OCEAN BOTTOM SEISMIC NODE SYSTEM

Abstract

There is described a system for deploying and retrieving seismic nodes on the seabed. The system uses a modular container that can be connected to a ROV. The container includes a magazine for storing a number of individual nodes, as well as having means for moving the nodes through the magazine onto the seabed.

Claims

1. A system for deploying and retrieving seismic nodes from the seabed using an ROV, wherein the nodes are stored in a modular container, the modular container being releasably connected to the ROV and that the modular container is configured to deploy nodes onto the seabed.

2. The system according to claim 1, wherein the modular container houses a revolver magazine in which the nodes are stored.

3. The system according to claim 2, wherein the modular container comprises means for turning the revolver magazine.

4. The system according to claim 2, wherein the modular container comprises openings for entering and/or exiting nodes.

5. The system according to claim 2, wherein the modular container comprises buoyancy tanks.

6. The system according to claim 1, wherein a retriever module is configured to be attached to the ROV, wherein the retriever module comprises means for connecting to the modular container.

7. The system according to claim 6, wherein the retriever module comprises a scoop that is configured to pick up modules from the seabed.

8. The system according to claim 6, wherein the retriever module comprises means for moving the nodes into the modular container.

9. The system according to claim 6, wherein the retriever module comprises means for reorienting the nodes before loading them into the modular container.

10. The system according to claim 6, wherein the retriever module comprises means for reading a label on the node containing node identification.

11. The system according to claim 6, wherein the retriever module comprises means to clean the node.

12. The system according to claim 10, wherein the node identification is stored together with data on pickup location.

13. A method for deploying seismic nodes in an array on the seabed, using a node deployment system according to claim 1, comprising the following operations: recording the speed and direction and altitude and position of the ROV, moving a node to an end of the magazine, and releasing the node when data indicates that the ROV has reached a correct position.

14. The method according to claim 13, wherein identifying labels on the nodes are read during retrieval and stored with location data.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0031] FIG. 1 shows an ROV to be used with the invention,

[0032] FIG. 2 also shows an ROV,

[0033] FIG. 3 shows a revolver module according to the invention,

[0034] FIG. 4 shows the revolver module from the reverse side,

[0035] FIG. 5 is a section drawn along line A-A on FIG. 3,

[0036] FIG. 6 shows a node retriever according to the invention,

[0037] FIG. 7 shows the node deployer from the reverse side, showing thrusters for propulsion internal parts,

[0038] FIG. 8 shows a detail of the retriever module,

[0039] FIG. 9 shows yet another detail of the retriever module,

[0040] FIG. 10 also shows a detail of the retriever module, with the revolver module attached,

[0041] FIG. 11 shows another detail of the retriever module, and

[0042] FIG. 12 shows a ROV deployer deployment and recovery on deck arrangement.

[0043] In FIG. 1 there is shown a ROV 10 having a front end 12 and a rear end 14. At the rear end of the ROV there is arranged thrusters 15 for propulsion. The ROV may be an autonomous ROV or be controlled using an umbilical, as is well known. In FIG. 1 there is also shown a node retriever module 30 and a node containing module 50 attached to the underside of the ROV. At the front of the retriever module is shown a scoop 32 which purpose will be described later. The node containing module also has means to enable nodes to be deployed onto the seabed.

[0044] FIG. 2 shows the ROV with side hatches 16, 17 open to show buoyancy tanks 18 that is part of a variable buoyancy system. Such system is used to trim the ROV to compensate for the variations in loads when deploying or retrieving modules.

[0045] FIG. 3 shows a node module according to the invention being in the form of a container 50 with a housing 51 for structural strength. The module comprises a front end 52 and a rear end 54. It also has means (not shown) for coupling the module to the ROV. Inside the module there is a magazine 56 for storing nodes. In the preferred embodiment the magazine is a revolver magazine that has compartments for storing nodes. Several nodes can be stored end to end along its length and the revolver can be rotated to bring a compartment in line with an exit or entry opening. In FIG. 3 there is shown an entry opening 57 to receive nodes from the retrieval module. This will be explained in more detail later. In FIG. 4 there is shown the exit opening 58 for deploying nodes onto the seabed.

[0046] The magazine facilitates loading and unloading of a large number of nodes. The nodes are loaded into the magazine on a vessel or prepared beforehand on land. The modularity allows for fast exchange of modules on the vessel deck (ref. FIG. 11).

[0047] The magazine can have a length sufficient to store many nodes end to end. It also preferably be equipped with a transport system for moving nodes towards the exit 58. This will be explained in more detail later.

[0048] In FIG. 5 there is shown the structure of the revolver magazine 56. The magazine rotates on rollers 67 driven by motors (not shown). The magazine has a generally circular shape with compartments 62 arranged along its periphery. The nodes 70 are stored end to end in the compartments 62. A transport system 64 moves individual nodes along the length of the compartments 62. This transport system may be a belt such as a ladder wire-belt with side support. When the drum is turning the node 70 will lift and slide on the belt. The drum motor will have enough torque rotate the drum with the nodes sliding on the belt. To avoid the sides of the compartments 62 touching the belt the revolver magazine may be rolling on a cam profile to slightly lift the drum between each rows.

[0049] A second alternative is to use a belt with brushes to push the nodes. When rotating the drum the fingers bend away. The fingers will also bend away when the node is transported at end of the row.

[0050] Buoyancy tanks 65 are located inside the module. The purpose of these are to compensate for the weight of the module in water. Preferably the buoyancy is arranged so that the module is neutral when half full of nodes.

[0051] FIG. 6 shows the retriever module 32. It comprises a frame 31 open at the top, sides 34, 35 and a front that has doors 36, 37 that can open to give access to the interior. In the front there is a scoop 32 for retrieving nodes lying on the seabed. FIG. 7 shows the interior of the retriever module. It has an observer system 38 with lights and camera to show an operator the inside of the module during observations. There is also a manipulator 39 for manual handling of nodes if necessary. An electronics unit controls the operations inside the module. A conveyor belt 42 or other transport means can move the nodes that have been scooped up from the seabed towards the deployer module.

[0052] The belt 42 may consists of several individual belts independently controlled. This enables the nodes 70 to be reoriented if they are scooped up with an incorrect orientation (as shown in FIG. 8). Angled guides 45 ensures that a node will slide down towards the belt 42. Angled deflectors 42, 44 is intended for guiding the nodes towards the belt(s). If the nodes still are not in the correct position the manipulator may be used to lift and reorient the nodes. The nodes may be equipped with labels and a reader 46 is arranged near the belt to read the label and thus identify the node being picked up from the seabed.

[0053] FIGS. 10 and 11 show yet more detail of the retriever module. The nodes being picked up by the scoop 32 will be loaded onto the belt and moved towards the entrance 57 of the node module 50. The node module may have transport means for moving the loaded nodes towards the front end of the node module. When the magazine is full, the drum can be rotated to align empty compartments with the entrance 57 for loading yet more nodules. Preferably the drum is rotated by around 180° at each step to balance the loads.

[0054] FIG. 12 shows a launch and recovery system for the use of exchanging modules and launching and loading the ROV. Node modules 50 are placed on a movable deck 80. When a ROV has been retrieved from the sea it is held by a crane in a correct position both horizontally and vertically to change out modules. The module 50′ on the ROV is released and when a new module 50 is moved towards the ROV the module 50 will push the old module 50′ out of the ROV and onto a stationary deck 84 and the new module 50 coupled to the ROV. The old module 50′ can now be filled with new nodes and made ready for another trip or, if the ROV has retrieved nodes that has recorded seismic activity the nodes will be taken out from the module and analyzed for seismic data.

[0055] With the invention a large number of nodes can quickly be placed on the seabed. Also the retrieval of nodes from the seabed can be done more efficiently and faster than hitherto has been the case.

[0056] Using the transport means in the node deployer module and coupled with information about the movements of the ROV, nodes can be positioned accurately on the seabed, that is at required spatial intervals. This is achieved by monitoring the speed and direction and altitude and position of the ROV and using the transport means on the node deployer to push the node out of the deployer at the correct time to ensure accurate landing position.

[0057] To more accurately positioning individual nodes onto the seabed, information about the position and speed of the ROV is used to calculate when a node should be dropped off. Then the transporting means inside the node module is operated to deploy a node onto the seabed. During this operation the coordinates of the drop-off location is recorded and stored in a computer. This will more quickly enable nodes to be retrieved again.

[0058] The retriever module comprises means to read off the identifying label on the node(s). This information is also stored in a computer and may be used when performing the calculations for the seismic data map(s). The retriever module may also have means for cleaning the node(s) (not shown).