OA17784A - Anchoring device for a chute support of a bottom-to-surface installation - Google Patents

Abstract

The present invention relates to a device comprising a rigid structure (5) maintained submerged at the sub-surface by floats (6) and anchored to the seabed by tendons (7), useful for supporting a plurality of chutes (4) in a bottom-to-surface connection installation comprising a plurality of flexible lines (1, la, 1b) extending to the bottom of the sea, said flexible lines being supported by said plurality of chutes, respectively, characterized in that said support structure of chutes (5) is connected to a base (8) resting and / or anchored to the seabed by a plurality of n tendons tensioned in parallel, preferably vertically, by said floats, n being at least equal to 6, a plurality p said tendons (7) among the n tendons, p being at least equal to (n-2) each being connected at one of their ends to a distance variation device (10) integral with said base (8) or with said support structure (5), said device if distance variation being able to vary the distance between said support structure (5) and said base

Description

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

More particularly the present invention relates to an installation of flexible bottom-to-surface links between wellheads, equipment or the ends of subsea pipelines lying on the seabed and a support floating on the surface, comprising a multiplicity of flexible lines. in particular flexible pipes, the lower ends of which are connected to the ends of a plurality of submarine pipes resting on the seabed or directly to wellheads or equipment resting on the seabed.

In the present description, the term “flexible line” is understood to mean conduits or cables capable of accepting large deformations without generating significant return forces, such as flexible conduits defined below, but also cables or conduits of. transfer of energy or information such as electric cables, control cables or hydraulic fluid transfer lines feeding hydraulic equipment such as jacks or lines containing optical fibers; or a control umbilical comprising one or more hydraulic lines and / or electric cables for the transmission of energy and / or information.

The technical sector of the invention is more particularly the field of the manufacture and installation of bottom-to-surface connections for the underwater extraction of oil, gas or other material t

soluble or fusible or a suspension of mineral matter from a submerged wellhead to a floating support, for the development of production fields installed in the 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 swells. It also generally comprises means for storing and processing the oil as well as means for unloading to removal tankers, the latter appearing at regular intervals to carry out the removal of the production. The common name of these floating media is the Anglo-Saxon term Floating Production Storage Offloading (meaning floating medium for storage, production and unloading), the abbreviated term FPSO of which is used throughout the following description.

But it can also be a semi-submersible floating platform installed provisionally for a few years, for example pending the construction and final installation of a floating support of the FPSO type.

Bottom-surface connections are known for an underwater pipe resting on the seabed, a connection of the hybrid-tower type comprising:

- a vertical riser whose lower end is anchored to the seabed by means of a flexible joint, and connected to a so-called pipe resting on the seabed, and the upper end is stretched by a submerged float in sub-surface to which it is connected, and

a connecting pipe, in general a flexible connecting pipe, between the upper end of said riser and a support floating on the surface, said flexible connecting pipe taking, where appropriate, by its own weight the shape of a curve in a plunging chain, that is to say descending widely below the float to then go up to said floating support.

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Also known are bottom-surface connections made by continuously going up to the sub-surface of resistant and rigid pipes made up of tubular steel elements of great thickness welded or screwed together, in a chain configuration with a continuously variable curvature. in their entire length in suspension, commonly called "Steel Catenary Riser" (SCR) meaning "steel riser in the form of a chain" and also commonly called "rigid pipe of the catenary type" or "riser of the SCR type". Such a catenary pipe can go up to the floating support on the surface or only up to a subsurface float which tensions its upper end, which upper end is then connected to a floating support by a plunging flexible connecting pipe.

Bottom-to-surface connections are also known making it possible to connect a floating support to conduits or installations on the seabed entirely made up of flexible conduits, in particular in the case where the water depth is not very great, for example 300 at 750m, even 1000m and where the wellheads or the subsea equipment are not very far from said floating support.

It will be recalled that the term “flexible pipe” here means 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 references API 17J and API RP 17 B. Such hoses are in particular manufactured and marketed by the company TECHNIPCOFLEXIP France. These flexible pipes generally comprise internal sealing layers of thermoplastic materials associated with layers resistant to the pressure internal to the pipe, generally of steel or of composite materials made in the form of spiral strips, contiguous inside the pipe. thermoplastic pipe to withstand the internal burst pressure and completed by external reinforcements above the thermoplastic tubular layer also in the form of contiguous spiral bands, but with a pitch

T longer, that is to say a lower angle of inclination of the helix, in particular from 15 ° to 55 °.

In certain field developments, several wellheads are connected in parallel thanks to a plurality of bottom-surface links joining the same floating support In this case, each of said bottom-surface links must be kept away from its immediate neighbors to avoid any interference and any impact, not only at the level of the floats, but also at the level of flexible pipes and electric cables and other flexible lines such as electric cables or umbilicals for transferring information signals ensuring connection with said floating support, when said flexible pipes are subjected to the effects of the current, and that said floating support is also subjected to the swell, the wind and the current.

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

We seek to implement a maximum of fund-surface links from a single floating support to optimize the exploitation of oil fields. This is why different systems have been proposed which 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-to-surface connections 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 making it possible to associate a large number of links to the same support. floating, despite the problem of the interference of the movements of said risers which are subjected to the same movement as their head tensioning float "

under the effect of the movements of the floating support on the surface subjected to swell, wind and currents.

In these installations, it has been proposed to have 2 flexible pipes superimposed or placed side by side between the floating support and the upper ends of the riser or SCR, the 2 flexible pipes being guided in the subsurface by respectively 2 chutes fixed in a superimposed or laterally offset manner. a tensioning float of a third riser placed closer to the floating support than the first 2 risers, each said chute thus delimiting 2 flexible pipe portions in a 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 said plunging double chain pipe being too deep.

When a multiplicity of bottom-to-surface connections made up exclusively of flexible pipes is used, it is also necessary to space the various connections apart from each other for at least the following reasons.

First of all, flexible pipes are fragile at the level of their outer sheath and it is essential to prevent them from colliding with each other.

On the other hand, the flexible pipes are implemented by passing through guide elements in the form of an arch called chutes defining a rigid bearing surface of convex curved shape explained below, to delimit 2 portions of flexible pipes comprising a first flexible pipe portion in the configuration of a double plunging chain between the floating support and said chute and a second flexible pipe portion in the configuration of a single chain between said chute and the point of contact and tangency of said flexible pipe with the bottom of the sea.

These arch-shaped guide elements called chutes are well known to those skilled in the art; they present :

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

- a cross section in the vertical plane perpendicular to the vertical axial longitudinal plane of the chute, having a shape with a curved bottom preferably circular with concavity facing upwards consisting of said upper outer surface framed by longitudinal side edges ensuring the maintenance and guiding the pipe in the longitudinal direction between said flanges.

In a known manner, the radius of curvature of the longitudinal curvature with a concavity facing downwards is greater than the minimum radius of curvature of the pipe passing through said chute.

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

The function of these chutes and flexible pipe arrangements is to create a plunging double chain curve upstream of the chute between the floating support and the chute, in order 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 seabed by creating trenches and weakening the pipe due to alternating bends in the area of the point of contact, forcing its structure to be reinforced and / or the sea floor to be protected . The stresses and movements of the point of contact of the flexible pipe with the seabed are effectively reduced because the stresses and displacements of pipes are damped by the first flexible pipe portion in the form of a 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 submarine flexible line suspended at its two ends takes, by its own weight, the shape of a so-called plunging double chain curve, known to those skilled in the art, that is to say descending in configuration. chain to a low point of horizontal tangent (see below) to then go up to said floating support, which plunging chain allows significant displacements of its ends absorbed by the deformations of the flexible pipe, in particular the rise or fall. descent of said low point of the plunging chain.

It is recalled that the flexible pipe portion between one end from which it is suspended and the low point of horizontal tangency, namely in the case of said second flexible pipe portion the point of contact at the seabed, adopts a geometric curve formed by a portion of pipe of uniform weight in suspension subjected to gravity, called a chain is a mathematical function of the 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 = Ro (cosh (x / Ro) ^_1 )

R = Ro. (Y / Ro + l) ² in which:

- x represents the distance in the horizontal direction between said point of contact and a point M of the curve,

- y represents the altitude of point M (x and y are therefore the abscissas and ordinates of a point M of the curve with respect to an orthonormal reference whose origin is at said point of contact),

- Ro represents the radius of curvature at said point of contact, i.e. at the point of horizontal tangency,

- R represents the radius of curvature at 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 _o in formula above). Under the effect of waves, wind and current, the surface support moves sideways and vertically, which has the effect of raising or resting the pipe in the shape of a chain, at seabed level.

In the case of a bottom-surface connection by simple chain, the most critical portion of the chain is located in the portion close to the point of contact and, the greatest part of the forces in this lower part of the chain are in fact generated by the proper movements of the floating support and by the excitations which occur in the upper part of the chain subjected to the current and to 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 the plunging double chain of flexible pipe upstream of the chute is therefore, more precisely 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, by mechanically decoupling the respective movements of said second flexible pipe portion in a single chain and of said floating support. However, another function is also to reduce the traction forces exerted by said second flexible pipe portion, on the marine equipment and / or the end of the pipe resting on the seabed to which it is connected, if applicable. .

In the prior art, these intermediate support chutes for said flexible pipes are maintained on the surface at a certain depth by floats supporting or from which each of the chutes are suspended. However, these floats are subjected to significant movements which requires providing a sufficient distance between the various floats to prevent them from colliding against each other.

These constraints imply a spreading out 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 level of the planks, to avoid interference between the different flexible connections and the 10 different floats. . This is why an attempt is made to provide an installation capable of using from a single floating support a plurality of bottom-surface connections of flexible type of reduced size and movement and which is also simpler to install and which can be manufactured at sea from a pipe laying vessel.

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

In the prior art, it is sought to minimize the number of tendons between the chute support structure and the base at the bottom of the sea, in order to be with no more than 2 upper attachment points aligned at the level of the support structure for chutes and therefore no more tendons aligned in the same plane, generally vertical, at their upper ends in order to obtain an isostatic mechanical connection. Indeed, if 3 tendons are used, maintaining an isostatic connection requires that the 3 upper attachment points of said tendons parallel to each other and substantially vertical, be in a triangular arrangement, preferably an equilateral triangle, in a plane. which is not a substantially vertical plane. The more said triangle is flattened, that is to say that its vertex tends towards an angle of 180 °, the closer we get to a configuration of three aligned points and the more we deviate from an isostatic configuration.

Mechanically, a configuration is said to be “isostatic”, when the distribution of the forces in said tendons is unequivocal and therefore calculable in a known manner. 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 mechanically "hyperstatic", that is to say that the distribution of the forces 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 assembly possibly becomes wobbly, some tendons being able to take up a greater part of the load, while others will be less loaded, or even in some cases completely. soft, i.e. they will not take any charge.

In the prior art described above, 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 the chutes in the case of two tendons. , or again in the case of three tendons arranged in a triangle in a plane which is not substantially vertical. This generally results in a very significant or even complete tilting of the trunking support structure which risks irreparably damaging the flexible pipes or the electric cables that they support and thus lead to the partial or total ruin of the pipe. bottom-to-surface installation. In addition, such incidents risk causing major pollution in the case of crude oil production lines.

These breaks are particularly feared in the case of installations where the water depth is not very great, that is to say a few tens or even a few hundred meters, because in these depths, the swell and the current act on any the water section and are then particularly aggressive with respect to 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 submerged support structure, therefore on the tendons and their upper and lower attachment points. Thus, when the depth is not very great, that is to say up to 300m of water depth and when the oceano-weather conditions are severe, the hoses, the supporting structure of the chutes and their connections with foundations at the bottom of the sea are particularly subject to significant, even extreme, forces 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 system with multiple tendons consists in designing a support structure for chutes having great flexibility, that is to say capable of being deformed significantly, which makes it possible to make participate then, but within certain limits, all the tendons. The main drawback of this configuration is that the feared fatigue and wear problems in the tendons and their attachment 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 an anchoring system for said support structure for which it is possible without difficulty to carry out maintenance operations consisting in changing any of the tendons, without disturbing the operation of the device, and therefore without needing to disconnect the tendons. pipelines 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 flexible pipe bottom-surface connections from the same support structure for chutes anchored to the seabed by a plurality of sinews. '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 carry out an easy manufacture and installation by manufacturing and sequential laying of the various pipes from a surface laying vessel, and to optimize the implementation of the buoyancy and tensioning and anchoring means. of the chute support structure in the case of installation spread over time over a long period of time between the installation of the various flexible bottom-surface connections, without it being necessary to know at the start the number of connections that are to be installed, nor 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 only incompletely known at this stage, production at full capacity then often requires reconsideration, after a few years, the initial production plans and the organization of associated equipment. Thus, during the installation of the initial system, the number of fund-surface links and their organization is defined in relation to estimated needs, said needs being almost systematically revised upwards after the field has been put into production, or to recovery of crude oil, either for the need to inject more water into the reservoir, 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 places in the field, so as to increase the overall recovery rate, which further complicates all the bottom-surface connections connected to the plating of the FPSO.

Another problem of the present invention is also to provide an installation of flexible bottom-surface connections of great resistance and of low cost, and of which the methods of manufacture and installation and of maintenance of the various constituent elements are simplified. and also of low cost, and can be carried out at sea from a laying vessel.

To do this, the present invention relates to a device comprising a rigid structure maintained submerged at the sub-surface by floats and anchored to the seabed by tendons, useful for supporting a plurality of support and guide elements in the form of a arch called chutes in an installation of fund-surface connections between the same floating support and the seabed, comprising a plurality of flexible lines comprising flexible conduits extending to the seabed where they are connected to wellheads , equipment or ends of submarine pipes resting on the seabed, said flexible lines being supported by said plurality of chutes respectively.

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 3, a plurality of p said tendons among the n tendons, p being at least equal to (n-2), each being connected at one of their ends 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 an attachment point integral with said support structure or respectively with said base, said device for variation of distance being able to be actuated to vary the distance between its point of attachment "

said tendon and said base or said support structure to which it is fixed or connected.

More particularly and preferably, the upper end of said tendon is fixed to an upper attachment point integral with said support structure or respectively with said distance variation device, the lower end of said tendon being attached to a lower attachment point integral of said distance variation device or respectively of said base, said distance variation device being capable of:

- vary the distance between said upper attachment point and said support structure, when said distance variation device is integral with said support structure, or

- Varying the distance between a said lower attachment 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 integral with said structure is fixed to said support structure on the underside of the latter, and when it is integral with said base, said distance variation device is attached. on the upper surface of said base.

It is understood that the reduction 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 respectively a decrease in the tension of said tendon. On the other hand, the increase in the tension of the said tendon can cause an elongation of the 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) attachment point and said base (or respectively said support structure), the difference resulting from the variation in length of the tendon when the tension in said tendon increases due to the fact that the distance between said base and said support structure decreases. More precisely, 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) attachment point and said base (or respectively said support structure) due to tendon elongation.

Thus, it is possible to configure at will during operation the distribution of the loads taken up by the different tendons as a function of the loads supported by said support structure at the level of 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 quasi-isostatic, and if necessary make it possible to distribute the load in a controlled manner on each of the tendons.

On the other hand, the distance variation device makes it possible to facilitate the maintenance and replacement of 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 in depth, the distance variation device makes it possible to adjust the distance between the upper and lower attachment points between 0 and 3m, from preferably between 0 and 1.5m which is sufficient to adjust the tensions according to the rebalancing required according to the loads created by said flexible pipes or lines at the level of the chutes.

It is understood that said distance variation device may be integral with (i) said support structure in which case said upper attachment point is integral with the distance variation device *

or (ii) preferably integral with said base at the bottom of the sea, in which case said lower attachment point is integral with the distance variation device.

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

Intervention at the level of a distance variation device, for its actuation or its handling, is easier when it is fixed on the base because it is more clear, in particular to allow handling using an underwater robot as described below, only when it is positioned on the underside of the support structure, taking into account the size associated with the multiplicity of pipes and flexible lines passing through the chutes. In this case, the distance variation device is a device for varying the distance between said lower attachment point and said base.

In known manner, a said tendon consists of a cable or a chain or else of a rigid bar articulated at its ends. Preferably, said tendon connected to a said device for varying the distance is a cable or a simple 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 attachment points of the three said tendons are f

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 device for varying the distance.

In FR 2 954 966, a device is described comprising a rigid structure for supporting a plurality of chutes of the type described above, said structure being anchored by a plurality of anchor lines, the upper attachment points of which are arranged. in pairs in four zones of the structure, the four zones being arranged in a trapezoidal shape. If a pair of tendons in one of the angles of the trapezoid fail, the other tendons are no longer certain to ensure the stability of the support structure in all circumstances like an unstable tripod, as explained later.

An aim of the present invention is therefore to provide an improved installation with a large quantity of flexible bottom-surface connections making it possible to connect a floating support with a plurality of wellheads and / or subsea installations installed at the bottom of the sea. the sea, comprising a support structure for submerged chutes anchored to the seabed by a plurality of tendons which overcomes the drawbacks mentioned above.

To do this, the present invention provides a device comprising a rigid structure maintained submerged at the sub-surface by floats and anchored to the seabed by tendons, useful for supporting a plurality of support and guide elements in the form of a. arch called chutes in an installation of fund-surface connections between the same floating support and the seabed, comprising a plurality of flexible lines comprising flexible conduits extending to the seabed where they are connected to wellheads , equipment or ends of submarine pipes resting on the seabed, said flexible lines being supported by said plurality of chutes, respectively, 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, a plurality of 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, 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 an attachment point integral with said support structure or respectively with 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 fixed or connected, and

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

- vary the distance between said upper attachment point and said support structure, when said distance variation device is integral with said support structure, or

- varying the distance between a said lower attachment point and said base, when said distance variation device is integral with said base, characterized in that said device comprises at least 6 upper attachment points including at least 3 first upper attachment points are inscribed in a circle (C), the at least 3 other upper attachment points being placed on or inside 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 attachment points are arranged near each of the longitudinal ends of said support structure.

It can therefore be understood that two of said attachment points are arranged near a first longitudinal end, the other said attachment point being arranged on the side of the opposite longitudinal end of said support structure.

It will be understood that all of said upper attachment points are distributed half 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 said upper attachment points on said rigid structure is applied near the center of gravity of said rigid structure corresponding substantially to the center of said circle.

Preferably, all of said upper attachment points are distributed so as to be arranged symmetrically with respect to the center of said circle.

More particularly, at least two said upper attachment points are diametrically opposed and arranged respectively near each of the opposite longitudinal ends of said support structure.

More particularly still, said upper attachment points according to the present invention are arranged and spaced in a plane of horizontal section of said structure such that at least two upper attachment points inscribed in said circle (C) are arranged at proximity respectively to each of the opposite longitudinal ends of said support structure and at least two said upper attachment points inscribed on the circle (C) are arranged respectively near each of the opposite transverse ends of said support structure, said transverse direction being the direction perpendicular to the longitudinal direction of said support structure in said plane of horizontal section.

More particularly still, when there are only three upper attachment 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 variation device. distance and said support structure comprises at least 6 said upper attachment points, of which 4 upper attachment points define the 4 angles of a rectangle, the other two upper attachment points being placed inside a circle ( C) circumscribed to said rectangle, preferably at or near the two long lengths of the rectangle, preferably also at the level of the transverse median axis (XX ') of said rectangle, the 4 corner attachment points being arranged near longitudinal ends of said support structure.

This form of support structure is the most practical for supporting 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 a trapezium provide stabilization of the support structure during the replacement of said tendon to be replaced. On the other hand, with only 5 tendons in the trapezoid, one would no longer be certain to ensure the stability of the support structure in all circumstances in the event of a tendon rupture with only 4 tendons remaining in tension, because in certain configurations, the trapezius is would transform into an unstable type triangle.

In one embodiment, said support structure comprises two parts articulated in rotation about an axis of rotation (XI X'i), substantially horizontal, preferably median, capable of allowing relative rotation of each of said two articulated parts. 'with respect 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 support structure parts, the two said articulated support structure parts being preferably symmetrical with respect to a median vertical plane passing through said axis of rotation (XI X'i), each of said two articulated parts being connected to said base by at least three said tendons of which at least one, preferably all three, is (are) connected at one of its (their) ends to a distance variation device.

More particularly, each said articulated part 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 attachment points arranged at the longitudinal ends of each said articulated part furthest from said axis of rotation (XI X'i), and

- An upper attachment point arranged closer to said axis of rotation than to said longitudinal end.

More particularly still, the upper attachment points of said first articulated support structure part are arranged symmetrically, at the three upper attachment points of the second articulated support structure part with respect to the substantially vertical plane passing through said axis of rotation, preferably in an 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 the tensions of the tendons due to the relative independence of the tendons of each of the two. half structures.

The distance variation device may be a system of cables with a said attachment point at its end cooperating with 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 cylinder, preferably a mechanical or preferably hydraulic cylinder.

The use 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 manometer or preferably a pressure sensor at an orifice of the cylinder body.

More particularly, said lower attachment point is integral with the movable rod of a said hydraulic cylinder, the cylinder body of which is integral with the base.

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

In a preferred embodiment, said cylinder comprises a manometer or preferably a pressure sensor at an orifice of the cylinder body and a locking device capable of locking the rod in position, preferably by sealing the chamber tightly. cylinder.

Also preferably, said hydraulic jack is connected or able to be connected to a pressurization fluid supply unit on board an underwater robot preferably piloted from a second vessel on the surface.

More particularly, said support structure supports 5 to 12 arch-shaped chutes with a radius of 1.5 to 3 m of curvature, said support structure measuring 3 to 5 m wide and 10 to 30 m long in own weight in the air from 30 to 50 T and said support structure comprising a buoyancy integrated under the face of the chutes so that each said tendon is subjected to a tension of 0.5 to 10 T, preferably from 1 to 5 T, 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.

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

More particularly still, said rigid support structure is suspended from an upper submerged 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 still, said support structure supports a plurality of chutes, preferably at least 5 chutes, laterally offset parallel in a direction (YY ') of said support structure, said chutes being in the form of an arch 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 held in a said chute by retaining means and / or hooking means; and

- The chutes supported by the same rigid support structure are arranged at different heights; and

- The ends of the troughs which it supports comprise a deflector whose profile is capable of preventing damage to the portion of flexible pipe which can come into contact with said deflector during the laying of the pipe on a said trough.

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

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

The present invention also provides a method according to the invention characterized in that the tension of a said tendon is reduced by actuating a said device for varying the distance to which it is connected and then the tendon is replaced.

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

The term “quasi isostatic” is understood here to mean, in a known manner, the fact that the tension in each of the tendons is known and that during the movements of the chute support structure under the effects of the swell, the current and the movements of the floating support. , said chute support structure moving substantially in a horizontal plane, the tension in each of said tendons varies in a known manner and within a limit set by the overall geometry of said tendons, preferably parallel to each other.

Other characteristics 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 an installation of bottom-surface connections according to the invention between a floating support 2 anchored 2b and a metal support structure 5 supporting a plurality of troughs in the form of arches 4, anchored on a base 8 resting on the seabed 3, by means of a plurality of tendons 7,

- Figure 2A is a side view of an installation of the prior art in the case of a single flexible pipe 1 resting on a single arch-shaped chute 4, anchored by a single tendon 7 ending at its upper end by a crow's feet 7c so that the tendon is hooked to the chute at the level of two upper attachment points 7a, a buoyancy element being located above the chute and connected to the latter,

- Figure 2B is a front view of an installation of the prior art comprising a structure supporting three chutes, said structure being anchored by two tendons, and equipped with a single float,

- Figure 3A is a front view in the YZ plane of an installation according to the invention comprising a structure 5 secured to a plurality of integrated floats 6a to said structure, supporting a plurality of chutes, namely six chutes 4a to 4f, said structure being anchored by six tendons 7 attached at six upper attachment points 7a to 7a6,

- Figures 3B and 3C are bottom views of the structure 5 with a rectangular horizontal section (XY plane) relating to Figure 3A detailing the arrangement in a rectangle of the six upper attachment points 7a to 7a6 of the six tendons,

- Figures 3D and 3E are bottom views of the structure 5 with a rectangular horizontal section (XY plane) showing two upper attachment points 7a3-7a4, located in the corbelled structure of the structure 5, 3 upper attachment points (fig. . 3E) or 4 upper attachment points (fig. 3D) being inscribed in a circle (C), the other upper attachment points being located inside circle C,

- Figure 4A is a side view in the XZ plane of Figure 3A detailing the buoyancy elements 6a consisting of section boxes in the XZ plane of prismatic or rectangular type integrated into the supporting structure 5 below the chutes, said boxes being filled with solid, liquid or gaseous compounds, lighter than sea water,

FIG. 4B is a side view of FIG. 3A detailing the buoyancy elements made up of cylindrical type caissons 6a with a section in the circular XZ plane integrated into the supporting structure of the chutes,

- Figure 5 is a side view of an installation at the level of a common base 8 comprising two distance variation devices 10 allowing the individual adjustment of the length of each of two tendons 7-1, 7-2 attached at lower attachment points 7bl, 7b2 at the level of the rod 10b of a jack 10 according to the invention, and

- Figure 6 is an alternative embodiment of a distance variation device 10 comprising a jack 10 equipped with a hydraulic pressure gauge 11c of the jack according to the invention, and

- Figures 7A to 7C show an embodiment in which said support structure 5 comprises two parts articulated in rotation 5-1, 5-2 relative to a median axis Χ1ΧΓ.

In Figure 1 there is shown a fund-surface connection installation comprising two flexible conduits or electric cables 1a, 1b connected at one end 2a to a floating support 2, held in position by anchor lines 2b, the other end of said pipes. hoses lying substantially at the bottom of the sea 3.

The flexible pipes la, lb are in a descending plunging chain configuration from the floating support 2, up to a point of horizontal tangency, respectively la ', lb', then in a rising chain configuration up to the inlet 4al d ' 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 1a enters at 4a in the chute 4a, then rests on said chute and comes out at 4a2 to join, in the configuration of a single chain la, the seabed 3 substantially at the. Each of the chutes 4a, 4b, etc. is positioned in lateral offset, with respect 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 secured to each other by means of said structure 5. Said structure comprises buoyancy elements 6 which can be either integrated 6a into said structure 5, or external. , usually in the form of floats

6b located above said structure and connected to the latter by means of a single tendon 6cl, as shown in Figure 2A, or a crow's feet 6c2, as shown in Figure 2B.

The support structure 5 is maintained substantially at an altitude h relative to the seabed thanks to a plurality of tendons 7 connected at their upper ends to upper attachment points 7a to said structure 5 and their lower ends to points d 'lower attachment 7b to a base 8 resting on the seabed 3, for example a weight base, or a suction anchor driven into the ground hereinafter called a 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 simple flexible pipe 1, as shown in FIG. 2A, a single tendon 7 is used, where appropriate connected to said structure 5 by means of a crow's feet 7c, said tendon then being in the same vertical plane as said flexible pipe. Likewise, in the case of a plurality of flexible conduits or electric cables arranged on a plurality of 3 chutes 4a to 4c juxtaposed laterally, as shown in FIG. 2B, the support structure 5 is connected to its base 8 by means of two tendons, connected if necessary to said support structure 5 by means of a crow's feet (not shown).

These two means of anchoring the support structure 5 are generally 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 FIG. 2B, consider implementing three tendons, but it would be appropriate, in order to maintain the isostatic character of the whole, that said attachment points of said tendons are not aligned but are in a triangular configuration, in any plane which is not a vertical plane.

Thus, in the prior art previously described, the rupture of a tendon either leads to the ruin of the installation as in the case of FIG. 2A where the tendon is unique, or leads to a dangerous imbalance of the structure 5 in the case of two tendons as shown in FIG. 2B, or in the case of three tendons arranged in a triangle in a plane which is not substantially vertical. This generally results in a very large, or even complete, tilting of the structure 5 which risks irreparably damaging the flexible pipes or the electric cables and thus leading to the partial or total ruin 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 risk causing major pollution in the case of crude oil production lines.

These breaks are particularly feared in the case of installations where the water depth is not very great, that is to say a few tens or even a few hundred meters, because in these depths, the swell and the current act on any the water section and are then particularly aggressive with respect to 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, therefore on the tendons 7 and their upper attachment points 7a and lower 7b. . Thus, when the depth is not very great, that is to say from 25 to 300m of water depth and when the ocean-weather conditions are severe, the hoses, the supporting structure of the gutters and their connections with the foundation are particularly subject to significant or even extreme stresses 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 attachment points, the device according to the invention advantageously anchors the structure 5 by means of at least 6 tendons distributed preferably from symmetrically on either side of the YY axis of said structure 5 as shown in a bottom view in FIG. 3B. Each of the upper attachment points 7a1-7a2-7a3-7a47a5-7a6 of the structure is connected to the corresponding lower attachment point, not shown, respectively 7bl-7b2-7b3-7b4-7b57b6, via a tendon, respectively 7i-7 ₂ -7 ₃ -7 ₄ -7 ₅ -7 ₆ , all the tendons preferably being mutually parallel and vertical.

In Figure 5, there is illustrated the lower attachment points 7bl7b2, as well as the tendons 7i-7 ₂ , said lower attachment points being integral, according to the invention, not directly to the foundation 8, but to a distance variation device 10 serving to adjust the distance L, respectively Li-L ₂ , of said lower attachment point to said foundation 8. In fact, a rigid structure 5 anchored by two tendons connected to the foundation, or even three tendons , provided that the three upper attachment points 7a of said tendons are not aligned, nor located in the same vertical plane, mechanically have a so-called "isostatic" configuration, that is to say that the distribution of the forces in said tendons is univocal and therefore calculable in a known manner, in particular as a function of the distribution of the load supported by the support structure 5 and of the buoyancy elements integrated into 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 the forces in each tendon can no longer be calculated univocally. In this hyperstatic case, as in the case of a four-legged stool, 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 even in some cases completely soft. , that is, they will not take any charge.

One solution for reducing the hyperstaticity of the multiple tendon system consists in designing a structure 5 exhibiting great flexibility, that is to say capable of being deformed significantly, which then makes it possible to involve, but within certain limits, all the tendons. The main drawback of this configuration $

is that the feared fatigue and wear problems in the tendons and their attachment points are then transferred to structure 5 and can thus lead, in the event of an 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, is advantageously installed on the tendons, preferably on each of the tendons, a distance variation device 10 according to the invention. , capable of allowing the distance between its upper attachment point 7a to be fixed to the structure 5 and its lower attachment point to the foundation 8.

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

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

In FIGS. 3D and 3E, two upper intermediate attachment points 7a3 and 7a4 are offset on either side of the median transverse axis XX of the structure and offset along XX outside the long sides of the rectangle, by in such a way that they are joined to said structure 5, but corbelled. On the face

3E, a small side of the rectangle is bordered by 2 upper corner attachment points 7a1, 7a2, the opposite side of the rectangle in the longitudinal direction comprising a single upper attachment point 7a6 in the middle position. In all cases, all the upper attachment points of the tendons are then located on or inside the circle C circumscribed by the rectangle formed by the four upper attachment points 7a1, 7a2, 7a5, 7a6 at the 4 angles (fig.3D) or the circle circumscribed to the triangle formed by the 3 upper attachment points 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 of 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.

The term “quasi-isostatic” is understood here to mean the fact that all the tendons collaborate in the resumption of the tension created by the resulting buoyancy directed upwards and that each of said tendons substantially takes up a known and adjustable percentage of said overall tension.

The device for varying distance and quasi-static adjustment 10 according to the invention makes it possible, at the level of each of the tendons of the device, and individually, to adjust the distance between the base 8 and the structure 5, and thus to distribute in a perfectly controlled manner the unit charge in each of said tendons, thus making the device almost isostatic.

To do this, the altitude L relative to the foundation 8, of the lower attachment point 7b of the tendon 7 can be adjusted using the distance variation device 10 shown here as being a hydraulic cylinder with mechanical rod locking, known those skilled in the art. Said distance variation device 10 according to the invention consists of a jack body 10a integral with the base, and a jack rod 10b at the top of which is the lower attachment point t

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 said cylinder by a conduit lia to a hydraulic unit (not shown) available on board an ROV 13, an automatic submarine piloted from an installation vessel 14 surface. Thus, by pressurizing the cylinder, the cylinder rod is forced to retract lengthwise downwards and the distance between the base 8 and the structure 5 and therefore the distance between the base 8 and the structure 5 and therefore the lengths which has for effect of increasing tension in the affected tendon. By acting successively on each of the tendons, the load which each of the tendons takes up is thus distributed advantageously and in a perfectly controlled manner, which makes it possible to make the whole “quasi-isostatic”.

When the jack 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 up by said tendon increases, and the other tendons generally see their tension decrease slightly.

Likewise, when the pressure P of the fluid in the cylinder is reduced, the rod of the cylinder is deployed, and the tension in the tendon concerned decreases so that the percentage of overall force taken up by said tendon decreases, and the others tendons generally see their tension increase slightly.

Thus, the pressurization or depressurization of a said jack makes it possible to adjust the distance between the foundation 8 and the upper attachment point 7a at the level of each of the tendons and individually, and therefore to adjust the percentage of the overall tension T taken up individually by said tendon. When the adjustment is complete, a locking device is actuated in position 12-12a of the rod 10b of the cylinder, then the cylinder pressure is released and the hydraulic supply hose 11a is disconnected. In this figure 5 there is shown on the right the distance variation device 10 relating to the tendon 7 ₂ in the locked position 12a at the altitude L2, and on the left, the distance variation device 10 relating to the tendon 7i in progress adjustment to the altitude L1, the ROV 13 (automatic intervention submarine piloted from the surface) connected by the duct 13a to the pressurization orifice 11 being in the process of adjusting the pressure P of the cylinder, therefore the tension in said tendon 7i. During this adjustment, the locking device 12 is held in the open position 12b, so the jack is free to move in extension or in 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. In fact, the two non-adjustable tendons, preferably located at the opposite longitudinal ends of the structure 5, then define the substantially horizontal anchor reference axis of the structure 5 with respect to the base 8, the adjustment of each of the other tendons then makes it possible to make the system quasi-isostatic, therefore allows the load to be distributed in a controlled manner on each of the tendons. Likewise, only n-1 distance variation devices 10 could be available for n tendons.

We can also install n-3 distance variation devices 10 for n tendons, the three tendons not adjustable and not aligned, then defining a substantially horizontal triangle and therefore a substantially horizontal reference plane for the structure 5 vis-à-vis of the base 8. The adjustment of each of the other tendons then makes it possible to make the system quasi-isostatic, therefore makes it possible 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.

In fact, in a preferred version of the invention where each of the tendons comprises a distance variation device 10 allowing the length adjustment of the tendons, it is then possible without difficulty to carry out maintenance operations consisting in changing any one of the tendons, without disturbing the operation of the device, therefore without having to stop oil production. Indeed, it suffices then to:

- reconnect the hydraulic circuit 13a of the ROV 13 to the port 11 of the cylinder 10a, then

- Unlock the device 12-12b and release the pressure of the jack to completely relax said tendon; then

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

- retensioning said tendon to its initial value; then

- lock device 12-12a and disconnect ROV 13.

During such a tendon maintenance operation, which generally occurs after the rupture of said tendon, the overall force T is provisionally distributed between the n-1 active tendons, the tensions generally increasing in all of said n- 1 tendons, then returning to the initial value when a new tendon has been reinstalled and its own tension readjusted by means of 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 the problems of fatigue and rupture, the consequences of which are feared.

For simplicity and clarity of the explanations, 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 thus makes it possible to know very precisely the tension T applied in the tendon concerned. However, it would very well have been possible to use a distance variation device 10 consisting of a mechanical screw jack or rack. But, in this case, it is also necessary to integrate in said device a cell for measuring the load or voltage applied to said tendon such as a dynamometer with direct reading by an ROV, or with data transmission to the surface up to command post located on board the floating support, so as to be able to correctly adjust the distribution of all the loads in the various tendons.

FIG. 6 shows a preferred version of the invention in which the cylinder 10 does not have a rod blocking device 12, but is hydraulically blocked by sealing 11b of the internal chamber of said cylinder. Thus, the jack is permanently under pressure and there is advantageously a manometer or a pressure sensor permanently installed 11a on the orifice 11 of said jack. There is thus a permanent display of the tension of each of the tendons, this tension being correlated with said pressure of the cylinder, and this display can be very simply consulted during routine inspections carried out at regular intervals, for example by an 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 available at the level command, a perfectly precise state of all the flexible arches and their anchoring system. In the event of a rupture of any of the tendons, the command will be instantly informed, and if necessary will be able to determine the failing tendon. Likewise, in the event of damage to a buoyancy element 6, either a complete rupture or a partial invasion, the overall vertical tension will decrease and certain tendons 7 will see their tension drop. The FPSO command will then be quickly informed and will be able to initiate corrective actions.

By way of example, a supporting structure 5 for chutes 4 comprises 5 to 12 chutes with a radius of 1.5 to 3 m of curvature and measures 3 to 5 m wide, 5 to 30 m long and its own weight in the air can reach and exceed 30 to 50 tons, or even more. The buoyancy 6a integrated into the structure 5 or in the form of a float 6b located above said structure is dimensioned so as to compensate for the own weight of said structure 5 equipped with its chutes and various (

accessories not shown, as well as the own weight of all the flexible pipes 1 in chain configuration. Additional buoyancy 6a is integrated into the assembly so as to create a permanent upward tension of 3 to 60 tonnes, preferably 6 to 30 tonnes. The device according to the invention thus makes it possible to adjust the tension in the various tendons by substantially dividing the previous forces by six, namely for each of the tendons, a permanent tension of 0.5 to 10 tons, preferably 1 ton to 5 tons. . In order to avoid the failure of the device in the event of rupture of a tendon or of an attachment point 7a-7b, or even in certain cases of two tendons or of their attachment points, the tendons and their attachment points will advantageously be dimensioned. respective attachment points with a safety factor of 2 to 4, for example; thus, for a nominal force of 2 tonnes, the tendon and its attachment points are dimensioned for forces of 5 to 10 tonnes. This avoids the problems of fatigue and wear as well as the risks of breakage, which even if it occurs, would not endanger the bottom-surface connection as a whole in any case.

In FIGS. 7A and 7C there is shown a said support structure 5 comprising two parts articulated in rotation 5-1, 5-2 about a median axis of rotation X1X1 ', substantially horizontal, capable of allowing a relative rotation of each of the two said parts articulated with respect to each other, at an angle alpha of -10 ° to + 10 °, preferably from -5 ° to + 5 °, said rotation being limited by upper stops 5a and lower stops 5b of each of the two said articulated parts of the support structure. The two said articulated support structure parts are of symmetrical shape and arrangement with respect to a median vertical plane passing through said axis of rotation Χ1ΧΓ. In practice, the upper plane of said first articulated part

5-1 varies by an angle alpha relative to the upper plane of said second articulated part 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 articulated part 5-1, 5 -2 of said support structure 5 has a longitudinal shape of substantially rectangular section in horizontal section, substantially symmetrical with respect to a median longitudinal vertical plane (YZ), each said articulated part 5-1, 5-2 of said support structure 5 comprising :

- two upper attachment points 7a1-7a2, 7a5-7a6 arranged at the longitudinal ends near the angles of each said articulated part furthest from said axis of rotation (Xl-X'l), and

an upper attachment point 7a3, 7a4 disposed closer to said axis of rotation than to said longitudinal end.

The 3 upper attachment points 7a4-7a2-7a3 of said first articulated part of the support structure 5-1 are arranged in an isosceles triangle symmetrically with the three upper attachment points 7a4-7a57a6 of the second articulated part of the support structure 5-2 with respect to the substantially vertical plane passing through said axis of rotation ,.

The term “floating support” is understood here to mean both a barge or ship and a semi-submersible platform of the type described above.

It is understood that said upper part of the support structure, supporting or on which said chutes are fixed 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 movements in said first portion of said flexible pipes.

The chute support structure 5 is a rigid structure, but the stresses and movements in particular at the point of contact of the pipes with the seabed are nevertheless considerably reduced due to the tensioning of said support structure by said floats.

To facilitate the laying of flexible pipes from a laying vessel as explained later in the description, the ends of the chutes include a deflector, the profile of which is able to avoid damaging the portion of the flexible pipe which may come into contact with it. said deflector in the course of laying the pipe on a said lower chute.

The top of the bottom of the chute is the point located at the mid-length of the chute.

Said support structure can also support chutes serving to guide and support flexible lines other than said flexible pipes and therefore of smaller diameter.

For the clarity of the figures, the chutes have been described as being portions of a truncated torus having a circular cross section, the diameter of which is slightly greater than the diameter of the flexible pipe, but the shape of the arch in the plane XZ 'can be quite it may also be of the ellipse, parabolic or any other shape with variable curvature, the maximum curvature of which is less than the critical limit curvature of said flexible pipe. Likewise, 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 portion of the chute 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 any axial sliding of said hose with respect to its own chute.

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

The simple chains 1a, 1b deform significantly when the floating support 2 moves with the swell, wind and currents. On the other hand, 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 variation and adjustment device has been described as being integral at one of its ends either with the base 8 or with the structure 5, the other end being integral with the tendon, but said device 10 can also be integral on one side of said tendon and on the other, with an articulated connection, for example a second tendon, the latter being integral at its other end either with the base 8 or with the structure 5. Thus, said device 10 is located between a first tendon and a second tendon, however, this particular arrangement does not constitute the preferred version of the invention.

Claims (21)

1. Device comprising a rigid structure (5) kept submerged at the sub-surface by floats (6) and anchored to the seabed by tendons (7), useful for supporting a plurality of support and shaped guiding elements. arch called chutes (4) in an installation of bottom-surface connections between a single floating support (2) and the seabed (3), comprising a plurality of flexible lines comprising flexible pipes (1,13,1b ) extending to the bottom of the sea where they are connected to wellheads, equipment or ends of subsea pipelines resting on the bottom of the sea, said flexible lines being respectively supported by said plurality of chutes, device in which : - Said chute 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 the bottom of the sea less equal to 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 varying 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 an attachment point integral with said support structure (5) or respectively with said base (8), said distance variation device (10) being able to be actuated to vary the distance between its attachment point 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 fixed to an upper attachment point (7a) secured to said support structure (5) or respectively to said distance variation device (10), the lower end of said tendon being fixed to a point d 'lower hook (7b) integral with said distance variation device (10) or respectively with said base (8), said distance variation device (10) being able to: - varying the distance between (i) said upper attachment 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) said lower attachment point (7b) and said base (8), when said distance variation device (10) is integral with said base (8). 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 6 tendons each connected to a said distance variation device (10), and said support structure (5) comprises at least 6 upper attachment points (7a) of which 4 upper attachment points (7al, 7a2,7a5,7a6) define the 4 angles of a rectangle, the other two upper attachment points (7a3,7a4) being arranged inside a circle (C) circumscribed to said rectangle, at or near the two long lengths of the rectangle, the 4 points of angle hook (7a1, 7a2,7a5,7a6) being arranged near the longitudinal ends of said support structure (5). 2. Device according to claim 1, characterized in that said two other upper attachment points (7a3, 7a4) are arranged inside said circle (C) circumscribed to said rectangle at the level of the transverse median axis (XX ') of said rectangle. 3. Device according to claim 1 or 2, characterized in that said support structure is supported by at least one integrated lower float (6a) on which it is fixed. 4. Device according to one of claims 1 to 3, characterized in that said support structure (5) comprises two parts articulated in rotation (5-1, 5-2) about an axis of rotation (XI X'i ), substantially horizontal, preferably median, capable of allowing a relative rotation of each of said two parts articulated with respect to one another, by an angle of -10 ° to + 10 °, preferably of -5 ° to + 5 °, said rotation being limited by upper stops (5a) and lower stops (5b) of each of the two said articulated support structure parts, the two said articulated support structure parts preferably being symmetrical with respect to a median vertical plane passing through said axis of rotation (XI X'i), each of said two articulated parts (5-1, 5-2) being connected to said base by at least three said tendons of which at least one, preferably the three is (are) connected at one of its (their) ends to a distance variation device (10). 5. Device according to claim 4, characterized in that each said articulated part (5-1, 5-2) of said support structure (5) has a longitudinal shape of substantially rectangular section in horizontal section, preferably substantially symmetrical with respect to at a median longitudinal vertical plane (YZ), the device comprising at least 6 tendons each connected to a said distance variation device (10), and said support structure (5) comprises at least 6 upper attachment points (7a) , each said articulated part (5-1, 5-2) of said support structure (5) comprising at least: - two upper attachment points (7a1-7a2, 7a5-7a6) arranged at the longitudinal ends of each said articulated part furthest from said axis of rotation (XI X'i), and - An upper attachment point (7a3, 7a4) arranged closer to said axis of rotation than to said longitudinal end. 6. Device according to claim 5, characterized in that the upper attachment points (7al-7a2-7a3) of said first articulated support structure part (5-1) are arranged symmetrically, at the three upper attachment points ( 7a4-7a5-7a6) of the second articulated part of the support structure (5-2) relative to the substantially vertical plane passing through said axis of rotation, preferably in an isosceles triangle. 7. Device according to one of claims 1 to 6, characterized in that the upper end of said tendon is fixed to an upper attachment point (7a) secured to said support structure (5) or respectively to said distance variation device. (10), the lower end of said tendon being fixed to a lower attachment point (7b) secured to said distance variation device (10) or respectively to said base (8), said distance variation device (10) being able to : - varying the distance between (i) said upper attachment 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) said lower attachment 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 attachment points (7a) of said p tendons are arranged at said support structure (5) and said lower attachment points (7b) said p tendons are disposed 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 distance variation device distance (10) makes it possible to vary the distance between said lower attachment 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 or preferably hydraulic jack. 11. Device according to claim 10, characterized in that said lower attachment point is integral with the movable rod (10b) of 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 jack comprises a manometer (11c) or preferably a pressure sensor at an orifice (11) of the jack body and a locking device ( 11b, 12) capable of locking 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 on board an underwater robot ( 13) preferably piloted from a second vessel (14) on the surface. 14. Device according to one of claims 1 to 13, characterized in that said support structure (5) supports 5 to 12 arch-shaped chutes of 1.5 to 3 m of radius of curvature, said support structure measuring 3 to 5 m wide and 10 to 30 m long own weight in air from 30 to 50 T and said support structure (5) comprising an integrated buoyancy on the underside of the chutes so that each said tendon is subjected at a tension of 0.5 to 10 T, preferably from 1 to 5T, said tendon being dimensioned to be able to withstand a tension of a multiple of 2 to 4 of said tension 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. 5 F 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). . 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 (YY ', YiY 'i, Y ₂ Y ^Z 2) of said support structure (5), said troughs preferably being in the form of an arch arranged symmetrically with respect to a vertical longitudinal axial plane (YZ) of said support structure. 18. Installation of bottom-to-surface connections between the same floating support (2) and the seabed (3), comprising a plurality of flexible lines comprising flexible conduits (l, la, lb) extending from said floating support to the bottom of the sea where they are connected to wellheads, equipment or ends of submarine pipes resting on the seabed, said flexible lines being respectively supported by a said plurality of chutes each delimiting two pipe portions comprising a first flexible line portion (1-1) in double chain plunging configuration between the floating support (2) and said chute and a second flexible line portion (1-2) in single chain configuration between said chute and the point of contact (l-2a, l-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. Method of modifying the tensions to which the various said tendons of a device according to one of claims 1 to 17 are subjected, characterized in that a said distance variation device (10) is actuated so as to adjust the distance. tension of said tendon to which it is connected to a desired controlled value. 20. Method according to claim 19, characterized in that the tension of a said tendon is reduced by actuating a said device for varying the distance to which it is connected and then the tendon is replaced. 21. Method according to claim 19, characterized in that the mechanical connection of the various tendons at the level of said support structure is made mechanically quasi-isostatic by actuating at least one said distance variation device.