Patent Application
20250236361
This application claims priority to and benefit of Norway patent application Ser. No. 20/240,060, entitled “Device for Tethering Equipment to the Floor of a Body of Water,” filed Jan. 24, 2024, which is herein incorporated by reference in its entirety.
Off-shore energy production systems such as off-shore oil & gas production systems may include devices or equipment, which are spaced from the main subsea installations, but which, nevertheless, are needed to be retained in a specific subsea location relative to the main subsea installations. Such devices could include wireless communications devices. Such devices are, however, vulnerable to damage from other marine vessels, or the gear suspended from such vessels. They are particularly vulnerable to damage from fishing gear being dragged through the water by a trawler or other fishing vessel.
As such, it is known to mount such devices inside or underneath a protective structure, which is installed on the seabed and designed to withstand the forces from fishing gear without deflecting or sustaining any significant damage.
Publications that may be useful to understand the background include GB2355034, WO98/04805, GB2426266, and WO 2021/173000. The latter discloses a structure for permitting over trawling of subsea equipment in which a protective body is mounted on a support arrangement installed on the sea bed, the structure being configured such that limited movement of the protective body relative to the support arrangement is permitted to occur when the protective body is subjected to lateral forces from fishing gear.
According to a first aspect of the disclosed technology we provide a device suitable for tethering equipment to the floor of a body of water, the anchor device comprising a support structure which is configured to house or support subsea equipment, a stiff elongate tethering element which has a first end on which the support structure is mounted and a second end which is provided with a connector for securing the anchor device to the floor of the body of water, wherein a first end of the device, comprising the support structure and the first end of the tethering element, is more buoyant than the second end of the device, wherein a first end of the device, comprising the support structure and the first end of the tethering element is more buoyant than the second end of the device; wherein the support structure comprises a hollow or at least partially hollow shell, wherein the support structure is configured to support equipment inside the shell.
In one embodiment, the support structure is buoyant.
In one embodiment, the tethering element comprises a rod. The rod may be generally cylindrical.
In one embodiment, the connector is flexible such that when the device is secured to the floor of the body of water via the connector angular movement of the tethering element relative to the floor of the body of water is permitted.
In one embodiment, the connector comprises two chain links.
In one embodiment, the support structure has a smooth outer surface.
In one embodiment, the support structure is generally spherical.
According to a second aspect of the disclosed technology we provide a subsea anchor system including a device according to the first aspect and a weight resting on the floor of the body of water, the second end of the tethering element being secured to the weight by means of the connector.
According to a third aspect of the disclosed technology we provide a subsea hydrocarbon production system comprising a device according to the first aspect, and a piece of subsea equipment mounted on or in the support structure.
The second end of the tethering element may be secured to sea bed via a weight.
Alternatively, the system may comprise a subsea installation which is located on the sea bed, and the second end of the tethering element secured to the sea bed via the subsea installation.
These and other characteristics will become clear from the following description of illustrative embodiments, given as non-restrictive examples, with reference to the attached drawings, in which:
The following description may use terms such as “horizontal,” “vertical,” “lateral,” “back and forth,” “up and down,” “upper,” “lower,” “inner,” “outer,” “forward,” “rear,” etc. These terms generally refer to the views and orientations as shown in the drawings and that are associated with a normal use of the disclosed system and device. The terms are used for the reader's convenience only and shall not be limiting.
A first end of the device 10, comprising the support structure 14 and the first end of the tethering element 18, is more buoyant than the second end of the device 10, so that when the second end 18b of the tethering element 18 is secured to the floor of the body of water, the support structure 14 is elevated above the second end of the tethering element 18b. This may be achieved by fabricating the tethering element such that its first end has a lower specific gravity than its second end 18b. For example, the first end 18a of the tethering element could have a specific gravity of less than 1, whilst the second end 18b of the tethering element has a specific gravity of more than 1. It could equally be achieved by securing a buoyant floatation device to the support structure 14 or the first end 18a of the tethering element 18. In this example, however, the buoyancy of the first end of the device 10 is achieved by using a buoyant support structure 14, whilst the tethering element 18 has a generally uniform specific gravity of greater than 1. In this embodiment, the tethering element 18 comprises a generally cylindrical rod. The tethering element 18 may be made from fibre-glass, or a polymeric material.
The connector 20 is flexible such that when the anchor device 10 is secured to the sea bed 12 via the connector 12, angular movement of the tethering element 18 relative to the sea bed 12 is permitted, as illustrated in
In this example, the connector 20 comprises two chain links 20a, 20b. The connector 20 could equally, however, comprise a cable or rope.
Advantageously, the support structure 14 has a smooth outer surface, with no vertices, edges or other sharp discontinuities in the surface topography. In this embodiment, the support structure is generally spherical, but it could equally form an ellipsoid or torus.
Also, in this embodiment, the support structure 14 is buoyant, and comprises a hollow shell, and is configured to support equipment 16 inside the shell. The equipment 16 could, equally be mounted on the exterior of the support structure 14.
The support structure 14 could equally be only partially hollow, and partially filled with a buoyant material such as a polymeric or ceramic foam. The support structure 14 could equally be entirely filled with such a buoyant material, and the equipment 16 mounted on the exterior of the support structure 14.
The anchor device 10 is, in this embodiment, secured to the sea bed 12 by means of a clump weight 22, which is resting on the sea bed 12, the second end 18b of the tethering element 18 being secured to the weight 22 by means of the connector 20. To facilitate this, the weight 22 is provided with a connection loop 22a. The first chain link 20a of the connector 20 is secured to the second end of the tethering element 18, whilst the second chain link 20b passes through the first chain link 20a and the connection loop 22a.
The anchor device 10 may be used in a subsea hydrocarbon production system 24, and the piece of equipment 16 mounted on or in the support structure 14 be subsea equipment, which is required for operation of the subsea production system, but which needs to be separated from the main subsea installations 26 of the production system such as the Christmas tree, well template, production manifold etc., and, perhaps held at a higher point above the sea bed 12. Such a production system is illustrated schematically in
The anchor device 10 could equally be secured to the sea bed 12 by securing the connector 20 to an anchor, which is embedded in the sea bed, such as a pile or suction anchor. Where the device 10 is used in a subsea hydrocarbon production system, the connector could equally be secured to one of the subsea installations in the production system, such a Christmas tree, manifold, template, pipeline end termination, pipeline end manifold, or subsea distribution manifold.
An alternative embodiment of subsea hydrocarbon production system is illustrated schematically in
By virtue of the use of a flexible connector, when fishing gear is dragged over the anchor device and exerts a generally horizontal force on the support structure 14, the tethering element 18 pivots relative to the sea bed 12 as illustrated in
By virtue of providing a stiff or rigid tethering element 18 (as opposed to connecting the support structure 14 to the weight 22 with an entirely flexible element such as a rope, chain or cable, the risk of the tethering element 18 becoming entangled in the fishing gear may be reduced. The connector 20 could be longer than that illustrated, but is ideally significantly shorter than the tethering element 18 to minimize the risk of entanglement. The use of a chain as the connector 20 may assist in returning the support structure 14 to the desired heading, after it has been deflected.
Configuring the support structure with a generally smooth exterior surface (i.e., having no vertices, edges or sharp discontinuities in the surface topography) may assist in minimizing the risk of the support structure becoming snagged on the fishing gear.
The disclosure is not limited by the embodiments described above; reference should be had to the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 20240060 | Jan 2024 | NO | national |
