EP2501889A1

EP2501889A1 - Facility having fanned seabed-to-surface connections

Info

Publication number: EP2501889A1
Application number: EP10785475A
Authority: EP
Inventors: Gianluca Sintini; Gianmarco Rota; Floriano Casola; Giulio Fatica
Original assignee: Saipem SA
Current assignee: Saipem SA
Priority date: 2009-11-17
Filing date: 2010-10-15
Publication date: 2012-09-26
Anticipated expiration: 2030-10-15
Also published as: BR112012011697B1; BR112012011697A2; US20120230770A1; US8647019B2; FR2952671A1; EP2501889B1; FR2952671B1; WO2011061422A1

Abstract

The present invention relates to a facility having fanned seabed-to-surface connections, said facility including a plurality of seabed-to-surface connections fanning out from a single floating substrate (1) including: 1) at least one first number (k) of first seabed-to-surface connections (3, 3-i with I = 1 to k) that each include a) a first riser, (3b, 3b-i) connected to a first underwater pipe (3e-i) resting on the seabed and tensioned in a substantially vertical manner by a first float (3c-i), and 10 b) a plunging first flexible connection pipe (3a, 3a-i) that ensures the connection between said floating substrate and said first riser; and 2) at least a second number (m) of second seabed-to-surface connections (4, 4-j with j = 1 to m) that include 2a) a second rigid pipe (4b, 4b-j) connected to a second underwater pipe (4e-j) resting on the seabed and tensioned by a second buoyancy element (4c, 4c-j), and 2b) a second flexible connection pipe (4a, 4a-j with j = 1 to m) ensuring the connection between said floating substrate (1) and said 20 second rigid pipe, each of said second flexible pipes passing through a chute (6, 6a-6b) attached to said first float.

Description

INSTALLATION OF BONDED SURFACE CONNECTIONS

IN EVENTAIL

The present invention relates to an installation of multiple bottom-surface connections between submarine pipes resting at the bottom of the sea and a floating support surface, comprising a multiplicity of hybrid towers consisting of a flexible pipe connected to a rising rigid pipe, or vertical riser, whose lower end is integral with an anchoring device comprising a base resting at the bottom of the sea. The technical sector of the invention is more particularly the field of the manufacture and installation of columns. production riser for the underwater extraction of oil, gas or other soluble or fuse material or a suspension of mineral material from wellhead immersed to a floating support, for development of offshore production fields offshore. The main and immediate application of the invention being in the field of oil production.

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

Background-to-surface bonds of an underwater pipe resting at the bottom of the sea are known, a tour-hybrid link comprising:

a vertical riser whose lower end is anchored to the seabed by means of a flexible articulation and connected to a said pipe resting at the bottom of the sea, and the upper end is stretched by a submerged submerged float to which it is connected, and

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

Also known are bottom-surface connections made by going up continuously to the subsurface of the resistant and rigid conduits consisting of tubular elements of thick steel welded or screwed together, in a chain configuration with a curvature continuously variable throughout their length in suspension, commonly called "Steel Catenary Riser" (SCR) meaning "chain-shaped steel riser" and also commonly called "catenary type rigid pipe" or "SCR type riser".

Such a catenary duct may go up to the floating support surface or only to a subsurface float that tensions its upper end, which upper end is then connected to a floating support by a plunger flexible connecting pipe.

Reinforced configuration catenary risers are described in WO 03/102350 of the applicant.

In WO 00/49267, it has been proposed as connecting pipe between the riser whose top is tensioned by a float immersed surface and the floating support, rigid pipes SCR type and installs the float head of the riser at a distance larger of the surface especially at least 300 m from the surface, preferably at least 500 m. In WO 00/49267 of the Applicant, there is described a multiple hybrid tower comprising an anchoring system with a tendon vertical consisting of a cable or a metal bar, or a pipe stretched at its upper end by a float. The lower end of the tendon is attached to a base resting at the bottom. Said tendon comprises guiding means distributed over its entire length through which passes a plurality of said risers vertical. Said base can be placed simply on the seabed and stay in place by its own weight, or remain anchored by means of batteries or any other device to keep it in place. In WO 00/49267, the lower end of the vertical riser is adapted to be connected to the end of a bent sleeve, movable, between a high position and a low position, with respect to said base, to which this cuff is suspended and associated with a return means bringing it up in the absence of the riser. This mobility of the bent sleeve makes it possible to absorb the length variations of the riser under the effects of temperature and pressure. At the top of the vertical riser, a stop device, integral with it, comes to rest on the support guide installed at the head of the float and thus maintains the entire riser in suspension.

The connection with the submarine pipe resting on the seabed is generally effected by a pig-shaped or S-shaped pipe portion, said S being then made in a vertical or horizontal plane, the connection with said underwater pipe being generally carried out via an automatic connector. Thus, there is a wide variety of bottom-surface bonds for connecting underwater wellheads to an FPSO-type floating support, and in some field developments, several wellheads are connected in parallel to a single base connection. surface so as to limit the occupation of the FPSO plating, because each of said bottom-surface links must be removed from its immediate neighbors to avoid any interference and shock, not only at the level of the floats, but also at the level of the flexible pipes and electrical cables connecting with said FPSO. In certain field developments, it is necessary to connect each of the wellheads individually to the said FPSO and we are left with a very large amount of bottom-surface connections that we do not know how to install because the length of the plank FPSO is limited and accepts only a limited number of bottom-surface bonds.

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

In WO 00/49267, there is described a multiple hybrid tower comprising an anchoring system with a vertical tendon consisting of either a cable or a metal bar, or a pipe stretched at its upper end by a float. The lower end of the tendon is attached to a base resting at the bottom. Said tendon comprises guiding means distributed over its entire length through which pass a plurality of said risers vertical. Said base can be placed simply on the seabed and stay in place by its own weight, or remain anchored by means of batteries or any other device to keep it in place. In WO 00/49267, the lower end of the vertical riser is adapted to be connected to the end of a bent sleeve, movable, between a high position and a low position, with respect to said base, to which this cuff is suspended and associated with a return means bringing it up in the absence of the riser. This mobility of the bent sleeve makes it possible to absorb the length variations of the riser under the effects of temperature and pressure. At the top of the vertical riser, a stop device, integral with it, comes to rest on the support guide installed at the head of the float and thus maintains the entire riser in suspension. The connection with the submarine pipe resting on the seabed is generally effected by a pig-shaped or S-shaped pipe portion, said S being then made in a vertical or horizontal plane, the connection with said underwater pipe being generally carried out via an automatic connector.

This embodiment comprising a multiplicity of vertical risers held by a central structure comprising guide means is relatively expensive and complex to install. On the other hand, the installation must be prefabricated on the ground before being towed at sea, then once on site, cabane to be put in place. In addition, its maintenance also requires relatively high operating costs.

In WO02 / 66786 and WO02 / 103153 in the name of the applicant, multi-riser towers have been described with vertical riser anchoring systems able to receive two risers side by side from the same base plate. anchoring, and whose floats at the head of said risers are integral and fixed to each other by means of a hinged structure in the form of a parallelogram. The two risers are also connected by means of tubular collars fixed on one of the risers and connected by rings sliding freely around the second riser, so that the two risers can follow substantially the same lateral movements while being relatively more independent in their vertical movements.

Indeed, when it is desired to associate a plurality of risers with the same floating support, there is the problem of the interference of the movements of said risers which are subjected to the same movement as their tensioning float at the head under the effect of displacements. floating surface support subjected to swell, wind and currents.

When implementing a multiplicity of round-hybrid-type bottom-surface links each comprising a single vertical riser, it is necessary in practice to space the differences in relation to each other, this for at least 2 following reasons: 1- First of all, the respective bases of the two hybrid towers when anchored by suction anchors anchored to the sea floor, must be spaced a distance of at least 5 times, preferably at least 10 times , the diameter of said anchors to avoid interference in the solidity of the sea floor and ensure reliable anchoring, and

2- on the other hand, the floats at the top of the risers are subject to displacements in a cone whose top is located at the level of the anchoring system, and whose angle requires to provide a sufficient distance between the different floats in head vertical risers to prevent them from coming up against each other.

These constraints involve a spreading of the operating area and a limitation of the number of bottom-surface connections that can be connected on the same floating support, at the edges to avoid interference between the different links.

In addition, since crude oil travels a great distance over several kilometers, it must be provided with an extremely costly level of insulation to, on the one hand, minimize the increase in viscosity which would lead to a reduction in the hourly production of the wells. and on the other hand to avoid the blockage of the flow by deposition of paraffin, or formation of hydrates when the temperature drops to around 30-40 ° C. These last phenomena are all the more critical, especially in West Africa, the temperature of the seabed is of the order of 4 ° C and the crude oils are paraffinic type. It is therefore desirable for the bottom-surface links to be of short lengths and thus for the bulk of the different links connected to the same floating support to be limited.

This is why it is sought to provide an installation capable of operating from the same floating support a plurality of bottom-surface links of the tower-hybrid type of reduced space and movement and which is also easier to install and can be manufactured at sea from a pipe laying vessel, in order to avoid prefabrication on the ground followed by on-site towing and a cabanage for the final installation of the facility.

An object of the present invention is therefore to provide an installation of a large amount of multiple bottom-surface bonds and of various types on one side of an FPSO for preferably individually connecting a plurality of well heads and underwater installations installed at the bottom of the sea at great depth, that is to say beyond 1000m of water depth.

More particularly, the problem posed according to the present invention is therefore to provide an installation with a multiplicity of bottom-surface connections from the same floating support, whose methods of installation and installation of the installation allow that time :

to reduce the implantation distance between the different bottom-surface connections, that is to say make it possible to install a plurality of bottom-surface connections in as little space as possible or in other words with a right-of-way reduced ground, this in order, among other things, to increase the number of bottom-surface connections that can be installed along the edge of an FPSO, without said bottom-surface links interfering with each other, and,

- Easy manufacturing and installation by manufacturing and sequential laying of the various pipes from a surface laying ship equipped with a J-laying tower, and finally

optimizing the implementation of the buoyancy means in the case of an implementation spread over time over a long period of time between the setting up of the different bottom-surface links and this, without it being necessary to know at the beginning the number of connections which are to pose, nor their characteristics in terms of dimensions, and of unit weight. Indeed, during the engineering phase of the development of an oil field, the oil reservoir is known at this stage only incompletely, production at full speed then imposes often, after a few years, to reconsider the initial production plans and the organization of associated equipment. Thus, during the installation of the initial system, the number of bottom-surface links and their organization is defined with respect to estimated needs, said needs being almost systematically revised upward after the production of the field, either for the recovery of crude oil, or for the need to inject more water into the tank, or to recover or reinject more gas. As the reservoir is depleted, it is generally necessary to drill new wells to reinject water or gas, or to drill production wells in new areas of the field, so that increase the overall recovery rate, which complicates all the bottom-surface links connected to the FPSO.

Another problem posed according to the present invention is to be able to make and install such bottom-surface connections for submarine pipes at great depths, such as beyond 1,000 meters for example, and of type comprising a vertical hybrid tower and the transported fluid must be maintained above a minimum temperature until it reaches the surface, minimizing components subject to heat loss, avoiding the disadvantages created by the clean thermal expansion, or differential, of various components of said tower, so as to withstand extreme stresses and cumulative fatigue phenomena over the life of the structure, which currently exceeds 20 years. Another problem of the present invention is also to provide a facility of multiple bottom-surface connections with hybrid towers whose anchoring system is of high strength and low cost, and whose manufacturing processes and implementation In place of the various constituent elements are simplified and also of low cost, and can be achieved at sea from a laying ship.

To do this, the present invention provides a bottom-surface bonding arrangement comprising a plurality of bottom-surface bonds arranged in a fan from the same floating support to a plurality of submarine pipes lying at the bottom of the sea, said bottom-surface links comprising at least:

1) a first number k of at least 2, preferably from 5 to 50, more preferably at least 10, first bottom-surface bonds, each said first bottom-surface bond forming a first hybrid tower each comprising:

la) a first rigid pipe consisting of a first vertical riser, whose lower end is fixed to a first base anchored to the seabed and connected to a first underwater pipe resting at the bottom of the sea and whose end upper is tensioned substantially vertically by a first submerged submerged float, preferably at least 100m deep, to which it is connected, and

lb) a first flexible plunger connecting pipe, providing the connection between said floating support and the upper end of said first riser, said first flexible pipes being hooked at a plating of said floating support, two hook points said first pipes successive flexible pipes being spaced apart from one another, the different said first flexible pipes being preferably regularly spaced from the same distance, and two virtual vertical planes respectively passing through two said first flexible connecting pipes at rest successive, being arranged angularly relative to each other by a first angle ai with i = 1 to k, the different vertical planes of the different said first flexible connection lines being substantially intersected at the same point C ₀ in a plan of horizontal section, preferably the different angles ai being all of the same value , and 2) a second number m of at least 1 second bottom-surface bond, each said second bottom-surface bond forming a second hybrid tower comprising:

2a. a second rigid pipe consisting of a riser comprising a second vertical riser or a second SCR type rigid catenary pipe, the lower end of which is connected to a second submarine pipe resting at the bottom of the sea and whose upper end is tensioned by a second buoyancy element submerged in subsurface, preferably at least 50m deep, to which it is connected, and

2b. a second flexible connection line providing the connection between said floating support and the upper end of said second rigid pipe, each said second flexible pipe passing through a chute fixed to a said first float thus delimiting two portions of second flexible plunging pipe, respectively on either side of said first float, the hooked point of each said second flexible pipe on said plating being located in proximity, preferably juxtaposed against, the point of attachment of said first flexible pipe in connection with said first float supporting said second flexible pipe.

Preferably, the bottom-surface connection installation according to the invention comprises:

at least 2, preferably 5 to 50, more preferably at least 10 said second bottom-surface bonds, and

the shortest distance between a hooked point of a said second flexible pipe on the floating support and the upper end of the said second rigid pipe to which it is connected, is greater than the longest distance between a point hooked from a said first flexible pipe to the floating support and the upper end of said first rigid pipe to which it is connected. "Hook point of second flexible pipe located near the hooking point of the first flexible pipe" means that the distance between the hooking point of the second flexible pipe and the hooked point of the first pipe flexible pipe is less than the distance between two successive hooked points of two first flexible pipes successively hooked to the edge of the floating support.

It is understood that said first floats, said first rigid pipes and said first flexible pipes are dimensioned in terms of buoyancy and developed lengths of flexible pipes and positioned between them so that said first angles ai-1 and ai with i = 2 to k, are greater than the second angles a'i of lateral angular deflection of said first floats or said upper ends of said respective first rigid pipes, in case of sea agitated by current, waves or waves, the angle of angular displacement a'i being a angle of same vertex C ₀ as said first angles ai and such that the bisector of a'i passes through said vertical plane Pi of said respective first flexible pipe.

In practice, by spacing the hooking points of said first flexible ducts arranged in a fan, corridors forming angular sectors are created in which the different elements of the first bottom-surface connection and the second bottom-surface connection do not risk hitting the elements of another so-called first bottom-surface connection and / or other said second bottom-surface connection. The present invention is particularly advantageous in that it makes it possible to take advantage of the implementation of said first floats to serve as intermediate support for said second flexible pipes longer than said first flexible pipes and thus to reduce the horizontal tension generated by said second flexible pipe at the upper end of said second rigid pipe, and without substantially increasing the horizontal tension at said first float, because they are balanced. However, the horizontal tensions generated by said flexible pipes at the upper ends of the rigid pipes and at the level of the floats to which they are connected are at the origin of the movements, lurching and lateral deflections of said upper ends of rigid pipes, in case of sea agitated.

It is recalled in this connection that the essential function of the plunging flexible pipes is to absorb at least in part the movements of the upper ends of rigid pipes to which one of their ends is connected and / or the floating support movements to which their other end is connected. by mechanically decoupling the respective movements of the upper ends of rigid pipes to which they are connected and floating supports to which they are also connected at their other end.

Another advantage of this type of installation is:

- tolerate greater lateral deflection of the upper ends of said second rigid pipes in view of their greater distance from the floating support relative to the upper ends of said first rigid pipes, and / or

- Allow to implement a plurality of second rigid pipes connected to a plurality of second flexible pipes attached to the same first float.

It will be understood that the first portions of said second flexible ducts extending between the floating support and said first float are situated above said first flexible ducts insofar as said first float is located above the upper end of said first one. rigid pipe to which is connected an end of said flexible pipe.

In known manner, a said flexible connecting pipe takes by its own weight the form of a plunging chain curve, that is to say falling well below its points hooked at each end with the support respectively. floating and the end upper of the rigid pipe to which it is connected, as long as the length of said flexible pipe is greater than the distance between its point of attachment to the floating support and the upper end of said rigid pipe to which it is connected. In fact, advantageously, said first float, preferably each said first float, supports at least two said second flexible conduits preferably passing through respectively at least two said troughs attached to the same said first float.

Advantageously, said second rigid pipe consists of a second vertical riser, whose lower end is fixed to a second base anchored to the seabed and connected to a said second underwater pipe resting at the bottom of the sea and whose upper end is tensioned substantially vertically by a second float immersed in subsurface, preferably at least 50m deep, to which it is connected.

Preferably, the distance between the floating support and the closest of said second bases is greater than the distance between said floating support and the farthest of said first bases.

Advantageously, said first floats are not located equidistant from the same flat edging of said floating support to which the ends of said first flexible pipes are connected, and preferably, said first floats are all equidistant from the point of intersection C _{0 of} said vertical planes Pi of said first flexible pipes hung on the same plating of said floating support, thus forming a first circular row Ri of said first floats.

It is understood that if said first floats are not all located substantially equidistant from said intersection point C ₀ located beyond the edge of said floating support, this means that said first floats are not aligned with each other in a straight row parallel to the said flat edged. Preferably, a plurality of said second floats, preferably at least the majority of said second floats, are situated at approximately the same distance L ₂ from the point of intersection C _{0 of} said vertical planes Pi of said first flexible pipes hung on the same bordered by said floating support with which said second floats are connected, thus forming a second circular row R ₂ of said second floats.

It is understood that if said first floats and / or said second floats are arranged in an order including a circular row, then said first bases and / or said respective second bases are also arranged in the same order, in particular in a circular row the case applicable.

Here, the term "second flexible pipe in connection with a second float" or "second flexible pipe in connection with a second base", that said second flexible pipe and said second float or so-called second base respectively belong to the same second connection base- area.

More preferably, the different said second floats in connection with the same said first float are not all located at the same distance from said first float and the different said second bases in connection with the same said first float, are not all located at the same distance from the point of hanging on the floating support of said second bottom-surface link corresponding.

Here, the term "second float or second base in connection with the same first float" that said second bottom-surface links comprising said second floats and / or said second bases comprise said second flexible pipes supported by the same said first float.

More preferably, said second floats form at least a second circular row R ₂ of second floats and a second third circular row R ' ₂ of second floats further away the ₂ than said second circular row of second floats.

It is understood that in the same way, said second bases form at least a second circular row of said second bases and a third circular row of said second bases further from the floating support than said second circular row of second bases.

Advantageously, at least two said second flexible pipes passing through the same said first float are attached to chutes arranged at different heights on said first float.

It is understood that this arrangement avoids interference between two flexible pipes close to one another in case of agitation.

Advantageously, at least two said second flexible pipes passing through the same said first float are attached to chutes disposed on opposite sides of said first float.

More particularly, an installation according to the invention further comprises at least one nth bottom-surface bond, n being an integer at least equal to 3 comprising:

a) an upright rigid duct consisting of a riser comprising an uth vertical riser or an nth rigid catenary duct of the SCR type, the lower end of which is connected to an nth underwater pipe resting at the bottom of the sea and whose upper end is tensioned by an nth submerged submerged buoyancy element, preferably an nth end float, immersed at least 100m deep to which it is connected, and

b) an nth flexible connecting line providing the connection between the floating support and the upper end of said nth rigid pipe, each said nth flexible pipe passing through n-1 chutes respectively fixed to n-1 intermediate floats immersed in subsurface thus delimiting n plunging portions of said nth flexible pipe, each of said n-1 intermediate floats being preferably a tensioning float of at least one, preferably all, of the (nl) ths rigid conduits, respectively (nl) ths bottom-surface bonds. It is understood that the bottom-surface link of order n-1 corresponds to said first bottom-surface bond and the bottom-surface link of order n-1 corresponds to an n-th bottom-surface bond.

In a particular embodiment, a second or nth rigid pipe, n being an integer at least equal to 3, is a catenary type pipe constituted by the end of a second or respectively nth underwater pipe resting at the bottom. from the sea up to the subsurface along a chain curve, essentially in a continuously variable curve to a said second or respectively nth end float. Preferably, said second or nth end float at the top of a said second or nth rigid catenary-type pipe is integral and fixed rigidly to at least one other said second or nth float in connection with a said second or respectively nth vertical riser, the different second, respectively nth end floats rigidly fixed together being in connection with the same said first float or the same n-1 said intermediate floats.

Here, the term "rigidly fixed" means that said two second floats are secured to each other in their movements by a rigid connection, and in particular any degree of freedom in rotation or translation of one of said second floats relative to the other is removed in the manner of a recess.

The installation according to the present invention thus has reduced bulk and movements and increased stability as described in WO 2007/023233. This system of arrangement and cooperation of two so-called second rigid pipes constituted by two so-called second vertical risers each with a so-called second clean float at the top of the independent anchors, allows on the one hand to manufacture the entire installation at sea from a laying and driving vessel and to simplify their respective installation at sea and on the other hand gives them a stability in operation by the mutual attachment of their floats, with identical movements of only the upper ends and the second floats, the minimum distance respected from the ground support points or second bases, although reduced, also contributing to the stabilization movements at the head of second risers. This allows to bring the two second floats without risk of interception between the 2 second floats in their respective movements.

Preferably, more particularly, at least two so-called second or respectively nth floats in connection with the same first float are fixed rigidly to each other and two said second or respective nth respective bases in connection with respectively said two second or nth end floats being spaced apart from each other by a distance sufficient to secure the reliability of the anchoring, in particular by a distance of at least 5 times, preferably at least 10 times the diameter of said anchors .

Preferably, said second closest bases are located at a distance from each other of at most 50 m, preferably 25 to 50 m.

More particularly, said bases comprise suction anchors driven into the seabed.

Thus, the two second vertical risers are linked at their upper end but comprise different anchors and spaced from each other, so that, in case of differential expansion due to different temperatures in each of the two vertical risers, it results in a deformation of the triangle whose vertex is the set of two second floats and whose base formed by the substantially horizontal line connecting the two said second bases.

In one embodiment, the bottom-surface connection installation according to the invention comprises a said second rigid pipe of the catenary type constituted by the end of a said second underwater pipe resting at the bottom of the sea going back up to in subsurface according to a chain curve essentially in a continuously variable curvature, up to a said second float. In this embodiment, the point of support and ground contact, substantially variable at the discretion of the movements of the upper part of said chain, from which said second catenary duct (or SCR) back in subsurface, stabilizes the base of said chain in a limited area and thus serves as a second base.

In this embodiment, preferably, said second float at the top of said second rigid catenary or SCR pipe is integral and rigidly attached to another second float in connection with another second rigid pipe, but vertical riser type on the one hand , the different second floats rigidly attached to each other being in connection with the same said first float. In this embodiment, it is said second vertical riser that stabilizes said second SCR type rigid pipe without requiring that the top of this SCR type pipe is stabilized by a cable or tie anchored to the seabed.

In a preferred embodiment, said second floats are fixed together by fixing means located at 2 points on each second float vertically distant so as to secure the respective movements of the second two floats, preferably fixing means located in 2 points close respectively to the upper and lower ends of the cylindrical containers constituting said second floats. Advantageously, the at least two so-called floats fixed together are inserted inside a peripheral screen of hydrodynamic shape, preferably cylindrical.

To connect the flexible pipes to said rigid pipe or riser are intercalated gooseneck devices known to those skilled in the art and an improved example is described in FR 2 809 136 in the name of the applicant.

In an advantageous embodiment variant, the hooking points of said second flexible connection lines at the upper ends respectively of the second rigid pipes are located at different heights and preferably, said second flexible connection pipes have different lengths and curvatures.

This configuration makes it possible to avoid the collision between the second flexible connection lines when they are animated by the effect of the swell, currents and / or the movement of the floating support.

In another variant embodiment, the hooking points of said second flexible connection pipes at the upper ends respectively of vertical risers and SCR-type rigid ducts are substantially at the same height and the second flexible ducts are of substantially the same length, of the same curvature. , and are connected to each other to be substantially integral with each other, so as to be subject, if necessary, to synchronous movements and to avoid any interference and shock between the second flexible pipes in case of motion related to the swell, currents and / or movements of the floating support.

In one embodiment, an installation according to the invention is characterized in that:

one end of a second or nth flexible pipe is directly connected, preferably by a system of flanges, to the upper end of a second or respectively nth vertical riser, and

the lower end of the second or ninth vertical riser comprises a terminal pipe element forming an inertial transition piece whose variation of inertia is such that the inertia of said terminal pipe element at its upper end is substantially identical to that of the pipe element of the running part of the second vertical riser to which it is connected, said inertia of the terminal pipe element gradually increasing to the lower end of said inertial transition piece, comprising a first fixing flange for fixing and embedding the lower end of said second or respectively nth vertical riser to a support and connection device secured to said second or respectively nth base anchored to the seabed, and an end portion of said second or respectively nth flexible pipe, on the side of its junction to the extr upper mity of said second or respectively nth riser, has a positive buoyancy, and at least the upper portion of the second or nth vertical riser also has a positive buoyancy, so that the positive buoyancy of said end portion of said second or nth flexible pipe and of said upper part of said second or nth vertical riser enable the tensioning of said second or nth riser in a substantially vertical position and the alignment or continuity of curvature between the end of said end portion of said second or nth flexible pipe and the upper part said second or nth vertical riser at their connection, said positive buoyancy being provided by a plurality of regularly spaced coaxial peripheral floats and / or a continuous coating of positive buoyancy material, and

said terminal portion of said second or n-th flexible conduit having positive buoyancy extends over a portion of the total length of said second or n-th flexible conduit, such as the portion of said second conduit extending between said first or second flexible conduit, respectively (nl) th float and the top of said second or respectively nth vertical riser has an S-shaped configuration, with a portion of the side of said first or (nl) th float having a concave curvature in the form of a chain with a plunging chain configuration and the remaining end portion of said second flexible pipe having a convex curvature in the form of a chain inverted by its positive buoyancy, the end of said end portion of said second or respectively nth flexible pipe, at the upper end of said second or respectively nième riser, being located preferably above and substantially in alignment with the inclined axis Z _X Z of said second riser at its upper end.

The term "vertical riser" is used here to account for the substantially vertical theoretical position of the second or nth riser when the latter is at rest, provided that the axis of the second or nth riser can experience angular movements with respect to the vertical and move in a cone angle γ ₂ , the apex of which corresponds to the point of attachment of the lower end of the second or nth riser on said base. The upper end of said second or ninth vertical riser may be slightly curved. Therefore, the term "second or nth flexible pipe end portion substantially in alignment with the axis ΖιΖΊ of said second or nth upper riser" that the end of the inverted chain curve of said second or nth flexible pipe is substantially tangent at the end of said second or ninth vertical riser. In any case, in continuity of variation of curvature, that is to say without singular point, in the mathematical sense.

By "inertia" is meant here the moment of inertia of said inertial transition line element with respect to an axis perpendicular to the axis of said inertial transition conductor element, which reflects the bending stiffness in each planes perpendicular to the axis XX 'of symmetry of said pipe element, this moment of inertia being proportional to the product of the section of material by the square of its distance from said axis of the pipe element. The term "continuity of curvature" between the upper end of the second vertical riser and the portion of the second flexible pipe having a positive buoyancy, that said variation of curvature does not present a singular point, such as a sudden variation of the angle tilt of its tangent or point of inflection.

Preferably, the slope of the curve formed by the second or nth flexible pipe is such that the inclination of its tangent relative to the axis Z _X Z of the upper part of said second or nth vertical riser increases continuously and progressively since the connection point between the upper end of the second or nth vertical riser and the end of said end portion of the second or nth flexible positive buoyancy pipe, no inflection point and no bend inversion point.

The installation according to the present invention thus makes it possible to prevent the tensioning of the second or nth vertical riser by a second or nth surface or subsurface float, to which its upper end would be suspended, on the one hand, and, on the other hand, to avoid the connection to said second or nth flexible pipe plunging via a device of gooseneck type. This results not only in a greater intrinsic reliability in terms of mechanical strength in time of the connection between the second or nth vertical riser and the second or nth flexible pipe, because the gooseneck devices are fragile. But above all, this type of installation confers increased stability in terms of angular variation (y ₂ ) of the angle of excursion of the upper end of the second or nth vertical riser relative to a theoretical position of vertical rest, because this angular variation is reduced in practice to a maximum angle not exceeding 5 °, in practice of the order of 1 to 4 ° with the installation according to the invention, whereas, in the embodiments of the prior art, the angular excursion could reach 5 to 10 ° or more.

Another advantage of the present invention is that, due to this small angular variation of the upper end of the second or nth vertical riser, it is possible to implement, at its lower end, a rigid recess on a second or nth base resting at the bottom of the sea, without having recourse to a transition piece of inertia of dimension too important and therefore too expensive. It is therefore possible to avoid the implementation of a flexible hinge, in particular of the spherical flexible ball type, provided that the junction between the lower end of the second or nth riser and said recess comprises an inertial transition piece .

The positive buoyancy of the second or nth riser and the second or nth flexible pipe can be made in a known manner by coaxial peripheral floats surrounding said pipes, or, preferably, with respect to the second or nth rigid pipe of the vertical riser, a coating of positive buoyancy material, preferably also constituting an insulating material, such as syntactic foam, in the form of a shell enclosing said pipe. Such buoyancy elements resistant to very high pressures, that is to say at pressures of about lOMPa per 1000m of water, are known to those skilled in the art and are available from the BALMORAL company (UK). More particularly, the positive buoyancy will be distributed evenly and uniformly over the entire length of said end portion 10a of the second or n-th flexible pipe and at least said upper portion 9b of said second or n-th rigid pipe. Preferably, to give maximum flexibility to the entire bottom-surface connection, said end portion of the second or n-th flexible pipe having a positive buoyancy extends over a length of 30 to 60% of the length of the portion of second or nth flexible pipe extending between the first float and the upper end of the second or nth vertical riser, preferably about half this portion length second or nth flexible pipe. More particularly, to give the entire bottom-surface connection the appropriate flexibility, said positive buoyancy exerted on the end portion of the second or n-th flexible pipe and at least the upper part of said second or nth riser, must exert a tension vertically on the foundation of the second base at the lower end of said second or nth rigid pipe as a function of the water depth according to the following formulation: F = kH, F being said vertical tension expressed in tonnes, H being said depth expressed in meters, and k being a factor of between 0.15 and 0.05, preferably equal to about 0.1.

If the overall positive buoyancy is distributed uniformly and regularly over the entire length of the second or nd rigid pipe and on a said second or nth flexible pipe end portion, said positive buoyancy must allow to obtain a resultant vertical thrust of 50 to 150 kg / m, that is to say that said required buoyancy must correspond to the apparent weight of said second or nth rigid pipe and said second pipe end or nth flexible portion plus an additional buoyancy of 50 to 150 kg / m . More particularly, an installation according to the invention is characterized in that:

said second or respectively nth vertical riser is connected at its lower end to at least a second or respectively nth underwater line resting at the bottom of the sea, and said second or ninth underwater line lying at the bottom of the sea comprises a first rigid elbow pipe element secured to said second or nth base resting at the bottom of the sea and said first rigid elbow pipe element is fixedly held relative to said second or nth base, with at its end a first connecting element part, preferably a male or female element of an automatic connector, and said first fastening flange at the lower end of said inertial transition piece is fixed to a second fastening flange at the end of a second rigid elbow pipe element secured to said fixed support and connection device; on said second or n-base and rigidly and rigidly supporting said second bent rigid pipe element, whose other end comprises a second connecting element part complementary to said first connecting element part and connected to it when said support and connection device is attached to said base. It will be understood that the static geometry of said first rigid pipe element terminating said second or nth underwater pipe resting at the bottom of the sea, with respect to said second or nth base, and the static geometry of said first and second pipe elements. rigid bent, relative to said support device and connection fixed to said second base, to position the respective ends of said first and second rigid pipe elements, so as to facilitate the connection of the complementary parts of automatic connectors once the device of support is connection is fixed to said base. In this embodiment, said first end pipe member of said bottom-lying pipe may preferably also be bent to coincide with the end of said second bent rigid pipe member and allow easy connection by a underwater automaton type ROV at the bottom of the sea.

According to another more particular aspect of the present invention, the subject of the present invention is a method for operating a petroleum field using at least one installation according to the invention in which fluids are transferred between a floating support and ducts under -marines resting at the bottom of the sea, fluids comprising oil, preferably a plurality of said installations, in particular from 3 to 20 said installations according to the invention connected to the same floating support. In known manner, to connect together the various lines are used connection elements, including the type automatic connectors, comprising the lock between a male part and a complementary female part, this lock being designed to be very simply at the bottom of the sea using a ROV, robot controlled from the surface, without requiring direct manual intervention of personnel.

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

FIG. 1 is a view from above of a fan-base bottom-fan connection installation according to the invention,

FIG. 2 is a side view of two of the second bottom-surface bonds of the second bond-bonding group G3 of the bottom-surface links of FIG. 1.

- Figure 2A is a sectional view along the XOZ plane of a said first float of said first bottom-surface connection of Figure 2 showing the passage of the three second flexible pipes.

FIG. 3 is a side view in the ZOY plane of the background-surface bond group G1 of FIG. 1.

FIG. 3A is a view in the XOZ plane of vertical risers tensioned at their upper end by floats rigidly fixed to one another and only one of which is shown in the side view of FIG. 3.

- Figure 3B is an alternative embodiment of the trunking arrangement for the first float of Figure 3.

FIG. 4 is a variant of FIG. 2 in which the second bottom-surface connection does not comprise said second head float, but a second buoyancy element consisting of a distributed buoyancy along the end portion of the second conduit. flexible link connected to the upper part of the second rigid pipe.

In Figure 1, there is shown in plan view a floating support 1, anchored by twelve rows of anchors and having on its side a structure lb integral with the edge of said floating support. Said structure 1b supports a plurality of connection interfaces 2.2-1 to 2-8 which are connected to a plurality of first flexible conduits 3a-1 to 3a-8 and second flexible lines 4a-1 to 4a-11 being part of first and second bottom-surface bonds 3-1 to 3-8 and 4-1 to 4-11, respectively. These pipes are mainly flexible pipes intended to convey crude oil, gas, or water that is injected into certain wells of the oil field. These pipes may be supplemented by umbilicals intended to control wellheads and other underwater equipment, or electric cables to provide power, for example to pumps or submarine valves.

More specifically, in FIG. 1, a bottom-surface link facility is described which comprises a plurality of bottom-surface links 3-i with i = 1 to k and k = 8, 4-j with j = 1 to m and m = 11, arranged in a fan from the same floating support 1 to a plurality of submarine pipes 3e-i with i = 1 to k, 4e-j with j = 1 to m resting at the bottom of the sea 12, said bottom-surface bonds comprising at least:

1) a first number k = 8, first bottom-surface bonds 3, 3-i with i = 1 to 8, each said first bottom-surface bond forming a first hybrid tower each comprising:

la) a first rigid pipe consisting of a first vertical riser 3b, 3b-i with i = 1 to k whose lower end is fixed to a first base 3d-i with i = 1 to k anchored at the bottom of the sea and connected to a first submarine pipe 3e-i with i = 1 to k resting at the bottom of the sea and whose upper end 3b 'is tensioned substantially vertically by a first float 3c-i with i = 1 to k immersed in subsurface, preferably at least 50m deep, to which it is connected by a chain 5a, and

lb) a first flexible connection line 3a, 3a-i with i = 1 to plunge, providing the connection between said floating support and the upper end of said first riser, said first flexible lines being hooked at the level of 2.2-i with i = 1 to k of a side edge of said floating support, two hooked points said first successive flexible pipes being regularly spaced from the same distance I, and two virtual vertical planes Pi, P _{i +} i with i = 1 to (k-1) respectively passing through two said first flexible connection lines 3a-i, 3a (i + 1) with i = 1 to k-1 successive at rest, being arranged angularly regularly with respect to the other of a first angle ai with i = 1 to k-1 of the same value between the different ai, the different vertical planes Pi being substantially intersected at the same point C ₀ in a plane of horizontal section, and

a second number m of the second bottom-surface bond 4,4-j with j = 1 to m and m = 11, and said second bottom-surface bond forming a second hybrid tower comprising:

at. a second rigid pipe (4b, 4b-j with j = 1 to 11) consisting of a riser comprising a second vertical riser (4b-1, 4b-2), whose lower end is fixed to a second base 4d-1 j anchored at the bottom of the sea 12 and connected to a second subsea line 4e-j with j = 1 to m resting at the bottom of the sea and whose upper end 4b 'is tensioned by a second float 4c, 4c- j with j = 1 to m immersed in subsurface, preferably at least 50m deep, to which it is connected, and

b. a second flexible connecting pipe 4a, 4a-j with j = 1 to m ensuring the connection between said floating support 1 and the upper end 4b 'of said second rigid pipe, each said second flexible pipe passing through a chute 6, 6a-6b-6c fixed to a said first float thus delimiting two portions 4a '-j, 4a "-j with j = 1 to m of second flexible pipe plunging, respectively from other said first float, the hooked point of each said second flexible pipe being located juxtaposed against the point of attachment of said first flexible pipe in connection with said first float supporting said second flexible pipe.

Said first floats are all spaced apart from each other by the same distance Ι_Ί and are all situated at equal distance Li from the point of intersection C ₀ of the vertical planes Pi of said first flexible pipes hung on the same plating of said floating support, thus forming a first circular row Ri of said first floats.

Nine of said second floats 4c-1 to 4c-6,4c-8 and 4c-10 to 4c-11, are located substantially at the same distance L ₂ from the point of intersection C ₀ of the vertical planes Pi of said first flexible pipes hung in 2-3,2-5,2-6,2-7 and 2-8 on the floating support with which said second floats are connected, thus forming a second circular row R ₂ of said second floats. Three so-called first floats 3c-3,3c-5 and 3c-6 each support three so-called second flexible ducts passing through respectively three chutes fixed to each of said first floats, namely:

for the first float 3c-3, the second pipes 4a, 4a-2 and 4a-3,

for the first float 3c-5, the second conduits 4a-4,4a-5 and 4a-6, and

for the first float 3c-6, the second lines 4a-7,4a-8 and 4a-9.

Two of said second floats 4c-7 and 4c-9 form a third circular row R ' ₂ of second floats farther away L' ₂ than said second circular row of second floats. The two portions 4a '-j and 4a "-j second flexible pipes in connection with said second floats or said second bases are not necessarily located in the same vertical plane relative to each other and the second plunging portion of second flexible pipe 4a -j will pass through a vertical plane forming an angle diverging or converging with the vertical plane in which extends the first portion of second flexible pipe 4a'-j passing through a chute fixed on the same face of said same first float.

Since the second floats have been moved away from the floating support by a distance L ₂ , the second floats on a circle R ₂ are relatively distant from one another so that it is possible from a same first float 3ci to have at least 3 second pipes ka-j, without the second floats 4c-j neighbors interfering with each other in case of agitation. A said second rigid pipe 4b-2 is a catenary type pipe or SCR formed by the end of a second underwater pipe 4e-2 resting at the bottom of the sea up to the subsurface along a chain curve, essentially according to a continuously variable curve to a said second terminal float 4c-2.

Said second end float 4c-2 at the top of said second catenary-type rigid pipe 4b-2 is secured to and rigidly attached to said two second floats 4c-1 and 4c-3 in connection with the two vertical risers 4b-1 and 4b-2. 3. Said second flexible pipes 4a-1, 4a-2 and 4a-3 pass through said first float 3c-3 on a chute 6a, 6b, 6c fixed above the chute 6a supporting the flexible pipe 4a-1, the latter being at the same level and on the face opposite the chute 6b of the other two second pipes 4a-1 and 4a-3. The different bottom-surface connections are installed along the edge of the floating support fan, which allows to increase the number of the fact that the connection interfaces between said second Flexible pipes and said second rigid pipes are farther away L ₂ from the floating support than the connection interfaces between the first flexible pipes and the first rigid pipes situated at a distance l_i from the floating support. This allows each of the bottom-surface links to be at a safe lateral distance from its immediate neighbor, for example with Ι_Ί of at least 40 m for the distance between the first floats. Thus, under the effects of currents, wind and waves on the floating support as well as on said bottom-surface links, there will be no shocks or interference between the floats of said bottom-surface links, or between said flexible pipes. link.

As an illustration, the first row of connection interface between said first flexible pipes and said first rigid pipes, and thus that said first bases extend on a circle Ri located at a distance from the edge of the floating support of I_i = 350m, while the second row R ₂ connecting interface between the second flexible pipes and second rigid pipes, and the second bases extend over a circle R ₂ beyond the circle Ri, for example 300m from the circle Ri , therefore at L ₂ = 650m from the floating support. Thus, it defines a plurality of possible lateral deflection corridors of the first floats in case of wind, swell or current, the width increases as one moves away from the floating support. As represented in FIG. 1, the axis of a corridor is distant from the axis of the neighboring corridor: of a length I, at the level of the interface supports 2b-2c between the flexible pipes and the floating support 2 , and

a length at the level of the first row RI of said first floats, and

a length l ₂ at the second row R2 of said second floats.

The axes of said corridors extend in the vertical plane Pi containing the first flexible pipes and two corridor axes consecutive pass through the planes Pi and Pi + 1 spaced an angle ai, the different angles ai here being all of the same value, of the order of 5 to 10 °. And, the angle a'i of the angular sector of a corridor is less than or equal to the value of the angles ai between two axes of consecutive corridors. The angle of angular displacement a'i has the same vertex C ₀ as the angle ai between two planes Pi and Pi + 1. And the angle a'i has a bisector passing through said plane Pi. The value of a ' i depends on the angular deflection angles γΐ of the first rigid pipes or first vertical risers 3 bi with respect to their anchoring point at the bottom of the sea in a vertical plane XOZ or XOY and the height of said first rigid pipe or riser vertical 3 bi and / or water level under said first float 3ci, for a height h of first float of 1000 to 3500 m. In practice, at distances L1 mentioned above, it is possible, with values γι less than 5 °, preferably from 3 to 5 °, to implement spacings of first floats such that the angles α1 have a value of 5 to 10 °.

Some second floats 4c-7,4c-9 and connection interfaces between second flexible pipes and second rigid pipes are connected to a third row R ' ₂ similar to the second row R ₂ , but slightly outwardly shifted, so as to increasing the distance between two neighboring second floats to reach a distance 13 as shown on the second link group G3 in Fig. 1, further increasing the safety distance from the dreaded impacts and interferences between the various second floats and various second flexible pipes.

FIG. 2 shows in side view 2 second connections, namely 4-7 and 4-8 of the group G3 of the second bottom-surface connection of FIG. 1. More precisely, a first ground-surface connection 3-6 consisting of a rigid riser 3b-6 connected to a first base 3d-6, for example a suction anchor, via a flexible mechanical connection capable of taking up the vertical traction forces created by the float 3c- 6 in solidarity with the upper end of said riser by means of a chain 5a. The riser 3b-6 is connected in a known manner, using a gooseneck device 8, at its upper end 3b ', and at its lower end to a first submarine pipe 3e-6 resting at the bottom. from the sea 12, via an S-shaped junction conduit 5c.

As shown in FIG. 2A, which is a side view along the axis YY 'of the first float 3c-6, the latter comprises three main chutes 6a-6b-6c intended to support said second flexible pipes 4a-7,4a. 8 and 4a-9, and a fourth smaller chute 6d for supporting electrical cables or various other umbilicals to reach the second row R ₂ . The different chutes 6a, 6b, 6c and 6d are supported by a support structure 6-1. The two second pipes 4a-7 and 4a-8 shown in FIG. 2 are arranged on the two troughs 6a, 6c juxtaposed on the same face 7a of the float, the second flexible pipe 4a-9, not shown in FIG. FIG. 2A passing on the chute 6b on the diametrically opposite face 7b of the float 3c-6.

In FIGS. 3, 3A and 3B, there is shown in side view the group G1 of the second bonds 4-1, 4, 2,4-3 of FIG. 1 in connection with the first bottom-surface bond 3-3. wherein in the second row R2, there are three second floats 4c-1, 4c-2 and 4c-3 interconnected as previously described.

The two risers 4b-1, 4b-3 in FIG. 3A together form an angle β of 1 to 10 ° by the spacing L4 of their bases 4d-1, 4d-3. Thus, in the case of differential expansion due to different temperatures in each of the two vertical pipes 4b-1 and 4b-3, this results in a possibility of deformation of the triangle of angle at the vertex βΐ and whose base is constituted by the straight line connecting the two bases 4d-l and 4d-3. When one of the two risers is cold and the other hot the triangle can deform and its vertex move to the right or to the left of Figure 3a. In addition, as shown in FIG. 3, the SCR 4b-2 disposed on the side of the risers 4b-1, 4b-3 furthest from the FPSO 1 for obvious reasons related to space constraints, creates a large horizontal tension H which tends to move the two second floats 4c-1 and 4c-3 FPSO 1 and generates a tilting risers 4b-1 and 4b-3 of a positive angle γ ₂ , whereas a slope γ ₂ of the links of the second vertical risers of FIGS. 2 and 4 is negative. The first rigid pipes of the first bottom-surface connections 3 can take a slope that is positive or negative depending on the effects of the swell, the current and the wind on the floating support and on each of the first floats, the dimensions of which are considerable. Thus, the configurations of the different constituent elements of the first bottom-surface links 3 are adjusted so as to contain excursions of said first floats and upper ends of said first rigid pipes in a cone of angle γ ₂ , preferably less than 5 °, in practice from 3 to 5 °. FIG. 1 shows grouping variants of a plurality of second bottom-surface bonds, as follows:

in the group G2, the three second floats 4c-4,4c-5 and 4c-6 are substantially regularly spaced apart from one another on the second row R2 because the second flexible pipe 4a-5 is deflected in its second portion 4a-5 after passage of the chute 6 on the first float 3c-5. By contrast, the second flexible pipe 4a-6 extends substantially in the same plane Pb for these two portions 4a'6 and 4a-6.

In the group of connections G4, there is shown a single second connection 4-10, and the second portion of second flexible conduit 4a "-

10 is deflected after passage of the chute 6 on the first float 3c-7 so as to maintain a constant distance relative to the second flexible pipe 4 "a-9 closest, the latter extending radially in the plane Pb. In the installation as shown in FIG. 1, second additional bottom-surface connections can be installed, in particular connection interfaces between the second flexible pipes and second rigid pipes arranged at rows R ₂ or R ' ₂ , and passing second flexible pipes at the free ducts of the first floats 3c-1, 3c-2,3c-4,3c-7 and 3c-8 .

In the present invention, the first row Ri and the second row R _{2 have been described} as circles of center C ₀ . But it is clear that the purpose of the invention is to physically separate from each other the connection interfaces of the bottom-surface connections of the same row Ri or R ₂ -R ' ₂ , any rectilinear or curvilinear arrangement can be adopted for each of those rows. Similarly, it is understood that one can advantageously consider additional rows to arrange the second floats.

Finally, it remains in the spirit of the invention considering third bottom-surface connection lines whose connection interfaces between the third flexible pipes and the third rigid pipes are arranged in row R ₃ more distant than R ₂ and R ₂ , in this case the second floats are intermediate floats whose chutes support the third lines of flexible links, the latter comprising three plunging portions in a chain, namely:

a first plunging portion between the floating support and the first float,

a second plunging portion between the first float and the second float, and

- A third portion diving between the second float and the third float.

Finally, in FIG. 4, there is shown an alternative embodiment in which the second rigid duct or second vertical riser 4b is tensioned not by a second float, but by a second buoyancy element consisting of an end portion 10a of the portion flexible pipe extending from the first float 3c to the upper end 4b 'of the vertical riser 4b. This embodiment, wherein the second buoyancy element is not a float, but a portion of flexible pipe of positive buoyancy is described in the patent application on behalf of the applicant FR-2930587 filed April 24, 2008. More specifically, the portion 10 of the second flexible connecting pipe 4a extending from the first float 3c to the upper end 4b 'of the vertical riser 4b comprises:

a first concave part 10b, 4a up to a substantially median point of inflection 10f, approximately half of the flexible pipe portion 10, in the form of a pipe in a plunging-pit configuration due to its negative buoyancy. Beyond the point of inflection lOf substantially at half length of the portion of the flexible pipe 10, a convex terminal portion 10a extending from the central inflection point 10f to the end 10c of the second pipe flexible, has a positive buoyancy by a plurality of floats lOd, preferably evenly spaced along and around the convex end portion 10a of the flexible pipe. The rigid steel rising pipe or "vertical riser" 4b is equipped with buoyancy means, not shown, such as semi-shells of syntactic foam distributed preferably uniformly over all or part of the length of said rigid pipe, and comprising at its lower end an inertia transition piece 14 equipped with a first fastening flange 14a at its lower end. The first fastening flange 14a is fixed on a second fastening flange 15a constituting the upper part of a support and connection device 15, itself anchored on a pile 16 integral with the base 4d resting at the bottom of the sea. 12, said support device and connection 15 for connecting the lower end of the riser 4 to a 4th pipe resting at the bottom of the sea, as explained below. The flexible pipe portion 10 has a variation of continuous curvature, first concave in the plunge chain configuration portion 10b, and then convex in the positive buoyancy end portion 10a with a point of inflection 10f between the two, thereby forming a S disposed in a substantially vertical plane.

In operation, as shown in Figure 4, when the upper part of the rigid pipe 4b is inclined ΖΊΖ 'at an inclination Y relative to the vertical ZZ', the end 10c of the end portion of the positive buoyancy 10a of the flexible pipe 4a remains substantially in the axial alignment ΖΊΖ 'of the upper end 4b' of the rigid pipe 4b, and in any case in continuity of curvature therewith. This confers a better mechanical resistance to the sealing connection 13 between the two pipes and makes it possible to avoid the use of a gooseneck device 8 as implemented in the prior art.

The advantage of this flexible pipe is to allow its initial portion 10b plunging to dampen the excursions of the first risers 3b and floating support 1 so as to stabilize the end 10c of the flexible pipe connected to the second rigid pipe rising 4b . The end of the portion of the floating end portion 10c of the flexible pipe carries a first fastening flange member 13 with the upper end of a rigid pipe extending from the seabed recessed at a 4d base resting at the bottom of the sea.

The vertical riser 4b is "tensioned" on the one hand by the buoyancy of the end portion 10a of the flexible pipe, but on the other hand and above all by floats regularly distributed at least over the upper part 4b ', preferably all along the rigid pipe, especially in the form of syntactic foam advantageously acting as both an insulation and buoyancy system. These floats and this syntactic foam can be distributed along and around the rigid pipe over its entire length or, preferably, only on a portion of its upper part. Thus, if the base 4d is at a depth of 2500 meters, it can be limited to coating the rigid pipe 4b of syntactic foam over a length of 1000 m from its upper end, which allows to implement a syntactic foam that must withstand less pressure than if it had to withstand pressures up to 2500 m, and therefore a radically reduced cost compared to a syntactic foam to withstand said depth of 2500 m.

The rigid pipe 4b according to the invention is therefore "tensioned" by a said second buoyancy element consisting in the convex end portion with positive buoyancy of said flexible pipe, but without implementation of a float surface or subsurface as in the prior art, which limits the effects of the current and the swell, and thus drastically reduces the excursion of the upper part of the vertical riser and therefore the efforts at the bottom of riser at the recess. The fastening flange system 13 between the upper end of the vertical riser 4b and the flexible pipe 4a, and the connection of the fastening flanges 14a, 15a between the lower end to the inertia transition piece 14 and the support connection 15, make sealed connections between the relevant conduits. The base 4d resting at the bottom of the sea supports a first curved or curved end pipe element 5b of said underwater pipe 4c resting at the bottom of the sea. This first curved or curved end pipe element 5b comprises at its end a first male or female part of an automatic connector 15b, which is disengaged laterally with respect to an orifice 16a and pile 16 passing through said base, but positioned in a fixed manner and determined with respect to the axis ZZ 'of said pile.

The support and connection device 15 supports a second rigid elbow pipe element 5b having at its upper end said second attachment flange 15a and at its lower end, a second complementary female or male portion of an automatic connector 15b. The support and connection device 15 consists of structural elements supporting said second rigid bent pipe element 5b, said rigid structure elements also ensuring the connection between said second attachment flange 15a and a lower support plate 15d supporting face a tubular pile 16 called tubular anchoring insert.

The fixing system of the upper end of the rigid pipe 4b with the flexible pipe 4a, 10 and the tensioning of said pipes gives greater stability to the upper end of the rigid pipe 4b with an angular variation γ not exceeding operation at 5 ° C.

Thus, it has been possible according to the present invention to achieve a rigid embedding of the lower end of the steel rigid pipe 4b on the base 4d using the connection support device 15. To do this, the lower end pipe element of the rigid pipe 4b comprises a conical transition piece 14 whose inertia in cross section increases gradually from a value substantially identical to the inertia of the pipe element of the riser 4b to which it is connected, in the tapered upper part of the transition piece 14, to a value 3 to 10 times greater than the level of its lower part connected to said first fastening flange 14a. The coefficient of variation of inertia essentially depends on the bending moment that the vertical riser must bear at said transition piece, said moment being a function of the maximum excursion of the upper part of the rigid steel pipe 4b, thus of the angle γ. To achieve this transition piece 14 is used high yield strength steels and in extreme cases of stress, it may be necessary to manufacture transition parts 14 of titanium.

Claims

1. Installation of bottom-surface bonds comprising a plurality of bottom-surface bonds (3-i with i = 1 to k, 4-j with j = 1 to m) arranged in a fan from a single floating support (1) up to to a plurality of underwater pipelines (3e-i with i = 1 to k, 4e-j with j = 1 to m) lying at the bottom of the sea (12), said bottom-surface links comprising at least:

1) a first number (k) of at least 2, preferably from 5 to 50, more preferably at least 10, first bottom-surface bonds (3,3-i), each said first bottom-surface bond forming a first hybrid tower each comprising:

la) a first rigid pipe consisting of a first vertical riser, (3b, 3b-i with i = 1 to k) whose lower end is fixed to a first base (3d-i with i = 1 to k) anchored to bottom of the sea and connected to a first underwater conduct

(3e-i with i = 1 to k) resting at the bottom of the sea and whose upper end (3b ') is tensioned substantially vertically by a first float (3c-i with i = 1 to k) immersed in subsurface, preferably at least 100m deep, to which it is connected (5), and

lb) a first flexible connection line (3a, 3a-i with i = 1 to k), which provides the connection between said floating support and the upper end of said first riser, said first flexible pipes being hooked at (2, 2-i with i = 1 to k) of a plating (la) of said floating support, two hooked points said first successive flexible pipes being spaced (I) from each other, the various said first flexible pipes being preferably regularly spaced by the same distance (I), and two virtual vertical planes (Pi, Pi + 1 with i = 1 to k-1) passing respectively through two said first flexible connection lines [3a-i, 3a - (i + l) with i = 1 at k-1] successive at rest, being arranged angularly relative to each other by a first angle ai with i = 1 to k, the different vertical planes (Pi with i = 1 to k) of the different said first flexible connection lines intersecting substantially at the same point (C ₀ ) in a plane of horizontal section, preferably the different angles ai being all of the same value, and

2) a second number (m) of at least one second bottom-surface bond (4,4-j with j = 1 to m), each said second bottom-surface bond forming a second hybrid tower comprising:

2c. a second rigid pipe (4b, 4b-j with j = 1 to m) consisting of a riser comprising a second vertical riser (4b-1, 4b-2) or a second rigid catenary pipe of the SCR type (4b-3) , whose lower end is connected to a second underwater line (4th-j with j = 1 to m) resting at the bottom of the sea and whose upper end (4b ') is tensioned by a second buoyancy element (4c, 4c-j with j = 1 to m) immersed in subsurface, preferably at least 50m deep, to which it is connected, and

2d. a second flexible connection line (4a, 4a-j with j = 1 to m) providing the connection between said floating support (1) and the upper end (4b ') of said second rigid pipe, each said second flexible pipe passing by a chute (6, 6a-6b) attached to a said first float thus delimiting two portions (4a'-j, 4 "-j with j = 1 to m) of second flexible plunging pipe respectively on each side said first float, the hooked point of each said second flexible pipe on the said plating being located (2.2-i with i = 1 to k) close, preferably juxtaposed against, the hooked point of said first flexible pipe in connection with said first float supporting said second flexible pipe.

2. bottom-surface connection installation according to claim 1, characterized in that it comprises:

at least 2, preferably 5 to 50, more preferably at least 10 second bottom-surface bonds (4,4-j with j = 1 to m), and

the shortest distance between a hooked point of a said second flexible pipe on the floating support and the upper end of the said second rigid pipe to which it is connected, is greater than the longest distance between a point hooked from a said first flexible pipe to the floating support and the upper end of said first rigid pipe to which it is connected.

3. Installation of bottom-surface links according to claim 1 or 2, characterized in that said first float (3c-2,3c-4 and 3c-5), preferably each said first float supports at least two so-called second flexible pipes passing preferably respectively at least two said chutes fixed to the same said first float.

4. Installation of bottom-surface connections according to one of claims 1 to 3, characterized in that said second rigid pipe consists of a second vertical riser (4b-1, 4b-3) whose lower end is fixed to a second base (4d-1, 4d-3) anchored at the bottom of the sea (12) and connected to a said second underwater pipe resting at the bottom of the sea and whose upper end (4b ') is tensioned so substantially vertical by a second float (4c-1, 4c-3) immersed in subsurface, preferably at least 50m deep, to which it is connected.

5. Installation of bottom-surface connections according to one of claims 1 to 4, characterized in that:

said first floats are not situated at equal distance from the same flat edging (1b) of said floating support to which the ends of said first flexible pipes are connected, and

preferably, said first floats are all located at equal distance (l_i) from the point of intersection (C ₀ ) of said vertical planes (Pi) said first flexible pipes hung on the same plating of said floating support, thus forming a first circular row (Ri) of said first floats.

6. Installation of bottom-surface links according to claim 4 or 5, characterized in that a plurality of said second floats, preferably at least the majority of said second floats (4c-1 to 4c-6,4c-8 and 4c -10 to 4c-11), are located substantially at the same distance (L ₂ ) from the point of intersection (C ₀ ) of said vertical planes (Pi) of said first flexible pipes hung on the same plating of said floating support with which said second floats are in connection, thus forming a second circular row (R ₂ ) of said second floats.

7. Installation of bottom-surface links according to one of claims 4 to 6, characterized in that the said so-called second floats in connection with the same said first float are not all located at the same distance from said first float and the different said second bases in connection with the same said first float, are not all located at the same distance from the hooked point on the floating support of said second bottom-surface connection corresponding.

8. Installation of bottom-surface links according to claim 7, characterized in that said second floats (4c-7 and 4c-9) form at least a second circular row (R ₂ ) of second floats and a third circular row (R ₂ ) second floats farther away (L ' ₂ ) than said second circular row of second floats.

9. Installation of bottom-surface links according to one of claims 2 or 8, characterized in that at least two said second flexible pipes passing through the same said first float are attached to chutes (6b, 6c) arranged at different heights on said first float.

10. Installation of bottom-surface connections according to one of claims 2 to 9, characterized in that at least two said second flexible pipes passing through a same said first float are fixed to chutes (6a, 6b) arranged on opposite faces of said first float.

11. bottom-surface bonding installation according to one of claims 1 to 10, characterized in that it further comprises at least one nth bottom-surface bond, n being an integer at least equal to 3 comprising:

b) an nth flexible connecting line providing the connection between the floating support and the upper end of said nth rigid pipe, each said nth flexible pipe passing through (n-1) chutes fixed respectively to (n-1) submerged intermediate floats in subsurface thus delimiting n plunging portions of said nth flexible pipe, each of said (n-1) intermediate floats being preferably a tensioning float of at least one, preferably all, rigid (nl) -th pipe conduits, respectively (nl) eighth bottom-surface bonds.

12. bottom-surface connection installation according to one of claims 1 to 11, characterized in that a said second or nth rigid pipe, n being an integer at least equal to 3, is a catenary-type pipe (4b- 2) constituted by the end of a second or respectively nth underwater line (4e-2) resting at the bottom of the sea going up to the subsurface in a chain-shaped curve, essentially according to a continuously variable curve up to a said second or respectively nth end float (4c-2).

13. bottom-surface connection installation according to claim 12, characterized in that said second or nth end float (4c-3) at the top of a said second or nth rigid catenary-type pipe (4b-3) is integral and rigidly fixed to at least one other said second or nth float (4c-1, 4c-2) in connection with a said second or respectively nth vertical riser (4b-l, 4b-2), the different second, respectively nth end floats (4c-1, 4c-2,4c-3) fixed rigidly together being in connection with the same said first float (3c) or the same (n-1) said intermediate floats.

14. Bottom-surface bonding installation according to one of Claims 1 to 13, characterized in that:

one end of a second or nth flexible pipe (10, 4a) is directly connected, preferably by a system of flanges (13), to the upper end of a second or respectively nth vertical riser (4b), and

the lower end of the second or ninth vertical riser comprises a terminal pipe element forming an inertial transition piece (14) whose variation of inertia is such that the inertia of said terminal pipe element at its end greater than, that is substantially identical to that of the pipe element of the running part of the second vertical riser to which it is connected, said inertia of the terminal pipe element progressively increasing up to the lower end of said transition piece d inertia, comprising a first fixing flange (14a) for fixing and embedding the lower end of said second or respectively nth vertical riser to a support and connection device (15) secured to said second or respectively n-base (4c) anchored at the bottom of the sea, and an end portion (10a) of said second or respectively nth flexible pipe, on the side of its junction at the upper end of said second or respectively nth riser, has a positive buoyancy, and at least the upper part (4b ') of the second or nth vertical riser also has a positive buoyancy, so that the positive buoyancy of said end portion of said second or nth flexible pipe and said upper portion of said second or nth vertical riser allow the tensioning of said second or nth riser in a substantially vertical position and the alignment or the continuity of curvature between the end of said end portion of said second or nth flexible pipe and the upper portion of said second or nth vertical riser at their connection, said positive buoyancy being provided by a plurality of floats coaxial peripherals (lOd), regulated spaced apart and / or a continuous coating of positive buoyancy material, and

said terminal portion (10a) of said second or n-th flexible conduit having a positive buoyancy extends over a portion of the total length of said second or n-th flexible conduit, such as the portion of said second conduit extending between said first or respectively (nl) th float and the top of said second or respectively nth vertical riser has an S configuration, with a portion (10b) on the side of said first or (n-1) th float having a concave curvature in the form of a chain with a plunging chain configuration and the remaining end portion (10a) of said second flexible pipe having a convex curvature in the form of a chain inverted by its positive buoyancy, the end (10c) of said end portion of said second or respectively nth pipe flexible, at the upper end of said second or respectively nth riser being located pref erence above and substantially in alignment with the inclined axis ZiZ'i of said second riser at its upper end (4b ').

15. Bottom-surface connection plant according to claim 14, characterized in that:

said second or respectively nth vertical riser is connected at its lower end to at least a second or respectively nth underwater line (4e) lying at the bottom of the sea, and

said second or ninth underwater pipe resting at the seabed comprises a first rigid angled terminal element (5b) integral with said second or nth base (4c) resting at the bottom of the sea and said first rigid pipe element angled terminal (5b) is fixedly held relative to said second or n-base, with at its end a first connecting member portion, preferably a male or female member of an automatic connector (15b), and

said first fastening flange (14a) at the lower end of said inertia transition piece (14) is attached to a second fastening flange (15a) at the end of a second bent rigid pipe member ( 5c), integral with said support and connection device (15) fixed on said second or n-base and rigidly and rigidly supporting said second bent rigid pipe element (5c), the other end of which comprises a second part complementary connecting member of said first connecting member portion and connected thereto when said support and connecting device (15) is attached to said base (4c).