OA16986A - Installation of multiple flexible bottom-to-surface connections on at least two levels. - Google Patents

Abstract

The present invention relates to an installation of bottom-surface connections between the same floating support (2) and the seabed, comprising a plurality of flexible lines comprising flexible conduits (1) extending from said floating support and the seabed. the sea, said flexible lines are respectively supported by a plurality of chutes (3, 3a3b) each delimiting two pipe portions comprising a first flexible line portion (1-1) in the configuration of a double plunging chain between the floating support (2) and said chute and a second portion of flexible line (1-2) in the configuration of a single chain between said chute and the point of contact (1-2a, 1-2b) of the flexible pipe at the bottom of the sea. comprises at least one support structure (4) comprising a lower part forming a base (4-1) resting and / or anchored or sunk into the seabed and an upper part (4-2, 4-2a - 4-2b) supporting at least two gou lower (3b) and respectively upper (3a) burbot arranged at different heights (Ha, Hb) such that the low point (1-1b) of the first portion (1-1) of flexible line passing through the lower chute (1b) is located below the low point (1-1a) of the first portion (1-1) of flexible line passing through the upper chute (3a).

Description

INSTALLING MULTIPLE FLEXIBLE BOTTOM-SURFACE CONNECTIONS ON

AT LEAST TWO LEVELS

The present invention relates to an installation of multiple flexible fund-surface connections between wellheads, equipment or the ends of submarine pipes resting 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 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” is understood to mean conduits or cables capable of accepting significant deformations without generating significant return forces, such as flexible conduits defined below, but also cables or conduits of 15. transfer of energy or information such as electric cables, control cables or hydraulic fluid transfer lines supplying hydraulic equipment such as jacks or lines containing optical fibers; or else 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 soluble or fusible material or of a suspension of. mineral matter from 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 includes anchoring means to stay in position despite the effects of currents, winds and swells. It also generally comprises means for storing and processing oil as well as means for unloading to removal tankers, the latter appearing at regular intervals to carry out removal of the production. The common name of these floating media is the Anglo-Saxon term Floating Production Storage Offloadlng (meaning floating medium of storage, production and unloading) which is used the abbreviated term FPSO 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-to-surface connections are known of a submarine pipe resting on the seabed, a tower-hybrid type connection 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 the floating support.

Also known are bottom-surface connections made by continuously ascending to the sub-surface, resistant and rigid pipes made up of very thick tubular steel elements 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 surface floating support or only to a subsurface float which tension 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 pipes or installations on the seabed entirely made up of flexible pipes, 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.

The present invention relates to flexible pipe support means for a multiple bottom / surface connection installation comprising multiple flexible pipes arranged on at least 2 levels in height.

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 bursting pressure and completed by external reinforcements above the thermoplastic tubular layer also in the form of contiguous spiral strips, but with a longer pitch, i.e. an angle d 'inclination of the lower propeller, in particular 15 ° to 55 °.

116986

In certain field developments, several wellheads are connected in parallel by virtue of 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 shock, 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 further subjected to swell, wind and 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 which 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.

Dn seeks to implement a maximum of fund-surface links from a single floating medium to optimize the exploitation of oil fields. This is why different systems 20 have been proposed which can combine several vertical rlsers 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 connections from a single floating support.

In WD 02/66786, WD 02/103153 and WD 2011/061422 in the name of the applicant, hybrid towers with multiple rlsers and flexible pipes have been described, arranged in fans, allowing a large number of links to be associated with 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 arranged side by side between the floating support and the upper ends of the riser or SCR, the 2 flexible pipes being guided in subsurface by respectively 2 chutes fixed in a superimposed or offset manner. laterally to a tensioning float of a third riser arranged 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 remote 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 15 consisting 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 support 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 30th sea.

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

I ‘

- 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 placed, 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 that 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 the floating support, which plunging chain allows significant displacements of its ends absorbed by the deformations of the flexible pipe, in particular the rise or the descent of said low point of the plunging chain.

It will be recalled that the portion of flexible pipe between one end from which it is suspended and the low point of horizontal tangency, namely in the case of said second portion of flexible pipe, the point of contact 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 a chain is a mathematical function of the hyperbolic cosine type Coshx = (ex + ex) / 2, connecting the abscissa and the ordinate of any point of the curve according to the following formulas:

y = Ro (cosh (x / Ro) **)

R = R _O. (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 frame of reference whose orlglne 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 Ro in the 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 form of a chain, at the level of the seabed.

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, most 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 chutes for intermediate support desdïtes flexible conduits are maintained in the subsurface at a certain depth by floats supporting or from which each of the chutes are suspended. However, these floats are subject to significant movements which requires providing a sufficient distance between the various floats to prevent them * I from colliding against each other.

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 plurality of chutes all arranged at one end. same height side by side offset laterally, said chutes being supported by a bulky structure resting on the seabed or by a bulky structure suspended from floats and anchored to the seabed.

These constraints imply a spreading out of the operating zone 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 various flexible connections and the various floats.

This is why an attempt is made to provide an Installation capable of operating from a single floating support a plurality of fund-surface connections of the flexible type of reduced size and movement and which is also simpler to install and which can be manufactured at sea from a vessel of pipe laying.

An aim of the present invention is therefore to provide an 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. sea, especially at medium or great depth, that is to say beyond 300m of water depth, or even up to a depth of 500-1000m.

More particularly still, the problem posed according to the present invention is therefore to provide an installation with a multiplicity of bottom-surface flexible pipe connections from a single floating support, including the methods for laying and installing the pipe. installation allow the fols:

- to reduce the installation distance between the various flexible bottom-surface connections, i.e. allow a large number of flexible bottom * surface connections to be installed in the smallest possible space or in other words with a reduced footprint, this in order, among other things, to increase the number of bottom-to-surface connections that it is possible to install along the side of an FPSO or a platform, without the bottom connections -surface do not interfere with each other, and,

- easy manufacture and installation by manufacturing and sequential laying of the various pipes from a surface laying vessel, and finally

- to optimize the implementation of the buoyancy means in the case of an installation spread over time over a long period of time between the installation of the various flexible bottom-to-surface connections, without it is necessary to know at the outset the number of links which 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, Initial production plans and 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-to-surface connections of great strength and low cost, and in which the manufacturing processes and installation of the various constituent elements are simplified and also available. 'low cost, and can be carried out at sea from a laying vessel.

Another object of the present invention is to provide an installation with a reduced number of support floats or tensioning of said flexible pipes, in particular at the level of the intermediate chutes.

To do this, the present invention 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 and the seabed where they are connected to wellheads, equipment or ends of subsea pipelines resting on the seabed of said installation, said flexible lines being respectively supported by a plurality of support and guide elements in the form of an arch called chutes each delimiting two pipe portions comprising a first flexible line portion in the configuration of a plunging double chain between the floating support and said chute and a second flexible line portion in the configuration of a single chain between said chute and the point of contact of the flexible pipe at the bottom of the sea. According to the present invention, said installation comprises at least one e chute support structure comprising a lower part forming a base resting and / or anchored or sunk into the seabed and an upper part supporting at least two lower and upper chutes respectively arranged at different heights such that the low point of the plunging double chain of the first flexible line portion passing through the lower chute is located below the low point of the plunging double chain of said first flexible line portion passing through the upper chute.

This configuration allows the point of contact with the seabed of the flexible line passing through the lower chute to be closer to said base than the point of contact with the seabed of the flexible line passing through the upper chute.

The advantages of the installation according to the present invention are in particular the following:

- The implementation of a chute support structure supporting a plurality of chutes makes it possible to relatively reduce the number of floats in accordance with the aim of the present invention, and

- the arrangement of the chutes and flexible pipes with their low point of horizontal tangency of the double plunging chain at different heights on the one hand and, where appropriate, the arrangement of the points of contact with the ground of flexible pipes at distances different, contribute to reducing or even eliminating the risks of contact and shock between said flexible pipes, in particular of their said first portion of pipe in a plunging chain.

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 according to the present invention are fixed, is a rigid structure other than a float.

More particularly, said upper part of said chute support structure comprises at least two lower and upper rigid support elements arranged at different heights and each supporting a plurality of chutes laterally offset in a direction (YY ') in a vertical plane perpendicular to the vertical axial plane of said support structure and said rigid support elements and / or perpendicular to the vertical longitudinal axial planes of said chutes, preferably mutually parallel, lesdltes chutes preferably being arranged symmetrically with respect to a vertical axial plane of said support structure and said rigid support members.

This embodiment is particularly advantageous insofar as it is possible from said chute support structure to move away angularly by an angle α from the second adjacent flexible pipe portion passing through 2 adjacent chutes supported by the same pipe element. inferior or superior rigid support, at an angle a2 greater than the angle a1 between the first 2 portions of corresponding flexible pipes of the same 2 flexible pipes.

It is thus possible to extend the angular spectrum of the range of said flexible pipes from said support structure and thus to extend the geographical area of implantation of wellheads or ends of submarine pipes that can be connected by flexible conduits to the same floating support.

Consequently, more particularly, the two second portions of flexible lines of two flexible lines passing through two adjacent chutes supported by the same rigid support element offset laterally are arranged angularly with respect to each other at an angle (a2 ) greater than the angle (a1) of the first two portions of flexible lines of the same two flexible lines.

Preferably, a bottom-to-surface connection installation according to the invention, it is understood that it comprises at least two said chute support structures whose vertical axial planes lesdlts are arranged angularly a.

More particularly, the number of chutes supported by the same rigid lower or upper chute support element may more particularly be from 10 to 30.

In a particular embodiment, a said flexible pipe is held in a said chute by retaining means and / or hooking means.

This characteristic aims to stabilize the flexible pipe and to promote the stresses and movements in said first portion of flexible pipe.

More particularly, said retaining means or hooking means are constituted by a tubular device forming a ring pre-positioned around said pipe at a predetermined distance from the end of the pipe fixed to the floating support, said ring being able to be blocked and / or locked in said chute, preferably said chute comprising a first internal channel portion containing or being able to contain said flexible pipe but not able to contain said pipe surrounded by said ring, said first chute part being located on the side of the chute closest to the floating support, the width, in particular the diameter, in cross section of the internal channel of said first chute part being smaller than that of the cross section of the internal channel of a second chute part arranged in the side of the chute furthest from the floating support, the internal channel of said second portion of the chute internal head containing or being able to contain a said flexible pipe surrounded by said ring, said ring being retained by a shoulder at the level of the zone of variation in width, preferably discontinuous variation in width, between the two internal channels of the two first and second chute parts.

Said ring may be formed of two half rings of semi-circular section applied against the pipe and assembled together, for example by bolting.

It is understood that the positioning of said ring is determined by the length of the first flexible pipe portion desired as a function of the height of the low point of said first flexible pipe portion in a double plunging chain, which also depends on the height of the chute and its distance from the floating support.

In a first particular variant embodiment, said rigid channel support elements form horizontal beams. The chutes supported by the same rigid support element are arranged at the same height.

In another variant embodiment, the chutes supported by the same rigid support element are arranged at different heights, preferably said rigid support element defining a flat and inclined chute support surface.

In all cases, preferably, the low points of two first portions of flexible lines passing through adjacent chutes supported by the same rigid support element are at different heights.

In a preferred embodiment, said chute support structure is a rigid structure comprising a rigid tower rising above a said base resting and / or anchored to the bottom of the sea to which it is rigidly fixed. By "rigid tower" is meant that said lower part forming a base and said upper part of the support structure supporting said chutes are connected by a rigid structure.

More particularly, said base is a metallic lattice structure extending horizontally resting on the bottom of the sea and said rigid tower is a metallic lattice structure rising vertically supporting at least two upper and lower rigid support elements forming beams s 'extending, preferably symmetrically, on either side of the tower over at least two height levels, beams above which are fixed said chutes, said tower being fixed to said metal truss structure of said base by Inclined rigid linkage and reinforcement elements.

It will be understood that the metallic lattice structure of said base has a sufficient distance to provide sufficient counterweight to stabilize the tower.

In this embodiment of the rigid support structure, the positioning symmetry of the chutes and flexible pipes and more generally of the support structure itself with respect to a said vertical longitudinal axial plane is intended for said structure to essentially support compressive forces, the bending forces being balanced on either side of the vertical rigid tower.

In another variant embodiment, said chute support structure is an articulated structure comprising at least two upper and lower rigid support elements forming beams arranged one above the other and connected to one another. another by first flexible connecting elements such as first stays, said lower chute support element being connected to said base by second flexible connecting elements such as second stays, said upper and lower rigid support elements being held in place. -above one another and above a said base by at least one submerged buoyancy element fixed to at least said upper chute support element capable of tensioning said first and second shrouds, said base being of preferably sunk to the bottom of the sea.

More particularly, said upper rigid support element is suspended from a submerged upper float to which it is connected by third flexible connecting elements such as slings, and preferably said upper rigid support element is supported by a lower float on which it is fixed.

In the 2 embodiments of a rigid support structure, it is preferred that the vertical longitudinal axial plane of the closest upper and lower chutes are coaxial and coplanal for the 2 chutes to avoid or reduce bending forces on said support structure.

In the variant embodiment in which the trunking support structure is an articulated structure, the second flexible pipe portion in a simple chain is less stabilized than in the case of a rigid support structure, but these stresses and displacements in particular at the level of the point of contact with the seabed are nevertheless considerably reduced due to the tenslonnement of said support structure by floats lesdlts.

To facilitate the laying of flexible pipes from a laying vessel as explained later in the description, said upper trunking support element or the ends of the troughs which it supports comprise a deflector whose profile is capable of avoiding 'Damage the portion of flexible pipe that can come into contact with said deflector during installation of the pipe on a said lower chute.

More preferably, said upper chute is at a height above the nearest Lower chute such that the segment passing through the longitudinal end of the upper chute and the top of the bottom of the Lower chute forms an angle a3 d ' at least 30 °, preferably at least 45 ° from the horizontal.

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

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

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 a bottom-surface connection installation according to the invention between an anchored floating platform 2 and a metal support structure 4 supporting two series of troughs in the form of arches 3, 3a-3b , resting on the bottom of the sea 5,

- Figure 2 is a side view of an installation of Figure 1 illustrating the deformations of flexible pipes 1 as a function of the excursion of said anchored floating platform, as far as lb and as close as compared to said structure support 4,

- Figure 3 is a top view of an installation of the type of that of Figure 1 but with two support structures 4, illustrating the fan-shaped arrangement of a plurality of flexible bottom-surface connections between a platform 2 and two 4 metal support structures resting on the seabed,

- Figure 4 is a side view of a bottom-surface connection installation according to Figure 1 between an anchored floating platform and two rigid support elements 4-2a, 4-2b, respectively supporting two series of d-shaped chutes 'arches, lesdltes rigid support elements being interconnected by a first series of shrouds, and connected to a foundation 4-1 resting on the seabed 5 by a second series of shrouds, the whole being tensioned upwards by means of a float 4-4a,

- Figure 5A illustrates in side view the first step of the installation of a flexible pipe on the lower chute 3b,

- Figure 5B illustrates in side view the second, third and fourth steps of the installation of a said flexible pipe on the lower chute 3b,

- Figure 6A is a top view of a chute 3 detailing the respective cross sections of a front part 3-1 and a rear part 3-2 of the chute whose internal channels 3-4 have different diameters , therefore different widths,

- Figure 6B is a top view of a flexible pipe equipped with an attached ring 7 intended to block said flexible pipe within said chute of Figure 6A,

- Figure 6C is a top view of the flexible pipe of Figure 6B installed in the chute of Figure 6A, a lock 8 being in the open position,

- Figure 6D is a top view relating to Figure 6C, the locking latch 8 of the attached ring 7 being in the closed position,

- Figure 7A is a transverse vertical sectional view of the pipe 1 with two semi-tubular portions 7a, 7b forming said ring 7 once applied against the pipe 1 and the latch 8 in the open position, Figure 7B shows the lock 8 in closed position (in the absence of pipes and ring 7 inside),

FIG. 8A is a transverse vertical section at the level of the top of the upper chutes 3a of a rigid support structure 4 comprising two horizontal beams 4-2a and 4-2b, supporting a plurality of upper chutes 3a and lower chutes 3b, showing in dotted the first portions of flexible pipes 1-1 with their low point 1-la, and showing in dotted the lower ducts 3b,

- Figure 8B is a view similar to Figure 8A, but the transverse vertical section being at the level of the tops of the lower chutes 3b and showing in dotted lines the first portions of flexible lines 1-1 and in dotted lines the upper chutes 3a,

- Figure 9 is a side view of a support structure in which the upper chutes are offset, relative to the lower chutes, towards the floating support,

- Figure 10 is an alternative embodiment of a chute support structure 4, in which the upper 4-2a and lower 4-2b rigid support elements are symmetrically inclined beams with respect to the vertical central tower 4-2c .

In Figure 1 there is shown a fund-surface connection installation comprising two flexible pipes 1 connected at one end 2a to a semi-submersible floating platform 2, held in position by anchor lines 2a, the other end of said flexible pipes resting in 1-3 at the bottom of the sea 5. The two flexible pipes 1 extend at different heights and come into contact with the sea floor 5 at contact points l-2a and l-2b at different distances from l 'ZZ axis' of floating support 2.

The installation of bottom-to-surface connections comprises a rigid support structure 4, comprising a rigid vertical tower 4-2c, consisting of a metal lattice structure, supporting at its top two upper rigid support elements 4-2a and lower 4 -2b forming horizontal beams, extending symmetrically on either side of the tower 4-2c. Upper chutes 3a are fixed over the upper beam 4-2a and Lower chutes 3b are fixed over the lower beam 4-2b. The upper chutes 3a and lower chutes 3b are all preferably of the same length and the same radius of curvature and are arranged parallel to each other, laterally offset in the transverse direction YY 'perpendicular to the longitudinal direction of the chutes XX'.

In Figures 1 to 3, the upper chutes 3a and Lower chutes 3b of the same support structure 4 are superimposed, that is to say are not offset from each other in the longitudinal direction XX 'of the chutes, unlike to the embodiment of FIG. 9, where the lower chutes 3b are offset forwards or downstream, that is to say slightly more distant from the floating support 2 with respect to the upper chutes 3a.

In FIG. 3, two installations have been shown with two support structures 4 arranged at a different distance from the floating support 2, but both having the same shape, one of the two structures, the one closest to the floating support, being shown in section just above the lower beam 4-2b and the lower chutes 3b, while the other support structure 4 furthest from the floating support 2 is shown in top view above the upper chutes and beams 3a, 4-2a. The second flexible pipe portions 1-2, passing through the upper chutes 3a, have a point of contact l-2a with the seabed 5, located substantially on a circle of radius R2 (for the support structure 4 of FIG. furthest from the floating support 2) or R4 (for the support structure 4 of FIG. 3 closest to the floating support 2). The point of contact l-2b of the second portions of pipes 1-2 passing through the lower chutes 3b is also situated substantially on a circle of radius RI (for the support structure 4 of FIG. 3 furthest from the floating support 2) or R3 (for the support structure 4 of Figure 3 closest to the floating support 2), with RI <R2 and R3 <R4.

In this same figure 3, the upper beam 4-2a supports ten upper chutes 3a, the tops of which reach the same height Ha, as shown in figure 1, and on which only four flexible pipes are arranged on the two chutes at the ends sides in the YY 'direction of the upper beam 4-2a. The Lower beam 4-2b supports nine Lower chutes 3b at the same height Hb on which were also installed four flexible pipes, namely two flexible pipes at the two chutes at both ends in the lateral direction YY 'of the beam.

The different flexible pipes 1, passing through the chutes 3a and 3b, each comprise a first flexible pipe portion 1-1 in the configuration of a double chain plunging between the floating support 2 and said chute, and a second flexible pipe portion 1-2 in the configuration of a single chain between said chute and the point of contact l-2a and l-2b of the flexible pipe or l-2a and l-2b of the flexible pipe at the bottom of the sea.

In Figures 1, 2 and 4, the low point 1-la of the first pipe portion 1-1 passing through the upper chute 3a is located above the low point 1-lb of the first pipe portion 1-1 passing through the Lower chute 3b, the second flexible pipe portions 1-2, passing through the upper chutes 3a, have a point of contact l-2a with the seabed 5, located substantially on a circle of radius R2 (for the support structure 4 of FIG. 3 furthest from the floating support 2) or R4 (for the support structure 4 of FIG. 3 closest to the floating support 2). The point of contact l-2b of the second portions of pipes 1-2 passing through the lower chutes 3b is also situated substantially on a circle of radius RI (for the support structure 4 of FIG. 3 furthest from the floating support 2) or R3 (for the support structure 4 of Figure 3 closest to the floating support 2), with RI <R2 and R3 <R4.

In FIGS. 1 to 3, flexible pipes 1 have been shown which are continuous from their point of attachment 2b on the platform 2 to beyond their point of contact l-2a, l-2b on the sea floor in the pipe portion. 1-3 resting on the seabed 5. However, it is also possible that the flexible conduits may consist of a plurality of flexible conduits connected to each other by Intermediate end fittings of the flange type 1-4 in particular or other means. connection, lesdlts connection means can moreover be located advantageously downstream of said chutes as shown in Figure 4.

Platform 2 is subject to the effects of swell, wind and current and therefore can move in all directions. The anchoring system 2a limiting the excursions of the platform 2 tends to bring it back to the neutral position of FIG. 1. FIG. 2 shows in side view the deformations of the flexible pipes 1, depending on whether the platform. shape approaches or moves away from structure 4 (configuration 1a) (configuration 1b). It will be noted that the second portions of flexible pipes 1-2 remain substantially fixed regardless of the movements of the platform on the surface as explained previously.

Due to the fact that the low points 1-la and l-2b of the first two pipe portions 1-1 of the two pipes are at different heights ha, hb on the one hand, and that, on the other hand, two second portions of conduits 1-2 of the two conduits passing through the two upper chutes 3a and lower 3b are also at different heights because they have contact points l-2a and 12b at different distances from the structure 4, the portions 1 -1 and 1-2 of upper and lower pipes in suspension cannot interfere with each other.

Said chute support structure 4 comprises a lower part 4-1 serving as a base, consisting of a metallic lattice structure extending horizontally resting or anchored to the seabed for a sufficient distance to act as a counterweight and stabilize the tower rigid 4-2c which is attached to its base. The rigid tower 4-2c is a metallic lattice structure fixed at its base to the lattice structure 4-1 forming a base and supported by rigid connecting and reinforcing elements Inclined 4-3.

In Figure 3, the two horizontal beams 4-2a and 4-2b supporting the upper chutes 3a and respectively lower chutes 3b, are superimposed and arranged at the same distance from the axis ZZ 'of the floating support 2. On the other hand, on Figure 9, the lower chutes 3b are offset slightly forward, that is to say at a greater distance from the axis ZZ 'of the floating support 2 than the upper chutes 3a, in order to facilitate the installation of a flexible pipe on the lower chute 3b, as explained below.

In FIGS. 8A and 8B, it is shown that the chutes 3a and 3b may have variable diameters, or widths, in vertical cross section adapted to the diameters of the flexible pipes or lines which are intended to hold.

In FIG. 8A, it is shown that the various low points 1-la of the first portions of flexible pipes upstream of the upper chutes 3a are arranged at variable heights so that the low points 1-la of two first portions of pipes hoses supported by adjacent upper chutes 3a supported by the upper beam 4-2a are at different heights HI and H2. In FIG. 8B, the low points 1-lb of two first portions of flexible pipes 1-1 supported by adjacent lower gutters 3b on the lower beam 4-2b are also at different heights ΗΓ and H2 '.

In FIGS. 3, 8A and 8B, the various pipes of the various flexible lines providing the flexible bottom-surface connections between the support 2 and equipment of the same wellhead are grouped together by upper 3a and lower 3b gutters located in a same angular corridor as narrow as possible of the range of all the flexible pipes ensuring the junction between the same floating support 2 and a plurality of wellheads. This grouping of flexible pipes, ensuring the junction of the same wellhead with the floating support, is made possible by the plurality of heights of the gutters Installed at least on two levels on the one hand, and, on the other hand, by the possibility of installing the low points 1-la and 1lb of the first portions of pipes at different heights on the one hand, and, on the other hand, the contact points l-2a and l-2b of the second portions of pipes with the ground at different distances from the support structure 4.

In FIG. 10, there is shown a second embodiment of a rigid support structure, in which the upper 4-2a and lower 4-2b channel support elements each consist of two rectilinear beams 4-2a '/ 4-2a and 4-2b '/ 4-2b, Inclined symmetrically to the rigid central vertical tower 4-2c. This embodiment has the additional advantage that the different upper gutters 3a and lower gutters 3b can be at different heights on their respective inclined beams, so that the arrangement of the different low points 1-la and l-2b of the first portions of adjacent 1-1 flexible pipes can be more easily arranged at different heights HI and H2.

In Figures 4 and 5, said channel support structure 4 is an articulated structure comprising two upper horizontal beams 4-2a and lower 4-2b, made up of structures ^f 9 "metal lattice, interconnected by first stays 43a. The set of two beams 4-2a and 4-2b forms the upper part of the support structure 4. The lower beam 4-2b is connected to a base 4-1 driven into the seabed 5 by second shrouds 43b. The upper beam 4-2a is suspended from an upper submerged float 4-4a, to which it is connected by slings 4-3c. The float 4-4a ensures the tensioning of the first and second shrouds 4-3a and 4-3b, so as to keep them in a vertical position and to ensure the maintenance of the upper beam 4-2a at a given height Ha, above the Lower beam 4-2b at Lower height Hb, as shown in figure 1.

The upper chutes 3a, fixed to the upper beam 4-2a, are themselves supported by additional floats 4-4b integrated into said beam to complete the tensioning of the first and second shrouds 4-3a and 4-3b.

Likewise, buoyancy elements are advantageously integrated into the structure of the lower beam 4-2b.

The upper beams 4-2a and Lower 4-2b support, as in Figures 3 and 8, a plurality of upper chutes 3a and respectively Lower chutes 3b.

For water depths of 500 to 1000m, and for a large quantity of flexible pipes, for example 18 or 24 flexible pipes, a rigid support structure 4 according to the embodiment of Figures 1, 2 and 3 may measure 100 150m high (Ha) and represent a weight of several thousand tons, for example 5 to 6000 tons. On the other hand, a support structure 4 of the articulated type according to Figures 4 and 5, has a considerably reduced weight compared to the weight of the rigid structure 4 of Figures 1 to 3. However, the buoyancy elements 4-4a and 4- 4b remain relatively more expensive than construction in a lattice metal structure.

Thus, the choice of a rigid structure type solution 4 as described with reference to FIG. 1, or of a floating and articulated type structure solution as described with reference to FIG. 4, will depend essentially on the means and the costs of prefabrication, transport 5 and installation available: the construction, transport and installation of unit structures weighing several thousand tonnes indeed requires considerable and specific means which are not always available in certain regions of the world .

In the articulated configuration of Figure 4, when the platform 2 moves, as shown with reference to Figure 2, the elements 4-1, 4-2a and 4-2b being hinged to each other, this results in movement in the same direction as said platform 2, but strongly attenuated, which implies a deformation of the second chain portions 1-2 in the same direction as the deformation of the first 15 chain portions 1-1, and a displacement of the contact points l -2a and l-2b in the same direction, namely the direction opposite to that of the platform 2 and the upper part 4-2. Thus, each of the rigid support structure variants 4 of the invention has advantages and disadvantages compared to the other.

In this same FIG. 4, there is shown a surface installation vessel 12 equipped with an ROV 11 (automatic intervention submarine piloted from the surface), near the chutes supporting the flexible pipes. The upper 3a and lower 3b chute levels are advantageously placed at a vertical distance hO of 10 to 20m from each other, so that said ROV can pass between the two levels of chutes without interfering with the flexible pipes. to Intervene if necessary.

In Figures 5A and SB, there is shown in side view a

Installation of a flexible pipe on a Lower chute 3b. In figure SA, the installation vessel 10 is positioned at a distance La from the vertical axis Ζ1ΖΓ of the support structure 4, then transfers in a known manner the flexible pipe to the platform 2 passing between the upper chutes 3a and the Lower chutes 3b.

In summary, the connection of the end 14 of the flexible pipe 1 to 2b on a plating of the platform 2 is carried out according to the following steps 5:

- step 1: a cable 13 is suspended vertically from the laying vessel 10, which vessel is positioned near the axis Ζ1ΖΓ of the support structure 4 at a reduced distance La, and

- step 2: the ROV 11 grasps the lower end of the cable 13 and passes it between the two chutes 3a and 3b to hook it in 2b on the platform 2, and

- step 3: if necessary, the cable 13 is replaced by a reinforced traction cable, and

- step 4: the vessel is positioned at the distance La from the axis Z1Z1 'and the end 14 of a flexible pipe stored on the vessel 10 is hooked to the free end of the cable 13, and

- step 5: the end 14 of the pipe 1 is transferred to the floating support 2 and it is hooked at 2b on a plating 2.

When the end 14 of the flexible pipe is secured to the platform 2, the installation vessel 10 approaches the axis Z1Z1 'and is at the distance Lb <La as detailed in FIG. 5B. The flexible pipe is then in configuration 1-lc and l-2c in which the upper downstream portion l-2c abuts against a deflector 9 at the end of the front part 3-2 of the upper chute 3a. Only the rear part 3-1 of the lower chute 3b supports the flexible pipe 1, the lower end of the portion l-2c of the pipe 1 not resting on the front part 3-2 of the lower chute 3b.

The two parts 3-1 and 3-2 of the chute 3 have, as shown in Figures 6A to 6D, Internal channels of different width in cross section, the chute part 3-1, having an Internal channel 3-4 of smaller width than that of the cross section of the Internal channel 3-4 of the second chute part 3-2, arranged on the side of the chute furthest from the floating support 2.

The internal channel 3-4 of greater width of the second chute part 3-2 is able to contain a flexible pipe surrounded by a ring 7, while the Internal channel 3-4 of the first chute part 3-1 is suitable for containing the flexible pipe 1 and cannot contain the pipe surrounded by said ring 7. Thus, the ring 7 is retained by a shoulder 3-3 at the level of the zone 10 of discontinuous variation in width between the two parts 3 -1 and 3-2.

The ring 7 consists for example of two semi-tubular half-shells 7a and 7b, assembled together by bolts so as to abut against the pipe 1 at a predetermined position relative to its end 14, as shown in Figure 7A.

At the stage of laying the pipe 1 as shown in figure SB, the ring 7 is located near the deflector 9 of the end of the front part 3-2 of the upper chute 3 in contact with the portion of pipe l-2c.

Due to the difference in height h0 between the upper chute 3a and the lower chute 3b, an angle a3 of at least 30 °, preferably about 45 °, with respect to the horizontal of the segment between the point of contact of the pipe l-2c with the deflector 9 at the end of the portion 3-2 of the upper chute 3a and the top of the lower chute 3b corresponding to the shoulder 3-3 between the parts 3-1 and 3-2 of the lower chute 3b. This angle a3 makes it possible to avoid an excessive curvature of the pipe portion l-2c and the presence of the deflectors prevents damage to the flexible pipe even in the event of insistent contact.

Thus, as illustrated in FIG. SB, when the vessel 10 continues to unwind the flexible pipe, due to the fact that it is at the distance Lb from the axis Ζ1ΖΓ, therefore closer to the axis of the structure 4, said flexible pipe naturally slides on the lower chute 3b, mainly on its left part 3-1, and the ring 7 then comes into abutment at 3-3 at the level of the diameter transition between the left part 3-1 and the right part 3 -2 of chute, as illustrated in Figure 5 6C.

When one continues the descent of the pipe portion l-2c, the ring 7 approaches the shoulder 3-3 until it is blocked by retained.

In this position, the flexible pipe 1 to the platform 2 is in the final configuration 1-ld and then does not move appreciably any more. The vessel 10 then continues to unwind the flexible pipe 1 so that the downstream pipe portion assumes the configuration 1-2d. Then, the ship continues to move forward so as to adjust the point of contact l-2b with the seabed 5 so that it is substantially at a distance RI from the axis 15 Ζ1ΖΓ. Finally, the vessel 10 continues in a known manner its current laying of the pipe in configuration l-2e towards the wellheads, not shown.

FIG. 6B shows a top view of the flexible pipe 1 equipped with its locking ring 7.

FIG. 6C shows a top view of the flexible pipe 1 equipped with its locking ring 7 in the abutment position on the transition zone 3-3 of the chute 3, a lock 8 being in the open position.

In FIG. 6D, the lock 8 is actuated by the ROV 11, 25 then preventing any movement of the flexible pipe 1, both upwards and to the right with respect to the chute 3.

To avoid damaging the flexible pipe during installation on the Lower chutes 3b, the upper chutes 3a are equipped as mentioned previously with a deflector 9, the external profile of which is able to avoid damaging a portion of the pipe. flexible being able to come into contact with said deflector during 't.

laying of the pipe. The deflector is advantageously present at each of the ends of the two parts 3 * 1 and 3-2. The deflector at the end of part 3-1 is more particularly useful during the initial phase of transferring the end 14 of the pipe to the platform 2 and of its attachment at 2b to said platform.

In Figures 7A and 7B, there is detailed a lock 8 comprising two semi-tubular portions 8a and 8b, articulated together by a hinge 8c, the lower part 8b being integral with the chute 3 and the upper part 8a being able to pivot. and come to rest against the top face of the ring 7 once in place at the transition from the retained and locked position 3-3.

For 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 (chute portion 3-1), or of that of the pipe. 'ring (portion of chute 3-2), but the shape of the arch in the XX plane' can just as well be of ellipse, parabolic or any other shape with variable curvature, whose maximum curvature is less than the curvature critical limit 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 inner width of the U in the chute portion 3-1 is slightly greater than the diameter of the flexible pipe, and that the interior width of the U in the chute portion 3-2 is slightly greater than the diameter of the ring. As a result, the hose will be correctly guided between the walls of the U, and the ring will then naturally lock in the region of the change in width of the U-shape of the chute, as explained previously.

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. , more particularly in the variants of the device described with reference to FIGS. 4, SA and SB.

In the floating and articulated version with reference to figure 4, the single chains 1-2a and 1-2b deform significantly when the floating support moves with the swell, wind and currents, and it is then Important that the radii RI and R2, respectively R3 and R4 are very different with R2> RI, respectively R4> R3, so as to avoid any contact between the flexible pipes supported respectively by the chutes 3a and 10 3b. On the other hand, in the case of a fixed structure 4, as described with reference to Figures 1, 2 and 3, the simple chain portions l-2a and l-2b remain substantially fixed whatever the movements of the floating support at the discretion of swell, wind and currents: the values of radii R1-R2, respectively R3-R4 are then no longer really critical, but we will still prefer, for future inspection considerations by ROV, distribute the pipes as indicated in the invention so as to avoid confusing flexible pipes coming from the upper chutes with pipes coming from the lower chutes, it being understood that the flexible pipes leave the seabed towards their respective chutes located 100 to 200m above, and that visibility in the deep sea is limited to a few meters, or even a few tens of meters at most.

Claims (15)

1. Installation of bottom-surface connections between the same floating support (2) and the seabed, comprising a plurality of flexible lines comprising flexible conduits (1) extending from said floating support and the seabed where they are connected to wellheads, equipment or subsea pipe ends resting on the seabed of said installation, the flexible lines being respectively supported by a plurality of arch-shaped support and guide elements called chutes (3, 3a-3b) each delimiting two pipe portions comprising a first portion of flexible line (1-1) in the configuration of a double plunging chain between the floating support (2) and said chute and a second portion of flexible line (1 -2) in the configuration of a single chain between said chute and the point of contact (l-2a, l-2b) of the flexible pipe at the bottom of the sea, characterized in that it comprises at least one support structure port of chutes (4) comprising a lower part forming a base (4-1) resting and / or anchored or sunk into the seabed and an upper part (4-2, 4-2a - 4-2b) supporting at least two lower (3b) and respectively upper (3a) chutes arranged at different heights (Ha, Hb) so that the low point (1-lb) of the double plunging chain of the first portion (1-1) of flexible line passing through the lower chute (3b) is located below the low point (1-la) of the double plunging chain of said first portion (1-1) of flexible line passing through the upper chute (3a), and, preferably, the point of contact (l-2b) with the seabed (5) of the flexible line (1) passing through the lower chute (3b) is closer to said base than the point of contact (l-2a) with the seabed (5) of the flexible line (1) passing through the upper chute (3a). 2. Installation of bottom-surface connections according to claim 1, characterized in that said upper part (4-2) of said trunking support structure (4) comprises at least two elements " rigid lower support (4-2b) and respectively upper (4-2a) arranged at different heights (Ha, Hb) and each supporting a plurality of channels offset laterally in a direction (YY ') in a vertical plane perpendicular to the plane vertical axial (P) of said support structure (4) and said rigid support elements (4-2a, 42b) and / or perpendicular to the vertical longitudinal axial planes of said gutters, preferably parallel to each other, said gutters preferably being arranged symmetrically with respect to a vertical axial plane (P) of said support structure (4) and said rigid support elements (4-2a, 4-2b). 3. Installation of bottom-surface connections according to claim 1 or 2, characterized in that it comprises at least two said gutters support structures (4) of which said vertical axial planes (P) are arranged angularly a. 4. Installation of bottom-surface connections according to one of claims 1 to 3, characterized in that the two second portions of flexible lines (1-2) of two flexible lines passing through two adjacent troughs supported by the same support element rigid laterally offset are arranged angularly with respect to each other by an angle (az) greater than the angle (ai) of the first two portions of flexible lines (1-2) of the same two flexible lines. 5. Installation of bottom-surface connections according to one of claims 1 to 4, characterized in that a said flexible pipe is held in a said chute by retaining means and / or hooking means (7,8 ). 6. Installation of bottom-surface connections according to claim 5, characterized in that said retaining means or hooking means consist of a tubular device forming a ring (7) pre-positioned around said pipe at a predetermined distance from at the end of the pipe fixed to the floating support, said ring being able to be blocked (3-1, 3-2) and / or " locked (8) in said chute, preferably said chute comprising a first part (3-1) of internal channel (3-4) containing or being able to contain a said flexible pipe but not able to contain said pipe surrounded by said ring, said first chute part being located on the side of the chute closest to the floating support, the cross-sectional width of the internal channel (3- 4) of said first chute part (3-1) being smaller than that of the cross section of the internal channel (3-4) of a second chute part (3-2) disposed on the side of the chute more remote from the floating support, the internal channel of said second part of internal chute containing or being able to contain a said flexible pipe surrounded by said ring, said ring being retained by a shoulder (33) at the level of the width variation zone, of preferably discontinuous variation in width, between the two internal channels of the two first and second chute parts (3-1, 3-2). 7. Installation of bottom-surface connections according to one of claims 1 to 6, characterized in that lesdlts rigid support elements (4-2a, 4-2b) of troughs form horizontal beams. 8 Installation of bottom-surface connections according to one of claims 1 to 6, characterized in that the chutes supported by the same rigid support element (4-2a, 4-2b) are arranged at different heights, preferably said rigid support member defining a flat inclined chute support surface. 9. Installation of bottom-surface connections according to one of claims 1 to 8, characterized in that the low points (1-la, 1-lb) of two first portions of flexible lines (1-1) passing through chutes adjacent ones supported by the same rigid support element (4-2a, 4-2b) are at different heights (H1-H2, Hl'-H2 '). 10. Installation of bottom-surface connections according to one of claims 1 to 9, characterized in that said chute support structure (4) is a rigid structure comprising a rigid tower (4 * f * r 2c) rising above a said base (4-1) resting and / or anchored to the bottom of the sea (5) to which it is rigidly fixed. 11. Bottom-surface connection installation according to claim 10, characterized in that said base is a metallic structure 5 horizontally extending trellis resting on the seabed and said rigid tower (4-2c) is a vertically rising metal truss structure supporting at least two upper (4-2a) and lower (4-2a) and lower (4) rigid support members. -2b) forming beams extending, preferably symmetrically, on either side of the tower over at least two height levels, beams above which are fixed said chutes (3a, 3b), said tower being fixed to said metallic lattice structure of said base (4-1) by inclined rigid connecting and reinforcing elements (4-3). 12. Installation of bottom-to-surface connections according to one of the 15 claims 1 to 9, characterized in that said chute support structure (4) is an articulated structure comprising at least two upper (4-2a) and lower (4-2b) rigid support elements forming beams arranged in the one above the other and connected to each other by first flexible connecting elements such as first guy ropes (4-3a), said lower chute support element (4-2b) being connected to said base by second flexible connecting elements such as second stays (4-3b), said upper rigid support elements (4-2a) and lower 4-2b) being held above each other and above said base (4-1) by at least one submerged buoyancy element (4-4) fixed to at least said upper chute support element (4-2a) adapted to tension said first and second shrouds, said base preferably being driven into the seabed (5). 13. Installation of bottom-surface connections according to claim 12, characterized in that said upper rigid support element (42a) is suspended from an upper submerged float (4-4a) to which it is connected by third flexible connecting elements such as slings (4-3c), and preferably said upper rigid support element (4-2a) is supported by a lower float (4-4b) on which it is fixed. 14. Installation of bottom-to-surface connections according to one of the 5 claims 1 to 13, characterized in that said upper trunking support element (4-4a) or the ends of the troughs which it supports comprise a deflector (9) the profile of which is adapted to avoid damaging the portion of flexible pipe able to come into contact with said deflector during the laying of the pipe on a said lower chute. 15. Installation of bottom-surface connections according to one of claims 1 to 14, characterized in that said upper chute (3a) is at a height (hO) above the lower chute (3b) closest such that the segment passing through the longitudinal end 15 of the upper chute and the top of the bottom of the lower chute forms an angle or at least 30 °, preferably at least 45 ° with respect to the horizontal.