EP1501999A1

EP1501999A1 - Seafloor/surface connecting installation for a submarine pipeline which is connected to a riser by means of at least one elbow pipe element that is supported by a base

Info

Publication number: EP1501999A1
Application number: EP03749918A
Authority: EP
Inventors: Giovanni Chiesa; Floriano Casola; François-Régis PIONETTI
Original assignee: Saipem SA
Current assignee: Saipem SA
Priority date: 2002-05-07
Filing date: 2003-05-05
Publication date: 2005-02-02
Anticipated expiration: 2023-05-05
Also published as: EP1501999B1; DE60303941D1; US20050271476A1; ATE319909T1; WO2003095788A8; WO2003095788A1; FR2839542A1; US7025535B2; AU2003249394A1; FR2839542B1

Abstract

A bottom-to-surface connection installation for an undersea pipe. The installation comprises a vertical riser having its bottom end connected to an undersea pipe on the sea bed, and having a float at its top end, and a pipe connecting a floating support at the top end of the vertical riser. The connection between the riser bottom end and the undersea pipe is via an anchor system having a base on the sea bed. The base holds and guides junction elements between the bottom end of the riser and the end of the lower end of the undersea pipe. The junction elements comprise a rigid pipe element presenting an angled bend and a pipe coupling element which are fixed to a moving support of the base. The junction elements are fixed to the moving support and are free to move only in translation in a single longitudinal direction.

Description

GROUND-SURFACE CONNECTION INSTALLATION OF A SUBSEA PIPE CONNECTED TO A RISER BY A WELDED PIPE ELEMENT HOLDED BY A SUBBASE

5 The present invention relates to a bottom-surface connection installation of at least one submarine pipe installed at great depth of the tour-hybrid type.

The technical sector of the invention is the field of manufacturing and installing production risers for the underwater extraction of oil, gas or other soluble or fusible material or a suspension of mineral matter. from submerged wellheads 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 petroleum production. 5 A floating support generally comprises anchoring means to remain in position despite the effects of currents, winds and swell. It also generally comprises means for storing and processing petroleum as well as means for unloading towards tanker-lifters, the latter being present at regular intervals to carry out the removal of production. The designation of 0 these floating supports is the Anglo-Saxon term "Floating Production Storage Offloading" (meaning "floating means of storage, production and unloading") whose abbreviated term "FPSO" will be used throughout following description.

Due to the multiplicity of lines existing on this type of installation, it has been necessary to implement bottom-surface connections of the tower-hybrid type in which substantially vertical rigid pipes here called "vertical riser", ensure the connection between the submarine pipes lying at the bottom of the sea and going up along a tower to a depth close to the surface, depth from which flexible pipes ensure the connection between the top of the tower and the floating support. The tower is then provided with buoyancy means to remain in the vertical position and the risers are connected, at the foot of the tower, to the underwater pipes by flexible cuffs which absorb the angular movements of the tower. The assembly is commonly called "Hybrid Tower", because it involves two technologies, on the one hand a vertical part, the tower, in which the riser is made up of rigid pipes, on the other hand the upper part of the riser made up of flexible in chain which ensure the connection to the floating support. We know the French patent FR 2 507 672 published on December 17, 1982 and entitled "riser for great water depths", which describes such a hybrid tower.

The present invention relates more particularly to the known field of type connections comprising a vertical hybrid tower anchored to the bottom and composed of a float located at the top of a vertical riser, the latter being connected by a pipe, in particular a flexible pipe. taking its own weight in the form of a chain from the top of the riser, to a floating support installed on the surface. The advantage of such a hybrid tower lies in the possibility for the floating support to be able to deviate from its normal position by inducing a minimum of stresses in the tower as well as in the portions of conduits in the form of suspended chains, both basically only on the surface.

The patent is known in the name of the present applicant, WO 00/49267 which describes a tower whose float is at a depth greater than half a water height and whose catenary connection to the surface ship is made at 1 using thick rigid pipes. The tower thus described requires, at its base, flexible connection cuffs making it possible to connect the lower end of the vertical risers of said tower to the underwater pipe resting on the bottom, so as to absorb the movements resulting from the expansions due to the temperature of the fluid transported.

More particularly, in WO 00/49267, the anchoring system comprises a vertical tendon constituted either by a cable, or by a metal bar, or else by a pipe stretched at its upper end by a float. The lower end of the tendon is attached to a base resting on the bottom. Said tendon comprises guide means distributed over its entire length through which said vertical risers pass. Said base can be simply placed on the bottom of the sea and remain in place by its own weight, or remain anchored by means of batteries or any other device capable of holding it in place. In WO 00/49267, the lower end of the vertical riser is capable of being connected to the end of a bent, movable cuff, between a high position and a low position, relative to said base, to which this cuff is suspended and associated with a return means bringing it back to the high position in the absence of the riser. This mobility of the bent cuff makes it possible to absorb variations in the length of the riser under the effects of temperature and pressure. At the head of the vertical riser, a stop device, integral with it, comes to rest on the installed support guide at the head of the float and thus keeps the entire riser in suspension.

The connection with the underwater pipe resting on the seabed is generally carried out by a section of pipe in the shape of a pigtail or in the shape of an S, said S then being produced in a plane either vertical or horizontal, the connection with said underwater pipe being generally carried out by means of an automatic connector.

In addition, crude oil traveling over very long distances, several kilometers, we seek to provide them with an extreme level of insulation to, on the one hand minimize the increase in viscosity which would lead to a reduction in the hourly production of well, and secondly to avoid blocking the flow by depositing paraffin, or hydrate formation when the temperature drops to around 30-40 ° C. These latter phenomena are all the more critical, particularly in West Africa, since the seabed temperature is around 4 ° C and the crude oils are of the paraffinic type. Numerous thermal insulation systems are known which make it possible to achieve the required level of performance and to resist the pressure from the bottom of the sea which is of the order of 150 bars at 1500m deep. Among others, there are the concepts of the "pipe-in-pipe" type, comprising a pipe conveying the hot fluid installed in an external protective pipe, the space between the two pipes being either simply filled with heat insulation, confined or not vacuum, or simply vacuum. Many other materials have been developed to provide high performance insulation, some of them being resistant to pressure, simply surround the hot pipe and are generally confined within a flexible or rigid outer jacket, in pressure and whose main function is to maintain a substantially constant geometry over time.

All these devices conveying a hot fluid within an insulated pipe exhibit, to varying degrees, phenomena of differential expansion. In fact, the internal pipe, generally made of steel, is at a temperature which we seek to maintain as high as possible, for example 60 or 80 ° C., while the external envelope, very often also made of steel, is at sea water temperature, i.e. around 4 ° C. The forces generated on the connecting elements between the internal pipe and the external envelope are considerable and can reach several tens, even several hundred tonnes and the resulting overall elongation is of the order of 1 to 2 m in the case of isolated pipes of 1000 to 1200m in length. The problem posed according to the present invention is to be able to produce and install such bottom-surface connections for underwater pipes at great depths, such as beyond 1000 meters for example, and of the type comprising a vertical tower and the transported fluid must be maintained above a minimum temperature until it reaches the surface, minimizing the components subject to heat loss, avoiding the drawbacks created by the proper thermal or differential expansion of the various components of said tower, so as to withstand the extreme stresses and phenomena of cumulative fatigue over the life of the structure, which commonly exceeds 20 years. Another problem of the present invention is to provide a bottom-surface connection installation of the tower-hybrid type, the anchoring system of which is of great resistance and of low cost, and the method of setting up the different components is simplified and also of low cost.

Another problem at the basis of the invention is to provide an installation which makes it possible to intervene inside the underwater pipe resting at the bottom of the sea, by a "coil-tubing" type process from the surface. and from the upper end of the vertical riser.

A solution to the problems posed is therefore a bottom-surface connection installation for an underwater pipe resting on the seabed, in particular at great depth, comprising: a) at least one vertical riser connected at its lower end to at least one pipe underwater resting at the bottom of the sea, and at its upper end at least one float, and b) at least one connecting pipe, preferably a flexible pipe, ensuring the connection between a floating support and the upper end of said vertical riser, and c) the connection between the lower end of said vertical riser and a said submarine pipe resting at the bottom of the sea is done by means of an anchoring system comprising a base placed on the bottom. According to the invention, the installation is characterized in that:

said base maintains and guides the junction elements between the lower end of said vertical riser and the end of the terminal rectilinear horizontal part of said pipe lying at the bottom of the sea, and

- Said junction elements include • a rigid pipe element having an elbow-shaped curvature and A pipe connection element, preferably a single connection element, more preferably a single automatic connector,

- Maintaining and guiding said junction elements being such that said junction elements can only move in a translational movement in a single longitudinal direction YY 'corresponding substantially to the axial direction of said horizontal rectilinear terminal part of said pipe under -marine resting at the bottom of the sea.

It is understood that said junction elements which can only move according to a single degree of freedom in linear translation, can thus absorb any movements of expansion and retraction of the pipe resting at the bottom of the sea in said direction, as will be explained more far.

Said junction elements are therefore not authorized for any other translational or rotational movement, and in particular, cannot move laterally or in height. Thus, according to the present invention, the substantially fixed point at altitude is located at the bottom of the tower at the flexible joint, which makes it possible to eliminate the bent connecting cuffs of the prior art, the vertical movements of the riser being absorbed by the float, free to move vertically at the top of said riser. The term “elbow-shaped curvature” is understood to mean two short rectilinear sections arranged at 90 °, separated and interconnected by a curved section having a radius of curvature, preferably a large radius of curvature, in particular a radius of curvature greater than 5 m, more particularly on the order of 5 to 10 m, said elbow-shaped pipe portion having an axial plane, comprising the axes of the two said straight pipe sections arranged at 90 °. In general, the curvature is in the form of an arc of a circle. One can use to produce this pipe element having a curvature, a rigid pipe element, in particular of length from 7 to 15 m.

Said elbow-shaped pipe portion providing the junction between said vertical riser and said pipe lying horizontally at the bottom of the sea, it is understood that said elbow-shaped pipe portion is arranged so that its said axial plane is in position vertical.

The term "vertical riser" is used here to account for the theoretical position of the riser when it is at rest, it being understood that the axis of the riser can have angular movements relative to the vertical and move in a cone d angle whose apex corresponds to the fixing point of the lower end of the riser on said base.

As regards the axial plane of the elbow-shaped pipe element, the term "vertical axial plane" means that this axial plane is in a position perpendicular to the plane of the seabed on which said base rests, which plane is theoretically a horizontal plane, and said axial plane comprises the axis of the rectilinear terminal part of the pipe lying at the bottom of the sea.

Said connection elements consist of a first male or female part which cooperate respectively with a second female or male part.

Said connection elements, in particular of the automatic connector type, are known to those skilled in the art and include locking between a male part and a complementary female part, this locking being designed to be done very simply at the bottom of the sea at using a ROV, robot controlled from the surface, without requiring direct manual intervention by personnel.

Said connecting pipe between the floating support and the upper end of the vertical riser can be:.

- a flexible or reduced rigidity pipe if the head float is close to the surface, or

- a rigid pipe if the head float is at a great depth. In an advantageous embodiment, said base comprises:

- a platform resting on the bottom of the sea, and

- a mobile support to which said junction elements are fixed, and - said mobile support being able to move, preferably in a controlled manner, on said platform according to a said translation in a said longitudinal direction YY 'corresponding substantially to the direction axial of the horizontal end part of said underwater pipe lying at the bottom of the sea.

The term “controlled movement” is understood to mean a movement the amplitude of which is limited by mechanical stops integral with the platform.

The platform comprises a structure constituting guide elements such as a barrier or slide which prevent any other movement of the mobile support in a lateral direction XX 'or in height, that is to say in a vertical direction 121. The installation according to the present invention is advantageous because it has a relatively static geometry of said junction elements relative to said base, and more particularly with respect to said mobile support, said junction elements being rigidly held on said mobile support. The lower part of the tower is thus perfectly stabilized and no longer supports any effort, especially at the connection between the vertical riser and the pipe resting at the bottom of the sea, since the longitudinal translation movements of the mobile support creates flexibility the end of the pipe - submarine lying at the bottom of the sea, said flexibility-being capable of absorbing by deformation the elongation or the retraction of the underwater pipe under the effect of temperature and pressure , thus avoiding creating considerable thrust forces within the submarine pipe, these forces being able to reach 100, even 200 tonnes or more, and transmitting them to the foundation structure of the riser tower.

In a preferred embodiment, said vertical riser comprises in its lower end part a flexible joint, preferably reinforced, which allows angular movements α of the part of said vertical riser situated above said flexible joint, and said junction elements comprise said flexible joint or a portion of vertical riser located below said flexible joint.

A flexible joint allows a significant variation in the angle a between the riser axis and its theoretical vertical position at rest, without generating significant stress in the pipe portions located on either side of said flexible joint: these flexible joints are known to those skilled in the art and can be constituted by a spherical ball joint with seal, or a laminated ball joint made of sandwiches of elastomer sheets and adhered sheet, capable of absorbing significant angular movements by deformation of the elastomers, while retaining a perfect seal due to the absence of friction seal. Said angle α is generally between 10 and 15 degrees.

In all cases, said flexible joint is hollow to allow the fluid to pass, and its internal diameter is preferably preferably of the same diameter as the adjacent conduits which are connected to it, in particular that of the vertical riser. The term “reinforced flexible joint” is understood here to mean a joint capable of transferring to the mobile support the vertical forces created by the tension generated by the sub-surface float, and the horizontal forces created by the swell, and the current acting on the portion vertical riser, float and flexible connection to the floating support, as well as by the movements of said floating support. When said joining elements comprise said flexible joint, said flexible joint is therefore fixedly held relative to said movable support. said flexible joint then corresponds to a terminal element of the junction elements ensuring the junction with said vertical riser.

Due to the presence of said flexible joint, and the flexible connection to the floating support located at the head of the vertical riser, the horizontal displacement of the base of the vertical riser which is at a substantially fixed point in altitude, does not generate significant effort in the articulated assembly consisting of said mobile support, said flexible joint, said riser and said connection to the surface support, under the effect of displacements of said mobile support within said base platform, displacement which n '' generally do not exceed 5m. Another advantage of the present invention is also the considerable reduction in the overall cost, resulting from the elimination of the cuffs used in the prior art to connect the vertical riser and the underwater pipe resting on the seabed.

The installation according to the invention makes it possible to eliminate all of these drawbacks of the prior art and to provide, at the best cost, a riser tower incorporating the most efficient insulation technologies.

According to a first alternative embodiment of the invention, the installation comprises:

a first part, preferably male, of a said connecting element, and integral with said flexible joint, disposed just below the latter, and

- Said underwater pipe resting on the bottom of the sea ends in a said rigid pipe element having a curvature in the form of an elbow having at its end a second part, preferably female, of a said connection element, suitable for cooperate with said first part to form said connecting element.

According to another alternative embodiment of the installation of the invention:

said rigid pipe element having an elbow-shaped curvature is fixed directly under the face of said flexible joint and comprises at its other end a first part, preferably female, of a said connecting element, and

- Said first part of the connection element, preferably female, cooperates with a second part of connection element, preferably male, at the end of a terminal horizontal part of an underwater pipe resting at the bottom from the sea to form a said connecting element.

Thus, said pipe element having an elbow-shaped curvature perhaps :

- either pre-installed at the end of the underwater pipe lying at the bottom of the sea and constituting the terminal pipe element thereof,

- Or pre-installed at the lower end of said vertical riser, more particularly below said flexible joint.

In both cases, said rigid elbow-shaped pipe element has at its free end a first part, male or female of a connection element, and the second complementary female or male part respectively of said connection element is located either the end of the rectilinear terminal pipe element of said pipe lying at the bottom of the sea, ie at the end of said vertical riser, more particularly, just below said flexible joint.

For reasons of installation of the installation at the bottom of the sea, as will be explained below, it is preferred to pre-install said rigid elbow-shaped pipe element at the end of the pipe resting on the bottom of the sea and making the first male part of said connection element cooperate at the end of said elbow-shaped curvature element with a second complementary female part of the connection element located on the underside of said flexible joint. Obviously, it is possible to envisage a short portion of rectilinear riser ensuring the junction between said flexible joint and, said second part of the connection element.

In an advantageous embodiment, said movable support comprises a central cavity open on the top by an upper orifice capable of receiving said rigid pipe element having an elbow-shaped curvature when the latter is lowered from the surface within said support mobile. This embodiment described above makes it easier to set up the installation and to connect the vertical riser and the underwater pipe resting on the ground during the installation of the installation.

More particularly, said upper orifice cooperates with blocking elements, preferably a wedge system, making it possible to block said reinforced flexible joint which is thus rigidly and fixedly secured to said movable support, and the horizontal end part of said pipe resting at the bottom. sea is fixedly held on the bottom of said movable support, preferably using a collar system.

Thus, all of said junction elements are fixedly fixed relative to said movable support and any expansion or retraction of the pipe which may occur in said axial longitudinal direction of the terminal part. horizontal of said pipe resting at the bottom of the sea generates a displacement of said mobile support with said junction elements by translation in the same longitudinal direction.

The following other characteristics taken separately or in combination are also advantageous:

said upper orifice has a peripheral internal wall in the form of a funnel with a large upper base and said corners allowing the blocking of said reinforced flexible joint consist of frustoconical corners,

said platform comprises elements for guiding and holding said mobile support so that said mobile support can only move on said platform by sliding in translation in a said longitudinal direction YY ′, preferably using sliding pads,

- Said movable support is held laterally between two lateral guide barriers of said platform, and said lateral guide barriers cooperate with movable blocking elements which in retracted release position allow the descent of said movable support from the surface to a position between the two said lateral barriers over said platform, and in the advanced locking position cooperate with the external shape of said mobile support so that the vertical movement 121 in height thereof is controlled,

said base comprises a platform resting at the bottom of the sea, which cooperates with stabilizing elements comprising dead bodies placed over said platform or suction anchors passing through said platform to be sunk into the ground and / or spade-like projecting elements arranged on the underside of said platform and sunk into the sea bottom to prevent any sliding of said platform at the bottom of the sea.

The junctions between the different components of the float assembly, flexible pipe and vertical riser being located not far from the surface, are subject to the combined effects of swell and current. In addition, the surface support being subjected not only to swell and current, but also to the effects of the wind, the overall movements create at the singular point that constitutes the junction between riser and flexible pipe, considerable efforts in the various mechanical components. Indeed, the float exerts a vertical traction upwards which can vary from a few tens of tonnes to several hundred tonnes or even beyond 1000 tonnes, depending on the water depth which can reach 1500m, even 3000m, and depending on the diameter internal of the pipe which can vary from 6 "to 14", even 16 ". Thus the efforts to be transmitted are considerable and the overall movements are clocked, among others, to the rhythm of the swell, that is to say with a period typically varying, in period agitated, between 8 and 20 seconds The fatigue cycles accumulated over the lifetime of the field thus reach values exceeding several tens of millions of cycles, this is why an installation according to the present invention advantageously comprises at least one float.

Another problem according to the present invention is to allow easy intervention inside said riser from the surface, in particular to allow inspection or cleaning of said vertical riser, by introduction of a rigid tube from the upper end of the float. , passing through said connecting device between float and vertical riser.

Indeed, these bottom-surface connections convey a multiphase fluid, that is to say a fluid composed of crude oil, water and gas. However, during the rise of the fluid, the local pressure decreases and the gas bubbles then increase in volume, creating phenomena of instability of the fluid stream which can lead to significant jolts. During production stoppages, the gas is found in the upper part and the oil-water mixture is trapped in the low points, that is to say in the lower part of the zone of the flexible chain, as well as in the lower part of the substantially vertical section of the riser or even beyond the bend located at the foot of the vertical riser, in the horizontal part of the underwater pipe resting on the bottom of the sea.

The multiphase mixture, consisting of crude oil, water and gas, tends, when the temperature drops below a value between 30 and 40 ° C, to create two types of plugs which may block production. A first type of plug is due to the formation of hydrates from the gas phase in the presence of water, another type is due to the freezing of paraffin contained in variable proportion in the crude oil of certain petroleum fields, particularly in West Africa. We know the intervention method inside the pipes, called

"coiled-tubing", consisting in pushing a rigid tube of small diameter, generally 20 to 50mm, through the pipe. Said rigid tube is stored wound by simple bending on a drum, then untwisted when it is unwound. Said tube can measure several thousand meters in a single length. The end of the tube located at the barrel of the storage drum is connected via a rotating joint to a pumping device capable of injecting a high pressure liquid and at high temperature. Thus, by pushing the thin tube through the pipe, maintaining pumping and back pressure, this pipe is cleaned by injecting a hot product capable of dissolving the plugs. This intervention method is commonly used during interventions on vertical wells or on pipes obstructed by paraffin or hydrate formations, common and feared phenomena in all crude oil production facilities. The ~ "coiled-tubing" process is referred to below as "continuous tubing cleaning" or NTC.

The installation according to the invention comprises a connection device between said float and the upper end of said riser comprising:

a second flexible pipe, the ends of which are embedded at the level of said float and of the upper end of the riser respectively,

- The connection of said second flexible pipe to the upper end of said riser is done by means of a swan neck device, which swan neck device also ensures the connection between said riser and a said connecting pipe with the floating support, preferably a so-called flexible pipe,

- Said second flexible pipe is preferably extended through said float by a rigid tubular pipe passing right through the float, so that one can intervene inside said vertical riser from the top of the float through said rigid tubular pipe, then said connecting device made up of said second flexible pipe and through said swan-neck device, so as to access the interior of said riser and clean it by injection of liquid and / or by scraping the internal wall of said riser, then of said underwater pipe resting on the bottom of the sea.

The installation according to the present invention is more particularly advantageous when:

- two so-called underwater pipes resting on the seabed are assembled in a bundle within the same flexible protective envelope making it possible to confine an insulating material, preferably a material with phase change of the type of paraffin, a gelled insulating compound, or a combination of the two, surrounding said conduits, and

- Said vertical riser comprises in its upper part above said flexible joint a system of insulated pipes consisting of a set of two coaxial pipes comprising an internal pipe and an external pipe, a fluid or insulating material, preferably a change material live from paraffin type, a gelled insulating compound, or a combination of the two, being preferably placed between the two said pipes, or by maintaining a high vacuum between two pipes.

Another advantage of the installation according to the invention is that all the elements can be prefabricated on the ground before being installed. They can thus be mounted "blank" to verify that all the elements cooperate correctly, including the locking means; thus, installation assembly is greatly simplified and the operational time of installation vessels minimized. In the prior art, the submarine conduits were laid and then, after installation of the risers, elbow connection cuffs were manufactured on the basis of a metrology of high precision carried out thanks to ROVs. The cuff, prefabricated on land or on site can measure several tens of meters and must then be installed by the same ROV, which represents a considerable operational time, therefore a very high cost due to the sophistication of specialized installation vessels. The gain achieved by the device and the method according to the invention is calculated in several days of installation vessel as well as in the elimination of the automatic connectors essential at each end of the prefabricated cuff, which represents a reduction in cost. considerable. The objectives of the present invention are therefore also obtained by a method of setting up an installation which comprises the steps in which:

1. a so-called base is installed at the bottom of the sea, and

2. one descends to the bottom of the sea, a so-called underwater pipe resting on the bottom of the sea with at its end at least part of said junction elements comprising at their end a first part of connection element, and

3. the horizontal rectilinear terminal part of said pipe resting on the seabed is secured to said base, and 4. said vertical riser is lowered comprising at its end at least the other part of said junction elements, comprising at their end lower at least one said second part of the connecting element, and

5. connecting said first part and said second part to form said connecting element, and 6. blocking said joining elements on said base.

More particularly, in the method of the invention in which said base includes a said platform and at least one said mobile support, the steps are carried out in which:

1. said platform is placed at the bottom of the sea, and said mobile support on said platform, and said latches are actuated to control and prevent the displacement in height of said mobile support relative to said platform forms while leaving free the movement of controlled translation of said movable support in said longitudinal direction YY ', and

2. one descends and sets up at the bottom of the sea a so-called submarine pipe fitted at its end with at least one part of said junction elements comprising at their end at least one said first part of connection element, and

3. the terminal horizontal rectilinear part of said pipe resting on the bottom of the sea is secured to the bottom of said mobile support, and

4. one descends a said vertical riser equipped at its lower end with at least the other part of said junction elements comprising at their end a said second part complementary to connection elements, and

5. the said first and second parts of the connection elements are brought together and the connection is made, and

6. blocking of said junction elements is carried out on said mobile support.

In an alternative embodiment of the method, the mobile support is assembled on the surface within the platform, then the assembly is then lowered and put in place on the seabed.

To implement a preferred embodiment of the method of the invention, said junction elements are such that: a) said underwater pipe resting on the seabed is equipped at its end with a said rigid pipe element having an elbow-shaped curvature, said elbow-shaped pipe element having at its upper end a said first part of a connection element, and b) said vertical riser is equipped at its lower end with a said flexible joint and of a said second part of connection element on the underside of said flexible joint.

Other characteristics and advantages of the present invention will appear in the light of the detailed description of the embodiments which follows, with reference to FIGS. 1 to 12.

Figure 1 is a side view of the top of a hybrid tower connected to a floating support of the FPSO type, with a ship 2 carrying out an intervention operation vertical to said tower.

2 shows a sectional view of the lower part of the installation according to the invention, after connection of the vertical riser with said underwater pipe resting on the bottom of the sea.

FIG. 3 represents a top view at the level of the upper orifice of the mobile support 14 of FIG. 2 with a frustoconical wedge system 17.

Figure 4 is a sectional side view of the lower part of the installation, after connection. Figure 5 is a sectional view of the base before installation of said movable support and said pipes to be connected.

Figure 6 is a side view of the base comprising the platform and the movable support put in place before the establishment of the pipes to be connected.

Figure 7 is a sectional view of the installation in its lower part showing the establishment of the pipe element having a curvature in the form of an elbow descending inside said movable support.

Figure 8 is a sectional view of the lower part of the installation in the installation step subsequent to the step of Figure 7 in which, after installation of the elbow-shaped pipe element , it descends, inside said movable support, the lower end of said riser equipped with a flexible seal and a female part of a connection element.

FIG. 9 represents a sectional view of the lower part of the installation after connection of the pipes on the underside of the flexible joint.

FIG. 10 represents a side view in section of FIG. 9. FIG. 11 represents a top view of a base according to the invention comprising a movable support which can slide in translation on a platform 15 supporting guide barriers 16ι, said translation being controlled by a termination stop 16 ₃ .

FIG. 12 shows a side view in section of an alternative embodiment of the connection of pipes of the installation according to the invention.

In Figure 1, the FPSO 1 is anchored on an oil field by 1500m of water height, by an anchoring system not shown and has at its plating a support system 2ι flexible pipes 3 of effluents tankers in chain configuration going up towards a device in the form of a swan neck 4-ι, itself secured to the upper end of a vertical riser 5. The whole is kept in tension by said float 6 installed at the head of the riser vertical 5 by means of a flexible pipe 7. Said float 6 is crossed by a pipe 8 in continuity with said flexible 7 to lead to an orifice closed by a valve 9. An intervention vessel 2 situated vertically above said float can perform a maintenance operation by coil-tubing through the float 6, so as to push in the vertical part of the pipe, a rigid pipe, not shown, of small diameter, generally 50mm, intended to clean the interior of the pipeline as it progresses. Coil-tubing devices being known to those skilled in the art in the field of interventions on oil wells will not be developed in more detail here. In Figures 2 to 4, and 6 to 12, there is shown the lower part of an installation according to the invention in which the connection between the lower end of said vertical riser 5 and said underwater pipe 10 resting at the bottom of the sea is done through an anchoring system comprising a base 4 placed on the bottom. Said base 4 includes:

a platform 15 resting on the bottom of the sea, and

a mobile support 14 to which said junction elements 11-13 are fixed, and

- Said movable support 14 being able to move in a controlled manner on said platform in a said translation in a said longitudinal direction

YY "corresponding to the axial direction of the horizontal terminal part of said underwater pipe resting on the bottom of the sea 10.

The platform 15 comprises a structure constituting guide elements 16ι such as barrier or slide which prevent any other movement of the mobile support in a lateral direction XX 'or in height, that is to say in a vertical direction 121.

Said base 4 rigidly maintains and guides the junction elements 11-13 between the lower end of said vertical riser 5 and the end of the rectilinear terminal horizontal part of said pipe lying at the bottom of the sea 10, and said elements junction 11-13 comprise a pipe element having an elbow-shaped curvature 11 and a pipe connection element 12, preferably a single connection element, more preferably, a single automatic connector, maintaining and guiding the said elements junction elements 11-13 being such that said junction elements 11-13 can only move in a translational movement in a single longitudinal direction YY 'corresponding to the axial direction of said part horizontal rectilinear terminal of said underwater pipe lying at the bottom of the sea 10.

Figures 2 and 9 show sections in front view of an installation according to the invention after installation of all the junction elements and pipes to be connected.

Figures 4 and 10 show side views of an installation according to the invention, after installation of the junction elements and the pipes to be connected.

On the other hand, FIGS. 5 to 8, as well as 11 and 12 represent views of different constituent elements of the installation according to the invention during the different phases of the installation procedure.

Thus, in Figure 5, there is shown the platform 15 surmounted by the lateral guide barriers 16ι which guide in the sliding in longitudinal translation in the direction YY 'of the movable support element whose lower part is maintained between said guide barriers 16ι.

In FIGS. 10 and 11, a stop element I6 _{3 has been shown} which makes it possible to control the sliding in translation and prevents excessive sliding of the movable support 14 inside the guide barriers I6 ₁ over the platform 15 This sliding in translation in the direction..YY 'is made possible by means of sliding pads 14-ι, arranged below said movable support 14, on its sides and on top. It is also possible to use rollers or any other device aimed at reducing friction during longitudinal displacements in the direction YY '.

In Figure 6, there is shown the movable support 14 lowered from the surface using cables not shown, inserted between the elevated structures constituting the guide barriers I6 ₁ disposed above the guide platform 15. This movable support 14 can move along a longitudinal axis YY 'thanks to the sliding pads 14ι but can neither move laterally along the axis XX', nor upward along the axis 12. Indeed, the upper part of the barriers guide 16 ₁ cooperates with movable blocking elements consisting of a wedge system 16, which can be engaged so that the external shape of the lower part of the movable support at a shoulder 14 ₄ on which rests sliding pads 14-ι, abut against said engaged corners 16 ₂ preventing the elevation of the movable support 14. In Figures 2, 10 and 11, it is shown that the guide barriers I6 ₁ arranged pa r above the platform 15, are spaced so as to provide a sufficient clearance, for example 1 cm, on either side of the movable support when the latter is placed on the platform between said guide barriers 16ι to avoid possible jamming during movements along the axis YY 'of the movable support 14 over the platform 15. The platform 15 is held in position on the seabed 20 either by its own weight, or by adding dead bodies 15 ₂ , or via dark suction anchors 15 ₃ across the platform, or again by a combination of these methods. Spades 15ι are advantageously provided on the underside of the platform 15 to avoid any sliding or horizontal displacement of the platform whatever the direction.

In Figures 2, 6 7, 8 and 12, there is shown the mobile support which rests on its lower pads 14ι on the platform 15. More specifically, the lower pads 14-ι rest on a notch at the base of the barriers guide 16ι. This type of position occurs when the upper float 6 of FIG. 1 is not completely deballasted and keeps the riser 5 in tension, and the self-weight of the mobile support 14 is such that said mobile support nevertheless rests on its pads lower 14-ι.

On the other hand, in FIG. 9, when the upper float 6 has been completely deballasted, the mobile support 14 is then in suspension but cannot rise due to the contact of the upper pads 14ι with the locking elements 16 ₂ which cooperate at the upper part of the guide barriers 16 ₁ so as to retain said movable support 14 by the external shape of its lower part in particular at the level of a shoulder 14 ₄ which comes into contact via the upper pads 14ι with the blocking corners 16 ₂ . By adjusting the buoyancy of the upper float 6, it is possible to balance the load so as to reduce the positive or negative contact forces, that is to say directed upwards or downwards, between the mobile support 14 and the anchored structure comprising the platform 15 and the guiding barriers 16ι This has the effect of reducing the wear of the contact pads 14-] and especially of minimizing the forces F transmitted by the underwater pipe 10 to the anchored base of the riser tower, as well as the internal compression forces in said underwater pipe 10, a potential source of buckling phenomena which can lead to the ruin of the installation.

For example, the platform 15 can have a length of 10 to 12 m and a width of 6 m, capable of receiving dead bodies 15 ₂ from 25 to 50 tonnes. The mobile support 14 can have a mass of 40 tonnes corresponding to the tension minimum required at the riser base, that is to say at the flexible joint 13. Said movable support 14 can measure approximately 1.5 m wide and 4 m long. During installation, the mobile support 14 is positioned substantially in the middle of the platform, which allows a relative displacement Δ of plus or minus 3 m, along the axis XX ', displacement generated by the expansion or the thermal shrinkage, as well as underwater pipe 10, as well as by the internal pressure of the underwater pipe 10 resting on the bottom.

In FIGS. 4 and 6 to 12, a mobile support 14 has been shown having a central cavity 18, the upper part of which comprises a peripheral internal wall which is flared in the form of a funnel, said cavity 18 being open in its upper part by a orifice 18ι corresponding to said large base of the upper part in the form of a funnel of the cavity 18. At the bottom of the cavity 18, a cradle-shaped base 14 ₃ makes it possible to receive and support the rigid pipe element having a elbow-shaped curvature 11 which is arranged inside said movable support 14 as shown in FIGS. 2 and 9.

In an alternative embodiment, the mobile support has an internal cavity also open at its base, so that one can set up the underwater pipe by temporarily installing it on the platform 15, then lower the support mobile over the underwater pipe insofar as the central cavity of the mobile support authorizes the passage of the elbow element 11 and the automatic connector 12, and finally, the underwater pipe is secured to the mobile support, the base 14 ₃ and said locking means 19-19ι are located on the wall of the internal cavity of the movable support located above said pipe initially installed on the platform 15. In Figures 4, 10 and 11, the pipe underwater 10 resting at the bottom of the sea ends in a rigid pipe element having an elbow-shaped curvature 11, ending at its upper part turned upwards by a first part 12-ι of an element connection 12, namely here, a male part. The horizontal rectilinear terminal part of the underwater pipe resting on the seabed 10 located before said elbow-shaped pipe element 11, is supported by the cradle 14 ₃ on the bottom of said mobile support 14, and it is locked by a device 19 ensures the locking of a ferrule 19ι welded to the outside of the underwater pipe 10. When moving the mobile support 14 created by the expansion of the underwater pipe 10 resting on the ground , under the effect of the temperature and the internal pressure, the said mobile support 14 will slide within the anchored platform 15-16-ι-16 ₂ between the barriers of lateral guide 16ι. Thus, the forces transmitted to said anchored base are radically reduced, as well as the compression forces within the underwater pipe resting on the bottom, and the risks of buckling and degradation of said underwater pipe are thus eliminated. 10. In the embodiment of FIGS. 2 to 11, in particular as shown in FIG. 8, the vertical riser comprises at its lower end a flexible joint 13, itself- integral with the underside of the second part 12 ₂ of the automatic connector 12, intended to cooperate with the first part 12 ₁ to make the connection of the connection element 12 consisting of an automatic connector. The internal passage of the flexible seal 13, as well as of the automatic connector 12 has an internal diameter preferably identical to that of the riser 5. The flexible seal 13 is reinforced by an external reinforcement structure which makes it possible to ensure its embedding in the orifice upper 18ι of the cavity 18 of the mobile support 14 to ensure the rigidity of the assembly when a system of frustoconical corners 17 comes to lock it in the final position in the cavity 18 at the upper orifice 18ι of the mobile support 14, as illustrated in the figures. The waterproof flexible joint can be of the mechanical ball joint type or of the elastomer flexible joint type, or even correspond to a limited length of flexible pipe capable of providing the same angular displacement relative to the vertical of the riser 5, in particular in a corner cone. α up to 15 degrees.

The pipe element having an elbow-shaped curvature 11 has a curvature comprising an arc of a circle with a large radius of curvature, in particular a radius of curvature greater than 5 m, more particularly of the order of 5 to 10 m produced by a curved pipe element measuring from 7 to 15 m.

In the process for installing an installation according to the invention, the following successive steps can be carried out:

1. a bottom of the sea is put in place, said platform 15 surmounted by the guide structure constituted by the barriers 16ι cooperating with the blocking elements or corner system 16 ₂ in their upper part, and

2. the platform 15 is anchored using different anchoring means such as dead bodies 15 ₂ which are lowered using cables or suction anchors 15 ₃ , and 3. a said mobile support 14 that Your inserts between the guide barriers 16ι over the platform 15 and Your activates the locking latches 16 ₂ which prevent the upward movement in the direction 121 of the mobile support 14 while leaving free the sliding in translation in the longitudinal direction YY 'of the mobile support 14, said sliding in translation in the direction YY' being controlled by the elements abutment I6 ₃ -I6 ₄ resting on the platform 15, and

4. one installs at the bottom of the cavity 18 of said movable support, by lowering it through the upper orifice 18-ι, a rectilinear pipe element constituting the horizontal end part of the underwater pipe resting at the bottom of the sea 10, said horizontal end part being fitted at its end with a said rigid pipe element having a bend-shaped curvature 11, which bent element 11 has at its upper end a first male part 12ι of an automatic connector 12, and

5. said elbowed rigid pipe element 11 is deposited at the bottom of the cavity 18 so that the horizontal rectilinear terminal part of the underwater pipe resting on the seabed rests on the cradle base 14 ₃ , and said part is secured horizontal terminal of the underwater pipe resting at the bottom of the sea 10 with a locking system 19, 19ι of the collar type, and

6. a vertical riser 5 is lowered equipped at its lower end with a flexible flexible joint 13 and with the second female complementary part 12 _{2 of} said automatic connector 12 on the underside of said reinforced flexible joint 13, then

7. after approaching said first and second parts 12 ₁ and 12 ₂ complementary to said connection element 12, said connection is made, and

8. once the connection has been made, said reinforced flexible joint or a portion of terminal pipe at the lower end of said riser is blocked below said reinforced flexible joint 13, inside the upper orifice I81 comprising a peripheral wall of flared shape, using a wedge system which locks between said funnel-shaped peripheral wall of said upper opening I8 ₁ and said reinforced flexible joint 13 or said portion of end pipe below said joint flexible 13.

Corners 17 shown in Figures 6 to 8 in the released position relative to said wall of the upper orifice I8 ₁ , are actuated by a ROV by means of hydraulic cylinders not shown to then come to engage inside the 'upper orifice I8 ₁ against its flared peripheral wall as shown in Figures 4, 9, 10 and 12. The frustoconical corners 17 abut in abutment on the reinforcing structure of said reinforced flexible joint 13 and keep it in fixed position relative to mobile support 14.

Complementary locks 14 ₂ are then actuated by a device not shown, thus making it possible to transfer to the movable support 14 all of the vertical load created by the riser 5 kept in tension by the upper float 6 of FIG. 1.

Figure 3 is a sectional view from above relating to the upper orifice 18ι showing three frustoconical corners 17, one of which is shown in the retracted upward position, and the other two in the jamming position engaged downwardly. inside the hole 18-ι. The installation according to the invention has been described in FIGS. 2 to 11 with a reinforced flexible joint 13 situated above a part 12 ₂ of automatic connector 12.

In another embodiment shown in FIG. 12, said rigid pipe element having an elbow-shaped curvature 11 is pre-installed on the underside of said reinforced flexible joint 13, said elbow-shaped pipe element 11 having its free lower end, a first part 12 ₂ of connection element of the automatic connector type 12.

In this case, said first part 12 ₂ of connection element has its axis disposed horizontally slightly above the bottom of the cavity 18 of the movable support 14, once the flexible seal 13 is locked in place in the upper opening 18ι of the movable support 14 using the corners 17. The connection is then made with the underwater pipe resting at the bottom of the sea 10, the horizontal rectilinear end part of which rests on a carriage 21 sliding on the platform 15 at the using sliding shoes 22, said rectilinear horizontal end portion of the underwater pipe resting at the bottom of the sea 10 being held by cradles 14 ₃ on the bottom of said movable carriage 21 and integral with said carriage 21 by a collar of lock 19-19ι. The connection is made by displacement, in said longitudinal direction YY ', of said movable carriage 21 between said sliding barriers 16ι on the platform 15. Finally, the carriage 21 is secured to the movable support 14 by means not shown.

Because of its complexity, it is preferable to install the female part 12 ₂ of an automatic connector 12 on the equipment handled last, but it is possible to reverse the said first and second male and female parts 12-ι-12 ₂ of Télément de connection. In FIG. 1, the installation comprises a connecting device 4-ι, 7 between said float 6 and the upper end of said riser 5, comprising: a second flexible pipe 7, the ends of which are embedded at the level respectively of the underside of said float 6 and of the upper end of the riser 5,

- The connection of said second flexible pipe 7 to the upper end of said riser 5 is made by means of a device in the form of a swan neck

4-ι, which device in the form of a swan neck 4-ι also provides the connection between said riser 5 and a so-called flexible pipe 3 with the floating support,

- Said second flexible pipe 7 being extended through said float 6 by a rigid tubular pipe 8 passing through the float right through, so that it can intervene inside said vertical riser 5 from the upper part of float 6 through said rigid tubular pipe 8, then said connecting device consisting of said second flexible pipe 7 and through said swan-neck device 4-ι, so as to access the interior of said riser 5 and clean it by injection of liquid and / or by scraping of the internal wall of said riser 5, then of said submarine pipe 10 resting at the bottom of the sea.

Said second flexible pipe 7 has at its ends elements of progressive variation of inertia of section 7ι, 7 ₂ at the level respectively of the underside of the float 6 and of the upper end of the swan neck.

The swan-neck device comprises an upper straight part which provides the junction between said vertical riser and said second flexible pipe connected to said float. On this so-called right part of the swan neck-shaped device, a curved elbow-shaped branch allows the junction between the end of said vertical riser and the end of said flexible pipe itself connected to said floating support. The ends of said curve being substantially tangent to the curve of the chain formed by said flexible pipe which provides the connection to the floating support, and substantially tangent with said straight part of the device in the form of a swan neck.

Claims

1. Bottom-surface connection installation for underwater pipe (10) resting on the seabed, in particular at great depth, comprising: a) at least one vertical riser (5) connected at its lower end to at least ¹ underwater pipe (10) resting on the seabed, and at its upper end with at least one float (6), and b) at least one connecting pipe (3), preferably a flexible pipe, ensuring the connection between a floating support (1) and the upper end (4) of said vertical riser (5), and c) the connection between the lower end of said vertical riser (5) and a said underwater pipe (10) resting at the bottom of the sea is done via an anchoring system comprising a base (4) placed on the bottom, characterized in that said base (4) ensures the maintenance and guidance of the junction elements (11 -13) between the lower end of said vertical riser (5) and the end of the terminal rectilinear horizontal part of said pipe resting on the seabed (10), and said junction elements (11-13) comprise an element of rigid pipe having an elbow-shaped curvature (11) and a pipe connection element (12), preferably a single connection element, more preferably, a single automatic connector, the holding and guiding of said junction elements (11 -13) being such that said junction elements (11-13) can only move in a translational movement in a single longitudinal direction YY' substantially corresponding to the axial direction of said horizontal rectilinear end part of said pipe under -marine resting at the bottom of the sea (10).

2. Installation according to claim 1, characterized in that said base (4) comprises:

- a platform (15) resting on the seabed, and

- a mobile support (14) to which said junction elements (11-13) are fixed, and

- said mobile support (14) being able to move, preferably in a controlled manner, on said platform according to a said translation in a said longitudinal direction YY' corresponding to the axial direction of the part horizontal terminal of said underwater pipe resting on the seabed (10).

3. Installation according to claim 1 or 2, characterized in that said vertical riser (5) comprises in its lower end part a flexible joint (13), preferably reinforced, which allows angular movements (α) of the part of said riser vertical (5) located above said flexible joint (13), and said junction elements (11-13) comprise said flexible joint (13) or a vertical riser portion located below said flexible joint (13).

4. Installation according to one of claims 1 to 3, characterized in that:

- a first part (12-ι), preferably male of said connection element (12) is integral with said flexible joint (13), and arranged just below it, and

- said underwater pipe resting on the seabed (10) ends in a said rigid pipe element having an elbow-shaped curvature (1) having at its end a second part (12 ₂ ), preferably female, of a said connection element (12), capable of cooperating with said first part to form said connection element (12).

5. Installation according to one of claims 1 to 3, characterized in that:

- said rigid pipe element having an elbow-shaped curvature (11) is fixed directly to the underside of said flexible joint (13) and comprises at its other end a first part (12ι), preferably female, of said element connection (12), and

- said first part (12ι) of connection element, preferably female, cooperates with a second part (12 ₂ ) of connection element, preferably male, at the end of a horizontal terminal part of a pipe under -marine resting on the bottom of the sea (10) to form a said connection element (12).

6. Installation according to one of claims 2 to 5, characterized in that said movable support (14) comprises a central cavity (18) open on top by an upper orifice (18-ι) capable of receiving said driving element rigid having an elbow-shaped curvature (11) when it is lowered from the surface within said movable support (14).

7. Installation according to claim 6, characterized in that said upper orifice (18-ι) cooperates with blocking elements, preferably a wedge system (17), making it possible to block said reinforced flexible joint (13) which is thus held rigidly and fixedly attached to said mobile support (14), and the horizontal end part of said pipe resting on the seabed (10) is held fixedly on the bottom of said mobile support, preferably using a system of necklace (19-19-ι).

8. Installation according to claim 7, characterized in that said upper orifice (18ι) has a peripheral internal wall, in the shape of a funnel with a large upper base and said corners (17) allowing the blocking of said reinforced flexible joint (13) are constituted by frustoconical corners (17).

-- 9: ^" Installation according to one of claims 2 to 8, characterized in that said platform comprises guiding and holding elements (I6 ₁ -I6 ₃ ) of said mobile support (14) so that said mobile support (14 ) can only move on said platform (15) by sliding in translation in a said longitudinal direction YY', preferably using sliding pads (1.

10. Installation according to claim 9, characterized in that said movable support (14) is held laterally between two lateral guide barriers (16 ₁ ) of said platform, and said lateral guide barriers (I6 ₁ ) cooperate with movable locking elements (16 ₂ ) which in the retracted release position allow the descent of said movable support (14) from the surface to a position between the two said side barriers (I6 ₁ ) over said platform (15) , and in the advanced blocking position cooperate with the external shape (14 ₄ ) of said mobile support (14) so that the vertical movement 12 in height thereof is controlled.

11. Installation according to one of claims 1 to 10, characterized in that said base (4) comprises a platform (15) resting at the bottom of the sea, which cooperates with stabilizing elements comprising dead bodies (15 ₂ ) placed on top of said platform (15) or suction anchors (15 ₃ ) passing through said platform to be driven into the ground and/or protruding spade-type elements (15ι) arranged on the underside of said platform and sunk into the seabed to prevent any sliding of said platform on the seabed.

12. Method for setting up an installation according to one of the preceding claims, characterized in that it comprises the steps in which:

1. a so-called base (4) is set up at the bottom of the sea (20), and

2. we descend to the bottom of the sea, a said underwater pipe resting on the bottom of the sea (10) with at its end at least a part of said junction elements (11-13) comprising at their end a first part (12^ of connecting element, and

3. the rectilinear horizontal terminal part of said pipe resting on the seabed (10) is secured to said base, and

4. we lower said vertical riser comprising at its end at least the other part of said junction elements (11-13),! comprising at their lower end at least one said second connection element part (12 ₂ ), and

5. the connection of said first part (12ι) and said second part (12 ₂ ) is carried out to form said connection element (12), and

6. we block said junction elements (13) on said base (4).

13. Method according to claim 12 in which said base comprises a said platform (15) and at least one said movable support (14) and the steps are carried out in which:

1. said platform (15) is placed at the bottom of the sea (20), and said mobile support (14) on said platform (15), and said locks (16 ₂ ) are actuated to control and prevent the movement in height of said mobile support relative to said platform while leaving free the controlled translation movement of said mobile support in said longitudinal direction YY', and 2. we descend and place it at the bottom of the sea (20 ) a said underwater pipe (10) equipped at its end with at least one part said junction elements (11 -13) comprising at their end at least one said first connection element part (12-ι), and

3. the rectilinear horizontal terminal part of said pipe resting on the seabed (10) is secured to the bottom (14 ₃ ) of said mobile support (14), and

4. we lower a said vertical riser (5) equipped at its lower end with at least the other part of said junction elements (11-13) comprising at their end a said second part (12 ₂ ) complementary to connection elements ( 12), and 5. said first and second parts (12^ and (12 ₂ )) of connecting elements (12) are brought together and the connection is made, and

6. said junction elements (11-13) are blocked on said mobile support.

14. Method according to claim 13, characterized in that: a) said underwater pipe resting on the seabed (10) is equipped at its end with a said rigid pipe element having an elbow-shaped curvature ( 11), said elbow-shaped pipe element having at its upper end a said first part (12-ι) of a connecting element (12), and b) said vertical riser (5) is equipped at its end lower part of said flexible joint (13) and of said second part (12 ₂ ) of connection element (12) on the underside of said flexible joint (13).