BACKGROUND

Typically when laying pipe or cable on a seabed, the pipe or cable is positioned in a trench and then covered with sand or stone. The covering of the pipe or cable by stone is predominantly to secure or protect the pipe or cable. When securing the pipe, the stone can be used as weight to counter balance any upward flotation forces and/or displacement of the pipe. Sand or silt are less suitable for securing the pipe, as they are susceptible to forces causing the sand or silt to flow away, leaving the pipe or cable less secure.

Typically, when using stone, it is transported, often over long distances, to the location for dumping by a specially designed vessel for dumping. The dumping of the stone must be executed very precisely to ensure the pipe or cable is not damaged. As this is often done in extremely deep water, an expensive fall pipe installation is often used. Figures la and lb shows a prior art vessel and fall pipe installation dumping stone onto a pipe on a sea bed.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, a method of securing a pipe in a seabed comprises digging a trench in the seabed; laying the pipe and a textile tube in the trench; filling the textile tube with materials from the seabed; and draining water from the textile tube as it is filled. The textile tube sits at least partially on top of the pipe.

This method allows for the use of local materials from the seabed for securing and/or protecting the pipe on the seabed. The textile tube is able to contain local materials, such as sand and/or silt, keeping them at least partially surrounding the pipe for protection and to counteract any flotation forces from pipe.

According to an embodiment, the method further comprises sealing the textile tube.

According to an embodiment, the step of filling the textile tube comprises filling a plurality of chambers within the textile tube with materials from the seabed.

According to an embodiment, the method is performed with a remote operated vehicle. According to an embodiment, the step of filling the textile tube with materials from the seabed comprises connecting a filling connection of the remote operated vehicle to an inlet on the textile tube; and filling the textile tube from the inlet.

According to an embodiment, the method further comprises securing the textile tube to the pipe prior to laying the pipe and textile tube in the trench.

According to an embodiment, the step of securing the textile tube to the pipe comprises securing the textile tube to the pipe with a plurality of straps.

According to an embodiment, the method further comprises aligning the textile tube and pipe so that it is laid with the pipe at the bottom of the trench and the textile tube is on top of the pipe. Optionally, the step of aligning the textile tube and pipe is done with one or more flotation devices. Further optionally, the one or more flotation devices are connected to one or more inlets of the textile tube.

According to an embodiment, the method further comprises inserting one or more additives into the chamber of the textile tube. Optionally, the one or more additives comprises a flocculant. This can help to solidify silt when it is being inserted into the textile tube.

According to an embodiment, the step of digging a trench in the seabed comprises digging a trench and depositing the dug material in proximity to the trench.

According to an embodiment, the stored material in proximity to the trench is used to fill the textile tube with materials from the seabed.

According to an embodiment, the method further comprises disconnecting the ROV from the textile tube.

According to an embodiment, the step of disconnecting the ROV from the textile tube comprises disengaging a filling connection of the ROV from an inlet of the textile tube. Optionally, this can further comprise severing the inlet from the textile tube.

According to a further aspect of the invention, a system for securing a pipe on a seabed comprises a textile tube connectable to a top side of the pipe, the textile tube being flexible and with an inner chamber; an inlet connecting to the inner chamber; and a cutting device able to cut the inlet from the textile tube and seal the textile tube closed. The inlet is able to receive a filling connection from a remote operated vehicle for filling the textile tube.

According to an embodiment, the inlet comprises a flotation device. According to an embodiment, the textile tube further comprises a plurality of straps for connecting to the pipe.

According to an embodiment, the textile tube is permeable.

According to an embodiment, the inlet comprises a cutting unit.

According to an embodiment, the system further comprises a vehicle with a filling connection which can selectively engage the inlet, the vehicle being able to dig a trench on the seabed, pick up materials from the seabed and pump the materials into the inlet of the textile tube to fill the inner chamber of the textile tube. Optionally, this can be a remote operated vehicle.

BRIEF DESCRIPTION OF THE DRAWINGS

Figure la is a perspective view of a prior art vessel dumping stone to cover a pipe on a seabed.

Figure lb is a schematic close-up cross-sectional view of the pipe, stone protection and an end portion of a fall pipe installation of Fig. la.

Figure 2 is a block diagram for a method to cover a pipe using local materials from a seabed.

Figure 3a is a schematic side view of a portion of a pipe and textile tube being lowered to a seabed.

Figure 3b is a schematic cross-sectional view of the pipe and textile tube of Fig.

3a.

Figure 4a shows a schematic side view of a remote operated vehicle connected to the textile tube of Figs. 3a-3b.

Figure 4b shows a schematic top view of Fig. 4a.

Figure 5a shows a schematic end view of a connection for connecting the remote operated vehicle of Fig. 4a to the textile tube of Figs. 3a-4b.

Figure 5b shows a schematic cross-sectional view of a connection between the remote operated vehicle and an inlet of the textile tube. DETAILED DESCRIPTION

Figure la is a perspective view of a prior art vessel 10 dumping stone to cover a pipe 12 in trench 13 on seabed 14, and Figure lb is a schematic close-up cross- sectional view of pipe 12, stone protection 16 and an end portion of a fall pipe installation 18.

Vessel 10 sits above the dumping location, and uses a fall pipe installation 18 to precisely place stone from the vessel 10 onto the pipe 12. This stone forms stone protection 16, which fills in trench 13 and covers and/or at least partially surrounds pipe 12 to protect pipe 12 and secure pipe 12 in place. The placement of the stone must be done precisely and carefully to ensure pipe 12 is not damaged during the process.

As pipe 12 is placed deep under water, in trench 13 dug into seabed 14, the placement of stone is difficult and expensive. While sand and silt or other materials typically found on seabed 14 could be used for the protection and/or securing of pipe 12, the physical properties of this free mass dredged material may be insufficient to counteract flotation forces of pipe, particularly when pipe 12 is filled with gas. Additionally, the sand or silt are susceptible to forces acting on it, such as sea currents causing it to be displaced.

Fig. 2 shows method 20 which enables the use of sand, silt or other local materials found on seabed 14 to be used in protection and securing of pipe 12, without the need for transporting stone from distances away. The method 20 also eliminates the need for a complex or expensive fall pipe installation 18 for placing the stone around pipe 12. Figs. 3a-5b show a system (including devices) which can be used to perform this method.

Method 20 includes the steps of: digging a trench in a seabed (step 22), laying a pipe and textile tube in the trench (step 24), filling the textile tube with local materials from the seabed (step 26), and disconnecting the filling device and closing inlets on the textile tube (step 28).

Step 22, digging a trench 13 in a seabed 14, can be done by, for example, a remote operated vehicle. The trench 13 can be deep enough to hold the pipe 12 and at least some of the textile tube. When digging the trench, the material displaced can be positioned in proximity to the trench 13. This can allow the material to be used later, for filling the textile tube (step 26). The remaining steps of method 20 will be explained in more detail in relation to the system and components shown in Figs. 3a- Figure 3a is a schematic side view of a portion of a pipe 12 and a textile tube 30 being lowered to a seabed 14 (step 24 of Fig. 2), and Figure 3b is a schematic cross- sectional view of pipe 12 and textile tube 30.

Textile tube 30 includes tube chambers 31a, 31b (currently empty in Figs. 3a-3b), straps 32, inlets 34 and flotation devices 36. Textile tube 30 is shaped and/or sized to cover at least a portion of pipe 12 and/or fill in at least a portion of trench 13 (see Figs. 4a-4b). Textile tube 30 is made of a flexible material which is permeable, for example, a woven thermoplastic fiber. Textile tube 30 can be one chamber or many chambers 31a, 31b, as seen in this embodiment. Each chamber 31a, 31b includes an inlet 34 which connects to an interior chamber of textile tube 30. Each inlet 34 includes a flotation device 36, in this case a flotation ring. Using a plurality of chambers 31a, 3 lb, can make textile tube easier to fill and more stable once filled and in position.

In this embodiment, textile tube 30 is connected to pipe 12 with straps 32 before lowering to seabed 14. In other embodiments, textile tube 30 could be lowered separately from pipe 12, and connected to pipe 12 underwater. This could be done using a remote operated vehicle or another device or system.

Flotation device 36 helps to ensure that textile tube 30 and inlets 34 remain upright during the lowering and placement of pipe 12 and textile tube 30 on seabed 14. Keeping the inlets 34 upright enables easier filling of textile tube 30.

Pipe 12 and textile tube 30 can be lowered and properly position in trench 13 using, for example, the remote operated vehicle used in digging trench 13. Alternatively, other devices or systems could be used for lowering and/or placement of pipe 12 and textile tube 30.

Figure 4a shows a schematic side view of a remote operated vehicle 38 connected to textile tube 30 for filling textile tube 30 (step 26 of Fig. 2), and Figure 4b shows a schematic top view of remote operated vehicle 38 and the connection to textile tube 30.

Figs. 4a-4b include pipe 12, trench 13, seabed 14, textile tube 30 with chamber 31, inlet 34 and remote operated vehicle 38 with pump 40, dredging portions 42, filling hose 44 with filling connection 46, and reservoir 47.

Remote operated vehicle 38 (hereinafter "ROV") can be used for digging the trench and/or filling textile tube 30. Dredging portions 42 can be used for both digging the trench and recovering materials from seabed 14 for filling textile tube 30. Filling hose 44 connects to inlet 34 of textile tube 30 through filling connection 46 (seen and discussed in more detail in relation to Figs. 5a-5b), and can be, in some embodiments, a quick connection. Materials can then be transported through filling hose 44 and inlet 34 to interior chamber 31 of textile tube 30. The materials used to fill textile tube 30 can be the materials removed while digging trench 13 or other materials found locally on seabed 14. In some cases, ROV 38 can inject one or more additives stored in reservoir 47, for example, flocculant can be added to silt to help solidify silt in interior chamber 31 of textile tube 30. Due to the permeable material used to form textile tube 30, as materials fill chamber 31, textile tube 30 will allow liquid to exit or bleed through textile tube 30 walls. This ensures that textile tube 30 fills entirely with sand or silt (or whatever other material is inserted into chamber 31) to cover and/or protect pipe 12.

Figure 5a shows a schematic end view of filling connection 46, and Figure 5b shows a schematic cross-sectional view of filling connection 46 connecting to inlet 34 of textile tube 30. Filling connection 46 includes flotation ring 48 and thrusters 50.

Flotation ring 48 and thrusters 50 help to bring filling connection 46 into proper alignment with an inlet 34 for filling a chamber 31 of textile tube 30. Additionally, when textile tube 30 is formed of multiple chambers, flotation ring 48 and thrusters 50 can help filling connection 46 move away from one chamber (when full) to another inlet 34 to start the connection and then filling process of another chamber.

Inlet 34 includes flotation ring 36, clamping mechanism 52, and cutting unit 54. Clamping mechanism 52 can be used to ensure that filling connection 46 connects securely to inlet 34 and stays connected throughout the time that materials are being transferred through filling hose 44 into textile tube 30.

Cutting unit 54 can be used sever the connection between textile tube 30 and

ROV 38 and/or to seal textile tube 30, and sever inlet 34 from textile tube 30. Cutting unit 54 can be, for example, a temperature wire for severing inlet 34 by melting the material of textile tube 30 and sealing interior chamber 31 shut in the process. Alternatively, cutting unit 54 could be a mechanical device for cutting and then sealing or any other device which is able to sever inlet 34 from textile tube 30 and seal interior chamber 31. Once inlet 34 has been severed from textile tube 30, flotation device 36 causes inlet 34 to float to the surface for collection. As discussed above in relation to Figs. 2-5b, through the use of textile tube 30, sand, silt and/or other local materials from seabed 14 can be used to secure and protect pipe 12. A trench 13 can be dug for receiving pipe 12, and then pipe 12 and textile tube 30 can be positioned in trench 13. Inlets 34 of textile tube 30 can include flotation devices 36 to ensure that textile tube 30 and inlets 34 are properly positioned during the lowering and placement, and are easily accessible for filling. A filling connection 46 connected to a ROV 38 can align (using flotation device 48 and thrusters 50) to connect to inlet 34 of textile tube 30, and can be secured to inlet 34 through clamping mechanism 52. ROV 38 can use dredging portions 42 to dredge materials from seabed 14 (in some cases materials removed from trench 13), and pump 40 pumps the material through filling hose 44 and into inlet 34 connecting to interior chamber 31 of textile tube 30. In some cases, an additive (stored in reservoir 47) can be added to the pumped material. The material fills interior chamber 31, causing textile tube 30 to expand and at least partially cover pipe 12 and/or fill in trench 13. Liquid from chamber 31 will exit walls of textile tube 30 due to the permeable materials, and eventually chamber 31 will be mostly or entirely filled with material. At this point, clamping mechanism 52 can release filling connection 46, and thrusters 50 can move filling connection 46 to connect to and fill another chamber. Cutting unit 54 can then sever inlet 34 from textile tube 30 and seal chamber 31, so as to keep materials in chamber 31 from escaping. Inlet 34 will float to a surface of the water body due to flotation device 36, allowing for collection and possible reuse.

The method and system of Figs. 2-5b allow for the use of local materials in the covering, securing and/or protection of pipe 12 without the need for the expensive and complicated task of transporting stones to the location and precisely placing them on pipe 12 using a fall pipe installation 18 (as done in past systems). By using textile tube 30; sand, silt and/or other local materials from seabed 14 can be used to protect and secure pipe 12 in place, as textile tube 30 contains the local materials in the desired place, over pipe 12. The weight of local materials inside chambers 31 of textile tube 12 is able to counteract any floating forces in pipe 12 (particularly when pipe 12 contains gas), and the flexibility of textile tube 30 allows textile tube 30 to position itself at least partially around pipe 12 for protection. The permeability of textile tube 30 allows for a high density of local materials to be transported into chambers 31 of textile tube 30, further protecting and securing pipe 12. The containment of sand, silt and/or other local materials by textile tube 30 simulates the properties of stones used in past systems, without requiring the importation of stone.

ROV 38 with filling connection 46 provides an efficient and easy way to connect to an inlet 34 of textile tube 30 and transport materials from seabed 14 into chambers 31. Thrusters 50 and flotation device 48 help filling connection 46 to easily be moved into position to connect to an inlet 34. Clamping mechanism 52 allows for a quick securing (and subsequent detachment) of filling connection 46 to inlet 34. Additionally, ROV 38 could be used to dig trench 13, place materials from trench 13 nearby and then use those same materials for the filling of textile tube 30, eliminating a need for multiple or different devices for different parts of the process.

Flotation rings 36 of inlets 34 keep inlets 34 upright for easy access to inlets 34 for alignment of filling connection 46. Cutting unit 54 allows for sealing and removal of inlets 34 once chambers 31 of textile tube 30 are full, thereby ensuring that the materials within textile tube 30 stay in place for protecting and securing pipe 12, and allowing for reuse of inlets 34. In summary, by using textile tube 30, sand, silt and/or other local materials from seabed 14 can be used to cover pipe 12, significantly reducing the investment in transport and dumping of stone required in past systems.

While Figs. 2-5b show a pipe 12, the system could be used to cover a cable or another subsea installation. Additionally, pipe 12 does not have to be laid in a trench 13, and could be simply placed on seabed 14 before using textile tube 20 to protect and secure it.

While Figs. 2a-2b show the lowering of pipe 12 and textile tube 30 together, in other embodiments, pipe 12 and textile tube 30 could be lowered separately, and then connected, for example with the help of the remote operated vehicle 38.

While the invention has been described with reference to exemplary embodiments, it will be understood by those skilled in the art that various changes may be made and equivalents may be substituted for elements thereof without departing from the scope of the invention. In addition, many modifications may be made to adapt a particular situation or material to the teachings of the invention without departing from the essential scope thereof. Therefore, it is intended that the invention not be limited to the particular embodiments disclosed, but that the invention will include all embodiments falling within the scope of the appended claims.