EP3495055B1

EP3495055B1 - A submarine structure and related method

Info

Publication number: EP3495055B1
Application number: EP17306708.3A
Authority: EP
Inventors: Henri Morand; Richard DANIELL; James TERRIS
Original assignee: Technip N Power SAS
Current assignee: TechnipFMC Subsea France SAS
Priority date: 2017-12-06
Filing date: 2017-12-06
Publication date: 2021-02-17
Anticipated expiration: 2037-12-06
Also published as: EP3495055A1; WO2019110657A1

Description

The present invention concerns a submarine structure capable of being in contact with a body of water, the submarine structure comprising at least one wall, an electrically conductive coating applied on one surface of the wall and a power source electrically connected to the electrically conductive coating.
The submarine structure is for example used in the production of liquid and gaseous hydrocarbons. The structure can convey the hydrocarbons such as a rigid pipe, a flexible pipe, a riser, or can support another structure conveying hydrocarbons such as a buoyancy module supporting a riser, a midwater arch or a floating platform.
During long term submarine exposure, a submarine structure can be affected by the biological fouling of the structure. The fouling can be due to the attachment and growth of submarine organisms such as mollusks or algae at the outside surface of the structure.
In the example of a buoyancy module, the marine growth will for example decrease the efficiency of a buoyancy module because of the added mass. The marine growth may also increase the drag leading to a possible failure of the structure.
US 4 283 461 discloses a coating comprising a film containing a piezoelectric polymer applied on the outside surface of a submarine structure. An electrical power source is configured to apply an alternating signal across the film. The film vibrates when electrically activated and therefore discourages the attachment and the growth of submarine organisms on the structure.
Moreover, another issue concerning submarine structures conveying liquid hydrocarbons is the risk of formation of hydrates in the structure at high pressures and low temperatures. Hydrate formation in a pipe can lead to a slurry of solid that is capable of accumulating and plugging the pipe. The coating disclosed in US 4 283 461 is not configured to prevent the formation of hydrates in the structure.
EP 2 493 262 describes a submarine structure aiming to prevent the formation of hydrates in the structure but is not configured to prevent biological fouling.
One aim of the invention is therefore to provide a submarine structure configured to prevent the biological fouling at the outside of the structure and/or to prevent the formation of hydrates in the structure.
To this aim, the subject-matter of the invention is a submarine structure of the above type, wherein the electrically conductive coating is configured to receive power from the power source to produce heat power.
The structure according to the invention comprises one or more of the following features, taken solely, or according to any technical feasible combination:

the electrically conductive coating is configured to reach a temperature of at least 10 °C, in particular a temperature comprised between 10 °C and 50 °C ;
the power generated by unit of surface by the electrically conductive coating is greater than 0.1 W/m², in particular a power generated by unit of surface by the electrically conductive coating comprised between 0.1 W/m² and 5 W/m²;
the wall is an outside wall of the submarine structure, the electrically conductive coating separating the outside wall and the surrounding water;
the submarine structure is a buoyancy module ;
the submarine structure comprises an outer coating, in particular a water permeable outer coating, disposed on the electrically conductive coating ;
the submarine structure comprises a protection coating disposed directly on the electrically conductive coating or on the outer coating ;
the submarine structure is a pipe capable of transporting liquid hydrocarbons ;
the pipe comprises an outer wall defining with the wall an annular space, the electrically conductive coating being located in the annular space and preferably on the wall ;
the wall is an inner wall delimiting an inner passage for conveying a fluid, the electrically conductive coating being located on an inner surface of the inner wall ;
the electrically conductive coating comprises graphite nanotube or an electrical conductive material such as carbon, or a metal possibly in a powder/paint form.

The invention further concerns a method of heating a submarine structure placed in a body water comprising the following steps:

providing a structure as defined above;
activating the power source to send power to the electrically conductive coating;
producing heat by the electrically conductive coating.

The method according to invention may comprise one or more of the following features, taken solely, or according to any technical feasible combination:

the temperature of electrically conductive coating is greater than 10°C, in particular comprised between 10 °C and 50 °C;
the electrically conductive coating is in contact with a surrounding body of water or in thermal contact with a surface of the structure placed in a surrounding body of water.

The invention also relates to a use of the method as defined above to prevent fouling due to the installation and the growth of submarine organisms on the structure and/or to prevent the formation of hydrates in the structure.
The invention will be better understood, upon reading of the following description, given solely as an example, and made in reference to the appended drawings, in which:

figure 1 is a schematic cutaway view of a structure according to the invention;
figure 2 is a cutaway view of a structure according to the invention, the structure being a buoyancy module;
figure 3 is a schematic side view of a structure according to the invention, the structure being a pipe;
figure 4 is a structure according to the invention;
figure 5 is a structure according to the invention.

A structure 10 according to the invention is shown in figure 1.
The structure 10 is adapted to be in contact with a body of water 12. In particular, the structure 10 is advantageously adapted to be submerged into the body of water 12. The body of water 12 is for example a sea, an ocean, a lake and/or a river.
The structure 10 is for example a buoyancy module 14 supporting a pipe 16 as illustrated in figure 2.
The pipe 16 is for example a rigid pipeline as defined by the offshore standard DNV-OS-F101 (October 2013) established by the Det Norske Veritas, or a flexible pipeline as for example risers and flowlines as defined by the standards API RP 17B (5th Edition, May 2014) and API 17J (4th Edition, May 2014) established by the American Petroleum Institute. The pipe 16 is configured to convey hydrocarbons from an oil well to a surface facility.
The buoyancy module 14 comprises for example a clamp 18.
The clamp 18 attaches the buoyancy module 14 to the pipe 16. The clamp 18 is attached circumferentially around a transversal section of the riser 16. Sometimes, the clamp 18 is fixed around a connection region defined by the area where two pipeline end terminations are securely connected.
The buoyancy module 14 is surrounded by the body of water 12.
The buoyancy module 14 comprises a buoyant foam element 19. The buoyant foam element 19 is here made of a material having a density lower than the density of the surrounding water 12. When submerged in the body of water 12, an upward buoyant force is exerted on the buoyancy module 14. Therefore, the buoyancy module 14 enables to maintain the pipe 16 in a substantially stable position in the body of water 12.
As shown in figure 1, the structure 10 comprises at least one wall 20, and according to the invention, an electrical conductive coating 22 applied on the wall 20. The structure 10 comprises a power source 24 and advantageously, an inner primer coating 26 for adhesion of the electrical conductive coating 22 on the wall 20, an outer coating 28 and a protection coating 30.
The wall 20 is here an outside wall of the submarine structure 10.
The electrical conductive coating 22 is applied on an outside surface of the wall 20.
The term « outside » is understood as being relatively closer to the body of water 12.
The electrically conductive coating 22 separates here the outside wall 20 and the surrounding water 12.
The electrically conductive coating 22 is deposited as paint on the wall 20, for example with a brush or a painting sprayer. The electrically conductive coating 22 has advantageously a thickness comprised between 0.2 mm and 5 mm.
Alternatively, the electrically conductive coating 22 is a tape spirally wound around the wall 20, for example with a spiraling machine as known by the skilled man of the flexible pipeline manufacturing. The tape has advantageously a thickness comprised between 0.2 mm and 5 mm.
The electrically conductive coating 22 is connected to the power source 24 and configured to receive electrical power to thus produce heat when receiving electrical power.
In an advantageous way, the electrically conductive coating 22 produces heat homogenously over all its surface.
The heat generated by the electrically conductive coating 22 depends on the application. For example for marine growth removal, the aim is to increase the temperature above the local marine growth acceptable temperature. For example for a pipeline, the aim would be to provide a low power continuous heat source along the pipeline.
Advantageously, the electrically conductive coating 22 is configured to reach a temperature of at least 10 °C, in particular a temperature comprised between 10 °C and 50 °C when receiving power. This temperature is measured for a structure 10 surrounded by water 12, the water 12 being at a temperature comprised between 4°C and 35°C.Advantageously, the electrically conductive coating 22 is also configured to generate a power by unit of surface greater than 0.1 W/m², in particular a power by unit of surface comprised between 0.1 W/m² and 5 W/m².
The electrically conductive coating 22 is for example made of a thin layer of carbon nanotubes. Alternatively, the electrically conductive coating 22 is for example a metallic-based electrical conductive material made of carbon, or of any other metal material exhibiting good electrically conductive properties. The electrically conductive coating 22 is applied in a powdered or in a painted form.
The power source 24 is electrically connected to the electrically conductive coating 22. The power source 24 is configured to provide electrical power to the electrically conductive coating 22.
The power source 24 is advantageously situated on an offshore surface installation, onshore or is attached to the structure 10. Alternatively, the power source 24 can be connected through an ROV using an electrical connection system known by the man of the art.
The primer coating 26 is placed between the wall 20 and the electrically conductive coating 22. The primer coating 26 is an undercoat that ensures adequate adhesion of the electrically conductive coating 22 when it is painted on the wall 20. The primer coating 26 also increases the painting durability and provides additional protection for the painting.
The primer coating 26 is advantageously made of a polymeric resin material. For example, the primer coating 26 can comprises an epoxy-based or a polyurethane-based.
The outer coating 28 is disposed on the outside surface of the electrically conductive coating 22. The outer coating 28 is advantageously made of an epoxy-based paint.
The outer coating 28 has advantageously a thickness comprised between 0.5 mm and 5 mm depending on the application.
The protection coating 30 is disposed on the outside surface of the outer coating 28.
The protection coating 30 is configured to protect the different coatings 26, 22, 28 from the surrounding water 12. In particular, the protection coating 30 is configured to provide toughness, wear resistance and corrosion protection to the structure 10.
The protection coating 30 has advantageously a thickness comprised between 0,1 mm and 5 mm.
The protective coating 30 is advantageously made of a polymeric material selected among epoxy resin, polylolefin such as polypropylene and in this application, performs better if it is as a high thermal conductivity.
In another embodiment, the protection coating 30 may comprise an insulation layer 31 to maintain the structure 10 and more specifically the pipe, at a convenient temperature, avoiding hydrate formations.
A first method of heating a submarine structure 10 according to the invention, placed in a body of water 12, will now be described.
The structure 10 is immersed in the body of water 12.
The power source 24 is activated and provides electrical power to the electrically conductive coating 22.
The electrically conductive coating 22 produces heat by Joule effect when receiving electrical power.
The electrically conductive coating 22 is in contact with the surrounding water 12 or in an advantageous way in thermal contact with a surface 26, 20 of the structure 10, the surface 26 being in contact with the wall 20.
Advantageously, the electrically conductive coating 22 reaches a temperature of at least 30 °C, in particular a temperature comprised between 40 °C and 50 °C.
This range of temperature of the electrically conductive coating 22 prevents the biological fouling on the structure 10. Indeed, the submarine organisms do not install and grow on a wall at this temperature. In case of a biological fouling already present on the structure 10, the heating of the electrically conductive coating 22 leads to the detachment of the submarine organisms from the structure 10.
The biological fouling of the structure 10 is therefore controlled over time by means of the electrically conductive coating 22. There is no use of aggressive and complicated means such as jetting or ROV (Remotely Operated Vehicle) intervention to remove the fouling from the structure 10.
Moreover, there is no need of using a chemical anti-fouling coating which are non-environmentally friendly and therefore limit their use in certain regions.
Alternatively, the structure 10 is for example a rigid pipe, a flexible pipe, a midwater arch or a floating platform.
Another structure 110 according to the invention is shown in figure 4. The structure 110 is a rigid pipe which comprises an inner wall 20 made of a metallic material selected among steel grades.
The structure 110 is adapted to be in contact with a body of water 12. In particular, the structure 110 is advantageously adapted to be submerged into the body of water 12. The body of water 12 is for example a sea, an ocean, a lake and/or a river.
The structure 110 is for example a pipe 32 as illustrated in figure 3.
The pipe 32 is for example a rigid pipe, a flexible pipe such as a riser or a flowline configured to transport liquid or gaseous hydrocarbons and defined respectively by the standards DNV-OS-F101, API 17J and API RP 17B already cited above.
As shown in figure 4, the structure 110 is a rigid pipe and more precisely a pipe-in-pipe. The structure 110 comprises at least one inner wall 20, an electrical conductive coating 22 applied around the inner wall 20, a power source 24, and an insulating outer wall 34. It advantageously comprises a primer coating 26, an outer coating 28 and a protection coating 30.
The inner wall 20 advantageously delimits an inner passage 36 for the circulation of liquid and/or gaseous hydrocarbons.
The volume between the inner wall 20 and the insulating outer wall 34 defines an annular space 40.
The term « inside » is understood as being relatively further to the body of water 12.
The electrical conductive coating 22, the power source 24, the primer coating 26, the outer coating 28 and the protection coating 30 are similar to those of structure 10 and will not be described again.
The insulating outer wall 34 is situated on the outside surface of the protection coating 30 and is in contact with the surrounding body of water 12.
The outer wall 34 is an outer metallic steel protection pipe. The configuration of the inner wall 20 and of the outer wall 34 ensure that the overall system has for example a thermal conductivity of less than 1W/m.K. It is configured to reduce the heat transfer between the structure 110 and the body of water 12. In particular, the outer wall 34 and the annular space 40 are configured to reduce the cooling of the structure 110 by the body of water 12.
Advantageously, to further reduce the cooling of the structure 110, it is worth considering having an additional insulation layer made of any known materials from the skilled man.
For example, in another embodiment of the structure 110 (not shown), the protection coating 30 is replaced by a gap filled with air, inert gas or vacuum-pressurized. Therefore, insulation performance of the structure 110 is enhanced.
The electrically conductive coating 22 is located in the annular space on the surface of the inner wall 20.
A method of heating a submarine structure 110 according to the invention placed in a body of water 12 will now be described.
The structure 110 is surrounded by a body of water 12.
In a similar way to the first method, the power source 24 is activated and sends electrical power to the electrically conductive coating 22. The electrically conductive coating 22 produces heat while receiving electrical power.
Advantageously, the electrically conductive coating 22 reaches a temperature of at least 10 °C, in particular a temperature comprised between 10 °C and 50 °C.
The heat produced by the electrically conductive coating 22 is conducted to the inner passage 36 through the inner wall 20.
This range of temperature of the electrically conductive coating 22 enables to prevent the formation of hydrates in the inner passage 36 of the structure 110.
Indeed, the risk of formation of hydrates in the structure 110 occurs at high pressures and low temperatures. The heat produced by the electrically conductive coating 22 maintains the liquid or gaseous hydrocarbons circulating into the structure 110 at a high enough temperature to prevent the formation of hydrates. This solution avoids the use of electrical cable and connection in the annular space 40 to conduct the electrical power along the pipeline.
In particular, the risk of formation of hydrates is important during production shutdowns in which the flow of hydrocarbons is very low or zero in the structure 110. Limiting the risk of formation of hydrates in the structure 110 enables an easier and a quicker restart of the production.
The risk of formation of hydrates is also high at connections between different structures such as a pipeline and submarine production units as PipeLine End Manifold (PLEM) or PipeLine End Termination (PLET). The insulation of these connections is possibly less effective and therefore the temperature reached by the hydrocarbons is possibly lower.
The use of the structure 110 at these connections reduces the risk of formation of hydrates at these locations.
Another structure 210 according to the invention is shown in figure 5.
The structure 210 is in contact with a body of water 12. In particular, the structure 210 is submerged into the body of water 12.
In the same way as the structure 110, the structure 210 comprises at least one inner wall 20, an electrical conductive coating 22 applied on the wall 20 and a power source 24. It advantageously comprises a primer coating 26, a coating 28, a protection coating 30 and an insulation coating 31 aiming at improving the thermal efficiency of the system.
The structure 210 is for example a rigid pipe.
The electrical conductive coating 22 is here applied on the inside surface of the wall 20 in the inner passage 36. The electrical conductive coating 22 is therefore directly in contact with the flow of liquid and/or gaseous hydrocarbons circulating in the inner passage 36.
The primer coating 26 is advantageously disposed between the wall 20 and the electrically conductive coating 22.
The outer coating 28 is disposed on the inside surface of electrically conductive coating 22.
The protection coating 30 is disposed on the outside surface of the wall 20.
The insulation coating 31 is disposed on the outside surface of the protection coating 30, in contact with the surrounding body of water 12.
The third structure 210 is configured to facilitate the welding issues as the welds are not affecting the coating.
Another structure differs from the previous ones in that the power source 24 is carried by a ROV (Remotely Operated Vehicle).
The fourth structure (not shown) is for example a pipe conveying hydrocarbons.
The ROV is configured to connect the power source 24 to the electrically conductive coating 22 and to provide electrical power to the electrically conductive coating 22.
In case of formation of hydrates at a precise location disturbing the hydrocarbons production, the ROV is configured to be send at this location and heat specifically this area. The heating of the electrically conductive coating 22 leads to the suppression of the hydrates and enables a restart of the production.

Claims

A submarine structure (10, 110, 210) capable of being in contact with a body of water (12) comprising :
- at least one wall (20);

- an electrically conductive coating (22) applied on one surface of the wall (20);

- a power source (24) electrically connected to the electrically conductive coating (22);
characterized in that the electrically conductive coating (22) is configured to receive power from the power source (24) to produce heat power,
in that the wall (20) is an outside wall of the submarine structure (10, 110, 210), the electrically conductive coating (22) separating the outside wall (20) and the surrounding water (12),
and in that the submarine structure (10, 110, 210) is a buoyancy module (14).
The submarine structure (10, 110, 210) according to claim 1, wherein the electrically conductive coating (22) is configured to reach a temperature of at least 10 °C, in particular a temperature comprised between 10 °C and 50 °C.
The structure (10, 110, 210) according to any one of claims 1 or 2, wherein the power generated by unit of surface by the electrically conductive coating (22) is greater than 0.1 W/m², in particular a power generated by unit of surface by the electrically conductive coating (22) comprised between 0.1 W/m² and 5 W/m².
The structure (10, 110, 210) according to any of one of the preceding claims, wherein the submarine structure (10, 110, 210) comprises an outer coating (28), in particular a water permeable outer coating (28), disposed on the electrically conductive coating (22).
The structure (10, 110, 210) according to any of one of the preceding claims, wherein the submarine structure (10, 110, 210) comprises a protection coating (30) disposed directly on the electrically conductive coating (22) or on the outer coating (28).
The structure (10, 110, 210) according to any of one of the preceding claims, wherein the submarine structure (10, 110, 210) is a pipe (32) capable of transporting liquid hydrocarbons.
The structure (10, 110, 210) according to claim 6, wherein, the pipe (32) comprises an outer wall (34) defining with the wall (20) an annular space, the electrically conductive coating (22) being located in the annular space and preferably on the wall (20).
The structure (10, 110, 210) according to any of one of the preceding claims, wherein the wall (20) is an inner wall delimiting an inner passage (36) for conveying a fluid, the electrically conductive coating (22) being located on an inner surface of the inner wall (20).
The structure (10, 110, 210) according to any one of preceding claims, wherein the electrically conductive coating (22) comprises graphite nanotube or an electrical conductive material such as carbon, or a metal possibly in a powder/paint form.
A method of heating a submarine structure (10, 110, 210) placed in a body of water (12) comprising :
- providing a structure (10, 110, 210) according to any one of the preceding claims;

- activating the power source (24) to send power to the electrically conductive coating (22);

- producing heat by the electrically conductive coating (22).
The method according to claim 10, wherein the temperature of electrically conductive coating (22) is greater than 10°C, in particular comprised between 10 °C and 50 °C.
The method according to any one claims 10 or 11, wherein the electrically conductive coating (22) is in contact with a surrounding body of water (12) or in thermal contact with a surface of the structure (10, 110, 210) placed in a surrounding body of water (12).
A use of a method according to anyone of claims 10 to 12 to prevent fouling due to the installation and the growth of submarine organisms on the structure (10, 110, 210) and/or to prevent the formation of hydrates in the structure (10, 110, 210).