EP1606490B1 - Device for heating and thermally insulating at least one undersea pipeline - Google Patents

Abstract

The insulating coating (2) surrounds a cylindrical internal chamber (4) which is coaxial with the external envelope and fills the annular space between the external envelope and the internal chamber. A heating fluid (5) is maintained at temperature (6) and circulated inside the internal chamber so the heating fluid surrounds the main pipe (1a) which is inside the internal chamber : The device includes a coating of a thermally insulating material (2) surrounding the main pipes. This coating is covered with a sealed external protection envelope (3), preferably cylindrical. The internal chamber has at least one internal gas injection line (7) running through it to allow the injection of gas into the main pipe. The gas injection line is connected to the main pipe at one end inside the internal chamber, and preferably the gas injection line extends out of the internal chamber in the form of an external injection line connecting the internal injection line to a floating support. The means of circulating the heating fluid comprise at least one internal supply line extending from the inside of the internal chamber through a first orifice (8) at one end of the internal chamber, and an outlet orifice at the second end of the internal chamber. The gas injection line is coiled in a spiral around the internal heating fluid supply line inside the internal chamber. Each end of the heating fluid supply line is extended by a flexible external line (62, 63) connecting the first and second orifices to a floating support. A pump circulates the heating fluid which is heated by a heater. The device has an end closure (11) at one or both ends, supporting the main pipe(s) and the means of circulation and with the first and second orifices passing through it. The second end closure has a large orifice with a diameter greater than that of the main pipe so the main pipe passes through it and the heating fluid is in contact with the seawater at the lower end of the internal chamber. Alternatively, the orifice is sealed to the main pipe. The main pipe is coated with a second insulating layer at least around this second end, with the heating fluid circulating outside this second layer. This layer is syntactic mousse or other solid insulating material and fills the space between the main pipe and a second coaxial pipe in which the main pipe is inserted. Alternatively, the second insulating layer is a material subject to migration and contained in a flexible or semi-rigid envelope. The material changes phase with a melting point of between 20 and 80[deg]C, greater than that of the environment and less than that at which the fluid in the main pipe suffers a damaging increase in viscosity. The insulating material is an alcane, preferably a paraffin with a hydrocarbon chain of at least 14 atoms, preferably tetracosane C24H50 with a melting point of around 50[deg]C. This can be mixed with a structural or gelling material such as polyurethane, reticulated polypropylene, or polyethylene or silicone. Two intermediate barriers and an number of centralizing and shaping plates are placed in the internal chamber to prevent excessive migration of the insulation.

Description

The present invention relates to devices and a method for heating and thermal insulation of at least one underwater pipe at great depth. It relates more particularly to the bottom-surface connection pipes connecting the seabed to floating surface supports.

The technical field of the invention is the field of the manufacture and assembly of insulation and heating systems outside and around the pipes in which circulate hot effluents whose heat losses are to be limited.

This invention applies more particularly to deep-sea oil field developments, ie offshore oil installations, in which surface equipment is generally located on floating structures, the wellheads being The ducts concerned by the present invention being more particularly the risers called bottom-surface connection pipes going up to the surface, but also the pipes connecting the well heads to said bottom surface connection pipes.

The present invention also relates to a bottom-surface connection installation of at least one deep-sea pipe installed at great depth of the hybrid tower type.

The main application of the invention is the thermal insulation and heating of submerged or underwater pipes or pipes, and more particularly at great depth, beyond 300 meters, and carrying hot oil products including a Too much cooling would be problematic both in normal production and in case of production stoppage. Deep sea developments are carried out by water depths currently reaching 1500 m. Future developments are envisaged by water depths up to 3000-4000 m and beyond.

• une forte augmentation de la viscosité qui diminue alors le débit de la conduite,
• une précipitation de paraffine dissoute qui augmente alors la viscosité du produit et dont le dépôt peut diminuer le diamètre intérieur utile de la conduite,
• la floculation des asphaltènes induisant les mêmes problèmes,
• la formation soudaine, compacte et massive d'hydrates de gaz qui précipitent à forte pression et faible température, obstruant ainsi brusquement la conduite.

In such applications, many problems arise if the temperature of the petroleum products decreases by a significant amount compared to their production temperature which is often above 60 to 80 ° C while the temperature of surrounding water especially at great depth can be well below 10 ° C and reach 4 ° C. If the petroleum products are cooled, for example, below 30 ° to 60 ° C. for an initial temperature of 70 to 80 ° C., it is generally observed:

• a sharp increase in viscosity which then decreases the flow of the pipe,
• a dissolved paraffin precipitation which then increases the viscosity of the product and the deposition of which may reduce the effective inner diameter of the pipe,
• flocculation of asphaltenes inducing the same problems,
• the sudden, compact and massive formation of gas hydrates that precipitate at high pressure and low temperature, thus abruptly obstructing the pipe.

Paraffins and asphaltenes remain attached to the wall and then require cleaning by scraping the inside of the pipe; on the other hand, hydrates are even more difficult, and sometimes even impossible to absorb.

In addition, in the risers, the gas mixed with crude oil with water tends to relax as it rises, because the hydrostatic pressure drops. This relaxation being quasi-adiabatic, the calories are taken from the multiphase fluid itself, and this results in a significant lowering of the internal temperature, the latter being able to reach 8 to 15 ° C on a slope of 1500m.

The thermal insulation and the heating of such pipes therefore has the function of delaying the cooling of the petroleum effluents conveyed not only in the established production regime, so that their temperature is for example at least 40 ° C when arriving at the surface, for a production temperature at the inlet of the pipe from 70 ° C to 80 ° C, but also in case of reduction or even stop of the production, in order to prevent the temperature of the effluents from falling for example below 30 ° C, to limit the above problems, or at least to allow to make them reversible.

In the case of the installation of single pipes or bundles of pipes (commonly called "bundles"), it is generally preferred to prefabricate said shore pipes in unit lengths of 250 to 500 m, which are then drawn from the open sea. using a tug. In the case of a tower-type bottom-surface connection, the length of pipe generally represents from 50 to 95% of the water height, ie it can reach 2400 m for a depth of water of 2500 m. When it is manufactured on land, the first unit length is pulled from the sea and then tied to the next, the tug holding the assembly in tension during the splicing phase, which can last several hours or even days. Where the entire pipe or pipe bundle has been launching, the assembly is towed towards the site, generally in subsurface, substantially horizontally, where it is then "cabane", that is to say rocked in vertical position, to reach the vertical position, then he set up in final position.

• d'une part d'éviter les endommagements qui peuvent se produire lors de la fabrication ou lors du remorquage comme lors de la pose, surtout dans les zones de faible profondeur d'eau, ledit remorquage pouvant dans certains cas se faire sur des distances de plusieurs centaines de kilomètres. A cet effet, on utilise des matériaux assez résistants tels qu'en acier, en composé thermoplastique ou thermodurcissable ou encore en matériau composite ;
• d'autre part de créer un confinement étanche autour du système d'isolation. Ce confinement est nécessaire dans le cas de revêtements extérieurs isolants constitués de matériaux sujets à migration, voire comprenant des composés fluides.

There is known a device for isolating at least one submarine pipe which can be in effect alone or assembled with other pipes, then constituting so-called "bundles" or "bundles" intended to be laid on the bottom at great depth, having an insulating outer coating surrounding it and an outer protective envelope. The insulation of the conduit (s) or bundle of pipe commonly known as "bundle" is then protected by an outer protective envelope which has a dual function:

• on the one hand to avoid damage that may occur during manufacture or during towing as during installation, especially in areas of shallow water, said towing may in some cases be done over distances of several hundred kilometers. For this purpose, fairly strong materials such as steel, thermoplastic or thermosetting compound or composite material are used;
• on the other hand to create a sealed containment around the insulation system. This confinement is necessary in the case of insulating outer coatings consisting of materials that are subject to migration, or even including fluid compounds.

Indeed, with 2000 m depth, the hydrostatic pressure is of the order of 200 bars, or 20 Mega Pascals, which implies that all the pipes and their coating of insulating material must be able to withstand not only these pressures without degradation during pressurization and depressurization of the pipe in which circulates the hot fluid, but also to temperature cycles which generate volume variations of the various components, and therefore positive or negative pressures that can lead to partial destruction or total of the envelope either by exceeding the allowable stresses, or by implosion of this external envelope (negative internal pressure variations).

Since crude oil travels a great distance over several kilometers, it is sought to provide them with an extreme level of insulation in order, on the one hand, to 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 about 30-40 ° C. These last phenomena are all the more critical, particularly in West Africa, that the temperature of the sea floor is of the order of 4 ° C and that the crude oils are of the paraffinic type.

Many thermal insulation systems are known which make it possible to reach the required level of performance and to withstand the pressure of the sea floor which is of the order of 150 bar to 1500 m of depth. Examples include "pipe-in-pipe" concepts, including a pipe carrying the hot fluid installed in an external protective pipe, the space between the two pipes being either simply filled with a heat insulation, confined or not under vacuum, or simply drawn to vacuum. Many other insulating materials have been developed to provide high performance insulation, some of them being pressure resistant. These insulating materials simply surround the hot pipe and are generally confined within a flexible or rigid outer shell, in equipression and whose main function is to maintain a substantially constant geometry in time.

All these devices carrying a hot fluid in an insulated pipe have, to varying degrees, differential expansion phenomena. Indeed the inner pipe, usually steel, is at a temperature that is sought to maintain the highest possible, for example 60 or 80 ° C, while the outer shell, often also steel, is at seawater temperature, ie around 4 ° C. The forces generated on the connecting elements between the inner pipe and the outer casing are considerable and can reach several tens or even hundreds of tons and the resulting overall elongation is of the order of 1 to 2 m in the case of insulated pipework. 1000 to 1200 m in length.

In patents WO 00/49263, WO 02/066786 and WO 02/103153 in the name of the applicant, there have been described various installations of the hybrid tower type, comprising isolated conduits.

A 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 1000 meters for example, and of type comprising a vertical tower and whose transported fluid must be kept 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 the various components of said tower so as to withstand the extreme stresses and phenomena cumulative fatigue over the life of the structure, which currently exceeds 20 years.

WO 00/40886 discloses a solid-liquid phase change thermal insulation material and latent heat of fusion, capable of restoring calories to the inner pipe, and confined around said inner pipe within a sealed envelope and deformable, which makes it able to track the expansion and contraction of various components under the influence of all environmental parameters, including internal and external temperatures.

More specifically, WO 00/40886 uses a solid-liquid phase change isolation material and latent heat of fusion, and whose phase change is effected at a temperature T ₀ greater than the temperature T _1. from which the oil circulating inside the pipe becomes too viscous, in general the temperature T ₁ is between 20 ° and 60 ° C and lower than the temperature T ₂ of the crude oil at the inlet of the conduct.

This phase-change material, hereinafter referred to as "PCM" (Phase Change Material), makes it possible, in case of production stoppage, to keep the fluid normally circulating inside the pipe at a high temperature, way to avoid the formation of paraffins or hydrates in the oil. Other phase-change materials are conceivable, such as hydrated or non-hydrated salts, storing and returning considerable energy during phase changes.

Thus, during production shutdowns, crude oil no longer circulates and remains in position within the pipe and the loss of heat to the outside environment, generally at 4 ° C by very deep bottom, is carried out to the detriment of PCM, the crude oil still remaining at a temperature greater than or substantially equal to that of said PCM.

During the entire phase of solidification or crystallization of the PCM, the temperature of the PCM remains substantially constant and equal to T ₀ , for example 36 ° C, and therefore, the internal pipe containing crude oil remains at a temperature greater than or substantially equal to that (T _o ) of the PCM, ie 36 ° C, thus preventing the formation of paraffins or hydrates in the crude oil.

The phase change materials described previously generally have a significant volume change when they change state, up to 20% in the case of paraffins. The outer protective casing must be able to accommodate without any damage from these variations in volume.

This is why, according to WO 00/40886, this phase-change insulating material is confined within a sealed and deformable envelope, which makes it capable of following the expansion and contraction of the various components under the influence. all environment parameters, including internal and external temperatures. The pipe is thus either confined within a thermoplastic flexible envelope, in particular polyethylene or polypropylene, for example circular, the increase or reduction of the internal volume, due to temperature variations, comparable to breathing is absorbed by the flexibility the envelope consisting for example of a thermoplastic material having a large elastic limit. To resist mechanical stresses, a semi-rigid envelope made of a resistant material such as steel or a composite material, such as a compound made from a binder such as an epoxy resin and inorganic or organic fibers such as glass or carbon fibers, but then the beam is given an ovoid or flattened shape, with or without counter-curvature, which gives it, at constant perimeter, a section smaller than the corresponding circle. Thus, the "breathing" of the beam, will lead, in the case of an increase and a reduction in volume, respectively to a "surrender to the round" of the envelope, or to an accentuation of the flattening of said envelope . In this case, the bundle-envelope assembly is designated by the term "flat bundle" as opposed to a circular envelope.

The problem of the present invention is, more particularly, to provide an improved thermal insulation system of an underwater pipe or a bundle of pipes incorporating an insulating material, in particular a PCM material, and whose behavior in phase restarting such that said restart can be performed in a reduced time compared to the prior art.

Indeed, in case of stopping for several days or weeks, during the active period of the PCM, it is generally taken care to purge the line by looping a loop of a substitute product, for example diesel so as to keep the assembly safe before allowing the pipe to cool down to 4 ° C. And, during the restart, the same diesel is generally used to reheat the pipe by circulating it in a loop from the floating support where it is heated by passing it through boilers or heat exchangers, recovering calories from gas turbines. Thus, during reheating, the calories will migrate from the inside of the pipe to the external ambient environment, generally at 4 ° C and, during the whole heating phase, most of the calories conveyed by the diesel fuel circulating will be absorbed by the PCM for its reliquefaction, which can take several days or weeks if the driving is very long, or if the production of calories at the floating support is insufficient. It is only after this heating phase with circulation of diesel, that we can reconnect the wellheads and resume production. Indeed, if the production is restarted prematurely, the PCM insulating material will be only partially liquid and the internal temperature will be less than or equal to T ₀ (phase change temperature), and therefore low, over the entire sub-pipe. marine, and we then observe the following phenomena.

During the progression of oil from the well at a high temperature, eg 75 ° C, to the FPSO, it provides calories to the PCM for liquefaction, and as a result, the temperature of the oil drops rapidly as the PCM plays the role, not of insulation system, but the reverse role of caloric absorber, leading to accelerated cooling of crude oil. Thus, after a journey of a few kilometers, or even a few hundred meters only, the oil temperature drops to the critical value of T ₁ at which dreaded phenomena of formation of hydrate or paraffin plugs within the oil circulating in driving can occur and then lead to a blockage of the crude oil flow. In the area near the wellheads, the PCM gradually reliquifies and the complete liquefaction front progresses slowly towards the FPSO. In a more distant zone, the temperature remains stable around T ₀ and liquefaction can only continue if the crude oil is always at a temperature above T ₀ . Thus, in the case of very long lines, for example 5 or 6 km, in an area very far from the hot source, ie close to the FPSO, there is not enough calories and the PCM then loses calories to the environment at 4 ° C. To provide these calories it gradually goes to the solid state.

For very long pipes, it appears that, during a restart, the PCM in the zone near the wellheads can be in reliquefaction phase, while at the other end, close to the FPSO, the PCM is in resolidification phase, because the loss of calories to the environment is higher than the calorie intake by the crude oil circulating in the pipe. In fact the PCM is waiting for a hot crude oil front that will turn it back into the liquid phase.

An object of the present invention is therefore to provide a pipe insulation system for heating and maintaining the temperature of the effluent flowing in an underwater pipe beyond a fixed value, so that after a stop prolonged, the duration of the restart phase is reduced and such that, for example, it may be possible, if necessary, just to partially heat the pipe without having to wait until all the PCM material, if any, is completely liquefied.

• un revêtement d'un matériau isolant thermique entourant la ou lesdites conduites principales,
• ledit revêtement isolant étant recouvert d'une enveloppe externe de protection étanche, de préférence de forme cylindrique,

caractérisé en ce qu'il comprend :

• a) une chambre interne de préférence de forme cylindrique et coaxiale à ladite enveloppe externe, telle que :
  • le dit revêtement isolant entoure ladite chambre interne et, de préférence, remplit l'espace annulaire entre ladite enveloppe externe et ladite chambre interne, et
  • ladite conduite principale est contenue à l'intérieur de ladite chambre interne, de préférence de forme cylindrique, et
• b) des moyens aptes à maintenir un fluide caloporteur en température et le faire circuler à l'intérieur de ladite chambre interne, ledit fluide caloporteur entourant la conduite principale contenue à l'intérieur de ladite chambre interne.

To do this, the present invention provides a device for heating and thermal insulation of at least one submarine main pipe for the circulation of a hot effluent, comprising:

• a coating of a thermal insulating material surrounding the at least one main pipe,
• said insulative coating being covered by an outer protective casing, preferably cylindrical,

characterized in that it comprises:

• a) an internal chamber preferably cylindrical in shape and coaxial with said outer envelope, such that:
  • said insulative coating surrounds said inner chamber and, preferably, fills the annular space between said outer shell and said inner chamber, and
  • said main pipe is contained within said internal chamber, preferably of cylindrical shape, and
• b) means capable of maintaining a heat-transfer fluid in temperature and circulating it inside said internal chamber, said coolant surrounding the main pipe contained inside said internal chamber.

The preamble before the characteristics a) and b) is known from document FR-A-2 821 917.

In an advantageous embodiment, said internal chamber is traversed by at least one internal gas injection pipe capable of allowing the injection of gas into said main pipe, said inner gas injection pipe being connected to said main pipe. at one end in the longitudinal direction of said main pipe, within said inner chamber, where appropriate at a lower end, and preferably said gas injection pipe extending outside said internal chamber in the form of an external gas injection pipe connecting said internal gas injection pipe to a floating support.

The gas injection at the bottom of a riser-type bottom-surface connection creates bubbles in the upwardly rising effluent, which reduces its density and thus promotes the rise of said effluent. This technology called "gas lift", ie elevation by gas injection, is well known to those skilled in the art and will not be described in more detail here.

In a particular embodiment, said internal chamber comprises means for circulating a coolant comprising at least one inner conduit for supplying a heat transfer fluid extending inside said internal chamber from a first orifice located at a first end of the inner chamber, preferably to near the second end of said inner chamber in the longitudinal direction, and a second outlet of said heat transfer fluid, preferably at said first end of the inner chamber, said inner conduit for supplying a coolant being located next to said main pipe, between the latter and said external insulating material.

Since the supply line of the heat transfer fluid travels the internal chamber over almost all of its length, it can also contribute to the heating of the interior of the inner chamber. Advantageously, there may be disposed on said supply line of the heat transfer fluid, orifices located at intermediate levels, so that a portion of the hot heat transfer fluid is transferred directly to the inner chamber at said intermediate level.

In this case, advantageously, said internal gas injection pipe is a spirally wound pipe around said inner pipe for supplying said heat transfer fluid inside said inner chamber, preferably a rigid pipe formed in a spiral.

This embodiment is particularly advantageous because it makes it possible to constitute a possible reserve of elongation of said internal gas injection pipe when said main pipe undergoes length variations as a result of the temperature variations of the hot effluent circulating at the same time. inside.

In addition, this configuration of the internal gas injection pipe wound spirally around the inner conduit for supplying the heat transfer fluid also makes it possible to heat the gas before injecting it into the main pipe and thus to improve the performance of "gas-lift".

In a first variant embodiment, said inner conduit for supplying the coolant is extended by a flexible external supply line for said heat transfer fluid from said first orifice to a floating support, and said second heat transfer fluid outlet orifice. is connected to a second flexible outer conduit for returning said heat transfer fluid to said floating support.

In this first embodiment, said heat transfer fluid can be heated by passing it into boilers or heat exchangers on board said floating support, in particular by recovering calories from, for example, gas turbines.

In a second variant embodiment, said internal conduit for supplying heat transfer fluid is connected to means for circulating and reheating the heat transfer fluid comprising a pump cooperating with said first heat transfer fluid supply orifice and with said second outlet orifice. heat transfer fluid at a said first end of the inner chamber, said pump for circulating the heat transfer fluid successively inside said inner pipe for supplying the coolant, and then inside the internal chamber and to make it come out of said internal chamber by said second orifice, then to recirculate it in a loop in said internal chamber through said first orifice, an external pipe for circulating the coolant between said floating support and the body of the pump or said first orifice, for adjusting the amount of coolant circulating in the cha in the various pipes

Preferably, in this second alternative embodiment the device according to the invention comprises a means for heating the heat transfer fluid inside said inner conduit for supplying the coolant, preferably in the form of an electrical resistance.

This heating means makes it possible to heat the heat transfer fluid in a very efficient manner, since the electrical resistance constitutes a very simple element that is easy to feed from the floating support by a small cable, as long as a high voltage is used. . In addition, the amount of energy transferred to the coolant can be simply adjusted by varying the voltage or intensity, or both.

In a preferred embodiment, the device according to the invention comprises at least one end wall transverse to at least one said first end, said transverse end partition supporting said main pipe and said circulation means and being traversed by said main pipe and, if appropriate, first and second ports allowing the circulation of said heat transfer fluid inside and outside said inner chamber through said orifices.

In a more particular embodiment, the device according to the invention comprises first and second end transverse partitions, respectively at each of the two ends of the internal chamber, said first end wall including, where appropriate, said first end walls. and second orifices, and the two said transverse end partitions supporting said outer envelope and said internal chamber and ensuring their tight connection, while ensuring, at least at said first end, the confinement of the heat transfer fluid inside the the internal chamber.

Preferably, the device according to the invention comprises a second end wall comprising a large orifice of diameter greater than that of the main pipe, through which orifice passes said main pipe, so that the coolant is in contact with the sea water at the lower end of the inner chamber. This embodiment is more particularly suitable when the coolant is a non-polluting fluid such as fresh water as explained in the detailed description below. This embodiment makes it possible to avoid difficulties that may result from differential expansions of the main pipe and the inner chamber.

In another embodiment, said second end wall comprises an orifice integrally surrounding a tubular sleeve within which said main duct can slide with reduced clearance, preferably sealingly. This embodiment is more particularly suitable if the coolant is a polluting fluid.

In all cases, it is advantageous that said main pipe is coated with a second insulating coating at least at said second end of the inner chamber, said coolant flowing in said inner chamber outside said second coating.

More particularly, said second coating is constituted by a thermal insulating material, preferably a solid insulating material, more preferably foam syntactically, said solid material directly surrounding said main duct, more preferably said second insulating material completely filling the space between said main duct and a second coaxial duct, acting as a sleeve, and inside which said duct is inserted main.

In a particularly advantageous embodiment of the present invention, said insulating coating around the inner chamber is an insulating material subject to migration and at least said outer shell and / or said inner chamber is or consist of a flexible solid material or semi-rigid adapted to follow the deformation of said insulating material and able to stay in contact with it when deformed.

As mentioned above, said insulating coating comprises a phase change insulating material having a liquid / solid melting temperature (T0) preferably between 20 and 80 ° C, higher than that (T2) of the marine environment of said conduct operation and less than that (T1) from which the effluents circulating inside the pipe have an increase in viscosity damaging to their circulation in said pipe.

Here, the term "insulating material" is intended to mean a material preferably having a thermal conductivity of less than 0.5 W × m ^-1 × K ^-1 , more preferably between 0.05 and 0.2 W × m ^-1 × K ^-1 (Watt / meter / Kelvin). ).

Said PCM insulating material is chosen in particular from materials consisting of at least 90% of chemical compounds chosen from alkanes, in particular comprising a hydrocarbon chain of at least 10 carbon atoms, or salts that are hydrated or not, glycols, bitumens, tars, waxes and other fatty substances which are solid at ambient temperature, such as tallow, margarine or fatty alcohols and fatty acids, preferably the incompressible material consists of paraffin comprising a hydrocarbon chain of from minus 14 carbon atoms.

More particularly, said phase change insulating material comprises chemical compounds of the alkane family, preferably a paraffin comprising a hydrocarbon chain of at least fourteen carbon atoms.

More particularly, said paraffin is heptacosane of formula C ₁₇ H ₃₆ or, preferably, tetracosane of formula C ₂₄ H ₅₀ having a melting temperature about 50 ° C. It is also possible to use an industrial paraffinic cut centered on heptacosane or tetracosane.

In one embodiment; said insulating material consists of an insulating complex comprising a first compound consisting of a hydrocarbon compound such as paraffin or gas oil, mixed with a second compound consisting of a gelling and / or structuring compound, in particular by crosslinking, such as a second compound of the polyurethane, crosslinked polypropylene, crosslinked polyethylene or silicone type, preferably said first compound being in the form of a particle or microcapsule dispersed within a matrix of said second compound and, more particularly, as first compounds; chemical compounds of the family of alkanes, such as paraffins or waxes, bitumens, tars, fatty alcohols, glycols, more particularly compounds whose melting temperature of the materials is between the temperature T ₁ of the hot effluents circulating in one of the pipes and the temperature T ₂ of the surrounding environment of the pipe in operation, or in fact in general a melting temperature of between 20 and 80 ° C.

These different insulating materials are materials "subject to migration", that is to say, liquid materials, pasty or solid consistency, such as the consistency of a fat, a paraffin or a gel, which are capable of being deformed by the stresses resulting from differential pressures between two distinct points of the envelope and / or of temperature variations within said insulating material.

Therefore, according to a preferred embodiment, the device according to the present invention comprises an insulating coating which consists of a viscous solid material subject to migration and at least two transverse transverse bulkheads, each of said transverse partitions. intermediates consisting of a closed rigid structure traversed by said inner chamber and secured to the walls of said chamber and said outer casing, preferably said intermediate transverse partitions being spaced at regular intervals along the longitudinal axis of the inner chamber and casing outer coaxial, preferably from a distance of 50 to 200 meters.

This rigid structure integral with the envelope prevents the displacement of said envelope facing said partition and with respect thereto and thus freezes the geometry of the cross section of the envelope at said partition. Here "sealed" and "closed" mean that said partition does not allow the passage of the material constituting said an insulating coating through said partition, and that in particular, the junction between said conduit and the orifices through which said conduit passes through said intermediate transverse partition does not allow the passage of said material of the insulating coating.

The said intermediate transverse transverse bulkheads ensure the confinement of the at least one insulating material (s) subject to migration constituting said insulating coating between said envelope and said partitions.

In the case of a bottom-surface connection, for example the vertical portion of a tower or the chain section connecting the top of the tower to the surface support, or pipes based on a steep slope of the bottom of the At sea, the external pressure varies along the pipe and decreases as one goes up to the surface. In the case of pasty or fluid insulating materials, the latter having a density lower than that of seawater, generally a density of 0.8 to 0.85, the differential pressure between the outside and the inside will vary along the said driving, increasing as one ascends to the surface. Thus, it follows accentuated deformations in the parts having the maximum differential pressure, thus inducing large fluid transfers parallel to the longitudinal axis of said pipe. In addition, the transfers are amplified by the phenomena of "breathing" due to temperature variations as described above.

A "flat bundle" is sensitive to variations in pressure due to declivities: overpressure at the bottom, depression at the top, and the towing phase is critical, because the length can reach several kilometers, the "bundle" is in fact never perfectly horizontally and this results in significant differential pressure variations during said towing and especially during the cabanage operation.

When the "bundle" is in a vertical position or at the bottom of the sea on a steep slope, the pressure differential created by the low density of the insulating material, associated with the volume variation created by the thermal expansion of the insulating material, generates movements of the insulating material that must be able to support the outer shell. It seeks to avoid particle movements parallel to the axis of the bundle, ie migrations of insulating material between two remote areas of the "bundle", as they may destroy the actual structure of the insulating material.

This device with transverse transverse bulkheads sealed can be manufactured at the best cost a "bundle" on the ground, to be able to set up a coating of insulating material of semi-fluid or pasty type, to tow in subsurface, cabaner in position vertical to install it, while respecting the integrity of the whole until it goes into production and throughout its lifetime, which generally exceeds 30 years.

This device with transverse intermediate transverse bulkheads also makes it possible to insulate at least one submarine pipe intended to be placed on the bottom, in particular at great depth, particularly in steep declining areas, starting from watertight "flat bundle" type casing, capable of providing substantial transverse flexibility to absorb volume variations, while maintaining sufficient longitudinal rigidity to allow handling, such as on-site prefabrication, site towing, and conservation the mechanical integrity of said envelope throughout the life of the product, which reaches and exceeds 30 years.

In a particular embodiment, said closed structure of said intermediate transverse sealed partition comprises a cylindrical piece which has a cross section whose perimeter has the same fixed shape as that of said cross section of the envelope.

The term "cross-section" is understood to mean the section in a plane XX ', YY' perpendicular to the longitudinal axis ZZ 'of said envelope, said envelope being of tubular shape and having a central longitudinal axis ZZ', and preferably, the section cross-section of said envelope defining a perimeter having two axes of symmetry XX 'and YY' perpendicular to each other, and to said longitudinal axis ZZ '.

In the present description, the term "perimeter of the cross-section" is understood to mean the closed-curve line defining the plane surface defined by said transverse section.

The perimeter of the transverse section of the outer envelope at the level of the watertight bulkheads is of fixed shape and can not therefore be deformed by contraction or by expansion of said envelope at this level.

According to different embodiments, said cross section of the outer envelope is circular in shape, or oval, or rectangular in shape, preferably with rounded corners.

Said intermediate transverse bulkheads create thermal bridges. It is therefore sought to space them as far as possible to reduce the diermic bridges.

In a particular embodiment, the spacing between two said successive transverse transverse bulkheads along said longitudinal axis ZZ 'of said envelope is from 50 to 200 meters, in particular from 100 to 150 meters.

To reduce the number of intermediate transverse bulkheads, according to a preferred characteristic, the device comprises at least one, preferably a plurality of jig (s) shaping (s), consisting (s) of a rigid structure integral with said internal chamber and traversed by it and secured to said outer shell at its periphery, disposed (s) between two said successive transverse transverse bulkheads, said shaping jig having openings allowing the passage of the constituent material of said insulating material subject to migration through said shaping jig.

As said intermediate transverse wall sealed, said shaping jig freezes the shape of the cross section of the outer casing and the inner chamber at said shaping jig, while minimizing thermal bridges.

More particularly, said open structure of said shaping jig comprises a cylindrical piece which has a cross section whose perimeter is in a geometrical figure identical to the geometrical figure defined by the shape of the perimeter of the cross section of said watertight partition.

Preferably, a device according to the invention comprises a plurality of shaping jigs arranged along said longitudinal axis ZZ 'of the envelope, preferably at regular intervals, two successive shaping jigs being preferably spaced 5 to 50 meters apart, preferably 5 to 20 meters.

In a preferred embodiment, the device according to the invention further comprises at least one centralizing template, preferably a plurality of centralizing templates, arranged preferably at regular intervals, between two said successive intermediate transverse bulkheads along of said longitudinal axis, each centralizing template being constituted by a rigid part integral with the wall of the internal chamber or of said outer casing, having a shape which allows a limited displacement of said outer casing or said inner chamber, in contraction and expansion, opposite said jig centralizer, at least said outer envelope or said inner chamber respectively being made of a flexible or semi-rigid material adapted, if necessary, to remain in contact with the insulating coating when it is deformed.

More particularly, said centralizing template is preferably constituted by a rigid piece with an external free surface or a cylindrical internal surface whose perimeter of the transversal section is set back relative to said outer envelope or said internal chamber respectively and limits the deformations of said outer casing or said internal chamber by mechanical abutment thereof on said rigid part in at least two opposite points of the perimeter of the cross section of said outer casing or said internal chamber respectively. Said displacement of the outer envelope or said internal chamber respectively, facing a said centralizing template can represent a variation of 0.1 to 10%, preferably 0.1 to 5%, of the distance between the two points opposite the perimeter of the cross section of said outer envelope or said inner chamber respectively. Thus, said rigid piece constituting said centralizing template having a part of the external or internal free surface sufficiently recessed with respect to the surface of the outer envelope or respectively of the internal chamber, and / or having perforations therethrough, of so as to create a space that allows the transfer of constituent material of said insulating coating through said centralizer template.

This centralizing template aims to ensure a minimum coating insulating coating around said inner chamber in case of deformation by contraction of the casing and transfer of said flowable material between the two said bulkheads.

More particularly, said centralizing template has a cross section whose perimeter is inscribed within a geometrical figure which is substantially homothetic with respect to the geometrical figure defined by the perimeter of the cross section of said intermediate transverse sealed partition.

The distance between two centralizing jigs along said longitudinal axis ZZ 'is such as to ensure that a quantity of material constituting said insulating coating, sufficient to ensure the minimum coating required for the insulation, is maintained. thermal of said inner chamber, given contraction deformations supported by said outer casing and / or said internal chamber.

Advantageously, the device according to the invention comprises a plurality of centralizing templates, and two successive centralizing templates are spaced along said longitudinal axis ZZ 'of the envelope by a distance of 2 to 5 meters.

These various transverse transverse bulkheads sealed, centralizing template and shaping jig, have been described in FR 2 821 915 in a different configuration because directly attached to the submarine pipe carrying the effluents.

As previously mentioned, advantageously, said outer envelope and said internal chamber are co-axial along a longitudinal axis ZZ 'and define a perimeter having at rest two symmetry axes XX' and YY 'perpendicular to each other and to said longitudinal axis ZZ ', and at least one of the constituent walls of said outer casing and / or inner chamber is made of a flexible or semi-rigid material (that is to say capable of following the deformations of the insulating material and able to remain in contact with the latter when deformed), preferably, the other envelope being rigid and preferably still circular cross section.

According to a first embodiment, said inner chamber is made of rigid material and said outer shell of flexible or semi-rigid material.

According to different embodiments, the cross section of the outer casing and / or the inner chamber is or are of circular or oval shape, or of rectangular shape, preferably with rounded corners.

In the case where the device comprises at least two pipes arranged in the same plane, the cross section of said outer envelope or said inner chamber is preferably elongate in the same direction as this plane.

More particularly, the outer perimeter of the cross section of said outer protective envelope or of said inner chamber is a closed curve whose ratio of the square and the length on the surface it delimits is at least 13, as described. in WO 00/40886.

During variations in internal volume, the outer envelope or said internal chamber will then tend to deform to a circular shape, which mathematically constitutes the shape having, at constant perimeter, the largest surface.

In the case of a circular profile, an increase in volume generates stresses in the wall, which are related to the pressure increase resulting from this increase in volume.

On the other hand, if the shape of the cross-section is flattened, the capacity of the envelope or of said internal chamber to absorb the expansions due to the expansion of the various components under the effect of the temperature is increased, without creating any significant overpressure. because the envelope has the opportunity to go back to the round.

In the case of an oval shaped profile, a variation in internal pressure will involve a combination of bending stresses and pure tensile stresses, since the variable curvature of the oval then behaves like an architectural vault with however the difference that in the case of our envelope, the constraints are tensile stresses and not compressive stresses. Thus, an oval or approximate shape of an oval will be possible for low expansion capacities and it will be appropriate to consider then ovals with a major axis length ratio ρmax on that of the small axis ρmin as high as possible for example at less 2/1 or 3/1.

The shape of the envelope will then be selected as a function of the overall expansion of the volume of the insulating outer coating, under the effect of temperature variations. Thus, for an insulation system mainly using materials subject to expansion, a rectangular shape, a polygonal shape or an oval shape allows an expansion by bending of the wall while inducing a minimum of tensile stresses in the outer casing .

In a first embodiment, the cross section of the inner chamber, preferably made of a rigid material, is of circular shape and the cross section of the outer envelope, preferably made of a flexible or semi-rigid material , is oval or rectangular in shape with rounded corners.

In another embodiment, the transverse section of the outer envelope, preferably made of a rigid material, is circular in shape and the cross section of said inner chamber, preferably made of a flexible or semi-rigid material, is oval or rectangular in shape with rounded corners.

Advantageously, said main pipe and, if appropriate, said inner pipe for supplying heat transfer fluid cooperate inside said inner chamber with centralizing elements which maintain said pipe or pipes substantially parallel to the axis ZZ 'of said internal chamber while allowing the movement of said pipes due to the differential expansions thereof along said axis ZZ '.

The present invention also relates to a device for heating and thermal insulation of a bundle of subsea main pipes, characterized in that it comprises a thermal insulation and heating device according to the invention comprising at least two said main pipes arranged in parallel and inside said internal chamber.

• a) au moins un riser vertical relié à son extrémité inférieure à au moins une dite conduite sous-marine reposant au fond de la mer, et à son extrémité supérieure à au moins un flotteur, ledit riser vertical étant inclus dans un dispositif d'isolation thermique et réchauffage selon l'invention, ledit riser vertical correspondant à ladite conduite principale, et ladite chambre interne s'étendant sur une hauteur d'au moins 1000 mètres, et
• b) au moins une conduite de liaison, de préférence une conduite flexible, assurant la liaison entre un support flottant et l'extrémité supérieure dudit riser vertical, et
• c) le cas échéant, desdites conduites flexibles externes de circulation du fluide caloporteur entre le support flottant et lesdits premier et second orifices de la première extrémité de la chambre interne et, le cas échéant, au moins une dite conduite externe flexible d'injection de gaz.

The present invention also relates to a bottom-surface connection facility between an underwater pipe resting at the bottom of the sea, in particular at great depth, and a floating support 10, comprising:

• a) at least one vertical riser connected at its lower end to at least one said underwater pipe resting at the bottom of the sea, and at its upper end to at least one float, said vertical riser being included in an isolation device thermal and heating according to the invention, said vertical riser corresponding to said main pipe, and said inner chamber extending over a height of at least 1000 meters, and
• b) at least one connecting pipe, preferably a flexible pipe, providing the connection between a floating support and the upper end of said vertical riser, and
• c) if applicable, said external flexible pipes for circulating the heat-transfer fluid between the floating support and said first and second orifices of the first end of the internal chamber and, where appropriate, at least one said flexible outer line of injection of gas.

Preferably, the connection between the lower end of the vertical riser and said underwater pipe resting at the bottom of the sea, is via an anchoring system comprising a base resting on the bottom, said base ensuring the maintenance and guidance of the connecting elements between the lower end of the vertical riser and the end of said pipe resting at the bottom of the sea, and said connecting elements comprising a curved pipe element and a pipe connection element , preferably a single connecting element, more preferably a single automatic connector, and said vertical riser comprising in its lower end portion a flexible joint allowing angular movements of the portion of the vertical riser located above said flexible joint, and said connecting elements comprising said flexible seal or vertical riser portion located below said flexible seal.

The term "vertical riser" is used here to account for the theoretical position of the riser when the riser is at rest, provided that the riser axis can know angular movements with respect to the vertical and move in a cone. angle α whose apex corresponds to the point of attachment of the lower end of the riser on said base.

Said connection elements, in particular of the automatic connector type, are known to those skilled in the art and comprise the 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. using a ROV, robot controlled from the surface, without requiring direct manual intervention of personnel.

The installation according to the present invention is advantageous because it has a relatively static geometry of said connecting elements relative to said base, and more particularly with respect to said movable support, said connecting elements being held rigidly on said movable 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 to the end of the submarine pipe resting at the bottom of the sea, said flexibility being able to absorb by deformation the elongation or retraction of the underwater pipe under the effect of temperature and pressure, avoiding thus to create considerable pushing forces within the underwater pipe, these efforts being able to reach 100, even 200 tons or more, and to transmit them to the foundation structure of the riser tower.

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

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

In all cases, said flexible seal is hollow to let the fluid, and its inner diameter is preferably of substantially the same diameter as the adjacent pipes connected thereto, in particular that of the vertical riser.

The term "reinforced flexible joint" here means a seal 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 the flexible connection to the floating support, as well as by the movements of said floating support.

When said connecting elements comprise said flexible seal, said flexible seal is thus fixedly fixed relative to said movable support. Said flexible seal then corresponds to an end element of the connecting elements ensuring the junction with said vertical riser.

By the presence of said flexible seal, and the flexible connection to the floating support located at the vertical riser head, the horizontal displacement of the base of the vertical riser which is at a substantially fixed point at altitude, does not generate significant effort in the articulated assembly consisting of said movable support, said flexible seal, said riser and said connection to the surface support, under the effect of the displacements of said movable support within said base platform, displacement which n ' exceed in general not 5 m.

The method of intervention inside the pipes, known as "coiled-tubing", consists of pushing a rigid tube of small diameter, generally 20 to 50 mm, through the pipe. Said rigid tube is stored wound by simple bending on a drum, then unstripped when uncoiling it. Said tube can measure several thousand meters in a single length. The end of the tube located at the drum of the storage drum is connected by via a rotating joint to a pumping device capable of injecting a liquid at high pressure and at high temperature. Thus, by pushing the fine tube through the pipe, maintaining pumping and back pressure, this pipe is cleaned by injecting a hot product capable of dissolving the plugs. This method of intervention 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 hereinafter referred to as "continuous casing cleaning" or CNT.

The installation according to the invention therefore advantageously comprises a device in the shape of a gooseneck ensuring the connection between the upper end of said riser and a connecting pipe with the floating support, so that one can intervene with the inside said vertical riser from the upper part of the float through said gooseneck-shaped device, so as to access the interior of the riser and clean it by liquid injection and / or by scraping the inner wall of said riser, then, if necessary, of the underwater pipe resting at the bottom of the sea.

Advantageously, the installation according to the invention comprises a second outer envelope with a circular cross section containing at least one insulation and heating device according to the invention, said outer envelope of said thermal insulation and heating device being made integral. said second outer envelope, preferably by elastic links and more preferably said second outer envelope comprises spiral means on its outer periphery capable of preventing the formation of vortex or tubular recess under the effect of marine current.

This embodiment is particularly advantageous when the insulation and reheating device according to the invention comprises an outer envelope of non-circular cross section or when the installation comprises at least two so-called insulation and heating devices with two said external envelopes side by side with circular or non-circular cross section.

The subject of the present invention is also a process for reheating and thermal insulation of at least one bottom-surface underwater main pipe intended to ensure the circulation of a hot effluent at the bottom of the sea or from the bottom of the sea to the surface, characterized in that a heating and thermal insulation device according to the invention is used, preferably in an installation according to the invention, and a heat transfer fluid is circulated inside. of said internal chamber.

In a particular embodiment, said coolant is selected from seawater, fresh water, diesel, oil.

Preferably, a heat transfer fluid with a density lower than that of the water is chosen so that it contributes to providing buoyancy to the insulation and reheating device according to the present invention. It may be, in particular gas oil density of the order of 0.85.

It is advantageous to use a heat transfer fluid of high specific heat such as seawater or fresh water, but it will be preferred because it remains less aggressive with respect to the metal walls of the internal chamber and when we add additives to prevent the proliferation of algae and other organisms, simply because of the difference in density with seawater, the interface between the two fluids existing at the bottom of the riser will be only slightly disturbed and said additives will remain for a long time in the circulating fresh water.

The method of heating and thermal insulation according to the invention is particularly advantageous when heating said main pipe by said circulation of said heat transfer fluid during a production restart phase after a prolonged shutdown.

• La figure 1 est une vue de côté d'une liaison fond-surface de type tour riser reliant une conduite sous-marine 13 reposant sur le fond de la mer 30 et un support flottant 10 en surface 31.
• La figure 1a est une vue en coupe d'une double conduite de circulation du fluide caloporteur.
• La figure 1b est une vue de l'extrémité inférieure du dispositif selon l'invention coopérant avec une embase d'ancrage 19 au fond de la mer 30.
• Les figures 2, 3 et 4 sont des sections transversales d'un dispositif d'isolation thermique et réchauffage selon l'invention dont l'enveloppe externe 3 est respectivement en configuration circulaire (fig. 2), de type rectangulaire (fig. 3) et de type ovale (fig. 4), la chambre interne 4 comportant deux conduites 1a, 1b de production, une conduite 7, d'injection de gaz et une conduite 6, de réchauffage,
• Les figures 5 et 6 représentent des sections d'un dispositif d'isolation thermique et réchauffage selon l'invention, de type inversé c'est-à-dire avec une enveloppe externe 3 en configuration circulaire et une chambre interne 4 en configuration de type ovale (fig. 5) et rectangulaire (fig. 6).
• La figure 7 est une coupe en vue de côté d'un dispositif d'isolation thermique et réchauffage 1 selon l'invention, comportant une conduite la de production, une conduite 6₁ de réchauffage par amenée du fluide caloporteur, traversant une chambre interne de réchauffage 4, celle-ci étant entourée d'une isolation périphérique avec un revêtement isolant thermique 2, la partie basse du dispositif.étant en communication directe avec l'eau de mer.
• La figure 8 est une variante de la figure 7, dans laquelle on a représenté des dispositifs 16₁ de maintien des conduites 1a et 6₁ à l'intérieur de la chambre interne de réchauffage 4 et des dispositifs 15, 16 et 17 permettant le contrôle des déformations de l'enveloppe externe 3, et dont la partie basse du dispositif comporte un système d'isolation supplémentaire 2₁ directement autour de la conduite, l'extrémité inférieure du dispositif étant complètement cloisonnée 11₂.
• Les figures 8A à C représentent une vue en section transversale, de la figure 8, au niveau des cloisons étanches, gabarits centraliseurs et gabarits conformateurs.
• La figure 9 est une coupe en vue de côté de la partie haute d'un dispositif selon l'invention, selon les figures 7 ou 8 et comportant un dispositif de pompage 9 et de réchauffage 6₄ du fluide caloporteur que l'on fait circuler en boucle à l'intérieur de la chambre 4 par l'intermédiaire de la conduite d'amenée 6₁ du fluide caloporteur.
• La figure 10 est une coupe en section transversale horizontale d'un double dispositif d'isolation et de réchauffage selon l'invention, équipé à sa périphérie d'une seconde enveloppe externe circulaire 3₁.
• La figure 11 est une vue de côté d'un dispositif selon la figure 10 dont ladite seconde enveloppe circulaire 3₁ est équipée d'une hélice visant à réduire les phénomènes de turbulence sous l'effet du courant.

Other characteristics and advantages of the present invention will emerge more clearly on reading the following description, given in an illustrative and nonlimiting manner, with reference to the appended drawings in which:

• FIG. 1 is a side view of a tower-riser type bottom-surface connection connecting an underwater pipe 13 resting on the bottom of the sea 30 and a floating support 10 on the surface 31.
• Figure 1a is a sectional view of a double heat transfer fluid circulation duct.
• FIG. 1b is a view of the lower end of the device according to the invention cooperating with an anchoring base 19 at the bottom of the sea 30.
• Figures 2, 3 and 4 are cross-sections of a thermal insulation device and heating according to the invention, the outer casing 3 is respectively in a circular configuration (Figure 2), rectangular type (Figure 3) and oval type (FIG 4), the inner chamber 4 having two production lines 1a, 1b, a pipe 7, gas injection and a pipe 6, reheating,
• FIGS. 5 and 6 represent sections of a thermal insulation and heating device according to the invention, of inverted type, that is to say with an outer envelope 3 in circular configuration and an internal chamber 4 in type configuration. oval (fig 5) and rectangular (fig 6).
• FIG. 7 is a cross-sectional view of a heat-insulating and heat-insulating device 1 according to the invention, comprising a production line 1a, a line 6 ₁ for heating by supplying the heat-transfer fluid, passing through an internal chamber of heating 4, the latter being surrounded by a peripheral insulation with a thermal insulating coating 2, the lower part of the device being in direct communication with the seawater.
• FIG. 8 is a variant of FIG. 7, in which there are shown devices 16 ₁ for holding the pipes 1a and 6 ₁ inside the internal reheating chamber 4 and devices 15, 16 and 17 allowing the control deformations of the outer casing 3 and whose lower part of the device comprises an additional insulation system January ₂ directly around the pipe, the lower end of the device being completely partitioned February _11.
• FIGS. 8A to C show a cross-sectional view of FIG. 8, at the level of the watertight bulkheads, centralizing jigs and conforming jigs.
• FIG. 9 is a sectional view from the side of the upper part of a device according to the invention, according to FIGS. 7 or 8, and comprising a device for pumping 9 and heating 6 ₄ of the heat transfer fluid which is circulated in loop inside the chamber 4 via the supply line 6 ₁ of the heat transfer fluid.
• Figure 10 is a horizontal cross-section in section of a double insulation and heating device according to the invention, equipped at its periphery with a circular second outer casing 3 _1.
• Figure 11 is a side view of a device according to Figure 10 in which said second circular casing 3 ₁ is equipped with a helix to reduce turbulence phenomena under the effect of the current.

• a) un riser vertical 1a, 1b relié à son extrémité inférieure à au moins une dite conduite sous-marine 13 reposant au fond de la mer, et à son extrémité supérieure à au moins un flotteur 14, ledit riser vertical étant inclus dans un dispositif d'isolation thermique et de réchauffage 1 selon l'invention, ledit riser vertical correspondant à ladite conduite principale, et ladite chambre interne 4 s'étendant sur une hauteur d'au moins 1000 mètres, et
• b) une conduite de liaison 12 flexible, assurant la liaison entre un support flottant 10 et l'extrémité supérieure dudit riser vertical 1, et
• c) une double conduite flexible externe 6₂, 6₃ de circulation respectivement d'amenée et de retour du fluide caloporteur 5 entre le support flottant 10 et lesdits premier et second orifices 8₁, 8₂ de la première extrémité 4₁ de la chambre interne 4 et une dite conduite externe flexible d'injection de gaz 7₂, et
• d) la liaison entre l'extrémité inférieure du riser vertical 1a, 1b et une dite conduite sous-marine 13 reposant au fond de la mer, se fait par l'intermédiaire d'un système d'ancrage comprenant une embase 19 posée sur le fond, ladite embase 19 assurant le maintien et le guidage des éléments de jonction entre l'extrémité inférieure du riser vertical 1a, 1b et l'extrémité de ladite conduite reposant au fond de la mer 13, et lesdits éléments de jonction comprenant un élément de conduite courbe 20 et un élément de raccordement de conduite 21, consistant en un unique connecteur automatique, et ledit riser vertical 1a, 1b comprenant dans sa partie terminale inférieure un joint flexible 22 permettant des mouvements angulaires de la partie du riser vertical 1a, 1b située au dessus dudit joint flexible 22, et lesdits éléments de jonction comprenant ledit joint flexible 22 ou une portion de riser vertical située au dessous dudit joint flexible 22.

FIG. 1 shows a bottom-surface connection installation between an underwater pipe 13 resting at the bottom of the sea, in particular at great depth, and a floating support 10 of the FPSO type, comprising:

• a) a vertical riser 1a, 1b connected at its lower end to at least one said submarine pipe 13 resting at the bottom of the sea, and at its upper end to at least one float 14, said vertical riser being included in a device heat insulation and heating 1 according to the invention, said vertical riser corresponding to said main pipe, and said inner chamber 4 extending over a height of at least 1000 meters, and
• b) a flexible connecting pipe 12, providing the connection between a floating support 10 and the upper end of said vertical riser 1, and
• c) a double external flexible pipe 6 ₂ , 6 ₃ of circulation respectively of supply and return of the coolant 5 between the floating support 10 and said first and second orifices 8 ₁ , 8 ₂ of the first end 4 ₁ of the chamber internal 4 and a said flexible external gas injection pipe 7 ₂ , and
• d) the connection between the lower end of the vertical riser 1a, 1b and a said underwater pipe 13 resting at the bottom of the sea, is done via an anchoring system comprising a base 19 placed on the bottom, said base 19 ensuring the maintenance and guiding of the connecting elements between the lower end of the vertical riser 1a, 1b and the end of said pipe resting at the bottom of the sea 13, and said connecting elements comprising an element of curved pipe 20 and a pipe connection element 21, consisting of a single automatic connector, and said vertical riser 1a, 1b comprising in its lower end portion a flexible seal 22 allowing angular movements of the portion of the vertical riser 1a, 1b located above said flexible seal 22, and said connecting elements comprising said flexible seal 22 or a vertical riser portion located below said flexible seal 22.

The various flexible pipes 6 ₂ , 6 ₃ , 7 ₂ and 12 are suspended on the edge of the FPSO and are connected to the top of the installation, the latter being called hereinafter turn, or at a table 11 ₁ , ie at a gooseneck device 24. All these flexible pipes adopt a chain configuration. The installation comprises indeed a gooseneck-shaped device 24 ensuring the connection between the upper end of said vertical riser 1a, 1b and a said connecting pipe 12 with the floating support 10, so that one can intervene inside said vertical riser from the upper part of said float 14 through said gooseneck-shaped device 24, so as to access the interior of said vertical riser 5 and clean it by liquid injection and / or by scraping the inner wall of said vertical riser 5, then, if necessary, said underwater pipe 13 resting at the bottom of the sea.

Said flexible pipe 12 of production is thus connected to the gooseneck 24 at the top of which is installed a float 14 of high capacity. The gooseneck 24 is connected to the float 14 via a flexible pipe, which makes it possible to carry out, from the surface, cleaning operations of the vertical pipe 1a with the aid of a ship 10 ₁ equipped with a "coiled-tubing" device known to those skilled in the art The production pipe 1a passes through the entire insulation and reheating device 1 according to the invention and ends in its lower part by a flexible seal 22 tight whose inner diameter substantially corresponds to the diameter of the main pipe 1a. The base 19 is anchored to the bottom of the sea 31 and connected via a pipe-shaped elbow 20 and an automatic connector 21, the underwater pipe 13 resting on the seabed 30 As explained above, said flexible seal 22 allows the angular movements of the insulating and reheating device 1 under the effect of the swell and the current and, in addition, is capable of taking up the vertical tensioning forces created by the float. 14, as well as the possible inherent buoyancy of the insulating components integrated in the insulating and reheating device 1.

The double circulation duct of the coolant 6 ₂ , 6 ₃ and the gas supply pipe 7 ₂ , between the floating support 10 and the top of the insulating device 1, cooperate with orifices 8 ₁ , 8 ₂ and respectively March ₈ provided in the transverse wall of upper end 11 _1, also referred to below upper board 11 _1, the vertex 4 ₁ of the insulation and heating device 1 according to the invention. As represented in FIGS. 7 to 9, the upper table 11 ₁ is integral with the vertical production line 1a and traversed 8 ₅ by thereof, while supporting the outer shell 3 ₁ and the tubular peripheral wall of the inner chamber 4. Thus the production line 1a supports the full tension created by the float 14, and in addition, supports the table greater than 11 ₁ and the components of the insulating and heating device 1 consisting of the outer casing 3 and the internal chamber 4.

• la conduite principale sous-marine 1a ou riser vertical 1a destiné à la circulation de pétrole chaud,
• une chambre interne 4 de forme cylindrique à section circulaire à l'intérieur de laquelle est contenu ledit riser vertical 1a,
• une dite enveloppe externe 3, également de forme cylindrique et coaxiale à ladite chambre interne 4.

FIGS. 7 to 9 show the heating and thermal insulation device 1 according to the invention, comprising:

• the underwater main pipe 1a or vertical riser 1a intended for the circulation of hot oil,
• an internal chamber 4 of cylindrical shape with a circular section inside which is contained said vertical riser 1a,
• an outer casing 3, also of cylindrical shape and coaxial with said internal chamber 4.

• un revêtement isolant thermique 2 remplissant l'espace entre la chambre interne 4 et l'enveloppe externe 3, et
• un fluide caloporteur 5 circulant à l'intérieur de la chambre interne 4 depuis son extrémité inférieure 4₂ jusqu'à son extrémité supérieure 4, au niveau dudit deuxième orifice 8₂ traversant la table supérieure 11₁.

The thermal insulation and heating means are constituted by:

• a thermal insulating coating 2 filling the space between the inner chamber 4 and the outer shell 3, and
• a heat transfer fluid 5 flowing within the internal chamber 4 from its lower end 4 ₂ until its upper end 4, at said second orifice 8 ₂ through the upper table ₁₁ January.

The heat transfer fluid is supplied at the top of the isolation device and reheating 1 according to the invention by the flexible outer pipe 6 _2, which is connected to an inner pipe 6 ₁ of circulation of the coolant within the chamber 4 at the first orifice 8 ₁ passing through the upper table 11 ₁ .

The inner pipe 6 extends parallel to the main pipe 1a in the longitudinal direction ZZ 'of the internal chamber 4, so that the coolant discharges into the internal chamber 4 at the end 6 ₅ of the supply conduit 6 ₁ near the lower end 4 ₂ of the insulating and reheating device 1. The circulation of the coolant 5 inside the chamber 4 is by suction at the outlet orifice 8 ₂ at the top 4 ₁ of the insulation and reheating device 1 according to two embodiments.

According to a first variant shown in FIGS. 7 and 8, the second outlet orifice 8 ₂ of the heat-transfer fluid is connected to a second flexible external duct 6 ₃ for returning said heat-transfer fluid to the floating support 10, and this is at the level of floating support 10 that is a pumping system and fluid heating.

According to a second alternative embodiment shown in Figure 9, a pump device 9 is installed on the upper Board 11 ₁ so as to cooperate with said first orifice 8 ₁ of coolant 5 and second orifice 8 ₂ output of the coolant fluid which allows the heat transfer fluid to circulate inside the chamber 4 in a loop.

As shown in FIG. 9, the pump 9 which can be electrical, hydraulic or pneumatic is contained inside a container 9 ₁ resting on the upper table 11 ₁ . The suction port of the pump is connected to outlet 8 of the orifice ₂ of the heat transfer fluid at the table 11 ₁ and the pump outlet is connected to the power 8 of the _1-hole fluid inside the chamber 4 at the level of the upper table 11 ₁ . The electrical resistance 6 ₄ dips inside the pipe 6 ₁ for a sufficient length so that the coolant 5 can be warmed to the proper temperature before continuing its course down the chamber 4. For clarity of the drawing the orifice 8 ₃ of the gas injection pipe 7 ₁ has been offset to the left with respect to the representation of FIGS. 7 and 8. The electrical resistance 6 ₄ and the motor of the pump 9 are supplied by a 6 ₆ electric cable chain configuration connecting the edge of the FPSO (not shown). The external flexible pipe 6 ₂ supplying heat transfer fluid cooperates with the orifice 6 ₇ and makes it possible to fill the heat transfer fluid of the chamber 5. The pump 9 and the electrical resistance device 6 ₄ within the container 9 ₁ can be maintained because the container 9 ₁ is independent and is connected by means not shown at the upper table 11 ₁ . It is therefore possible to disconnect the container 9 ₁ and lifting it to an intervention vessel 10 ₁ positioned vertically to the table 11 ₁ . After repair or replacement, the container 9 ₁ is down, the electrical cables are reconnected, the isolation valves, not shown, are open and the heat transfer fluid 5 can be recirculated and reheated as needed.

This second embodiment with a pump 9 installed at the top of the insulating device 1 is advantageous in the case where the heat necessary for heating the heat transfer fluid 5 are produced by electric generators. On the contrary, the first variant represented in FIGS. 7 and 8 is advantageous in the case where the calories are recovered in various existing installations on board the floating support and, in particular, at the level of gas turbines, diesel units or pollutant disposal furnaces.

In Figures 7 and 8, it is shown that the upper table 11 ₁ is secured to the main pipe 1a at the level of reinforcement 11 ₄ and supported by the latter. The wall of the inner chamber 4 and the outer casing 3 are tightly secured to the upper table 11 ₁ . The inner supply line 6 ₁ of the heat transfer fluid is supported in a sealed manner by the upper table 11 ₁ by means of reinforcement 11 ₅ , said supply line 6 ₁ traverses the entire height of the internal chamber 4 to open into a point 6 ₅ near the bottom 4 ₂ . Thus the coolant 5 fills the entire space between the various pipes 1a, 6, inside the inner chamber 4, the space defined at its apex by the upper table 11 ₁ . Then the fluid exits through the second orifice 8 ₂ to join, via a flexible external connection 6 ₃ , the floating support 10 where the heat transfer fluid is heated and then pumped back to the supply port 8 ₁ through the flexible external pipe supply 6 ₂ , so as to ensure a continuous circulation and maintain all components at a temperature preventing blockages of pipes by paraffin or hydrate formation. The internal gas injection pipe 7 ₁ is sealingly secured to the upper table 11 ₁ with the aid of reinforcement 11 ₆ where it is kept in suspension. The inner pipe 7 gas injection is advantageously spirally wound around the feed line 6 ₁ of hot heat transfer fluid to be finally connected directly ₄ to 7 the main pipe 1a production to perform the "gas- lift "(elevation by gas injection).

In the production configuration, the gas is injected under a pressure slightly greater than the internal pressure prevailing in the main pipe 1a at the orifice 7 ₄ , for example 0.5 to 2 bars more, which produces bubbles 7 ₃ at in crude oil, which have the effect of modifying the density and thus create an accelerating effect on the fluid vein. Gradually, as the bubbles rise March _7, the hydrostatic pressure within the crude oil decreases, which causes an increase of the volume of the bubbles, thus reducing the bulk density of the oil and accelerating the process of transferring the crude oil from the bottom of the sea to the FPSO.

• d'une part, la conduite d'injection de gaz 7₁ se trouve au plus près de la conduite externe d'amenée 6₁ du fluide caloporteur chaud et maintient donc le gaz à une température optimale jusqu'à ce qu'il soit injecté à la base de la conduite principale la de production,
• d'autre part, ladite conduite 7₁ étant fixée rigidement 11₅, dans sa partie supérieure, au niveau de la table supérieure 11₁, et dans sa partie inférieure, au niveau de l'orifice 7₄ d'injection, les dilatations différentielles entre la conduite principale 1a de production et la conduite d'injection de gaz 7₁, sont absorbées sans dommages par déformation élastique de la spirale que forme ladite conduite 7₁ enroulée en spirale autour de la conduite 6₁ de fluide caloporteur, ce qui autorise l'emploi de simples conduites en acier.
• enfin, en cas d'arrêt de l'installation, le riser 1a est rempli de pétrole brut, lequel envahit aussi la conduite d'injection de gaz 7₁ sur une certaine hauteur, en raison de l'absence de clapet anti-retour au niveau de l'orifice d'injection 7₄; en effet, on évite d'installer de tels clapets anti-retour car ils nécessitent de l'entretient et risquent de causer des pannes intempestives au cas où ils ne rempliraient plus leur tâche, par exemple en fuyant ou en se bloquant en position ouverte ou fermée. Ainsi, lors de redémarrages, on fait avantageusement circuler du fluide caloporteur 5 dans la chambre 4, ce qui a pour effet immédiat de fluidifier le brut contenu dans la conduite d'injection 7₁ de gaz enroulée en spirale et en contact direct avec la conduite d'amenée de fluide chaud 6₁, et de le maintenir à une température élevée, tout en réchauffant petit à petit le pétrole brut contenu dans la conduite principale 1a de production. En maintenant une pression de gaz suffisamment élevée, dès que le pétrole dans le riser 1a est suffisamment fluide, la conduite d'injection 7₁ de gaz se purge rapidement et le "gas-lift" entre en action sans délai, permettant ainsi un redémarrage optimal de l'installation.

The spiral arrangement of the inner pipe gas injection Group 7 ₁ shows three individual advantages:

• on the one hand, the gas injection pipe 7 ₁ is located as close as possible to the external feed pipe 6 ₁ of the hot heat transfer fluid and thus keeps the gas at an optimum temperature until it is injected at the base of the main production line,
• on the other hand, said pipe 7 ₁ being rigidly fixed 11 ₅ , in its upper part, at the level of the upper table 11 ₁ , and in its lower part, at the orifice 7 ₄ injection, the differential expansions between the main pipe 1a of production and the gas injection pipe 7 ₁ , are absorbed without damage by elastic deformation of the spiral formed by said pipe 7 ₁ wound in a spiral around the pipe 6 ₁ heat transfer fluid, which allows the use of simple steel pipes.
• finally, in case of shutdown of the installation, the riser 1a is filled with crude oil, which also invades the gas injection pipe 7 ₁ to a certain height, because of the absence of nonreturn valve at level of the injection port 7 ₄ ; indeed, it avoids installing such check valves because they require maintenance and may cause untimely breakdowns in case they no longer fulfill their task, for example by fleeing or by blocking in the open position or closed. Thus, during restarts, heat transfer fluid 5 is advantageously circulated in the chamber 4, which has the immediate effect of fluidifying the crude contained in the gas injection pipe 7 ₁ wound spirally and in direct contact with the pipe. supply of hot fluid 6 ₁ , and maintain it at a high temperature, while warming little by little the crude oil contained in the main pipe 1a production. By maintaining a sufficiently high gas pressure, as soon as the oil in the riser 1a is sufficiently fluid, the injection pipe 7 ₁ of gas is purged quickly and the "gas-lift" comes into action without delay, allowing a restart optimal installation.

In Figure 7, the insulating coating 2 is confined in the space between the upper Board 11 ₁ the internal chamber 4, the outer casing 3, and the transverse partition 11 ₂ located at the lower end 4 of the device ₂ insulation and warming 1. This transverse end partition 11 ₂ to the lower end 4 ₂ of the device is open at its center by an 8 port ₄ so that the bottom of the device 1, the inside of the chamber 4 is in direct contact with the seawater. Insofar as the coolant is sufficiently immiscible with the seawater and of lower density, an interface zone is created between the hot heat transfer fluid and the seawater. The heat transfer fluid can be hot fresh water and the possible mixing of the water does not present any major inconvenience if it is not to lose locally a small portion of the calories of the coolant. In addition, for To improve the insulation of the riser 1, an additional insulation 2 ₁ is advantageously provided, for example syntactic foam or a section of pipe in pipe extending, for example, over a height of 30 to 40 meters, centered on the interface zone between coolant and seawater, in the longitudinal direction ZZ '. Thus, by arranging the lower end 6 ₅ of the supply line 6 ₁ of the heat transfer fluid to, for example, 20 meters from the low point 4 ₂ of the internal chamber 4 and advantageously still equipping the end 6 ₅ of the supply duct 6 ₁ of heat transfer fluid, a deflector 6 ₆ , the hot water-cold water interface is maintained largely above the low point 4 ₂ of the internal chamber 4 and unnecessary heat losses are minimized. Moreover the complementary insulation 2 ₁ extending well above the baffle 6 ₈ , is guaranteed, in addition to an excellent level of insulation, fully effective heating to the pipe 1a in its lower portion. This embodiment, wherein the lower end 4 ₂ of the internal chamber 4 is opened by an orifice 8 ₄ of diameter greater than that of the main pipe 1a equipped with its coating supplementary insulator 2 ₁ is advantageous because it allows elongation and retraction of the riser 1a as a result of the temperature variations without having to deal with the mechanical difficulties of interface for the connection of the lower end of the main pipe 1a with the lower end transverse wall 11 ₂ of the isolation device 1 according to the invention.

FIG. 8 shows an alternative embodiment, in which the lower end transverse partition 11 ₂ cooperates with a tubular sleeve 11 ₃ surrounding the lower end of the main pipe 1a equipped with its complementary insulating coating 2 ₁ of so as to confine, preferably in a sealed manner, the interior of the chamber 4. Thus, the exchanges with the outside are minimized, which is preferable when the coolant is a polluting fluid such as diesel fuel. In addition, the diesel fuel is interesting because, because of its low density (d = 0.85), the diesel fuel can contribute to bring buoyancy to the insulation and reheating device 1 as a whole. The outer surface of the insulating means 2 ₁ surrounding the main pipe 1a at its lower end slides with reduced clearance inside the tubular sleeve 11 ₃ , and, to eliminate the risk of leakage, it is advantageous to install gaskets , not shown, at least one of the two ends of the tubular sleeve 11 _3, the latter being secured to the bulkhead lower end 11 ₂

In FIG. 8, centralizing elements 16 ₁ are shown inside the internal chamber 4, which make it possible to maintain the pipes 1a and 6 ₁ substantially parallel in the longitudinal direction ZZ 'of the chamber, while allowing the movements due to the differential expansions along said axis ZZ'.

On the other hand, in Figure 8, there is also shown an alternative embodiment with intermediate bulkheads 15, centralizers 16 and shaping templates 17 in the space between the inner chamber 4 and the outer shell 3 in the case where the insulating coating 2 is a material subject to migration. Intermediate watertight partitions 15, centralizing templates 16 and conforming templates 17 limit the expansion and contraction of the insulating material subject to migration, and therefore the deformations of the outer shell 3 as explained above. The intermediate transverse bulkheads 15 as well as the end bulkheads 11 ₁ , 11 ₂ consist of a closed solid rigid structure, traversed by the wall of said inner chamber 4 and integral with the wall of the outer shell 3; they are preferably spaced at regular intervals of at least 200 meters in the direction ZZ '. In the space between two transverse sealed partitions 11 ₁ , 11 ₂ , there is at least one centralizing template 16. Each centralizing template 16 consists of a rigid part integral with the wall of the internal chamber 4 and has a shape that allows a limited displacement of the outer shell 3 both contraction and expansion. This embodiment is suitable for an internal chamber whose wall is rigid, in particular of circular shape, and the outer envelope 3 is made of a flexible or semi-rigid material able to remain in contact with the outer surface of the insulating coating 2 when it is deformed. FIG. 8A shows an embodiment where the perimeter of the cross-section of the cylindrical outer free surface of the rigid part constituting the centralizing template 16 is set back from that of the intermediate bulkhead 15 and limits the deformations of the outer casing 3 by mechanical stop of the latter on the rigid part 16 in at least two opposite points of the perimeter of the cross section of said outer casing 3. As described in FR 2 821 915, the rigid part 16 has a portion of its cylindrical outer free surface sufficiently recessed with respect to the surface of the outer casing 3 and / or has perforations therethrough so as to create a space which allows the transfer of insulating material 2 through the centralizing template or around the centralizing template 16.

In an alternative embodiment not shown, when the outer envelope 3 is made of rigid material and has a profile of circular horizontal cross section and it is the inner chamber 4 which is made of flexible or semi-rigid material, preferably with an oval or elongated rectangular cross-sectional profile of rectangular type, the rigid piece constituting centralizing templates 16 is integral with the outer casing 3 and it is the cylindrical internal free surface of the rigid part 16 which is then set back relative to the wall of the internal chamber 4, so as to allow the expansion or contraction of the wall of the internal chamber 4 facing the centralizing template 16.

It is also advantageous to provide shaping jigs 17 between two centralizing jigs 16 as shown in the lower compartment between the lower end wall 11 ₂ and the first intermediate transverse bulkhead 15 in FIG 8. This shaping jig 17 consists of a rigid structure integral with the walls of the outer casing 3 and the inner chamber 4. In FIG. 8C, the shaping jig 17 has openings 17 ₁ allowing the passage of the material subject to migration of said insulating material 2 through the forming jig 17 and then to obtain the technical effect described above described in FR 2 821 915.

FIGS. 2 to 6 show different types of geometrical configuration of the horizontal cross-section of the internal chambers 4 and outer casing 3, first of all the internal chambers 4 and outer casings 3 may both consist of a material rigid and have a horizontal cross section of circular configuration. This type of configuration may be suitable when the thermal insulating material 2 is a rigid material such as syntactic foam.

However, when the thermal insulating material 2 is a material subject to migration, in particular of the gel type, and more particularly still a phase-change compound such as paraffin or a combination of these various insulation and storage accumulation systems. energy, it is preferable that the outer envelope 3 and / or the inner chamber 4 are made of a flexible or semi-rigid material adapted to follow the deformations of said insulating material Various configurations may be envisaged.

Note that in Figures 2 to 6, there is shown an insulation and heating device which comprises a bundle of pipes 1a, 1b arranged parallel to the interior of the inner chamber 4 along its longitudinal direction ZZ '.

In FIGS. 3 and 4, there is shown an isolation device 1 more particularly adapted to the insulating coating 2 of gel type or phase change material subject to large volume variations due to the temperature and / or the phenomena of change. of phases. These devices have the capacity to absorb large volume variations by "rounded" the shape of the outer casing shown in Figure 3 with a horizontal cross section of rectangular type with rounded corners and in Figure 4 with a horizontal cross section in oval configuration. The outer casing 3 deforms in expansion towards a circular shape without generating significant stress in the outer casing 3 during increases in internal volume. In this version, the outer casing can be made of semi-rigid material, steel or any other metal or composite material. In these embodiments of Figure 3, the wall of the inner chamber 4 may itself be made of semi-rigid material but it is preferably made of rigid material type.

FIGS. 5 and 6 show an inverted configuration of the horizontal cross-section of the internal chambers 4 and outer envelopes 3. The deformable shape under the effect of the expansion / contraction of the insulating material 2 is constituted by the wall of the inner chamber 4 whose horizontal cross section has an elongate shape of rectangular type with rounded edge (Figure 6) or oval (Figure 5) and the outer casing 3 then being of circular configuration and may be made of a rigid material. Thus, during the retraction of the insulating material 2, the wall of the chamber 4 tends to return to the round, while it flattens when the insulating material 2 expands.

In Figure 10, there is shown in horizontal section an installation comprising two insulating and reheating devices 1 according to the invention, each having an outer casing 3 whose horizontal cross section has a rectangular profile with a rounded angle. Both devices 1 are installed at the center of a second circular outer casing 3 ₁ acting as screen. Second circular screen envelopes have also been described in the state of the art. Said second circular envelope 3 ₁ minimizes the clean hydrodynamic coefficients of the assembly and therefore the forces due to the marine current. This second circular casing 3 is made integral with _one of the devices 1 by resilient pads 3 _5, made of elastomer or thermoplastic material or by simple springs. FIG. 11 shows spiral-shaped fins 2 ₂ attached to the outside of the second circular envelope 3 ₁ and whose function is to prevent the formation of vortex or vortex jolts under the effect of marine currents. . These arrangements are also known to those skilled in the art and other equivalent arrangements can be envisaged.

The invention has been described in detail for the case of a riser, but it remains in the spirit of the invention since the various provisions of the invention are applied to submarine lines resting on the bottom of the sea.

Claims (30)

1. Apparatus (1) for heating and lagging at least one undersea main bottom-to-surface connection pipe (1a, 1b) for carrying a flow of hot effluent, the apparatus comprising:

   - a covering of one thermally insulating material (2) surrounding said main pipe(s) (1a, 1b);

   - said insulating covering (2) being covered by a leaktight outer protective casing (3) that is preferably cylindrical in shape;

   the apparatus being characterised in that it comprises:

   a) an internal chamber (4) preferably of cylindrical shape and coaxial (ZZ') inside said outer casing (3), such that:

   - said insulating covering surrounds said internal chamber and preferably fills the annular space between said outer casing (3) and said internal chamber (4); and

   - said main pipe (1a, 1b) is contained inside said internal chamber (4), that is preferably cylindrical in shape; and

   b) means (6₁, 9) suitable for maintaining the temperature of a heat-transfer fluid (5) and for causing it to circulate inside said internal chamber, said heat-transfer fluid (5) surrounding the main pipe (1a, 1b) contained inside a said internal chamber (4).
2. Apparatus according to claim 1, characterised in that said internal chamber (4) conveys at least one internal gas-injection pipe (7₁) suitable for enabling gas to be injected into said main pipe (1a, 1b), said internal gas-injection pipe (7₁) being connected (7₄) to said main pipe (1a, 1b) at one end (4₂) in the longitudinal direction (ZZ') of said main pipe (1a, 1b) inside said internal chamber (4), and preferably said gas-injection pipe (7₁) extending outside said internal chamber (4) in the form of an external gas-injection pipe (7₂) connecting said internal gas-injection pipe (7₁) to a floating support (10).
3. Apparatus according to claim 1 or claim 2, characterised in that it comprises fluid-circulation means for circulating a heat-transfer fluid (5), said fluid-circulation means comprising at least one internal heat-transfer fluid feed pipe (6₁) extending in the longitudinal direction (ZZ') inside said internal chamber (4) from a first orifice (8₁) situated at a first end (4₁) of the internal chamber (4), preferably as far as the vicinity of the second end (4₂) of said internal chamber (4), and a second orifice (8₂) for outlet of said heat-transfer fluid, preferably level with said first end (4₁) of the internal chamber (4), said internal heat-transfer fluid feed pipe (6₁) being situated beside said main pipe, between it and said outer insulating material.
4. Apparatus according to claim 2 or claim 3, characterised in that said internal gas-injection pipe (7₁) is a pipe that is spiral-wound around said internal heat-transfer fluid feed pipe (6₁) inside said internal chamber (4).
5. Apparatus according to claim 3 or claim 4, characterised in that said internal heat-transfer fluid feed pipe (6₁) is extended from said first orifice (8₁) to a floating support (10) by an external flexible pipe (6₂) for feeding said heat-transfer fluid, and said second orifice (8₂) for outlet of heat-transfer fluid is connected to a second external flexible pipe (6₃) for returning said heat-transfer fluid to said floating support (10).
6. Apparatus according to claim 3 or claim 4, characterised in that said internal heat-transfer fluid feed pipe (6₁) is connected to heat-transfer fluid circulation means comprising a pump (9) co-operating at said first end (4₁) of the internal chamber (4) with said first orifice (8₁) for feeding heat-transfer fluid and with said second orifice (8₂) for outlet of heat-transfer fluid, said pump (9) enabling the heat-transfer fluid to be circulated successively inside said internal heat-transfer fluid feed pipe (6₁), then inside the internal chamber (4), then out from said internal chamber (4) via said second orifice (8₂), and finally recirculating in a loop back into said internal chamber (4) via said first orifice (8₁), an external flexible pipe (6₂) for circulating heat-transfer fluid providing a connection between said floating support and the body of the pump (9) or said first orifice (8₁).
7. Apparatus according to claim 6, characterised in that it includes heater means (6₄) for heating the heat-transfer fluid inside said internal heat-transfer fluid feed pipe (6₁), the heater means preferably being in the form of an electrical resistance element.
8. Apparatus according to one of claims 1 to 7, characterised in that it includes at least one transverse end partition (11₁) at at least a said first end (4₁), said end transverse partition (11₁) supporting said main pipe (1a, 1b) and also said fluid-circulation means (6₁, 9), and having said main pipe (1a, 1b) passing therethrough and, where appropriate, having first and second orifices (8₁, 8₂) enabling said heat-transfer fluid (5) to be caused to circulate inside and outside said internal chamber (4) via said orifices (8₁, 8₂).
9. Apparatus according to claim 8, characterised in that it has first and second transverse end partitions (11₁, 11₂) each at a respective one of the two ends (4₁, 4₂) of the internal chamber (4), said first end partition (11₁) including, where appropriate, said first and second orifices (8₁, 8₂), and said two transverse end partitions (11₁, 11₂) supporting said outer casing (3) and said internal chamber (4) and connecting them together in leaktight manner, while also ensuring, at least at a first end (4₁), that the heat-transfer fluid (5) is confined inside the internal chamber (4).
10. Apparatus according to claim 9, characterised in that said second end partition (11₂) includes a large orifice (8₄) of diameter greater than that of the main pipe, through which orifice said main pipe (1a) passes, so that the heat-transfer fluid (5) is in contact with sea water at the bottom end (4₂) of the internal chamber (4).
11. Apparatus according to claim 9, characterised in that said second end partition (11₂) includes an orifice (8₄) surrounding and secured to a tubular sleeve (11₃) inside which said main pipe (1a) can slide with little clearance, preferably in leaktight manner.
12. Apparatus according to one of claims 1 to 11, characterised in that said main pipe (1a) is covered in a second insulating covering (2₁), at least at said second end (4₂) of the internal chamber (4), said heat-transfer fluid circulating in said internal chamber (4) outside said second covering (2₂).
13. Apparatus according to claim 12, characterised in that said second covering (2₁) is constituted by a thermally insulating material, preferably a solid thermally insulating material, more preferably syntactic foam, said solid material directly surrounding said main pipe (1a), more preferably said second insulating material completely filling the space between said main pipe (1a) and a second pipe that is coaxial therewith, having said main pipe inserted therein.
14. Apparatus according to one of claims 1 to 13, characterised in that said insulating covering (2) comprises an insulating material that is subject to migration, and at least said outer casing (3) and/or said internal chamber (4) is/are constituted by a solid material that is flexible or semi-rigid and suitable for tracking deformations of the insulating material (2) and for remaining in contact therewith when it deforms.
15. Apparatus according to one of claims 1 to 14, characterised in that said insulating material (2) is a phase-change material presenting a liquid/solid melting temperature (T₀) that preferably lies in the range 20°C to 80°C, said temperature being greater than the temperature (T₂) of the sea water environment surrounding the pipe in operation and less than the temperature (T₁) above which the effluent flowing inside the pipe presents an increase in viscosity that is damaging for flow thereof in said main pipe (1a, 1b).
16. Apparatus according to claim 15, characterised in that said phase-change insulating material (2) comprises chemical compounds of the alkane family, preferably a paraffin having a hydrocarbon chain of at least 14 carbon atoms, more preferably tetracosane of formula C₂₄H₅₀ presenting a melting temperature of about 50°C.
17. Apparatus according to one of claims 1 to 16, characterised in that said insulating material (2) comprises an insulating mixture comprising a first compound consisting in a hydrocarbon compound such as paraffin or gas oil, mixed with a second compound consisting in a gelling compound and/or a compound having a structuring effect, in particular by cross-linking, such as a second compound of the polyurethane type, cross-linked polypropylene, cross-linked polyethylene, or silicone, preferably said first compound is in the form of particles or microcapsules dispersed within a matrix of said second compound, and said first compound preferably being selected from alkanes such as paraffins, waxes, bitumens, tar, fatty alcohols, or glycols, more preferably said first compound being a phase-change compound.
18. Apparatus according to one of claims 1 to 17, characterised in that it includes a said insulating covering (2) comprising one said viscous solid material that is subject to migration and at least two intermediate transverse partitions (15) that are leaktight, each of said intermediate transverse partitions (15) being constituted by a closed rigid structure having said internal chamber (4) passing therethrough and secured to the walls of said internal chamber (4) and to said outer casing (3), said intermediate transverse partitions (15) preferably being spaced apart from one another at regular intervals along the longitudinal axis (ZZ') of said internal chamber (4) and outer casing (3) coaxial therewith, more preferably at a distance of 50 m to 200 m.
19. Apparatus according to claim 18, characterised in that it includes at least one centralizing template (16) and preferably a plurality of centralizing templates (16) preferably disposed at regular intervals between two of said leaktight intermediate transverse partitions (15) in succession along said longitudinal axis (ZZ'), each centralizing template (16) being constituted by a rigid piece secured to the wall of the internal chamber (4) or of said outer casing (3), and presenting a shape which allows limited displacement of said outer casing (3) or respectively of said internal chamber (4) in contraction and in expansion facing said centralizing template (16), at least said outer casing (3) or respectively said internal chamber (4) being made of a material that is flexible or semi-rigid and suitable, where appropriate, for remaining in contact with the insulating covering when it deforms.
20. Apparatus according to claim 18 or claim 19, characterised in that it comprises at least one and preferably a plurality of shaping templates (17) each constituted by a rigid structure secured to said internal chamber which passes therethrough and secured to said outer casing (3) at its periphery, being disposed between two of said leaktight intermediate transverse partitions (5) that are disposed in succession, each shaping template presenting openings allowing the material constituting said insulating material (2) that is subject to migration to pass through said shaping template (17).
21. Apparatus according to one of claims 1 to 17, characterised in that said outer casing (3) and said internal chamber (4) are coaxial along a longitudinal axis (ZZ') and define a perimeter presenting, at rest, two axes of symmetry (XX' and YY') that are mutually perpendicular and perpendicular to said longitudinal axis (ZZ'), and at least one of the walls constituting said outer casing (3) and/or said internal chamber (4) is made of a material that is flexible or semi-rigid, while preferably the other wall is constituted by a material that is rigid, and more preferably of cross-section that is circular in shape.
22. Apparatus according to claim 21, characterised in that the cross-section of the outer casing (3), which is preferably made of a material that is rigid, is circular in shape, while the cross-section of said internal chamber (4), which is preferably made of a material that is flexible or semi-rigid, is oval in shape or rectangular in shape with rounded corners.
23. Apparatus according to claim 21, characterised in that the cross-section of the internal chamber (4), which is preferably made of a material that is rigid, is circular in shape, while the cross-section of the outer casing (3), which is preferably made of a material that is flexible or semi-rigid, is oval in shape or rectangular in shape with rounded corners.
24. Apparatus according to one of claims 1 to 23, characterised in that said main pipe (1a) and, where appropriate, said internal heat-transfer fluid feed pipe (6₁), co-operate(s) inside said internal chamber (4) with centralizing elements (16₁) which hold said pipe(s) (1a, 6₁) substantially parallel to the axis (ZZ') of said internal chamber (4) while allowing said pipes (1a, 6₁) to move due to differential expansion thereof.
25. Apparatus (1) for heating and lagging a bundle of undersea main pipes (1a, 1b), the apparatus being characterised in that it comprises apparatus according to one of claims 1 to 24 containing at least two of said main pipes (1a, 1b) disposed in parallel inside said internal chamber (4).
26. A bottom-to-surface connection installation between an undersea pipe (13) resting on the sea bottom, in particular at great depth, and a supporting float (10), the installation comprising:

    a) at least one vertical riser (1a, 1b) connected at its bottom end to at least one said undersea pipe (13) resting on the sea bottom, and at its top end to at least one float (14) said vertical riser being included in apparatus (1) according to one of claims 1 to 25, said vertical riser corresponding to said main pipe, and said internal chamber (4) extending over a depth of at least 1000 meters;

    b) at least one connection pipe (12) preferably a flexible pipe, connecting a floating support (10) with the top end of said vertical riser (4); and

    c) where appropriate, said external flexible pipes (6₂, 6₃) for circulating the heat-transfer fluid (5) between the floating support (10) and said first and second orifices (8₁, 8₂) at the first end (4₁) of the internal chamber (4), and, where appropriate, at least one said flexible external pipe (7₂) for injecting gas.
27. An installation according to claim 26, characterised in that it includes a second outer casing (3₁) of circular cross-section containing at least one lagging and heating apparatus (1) according to one of claims 1 to 25, said outer casing (3) of said lagging and heating apparatus (1) being secured to said outer second casing (3₁), preferably via resilient links (3₅), and more preferably said outer second casing (3₁) having spiral-shaped means (3₂) on its outside periphery suitable for preventing vortices forming or turbulence separating under the effect of sea currents.
28. A method of heating and thermally insulating at least one main undersea pipe (1a, 1b) providing a bottom-to-surface connection for delivering a flow of hot effluent to or from the bottom of the sea and the surface, the method being characterised in that a heating and lagging apparatus (1) according to one of claims 1 to 25 is used, preferably in an installation according to claim 26 or claim 27, and a said heat-transfer fluid (5) is caused to flow inside a said internal chamber (4).
29. A method according to claim 28, characterised in that said heat-transfer fluid is selected from sea water, fresh water, gas oil, and oil.
30. A method according to claim 28 or claim 29, characterised in that said main pipe is heated by said flow of said heat-transfer fluid during a stage of restarting production after a prolonged stoppage.

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