WO2018080314A1

WO2018080314A1 - A buoy assembly

Info

Publication number: WO2018080314A1
Application number: PCT/NO2017/050270
Authority: WO
Inventors: Erik GODØY; Gary Winfield
Original assignee: Polarcus Dmcc
Priority date: 2016-10-25
Filing date: 2017-10-23
Publication date: 2018-05-03
Also published as: GB2567584B; NO20161686A1; GB201902055D0; GB2567584A; NO341587B1

Abstract

A buoy assembly (1) adapted to be attached to a seismic streamer comprises floating means (3), electronic equipment means (7), a power supply (8) and 5 positioning sensor(s) (9). The buoy assembly (1) comprises a substantially rigid tube (10) comprising a first end, (11) an opposite placed second end (12) and a circumferential wall (24). The tube (10) is connected to the floating means (3) in a pivotal connection (13), allowing the tube (10) to pivot in relation to the floating means (3) at 10 least in a direction vertical/horizontal. An acoustic sensor (14) is placed inside or outside the tube (10).

Description

A BUOY ASSEMBLY

Description

The present invention relates to a buoy assembly adapted to be attached to a seismic streamer, the buoy assembly comprising

- floating means adapted to float the buoy assembly on the water surface in such a way that a lower part is placed below the waterline and an upper part is placed above the water line

electronic equipment means and a power supply

positioning sensor(s) such as a GPS/GNSS sensor placed above the water line.

US5616059 describes a buoy comprising a frame assembly, a mast assembly, rudder assembly, floating saddles and a bulkhead floating tanks adapted to flow on the water surface. The buoy is towed through the water whereby the mast reaches its vertical position. Electronic equipment is carried in a separate equipment well of the buoy. During the towing of the buoy, the mast is held in an approximately vertical deployed position. However, there is a risk that the cable towing the buoy will jerk whereby the buoy will change orientation regularly. Further, the towing angle of the streamer might change uncontrollably through towing the buoy. In addition, the buoy is large and very cumbersome to manage onboard the vessel.

The present invention seeks generally to improve a buoy assembly such, that the abovementioned insufficiencies and drawbacks of today's buoy assemblies are overcome or at least the invention provides a useful alternative.

According to the invention, a buoy assembly is provided, as per the introductory part of this specification, and wherein the buoy assembly comprises a substantially rigid tube comprising a first end and an opposite placed second end and a circumferential wall, said tube encloses the electronic equipment and the power supply,

said tube is connected to the floating means in a pivotal connection allowing the tube to pivot in relation to the floating means at least in a direction vertical/horizontal such, that an above water segment of the tube is adapted to be placed substantially above the water line during towing through the water of the buoy assembly,

and at least one acoustic sensor is placed inside or outside the tube in a region adapted to be placed below the water line during towing through the water of the buoy assembly.

By this construction, the floating means would sit more "on top of" the water, rather than being pulled through it, thereby causing less drag compared to known buoy assemblies.

By making a long tube, the acoustic sensor is allowed to get deeper than normal while also making the overall system easier to handle compared to a very large buoy with a large cradle underneath.

The tube is intentionally stiff, and does not bend or pivot in relation to itself. The entire tube will tilt around this pivot region/connection, which is basically, where the tube is mounted to the floating means. The pivot region/connection may be constructed in such a way that the tube is allowed to rotate /swivel inside the float. This eliminates the need for a swivel joint in the tail of the streamer.

The acoustic sensor is a sensor, which emits and receives sound waves for measuring distance between itself and adjacent sensors of the same type. It is placed in a second section of the tube -a below water segment of the tube - between the second end and the pivotal connection. The acoustic sensor is places near the second end preferably on the second end.

The construction of the buoy assembly attempts to be both easy to handle, provide very good capabilities for measuring the positioning of the spread and reduces equipment damage due to being easy to handle. The construction is light enough to be wheeled around on deck manually. Buoys known from prior art have to be moved by winches and cranes, or by using many people. A single person can move this inventive buoy assembly relatively easily.

The buoy assembly provides the capability to position the spread very well by virtue of having GNSS and acoustic positioning sensor attached the same stiff body (the tube). With the optional addition of an attitude sensor, any doubt over the relative X, Y, Z locations of the GNSS and acoustics sensors can be minimized.

The "vertical/horizontal direction" expression also covers that the tube is allowed to pitch up and down in the plane the buoy assembly is towed from. The first end and a region close to the pivot region define the above water segment of the tube. By a region close to the pivot region is to understand a region of the tube that during use is placed slightly above the water line or slightly below the water line or in the waterline.

According to one embodiment, an attitude sensor is placed in the tube and is adapted to provide orientation of the tube and resolve the relative locations of the above water segment and below water segment placed sensors. The attitude sensor registers and measures the heading, pitch and roll of the tube. By placing the sensor in the tube, it is possible to measure the relative location of the positioning sensor above the water surface and the acoustic sensor below the water. The data from the attitude sensor will be passed back to the vessel via some means most likely radio link, and may optionally be processed in the electronics equipment on the buoy. The below water segment of the tube is the part of the tube not being the above water segment.

According to one embodiment, the electronic equipment means and the power supply are all placed inside the tube, and the acoustic sensor is mounted to a below water segment of the tube and close to the second end. The positioning sensors may be satellite navigation system such as the Global Positioning System (GPS) or GNSS. The sensors are processing data and transmitting the position of the buoy assembly to a tracking system, which might be placed on a vessel towing the buoy assembly. The GPS/GNSS is placed at the top of the tube, which acts as a sort of mast. The position data locates the buoy assembly and also locates the position of the acoustic sensor placed opposite the GPS/GNSS

The acoustic sensor can measure range information to adjacent buoy assemblies, and to acoustic sensors mounted on or inside the streamer towing the buoy assembly, or to adjacent streamers.

The electronic equipment, power supply, the acoustic sensor and the positioning sensors can easily slide in and out of the tube to allow maintenance etc. The tube may or may not be watertight.

According to one embodiment, the tube protrudes through the floating means and is pivotally mounted to the floating means

This makes the buoy assembly very stable also when the water/weather is rough. By allowing free pivoting, it allows the tube to orient in the most suitable/natural angle based on the angle of the streamer. Furthermore, the streamer, which is towing the tube/buoy, can be set at different depths. The pivotal connection might be the centre mass of the buoy assembly.

According to one embodiment, the longitudinal length of the above water segment of the tube is 20-30% of the longitudinal length of the tube.

By having the shortest part of the tube above the water surface, it is possible to fold the above water segment of the tube into the float. By this arrangement, any protruding components of the positioning sensor(s) (antennae etc.) is/are protected from damage during deployment or recovery of the buoy assembly. It also protects it when being wheeled around the deck of the vessel. The total length of the tube is typically around 4 meters. Further, this construction makes the buoy assembly more stable when working in the water.

The free pivoting of the tube may be restricted by a locking mechanism. This mechanism is activated during deployment of the buoy from the towing vessel, and optionally prevents the free pivoting of the tube when this is desirable.

This mechanism can be un-locked during recovery of the buoy to allow the protruding components to fold away into the float. According to one embodiment, the buoy assembly further comprises power sources such as a solar panel and/or generator wheels for providing power to the power supply; said power supply is preferably batteries such as lithium batteries preferably iron lithium phosphate batteries.

Thereby the batteries are continuously provided with power, during use of the buoy assembly, and does not run out. By this arrangement, the buoy assembly can stay in the water for long periods without power from the streamer. When the power source is generator wheels, they are placed below the water line receiving energy from the water flow. They may be placed at aft end of the floats. When the power source is a solar panel, it is placed at the very top of the float, or wrapped around the exterior of the tube above the water line. Advantageously the buoy assembly comprises both power sources.

According to one embodiment, is the tube made in a metal such as steel or aluminium or in plastic, fibre glass or carbon fibre.

According to one embodiment, the tube is provided with a fairing at least in the part of the tube adapted to be placed below the water line and at least at one side of the tube.

The fairing reduces drag and limits the amount that the tube may vibrate due to vortex induced vibrations. According to one embodiment, the tube is provided with several connector devices placed different places at the outside of the tube and for fastening to the buoy assembly.

According to one embodiment, the tube is rigid and does not bend in relation to itself, said tube is 3-6 meter long preferably, around 4 meter long.

According to one embodiment, the buoy assembly is adapted to be attached to the tail end of a streamer or at other points along the length of the streamer.

Brief description of the drawings

FIG. 1 A is a plane view of a first embodiment of a buoy assembly according to the present invention.

FIG. 1 B is a cross-sectional view of the embodiment shown in fig. 1 A along the line B-B. FIG. 1 C is a cross-sectional view of the embodiment shown in fig. 1 A along the line C-C.

FIG. 2 is a plane view of a second embodiment of a buoy assembly according to the present invention.

FIG. 3 is a plane view of a tube used in the embodiments shown in fig 1 and fig. 2

The invention will be described with reference to fig. 1 A showing a plane view of a first embodiment of a buoy assembly 1 according to the present invention. The buoy assembly 1 comprises a floating means 3 comprising a lower part 5 adapted to be placed under the water line 4, when the buoy assembly is placed in water, and an upper part 6 adapted to be placed above the water line 4. The floating means 3 sees to that the buoy assembly 1 is able to float on the water and is made as light and small as possible. The floating means 3 could also be formed as a catamaran.

A tube 10 - preferably cylindrical - is connected to the floating means 3 in a pivotal connection 13 placed above or near the water line 4. The tube 10 has preferably a length of 3-6 meter preferably around 4 meter. The tube 10 is at least partly hollow as different components is placed inside the tube 10. This will be explained with reference to fig. 3. The tube 10 comprises a first end 1 1 and an opposite second end 12 and a wall 24 enclosing the different components. At the top of the tube that is at the first end 1 1 - said tube 10 during use works as a mast - a positioning sensor 9 such as a GPS or GNSS sensor is placed. Opposite this sensor 9 at the second end 12, an acoustic sensor 14 is placed. The buoy assembly 1 is towed from a seismic streamer arrangement 25, commonly from the tail end of the streamer, but also potentially from other connections along the length of the streamer. A towing cable 25 may be the seismic streamer itself, or an adapter cable suitable for towing the buoy assembly 1 . The section of the tube 10 delimited by the pivotal connection 13 and the first end 1 1 is named the above water segment 16 of the tube 10 and is the part that at least in calm water/weather will be placed over the water line 4. The length of this section 16 is around 20-30% of the total length of the tube 10. When the tube 10 has a length of 4 meter, a suitable length of the above water segment 16 is around 1 meter.

The buoy assembly 1 is featured with power sources 18 that deliver energy to a power supply such as batteries. The power sources 18 is in this embodiment a solar panel 19 and generator wheels 20.

FIG. 1 B is a cross-sectional view of the embodiment shown in fig. 1 A along the line B-B and shows the placement of the solar panel 19. The solar panel 19 is placed at the upper part 6 of the floating means 3 preferably placed at the top of the floating means 3 - and in the front - that is as far away as possible from the water line 4.

FIG. 1 C is a cross-sectional view of the embodiment shown in fig. 1 A along the line C-C and shows the placement of the generator wheels 20. The generator wheels 20 are placed at the lower part 5 of the floating means 3 preferably placed at the aft end of the floating means 3.

FIG. 2 is a plane view of a second embodiment of a buoy assembly 1 according to the present invention. The difference between this

embodiment and the embodiment shown in fig. 1 A is the construction of the floating means 3. The floating means 3 is in this embodiment constructed as a pedalo float comprising two floating wheels (only one is visible at the drawing) and placed between the wheels, the tube 10 is fastened in a pivotal connection 13 being the mass centre of the buoy assembly 1 . The pivotal connection 13 is placed above the water line 4, as is the case in the embodiment of fig 1 A. The tube 10 has its above water segment 16 placed above the water line 4 during use in the water and the acoustic sensor 14 is placed at the second end 12 of the tube 10. In this embodiment, the lower part 5 of the floating means 3 is significantly smaller than the upper part 6 of the floating means 3.

In this embodiment, "the wheels" will rotate freely around the pivot point of the tube 10 and can be used to generate electrical power through this rotation. This would involve some sort of mechanism to generate the power similar to the wheels in Figure 1 a/b/c. It could also involve some sort of inductive coupling between the wheels and a suitable inductive power generator mounted on or inside the tube 10.

FIG. 3 is a plane view of a tube 10 used in the embodiments shown in fig 1 and fig. 2. The tube 10 comprises in this example a cylindrical wall 24 but could also be a squared wall or have other designs. The tube 10 is closed in each end and at least in the first end 1 1 the tube 10 is closed with a releasable lid 26. The lid 26 may be waterproof. Different components are placed inside the tube 10 in the above water segment 16. At least the above water segment 16 is hollow. The components may include power supply 8 such as batteries, float devices, electronic equipment 7 such as the attitude sensor 15, or a processing capability to interface to the

GNSS/positioning sensor, attitude sensor, and acoustic sensor in order to package the data for transmission to the vessel. Further, it may include a power regulator board to manage the power coming from the streamer, the water powered generators, or solar panel(s). If the entire tube 10 is water tight, the electronics, attitude sensor 15 etc. could be anywhere in the length of the tube 10. In this example, the positioning sensor 9 is placed at the first end 1 1 and the acoustic sensor 14 is placed at the second end 12. Inside the tube 10, equipment connectors 27 are fastened to the wall. A purpose could be to fasten the different components placed inside the tube 10 to a specific place in the tube 10 and in such a way that they do not move when the tube 10 is working in the water. It is possible to provide a connection 23 between the internal and external devices via the connector 27 mounted on the wall of the tube. The purpose of this is then to allow a connection between the components mounted on the float (e.g. solar panel referred to in Fig 1 and 2, and/or generator getting power from the wheels). This power will be passed to the power regulator electronics inside the tube 10 and used to charge the battery.

The pivotal connection 13 may comprise a shaft connected to the floating means, and which allow the tube to pitch up and down in the plane that the buoy assembly 1 is towed from. The pivot connection 13 may also be a flange, which mates with an attachment point at the floating means 3. It allows the tube 10 to rotate and swivel inside the floating means 3 and eliminates the need for a swivel joint at the tail of a streamer. The flange might be a circular plate fastened to the outside of the tube for instance by welding and placed at the chosen pivot point. At the outside of the wall 24 of the tube 10, connector devices 22 are placed. The purpose is to establish connection possibilities for streamers. Further at the outside of the tube 10 and in the section placed between the pivotal connection 13 and the second end 12 a hydrodynamic fairing 21 may be established. This construction reduces the drag.

This buoy assembly according to the invention is easy to handle, provides very good capabilities for measuring the positioning of the spread, reduces drag from the buoy, and reduces equipment damage.

Claims

A buoy assembly (1 ) adapted to be attached to a seismic streamer the buoy assembly (1 ) comprising

- floating means (3) adapted to float the buoy assembly (1 ) on the water surface in such a way that a lower part (5) is placed below a waterline (4) and an upper part (6) is placed above the water line (4)

- electronic equipment means (7) and a power supply (8)

- positioning sensor(s) (9) such as a GPS/GNSS sensor placed above the water line (4) characterized in

that the buoy assembly (1 ) comprises a substantially rigid tube (10) comprising a first end (1 1 ) and an opposite placed second end (12) and a circumferential wall (24), said tube (10) encloses the electronic equipment (7) and the power supply (8),

said tube (10) is connected to the floating means (3) in a pivotal connection (13) allowing the tube (10) to pivot in relation to the floating means (3) at least in a direction vertical/horizontal such that an above water segment of the tube (10) is adapted to be placed substantially above the water line (4) during towing through the water of the buoy assembly (1 ),

and at least one acoustic sensor (14) is placed inside or outside the tube (10) in a region adapted to be placed below the water line (4) during towing through the water of the buoy assembly (1 ).

A buoy assembly (1 ) according to claim 1 characterized in that an attitude sensor (15) is placed in the tube (10) and is adapted to provide orientation of the tube (10) and resolve the relative locations of the above water segment (16) and below water segment placed sensors. A buoy assembly (1 ) according to claim 1 or 2 characterized in that the electronic equipment means (7) and the power supply (8) all are placed inside the tube (10), and the acoustic sensor is mounted to a below water segment of the tube (10) and close to the second end (12).

A buoy assembly (1 ) according to any of the previous claims characterized in that the tube (10) protrudes through the floating means (3), and the tube (10) is pivotally mounted to the floating means (3).

A buoy assembly (1 ) according to any of the previous claims characterized in that the longitudinal length of the above water segment of the tube (16) is 20-30% of the longitudinal length of the tube (10).

A buoy assembly (1 ) according to any of the previous claims characterized in the buoy assembly (1 ) further comprises power sources (18) such as a solar panel (19) and/or generator wheels (20) for providing power to the power supply (8); said power supply (8) is preferably batteries such as lithium batteries preferably iron lithium phosphate batteries.

A buoy assembly (1 ) according to any of the previous claims characterized in that the tube (10) is made in a metal such as steel or aluminium or made in plastic, fiberglass or carbon fibre.

A buoy assembly (1 ) according to any of the previous claims characterized in the tube (10) is provided with a fairing (21 ) at least in the part of the tube (10) adapted to be placed below the water line (4) and at least at one side of the tube (10). A buoy assembly (1 ) according to any of the previous claims characterized in the tube (10) is provided with several connector devices (22) placed different places at the outside of the tube (10) and for fastening streamers to the buoy assembly (1 ).

0. A buoy assembly (1 ) according to any of the previous claims characterized in that the tube (10) is rigid and does not bend in relation to itself, said tube (10) is 3-6 meter long preferably around 4 meter long.