot 7c so that the tendon is hooked to the chute at 2 points of upper hook 7a, a buoyancy element being located above the chute and connected thereto,

FIG. 2B is a front view of an installation of art former having a structure supporting three chutes, said structure being anchored by two tendons, and equipped with a single float,

FIG. 3A is a front view in the YZ plane of an installation according to the invention comprising a structure integral with a plurality of integrated floats 6a to said structure, supporting a plurality of troughs, namely six chutes 4a to 4f, said structure being anchored by six tendons 7 hooked at six points hooked upper 7al to 7a6, - Figures 3B and 3C are views from below of the structure 5 horizontal section (XY plane) rectangular relative to Figure 3A detailing the arrangement in a rectangle of the six points of hanging upper 7al to 7a6 of the six tendons,

FIGS. 3D and 3E are bottom views of the rectangular horizontal section (XY plane) structure 5 showing two upper hooked points 7a3-7a4, situated in corbelling of the structure 5, 3 upper hooked points (FIG. 3E) or 4 upper hooked points (FIG. 3D) being inscribed in a circle (C), the other upper hanging points being located inside the circle C, FIG. 4A is a side view. in the plane XZ of FIG. 3A detailing buoyancy elements 6a consisting of section boxes in the XZ plane of prismatic or rectangular type integrated into the supporting structure 5 on the underside of the troughs, said caissons being filled with solid, liquid or gaseous, lighter than seawater,

FIG. 4B is a side view of FIG. 3A detailing buoyancy elements consisting of cylindrical caissons 6a with a section in the circular XZ plane integrated into the supporting structure of the troughs; FIG. 5 is a side view of FIG. an installation at a common base 8 comprising two devices for varying the distance 10 allowing the individual adjustment of the length of each of two tendons 7-1, 7-2 hooked to lower hook points 7b1, 7b2 at the rod 10b of a jack 10 according to the invention, and

FIG. 6 is an alternative embodiment of a distance variation device comprising a jack equipped with a hydraulic pressure gauge 11c of the jack according to the invention, and

FIGS. 7A to 7C show an embodiment in which said support structure 5 comprises two parts articulated in rotation 5-1, 5-2 with respect to a median axis Χ1Χ. FIG. 1 shows a bottom-surface connection installation comprising two flexible pipes or electric cables 1a, 1b connected at one end 2a to a floating support 2, held in position by anchoring lines 2b, the other end said flexible pipes lying substantially at the bottom of the sea 3. The flexible pipes 1a, 1b are in descending downward chain configuration from the floating support 2, to a point of horizontal tangency, respectively the ', lb', then in ascending chain configuration to the inlet 4al of a chute, respectively 4a and 4b, whose radius of curvature R is greater than the minimum radius of curvature acceptable by said flexible pipes or said cables. Thus, the flexible pipe enters 4al in the chute 4a, then rests on said chute and spring 4a2 to join in single chain configuration lal, the sea floor 3 substantially in the. Each of the chutes 4a, 4b, etc. is positioned laterally offset, relative to each other, on the structure 5, as shown in Figures 2B and 3A. In general, the chutes of the same installation all have the same radius of curvature and are joined together by means of said structure 5. Said structure comprises buoyancy elements 6 which can be either integrated 6a to said structure 5 or external in general in the form of floats 6b located above said structure and connected thereto by means of a single tendon 6c1, as shown in FIG. 2A, or a crowbar 6c2, as shown in Figure 2B.

The support structure 5 is maintained substantially at an altitude h with respect to the seabed by virtue of a plurality of tendons 7 connected at their upper ends to points of upper hooking 7a to said structure 5 and their lower ends to points of contact. hooked lower 7b to a base 8 resting on the seabed 3, for example a base weight, or a suction anchor sunk into the ground hereinafter foundation.

In the prior art, shown in Figures 2A and 2B, it is generally sought to minimize the number of tendons between the structure 5 and the base 8. Thus, in the case of a flexible pipe 1 simple, as shown on FIG. 2A uses a single tendon 7, possibly connected to said structure 5 by means of a crowbar 7c, said tendon then being in the same vertical plane as said flexible pipe. Similarly, in the case of a plurality of flexible pipes or electrical cables arranged on a plurality of 3 troughs 4a to 4c juxtaposed laterally, as shown in Figure 2B, the support structure 5 is connected to its base 8 by means of two tendons, connected if necessary to said support structure 5 through a crowbar (not shown).

These two means of anchoring the support structure 5 are in general preferred because they make it possible to minimize the number of tendons, and therefore the overall cost, and moreover they each represent an isostatic anchoring mode. To remain isostatic, one could, in the case of Figure 2B consider to implement three tendons, but it would be advisable, to maintain the isostatic character of the assembly, that said points of attachment of said tendons are not aligned but are in triangular configuration, in any plane that is not a vertical plane. Thus, in the prior art previously described, the rupture of a tendon, leads to the ruin of the installation as in the case of Figure 2A where the tendon is unique, or leads to an imbalance 5 in the case of two tendons as shown in Figure 2B, or in the case of three tendons arranged in a triangle in a non-substantially vertical plane. This usually results in a very important, or even complete, tilting of the structure 5 which may irreparably damage flexible pipes or electrical cables and thus lead to the partial or total failure of the bottom-surface installation. In the case of a single tendon, the structure 5 is then completely free to move upwards and in all directions, without any possible control. In addition, such incidents are likely to cause major pollution, in the case of crude oil production lines.

These ruptures are particularly feared in the case of installations where the water depth is not very important, that is to say a few tens or even a few hundred meters, because in these depths, the swell and the current act. over the entire water portion and are then particularly aggressive vis-à-vis the structure 5 equipped with its chutes and its buoyancy elements. In addition, the swell, the wind and the currents also destabilize the floating support and the movements created are reflected through the flexible pipes on the structure 5, thus on the tendons 7 and their upper hook points 7a and 7b . Thus, when the depth is not very important, that is to say from 25 to 300m of water depth and when the ocean-weather conditions are severe, the hoses, the structure carrying the chutes and its connections with the foundation are particularly subject to significant efforts, even extreme, creating wear and fatigue, mainly at the ends of the tendons and their attachment points. Such accidents have already occurred in the recent past.

In order to avoid the consequences of the rupture of a tendon, or of one of its points of attachment, the device according to the invention advantageously anchors the structure 5 by means of at least 6 tendons, preferably distributed symmetrical manner on either side of the YY axis of said structure 5 as shown in bottom view on the Figure 3B. Each of the upper hooking points 7al-7a2-7a3-7a4-7a5-7a6 of the structure is connected to the corresponding lower hooked point, not shown, respectively 7bl-7b2-7b3-7b4-7b5-7b6, by the intermediate of a tendon, respectively 7i-7 ₂ -7 ₃ -7 ₄ -7 ₅ -7 ₆ , all the tendons are preferably parallel to each other and vertical.

In FIG. 5, the lower hook points 7bl-7b2 and the tendons 7i-7 ₂ are illustrated, the said lower hook points being integral, according to the invention, not directly from the foundation 8, but a distance variation device 10 for adjusting the distance L, respectively Li-L ₂ , of said lower hook point to said foundation 8. Indeed, a rigid structure 5 anchored by two tendons connected to the foundation, or three tendons, provided that the three points of upper hooking 7a of said tendons are not aligned or located in the same vertical plane, mechanically have a configuration called "isostatic", that is to say that the distribution of efforts in said tendons is unequivocal and therefore computable in known manner, in particular according to the distribution of the load supported by the support structure 5 and buoyancy elements integrated in said structure. On the other hand, in the case of three tendons whose upper attachment points are aligned, as well as in the case of more than three tendons, the system becomes "hyperstatic", that is to say that the distribution of efforts in each of the tendons can no longer be calculated unambiguously. In this case hyperstatic, as in the case of a stool with four feet, the whole can become wobbly and some tendons will take up a large part of the load, while other tendons will be lightly loaded, or in some cases completely soft that is, they will not take over any load.

One solution to reduce the hyperstaticity of the multiple tendon system is to design a structure 5 having great flexibility, that is to say can be deformed significantly, which allows to participate then, but within certain limits, all the tendons. The main disadvantage of this configuration is that fatigue and wear problems feared at the tendons and their attachment points, are then reported to the structure 5 and can thus lead, in case of incident to even worse damage. To restore a pseudo or quasi-isostatic character, that is to say to reduce the hyperstaticity of the multiple tendon system, it is advantageous to install on the tendons, preferably on each of the tendons, a distance variation device 10 according to the invention. invention, able to allow the adjustment of the distance between its upper attachment point 7a to the structure 5 and its lower attachment point to the foundation 8.

FIGS. 3 to 6 show, in side view, a device intended to render the overall anchoring device of the structure 5 on the base 8 quasi-isostatic, whatever the number of tendons 7, that is to say 3 tendons in the case of a single row of tendons located in the same longitudinal median vertical plane of the structure 5, or preferably six tendons arranged in a rectangle in the case of two parallel rows of 3 tendons substantially aligned in a same substantially vertical plane respectively arranged on the lengths of the rectangle with 4 hooked points greater than the 4 corners of the rectangle as shown in Figures 3B, 3C and 3D.

In FIG. 3B the two intermediate upper hooking points 7a3 and 7a4 are arranged at the center transverse axis XX of the structure 5 while in FIG. 3C the two intermediate top hooking points 7a3 and 7a4 are offset by on either side of the median transverse axis XX of structure 5.

In FIGS. 3D and 3E, two intermediate upper hooking points 7a3 and 7a4 are offset on either side of the median transverse axis XX of the structure and offset along XX to the outside of the long sides of the rectangle, such that they are secured to said structure 5, but corbelled. In Figure 3E, a small side of the rectangle is bordered by 2 hanging points upper angle 7al, 7a2, the opposite side of the rectangle in the longitudinal direction having a single point hooked upper 7a6 in the middle position. In all cases, the set of upper hook points of the tendons is then on or inside the circle C circumscribing the rectangle formed by the four points of the upper hook 7al, 7a2, 7a5, 7a6 at the four angles (fig.3D) or the circle circumscribing the triangle formed by the 3 points of upper hanging 7al, 7a2 and 7a6 (fig.3E).

Thus, a non-symmetrical configuration such as in FIGS. 3C, 3D or 3E will advantageously be suitable in certain cases for disparities in the sizes of flexible pipes, that is to say of disparities in the vertical forces induced by these pipes and their respective location. on said structure 5 as well as in the distribution of the buoyancy elements. Here is meant by "quasi-isostatic", the fact that all the tendons collaborate to the recovery of the tension created by the resultant buoyancy directed upwards and that each of said tendons substantially returns a known and adjustable percentage of said overall tension. The device for variation of distance and quasi-isostatic adjustment 10 according to the invention allows, at each of the tendons of the device, and individually, to adjust the distance between the base 8 and the structure 5, and of thus distribute in a perfectly controlled manner the unit load in each of said tendons, so to make the device almost isostatic.

To do this, the altitude L with respect to the foundation 8, of the lower hooking point 7b of the tendon 7 can be adjusted by means of the distance variation device 10 represented here as being a hydraulic cylinder with a mechanical locking rod, known of the man of the art. Said distance variation device 10 according to the invention consists of a cylinder body 10a integral with the base, and a cylinder rod 10b at the top of which is the bottom hooked point 7b of the tendon 7. The axis of said cylinder 10a-10b is preferably vertical. The cylinder body 10a is provided with an orifice 11 making it possible to connect via a conduit 11a to said jack to a hydraulic power unit (not shown) available on board an ROV 13, an automatic submarine piloted from an installation vessel 14 surface. Thus, by pressurizing the jack, the jack rod is forced to retract in length downwards and the distance between the base 8 and the structure 5 and thus the lengths is thus adjusted and reduced, which has the effect of effect of increasing the tension at the tendon concerned. By acting successively on each of the tendons, this advantageously distributes and perfectly controlled the load that resumes each of the tendons, which makes the whole "quasi-isostatic".

When the cylinder is forced by increasing the pressure P of the fluid in the jack, the rod of the latter retracts, and the tension in the tendon concerned increases. Thus, the percentage of overall effort taken by said tendon increases, and the other tendons generally see their tension decrease slightly.

Similarly, when the pressure P of the fluid in the jack is reduced, the rod of the jack deploys, and the tension in the tendon concerned decreases so that the percentage of overall effort taken by said tendon decreases, and the others Tendons usually see their blood pressure increase slightly.

Thus, the pressurization or depressurization of a said cylinder, makes it possible to adjust the distance between the foundation 8 and the upper hook point 7a at each of the tendons and individually, and therefore to adjust the percentage of the global tension T taken individually by said tendon. When the adjustment is completed, a locking device is actuated at position 12-12a of the rod 10b of the jack, then the pressure of the jack is released and the hydraulic supply hose 11a is disconnected. In this figure 5 is shown on the right the distance variation device 10 relative to the tendon 7 ₂ in the locked position 12a at the altitude L2, and on the left, the distance variation device 10 relative to the tendon 7i being adjusted to the altitude L1, the ROV 13 (automatic underwater intervention driven from the surface) connected by the conduit 13a to the port of pressurization 11 being adjusting the pressure P of the cylinder, so the tension in said tendon Ί _x . During this adjustment, the locking device 12 is kept in the open position 12b, so the cylinder is free to move in elongation or retraction.

For reasons of symmetry, it is generally preferred to equip each of the tendons 7 with its own distance variation device 10. However, in the case of n tendons, it may be sufficient to have n-2 distance variation devices 10 Indeed, the two non-adjustable tendons, preferably located at the opposite longitudinal ends of the structure 5, then define the substantially horizontal axis of anchoring reference of the structure 5 vis-à-vis the base 8, l adjustment of each of the other tendons then makes it possible to make the system almost isostatic, so allows the load to be distributed in a controlled manner on each of the tendons. One could likewise have only n-1 distance variation devices 10 for n tendons. We can even install n-3 distance variation devices

10 for n tendons, the three non-adjustable and non-aligned tendons, then defining a substantially horizontal triangle and therefore a substantially horizontal reference plane for the structure 5 vis-à-vis the base 8. The adjustment of each of the others tendons then makes the system almost isostatic, so allows to distribute the load in a controlled manner on each of the tendons, but these three alternatives do not constitute the preferred version of the invention.

Indeed, in a preferred version of the invention where each of the tendons has a distance variation device 10 for adjusting the length of the tendons, it is then easy to carry out maintenance operations consisting of changing any of the tendons, without disturbing the functioning of the device, so without the need to stop oil production. Indeed, all that is needed is:

reconnecting the hydraulic circuit 13a of the ROV 13 to the orifice 11 of the jack 10a, then unlocking the device 12-12b and releasing the pressure of the jack to completely relax said tendon; then

- disconnect the tendon and replace it with a new tendon; then

- Retension said tendon to its initial value; then - lock the device 12-12a and disconnect the ROV 13.

During such a maintenance operation of a tendon, which usually occurs after the rupture of said tendon, the overall force T is distributed temporarily between the n-1 active tendons, the tensions generally increasing in all of said n-1 tendons. 1 tendons, then returning to the initial value when a new tendon was reinstalled and its own tension readjusted through the device 10, as explained above. These tendon change operations can advantageously be carried out in a preventive manner, for example every 5 years, so as to avoid problems of fatigue and rupture whose consequences are feared.

For simplicity and clarity of explanation, the distance variation and adjustment device 10 has been described on the basis of a single-acting hydraulic cylinder, because the measurement of the pressure P of the cylinder makes it possible to know very precisely the tension T applied in the tendon concerned. However, it could very well have been possible to use a distance variation device constituted by a mechanical jack with screw or rack. But, in this case, it is furthermore necessary to integrate in said device a load measuring cell or voltage applied to said tendon such as a direct reading dynamometer by an ROV, or data transmission to the surface until position of command located on board the floating support, so as to adjust correctly the distribution of all loads in the various tendons.

FIG. 6 shows a preferred version of the invention in which the jack 10 does not have a rod locking device 12, but is hydraulically locked by sealing 11b of the internal chamber of said jack. Thus, the cylinder is permanently pressurized and advantageously there is a manometer or a pressure sensor installed permanently lia on the orifice 11 of said cylinder. This provides a permanent display of the tension of each of the tendons, this voltage being correlated to said cylinder pressure, and this display can be very simply consulted during routine inspections performed at regular intervals, for example by a ROV 13 By equipping said orifice 11 with a pressure sensor 11a, the information can then be transmitted automatically and permanently to the FPSO, either by an electric cable or acoustically, and it is then possible to of the command, a perfectly precise state of the set of flexible arches and their anchoring system. In case of rupture of any of the tendons, the command will be instantly informed, and if necessary will be able to determine the defective tendon. Similarly, in case of damage to a buoyancy element 6, either complete failure or partial invasion, the overall vertical tension will decrease and some tendons 7 will see their tension drop. The command of the FPSO will then be quickly informed and will be able to initiate the corrective actions.

For example, a support structure 5 of troughs 4 has from 5 to 12 troughs 1.5 to 3m in radius of curvature and measures from 3 to 5m wide, 5 to 30m long and its own weight in the air can reach and exceed 30 to 50 tons or even more. The integrated buoyancy 6a in the structure 5 or float 6b located above said structure is dimensioned so as to compensate for the weight of said structure 5 equipped with its trunking and various accessories not shown, as well as the weight of all flexible pipes 1 in chain configuration. An additional buoyancy 6a is integrated into the assembly so as to create a permanent tension upwards of 3 to 60 tons, preferably 6 to 30 tons. The device according to the invention thus makes it possible to adjust the tension in the various tendons by substantially dividing the preceding forces by six, namely for each of the tendons, a permanent tension of 0.5 to 10 tons, preferably of 1 ton to 5 tons. . In order to avoid the failure of the device in the event of rupture of a tendon or an attachment point 7a-7b, or in some cases of two tendons or their points of attachment, the tendons and their respective attachment points with a safety factor of 2 to 4, for example; thus, for a nominal effort of 2 tons, we size the tendon and its attachment points for efforts of 5 to 10 tons. This avoids the problems of fatigue and wear as well as the risk of rupture, which even if it occurs, would in any case not endanger the bottom-surface connection as a whole.

FIGS. 7A and 7C show a support structure 5 comprising two parts articulated in rotation 5-1, 5-2 around a median axis of rotation Χ1Χ, substantially horizontal, able to allow a relative rotation of each of the two said parts articulated with respect to each other, with an alpha angle of -10 ° to + 10 °, preferably of -5 ° to + 5 °, said rotation being limited by upper stops 5a and stops lower 5b of each of said two articulated portions of support structure. Both said articulated portions of support structure are of symmetrical shape and arrangement with respect to a median vertical plane passing through said axis of rotation Χ1Χ. In practice, the upper plane of said first articulated portion 5-1 varies by an angle alpha relative to the upper plane of said second articulated portion 5-2. Each of said two articulated parts 5-1, 5-2 is connected to said base by three said tendons each connected at one of their ends to a distance variation device (not shown). Each said hinged portion 5-1, 5-2 of said support structure 5 has a longitudinal section substantially rectangular in horizontal section, substantially symmetrical with respect to a median longitudinal vertical plane (YZ), each said articulated portion 5-1, 5-2 of said support structure 5 comprising:

two upper hooking points 7al-7a2, 7a5-7a6 arranged at the longitudinal ends near the angles of each said articulated part furthest from said axis of rotation (X1-X'l), and

- An upper hooked point 7a3, 7a4 disposed closer to said axis of rotation than a said longitudinal end.

The upper 3 hook points 7al-7a2-7a3 of said first hinged portion of the support structure 5-1 are arranged in isosceles triangle symmetrically to the three upper hung points 7a4-7a5- 7a6 of the second hinged portion of the support structure 5 -2 with respect to the substantially vertical plane passing through said axis of rotation ,.

Here is meant by "floating support" both a barge or vessel that a semi-submersible platform of the type described above.

It is understood that said upper part of the support structure, supporting or on which are fixed said troughs according to the present invention, is a rigid structure other than a float.

In a particular embodiment, a said flexible pipe is held in a said chute by retaining means and / or hooking means. This feature aims to stabilize all the flexible pipes and to promote the stresses and displacements in said first portion of said flexible pipes.

The channel support structure 5 is a rigid structure, but the stresses and displacements especially at the point of contact of the pipes with the sea floor are nevertheless considerably reduced because of the tensioning of said support structure by said floats. To facilitate the laying of flexible pipes from a laying ship as explained later in the description, the ends of the troughs comprise a deflector whose profile is adapted to avoid damaging the portion of flexible pipe that can come into contact with said baffle during laying of the pipe on a said lower chute.

The top of the bottom of the chute is the point located halfway curvilinear length of the chute.

Said support structure may also support chutes for guiding and supporting flexible lines other than said flexible pipes and therefore smaller diameter.

For the clarity of the figures, the chutes have been described as portions of truncated torus having a circular cross section whose diameter is slightly greater than the diameter of the flexible pipe, but the shape of the arch in the plane XZ 'can all as well be elliptical, parabolic or any other form with variable curvature, whose maximum curvature is less than the critical limit curvature of said flexible pipe. Similarly, the cross section of the chute may be of any shape, for example U-shaped, it being understood that the internal width of the U in the trough portion is slightly greater than the diameter of the flexible pipe. A locking device, not shown, secures each of the hoses to its respective chute, so as to prevent axial sliding of said hose relative to its own chute.

The radius of curvature of the various troughs has been shown in the various figures to be identical, but it will advantageously adopt radii of curvature adapted to each of the pipes, which will minimize the weight of the assembly and thus reduce the necessary buoyancy .

The simple chains la, lb deform in a manner significant when the floating support 2 moves at the mercy of the swell, wind and currents. By against the simple chain portions lal and lbl will deform very little and therefore remain substantially fixed regardless of the movements of the floating support. The distance and adjustment device has been described

10 as being secured to one of its ends is the base 8 or the structure 5, the other end being secured to the tendon, but said device 10 may also be secured to one side of said tendon and the other , an articulated connection, for example a second tendon, the latter being secured at its other end is the base 8 or the structure 5. Thus, said device 10 is disposed between a first tendon and a second tendon however, this particular provision is not the preferred version of the invention.

Claims

1. Device comprising a rigid structure (5) maintained immersed in the sub-surface by floats (6) and anchored to the seabed by tendons (7), useful for supporting a plurality of support elements and shaped guidance of arches referred to as troughs (4) in a bottom-surface connection arrangement between the same floating support (2) and the seabed (3), comprising a plurality of flexible lines comprising flexible lines (l, la, lt >) extending to the bottom of the sea where they are connected to wellheads, equipment or ends of submarine pipes lying at the bottom of the sea, said flexible lines being supported by respectively said plurality of troughs, in which :

said channel support structure (5) is connected to a base (8) resting and / or anchored to the seabed by a plurality of n tendons tensioned substantially parallel, preferably substantially vertically, by said floats, n being at less than 6, a plurality of p said tendons (7) among the n tendons, p being at least equal to (n-2), being connected at one of their ends (7a, 7b) each to a device for variation of distance (10), said distance variation device being connected to said base (8) or said support structure (5) or integral with said base (8) or said support structure (5), the other end of said tendon being fixed to a hooked point integral with said support structure (5) or respectively of said base (8), said distance variation device (10) being able to be actuated to vary the distance between its point hooked to said tendon and said base or said struct a support to which it is attached or attached, and

the upper end of said tendon is fixed to an upper hooked point (7a) integral with said support structure (5) or said distance variation device (10) respectively, the lower end of said tendon being fixed at a point d hung lower (7b) integral with said distance variation device (10) or respectively of said base (8), said distance variation device (10) being able to:

varying the distance between (i) said upper hook point (7a) and said support structure, when said distance variation device (10) is integral with said support structure (5), or

varying the distance between (i) a said lower hooked point (7b) and the said base (8), when the said distance variation device (10) is integral with the said base (8), characterized in that the device comprises at least 6 upper hooking points (7al, 7a2, 7a3, 7a4, 7a5 and 7a6) of which at least 3 first hooked upper points (7al, 7a2, 7a6) are inscribed in a circle (C), the at least 3 other upper hook points (7a3, 7a4, 7a5) being disposed on or within said circle (C).

2. Device according to claim 1, characterized in that said support structure (5) has a longitudinal shape of substantially rectangular section in horizontal section, and the at least 3 said first upper hook points (7al, 7a2, 7a6) are arranged near each of the longitudinal ends of said support structure (5).

3. Device according to claim 1, characterized in that said support structure (5) has a longitudinal shape of substantially rectangular section in horizontal section, preferably substantially symmetrical with respect to a median longitudinal vertical plane (YZ), the device comprising at least at least 6 tendons each connected to a said distance variation device (10), and said support structure (5) comprises at least 6 upper hooking points (7a), including 4 upper hooking points (7al, 7a2, 7a5, 7a6) define the four angles of a rectangle, the two other upper hook points (7a3, 7a4) being disposed within a circle (C) circumscribed in said rectangle, preferably at or near the two great lengths of the rectangle, preferably still at the level of the transverse central axis (XX ') of said rectangle, the 4 hooked points of angle (7a1, 7a2, 7a5, 7a6) being arranged near the longitudinal ends of said structure support (5).

4. Device according to claim 1 or 2, characterized in that said support structure (5) comprises two parts articulated in rotation (5-1, 5-2) about an axis of rotation (XI ΧΊ), substantially horizontal, preferably median, adapted to allow a relative rotation of each of said two parts articulated with respect to each other, an angle of -10 ° to + 10 °, preferably -5 ° to + 5 ° , said rotation being limited by upper stops (5a) and lower abutments (5b) of each of said two articulated support structure parts, the two said articulated portions of support structure being preferably symmetrical with respect to a median vertical plane passing through by said axis of rotation (XI ΧΊ), each of said two articulated parts (5-1, 5-2) being connected to said base by at least three so-called tendons, at least one, preferably the three, is (are) connected (s) to one of its (their) ends to a disposi tif of distance variation (10).

5. Device according to claim 3, characterized in that each said articulated portion (5-1, 5-2) of said support structure (5) has a longitudinal shape of substantially rectangular section in horizontal section, preferably substantially symmetrical relative at a median longitudinal vertical plane (YZ), the device comprising at least 6 tendons, each connected to a said distance variation device (10), and the said support structure (5) comprises at least 6 upper hooking points (7a) each said articulated portion (5-1, 5-2) of said support structure (5) comprising at least:

two upper hooking points (7al-7a2, 7a5-7a6) arranged at the longitudinal ends of each said articulated part furthest from said axis of rotation (XI ΧΊ), and - An upper hook point (7a3, 7a4) disposed closer to said axis of rotation than a said longitudinal end.

6. Device according to claim 4, characterized in that the upper hooking points (7al-7a2-7a3) of said first articulated support structure portion (5-1) are arranged symmetrically at the three upper hook points ( 7a4-7a5-7a6) of the second articulated portion of support structure (5-2) relative to the substantially vertical plane passing through said axis of rotation, preferably isosceles triangle.

7. Device according to one of claims 1 to 6, characterized in that the upper end of said tendon is attached to an upper hooked point (7a) integral with said support structure (5) or said distance variation device respectively (10), the lower end of said tendon being fixed to a lower hooked point (7b) integral with said distance variation device (10) or said base (8) respectively, said distance variation device (10) being able to :

- vary the distance between (i) a said lower hooked point (7b) and said base (8), when said distance variation device (10) is integral with said base (8).

8. Device according to one of claims 1 to 7, characterized in that said upper hook points (7a) of said tendons are disposed at said support structure (5) and said lower hook points (7b) said tendons are arranged at said distance variation devices (10), said distance variation devices being integral with said base, preferably fixed on the upper surface of said base (8), and each said device for variation of distance distance (10) makes it possible to vary the distance between said lower hook point (7b) and said base.

9. Device according to one of claims 1 to 8, characterized in that said tendons are cables or chains.

10. Device according to one of claims 1 to 9, characterized in that it comprises at least one said distance variation device (10) comprising a jack, preferably a mechanical jack or preferably hydraulic.

11. Device according to claim 10, characterized in that said lower hooked point is secured to the movable rod (10b) of a said hydraulic cylinder whose cylinder body (10a) is integral with the base (8). .

12. Device according to one of claims 10 or 11, characterized in that said cylinder comprises a pressure gauge (11c) or preferably a pressure sensor at an orifice (11) of the cylinder body and a locking device ( 11b, 12) adapted to lock the rod in position, preferably by sealing the cylinder chamber.

13. Device according to claim 10, 11 or 12, characterized in that said hydraulic cylinder (10) is connected (11a) or adapted to be connected to a pressurization fluid supply unit embedded in an underwater robot ( 13) preferably driven from a second ship (14) at the surface.

14. Device according to one of claims 1 to 13, characterized in that said support structure (5) supports from 5 to 12 troughs arches 1.5 to 3 m radius of curvature, said support structure measuring 3 to 5 m wide and 10 to 30 m long clean weight in air from 30 to 50 T and said support structure (5) comprising an integrated buoyancy under the face of the troughs so that each said tendon is subject at a tension of 0.5 to 10 T, preferably 1 to 5T, said tendon being sized to be able to withstand a voltage of a multiple of 2 to 4 of said voltage to which it is subjected.

15. Device according to one of claims 1 to 14, characterized in that said support structure is a lattice metal structure extending longitudinally horizontally.

16. Device according to one of claims 1 to 15, characterized in that said rigid support structure is suspended from at least one submerged upper float (6b) to which it is connected by flexible connecting elements such as slings (6c). and / or preferably said support structure is supported by at least one integrated lower float (6a) to which it is attached.

17. Device according to one of claims 1 to 16, characterized in that said support structure (5) supports a plurality of chutes (4), preferably at least 5 chutes offset laterally parallel in a direction (ΥΥ ', ΥιΥΊ , Y ₂ Y ' ₂ ) of said support structure (5), said chutes being arch-shaped preferably arranged symmetrically with respect to a vertical longitudinal axial plane (YZ) of said support structure.

18. Installation of bottom-surface links between the same floating support (2) and the seabed (3), comprising a plurality of flexible lines comprising flexible pipes (1, 1a, 1b) extending from said floating support to the bottom of the sea where they are connected to wellheads, equipment or ends of subsea pipes resting at the bottom of the sea, said flexible lines being supported by respectively said plurality of troughs delimiting each two portions of pipe comprising a first portion of a flexible line (1-1) in the form of a double plunging chain between the floating support (2) and said chute and a second portion of flexible line (1-2) in a simple chain configuration between said chute and the point of contact (1-2a, 1-2b) of the flexible pipe at the bottom of the sea, said chutes being supported by a device according to one of claims 1 to 17.

19. A method of modifying the tensions to which the various said tendons of a device are subjected according to one of the Claims 1 to 17, characterized in that a said distance variation device (10) is actuated so as to adjust the tension of said tendon to which it is connected to a desired controlled value.

20. The method of claim 19, characterized in that the tension of a said tendon is reduced by actuating a said distance variation device to which it is connected and then the tendon is replaced.

21. The method of claim 19, characterized in that the mechanical connection of the various tendons at said support structure is rendered mechanically quasi-isostatic by operating at least one said distance variation device.