NO345544B1

NO345544B1 - System for deploying and recovering seismic ocean bottom nodes from a ship or platform equipped with ROVs

Info

Publication number: NO345544B1
Application number: NO20191169A
Authority: NO
Inventors: Mikhail Makhorin
Original assignee: Mikhail Makhorin
Priority date: 2019-09-30
Filing date: 2019-09-30
Publication date: 2021-04-12
Also published as: NO20191169A1

Description

Technical field

The technical field of the invention is off-shore technology, more specifically it relates to a system for distribution of seismic nodes on the ocean floor.

Abbreviations:

NOAR Nodes on a Rope

NOAW Nodes on a Wire

ROV Remotely Operated Vehicle

LARS Launch And Recovery System

AHC Active Heave Compensation

TMS Tether Management System

Background

Ocean Bottom Nodes are used for Seismic surveys in congested areas, or in areas that require a higher quality of Seismic image than typically acquired using towed streamer techniques.

Handling of the Nodes from vessels is normally 1 of 2 techniques:

1. Nodes on a Rope or Wire, typically abbreviated to NOAR or NOAW.

2. Nodes handled by ROV(s)

This invention is specifically related to the ROV application. When deploying the nodes on the ocean floor using a ROV it is common practice to load the skid of the ROV and deploy all the nodes in the skid and then return to surface for new load of nodes. Time is lost during the travel of the ROV from the ocean floor to the ship for reloading and back to the ocean floor. If the survey is done on deeper locations, it is common practice to lower baskets with nodes to the ocean floor from which the ROV may reload nodes when the nodes in the skid are distributed. Often this involves mounting a new offshore crane on the survey ship for handling the node basket because this cannot be coupled directly to the offshore cranes handling the ROVs. Here time is lost during mounting of extra equipment on the ship or platform equipped with ROVs and also it might be problematic to couple the ROV to the basket when it is on the ocean floor.

Another problem related to using other cranes that may not be equipped with latching snubbers that are compatible with the basket, is swinging suspended loads which can be a hazard to deck crew.

The current invention minimizes the loss of time and operational risk in all of the mentioned situations.

WO 2018204084 A1 describes systems and methods, for deploying ocean bottom seismic nodes. Two or more underwater vehicles may be deployed by a surface vessel and each connected to the surface vessel by a ROV deployment line. A catenary shape of each ROV deployment line may be modeled for more accurate and efficient subsea ROV operations. Real-time modeling and predictive modeling of the catenary shape of the deployed lines may be performed, and the surface vessel and/or ROVs may be positioned based on the modeled catenary shapes. The ROVs may be automatically positioned and/or controlled based on commands from a dynamic positioning (DP) system. An integrated navigation system (INS) may be located on the surface vessel and directly coupled to the one or more DP systems. The surface vessel may travel backwards during deployment operations and deploy one or more subsea baskets astern from the ROVs.

US 2017235005 A1 relates to a method for seismic survey by autonomous seismic nodes at a sea floor, comprising: —attaching the seismic nodes to a rope; —loading the rope with the seismic nodes into a node deployer; — lowering the node deployer into the sea; —towing the node deployer above the sea floor; —deploying the rope with the seismic nodes at the sea floor; —collecting seismic data by the seismic nodes; —retrieving the rope with the seismic nodes from the sea floor, and —unloading seismic data from the seismic nodes. The invention also relates to a node deployer for deploying a rope with seismic nodes at the sea floor, comprising a magazine for the rope with the seismic nodes.

US 2019265378 A1 describes a system, apparatus, and method for individually identifying, handling, tracking, deploying, and recovering a plurality of seismic nodes by an underwater vehicle for subsea operations. The deployment and positioning and retrieval of seismic nodes to and from the seabed may be managed automatically by software and/or manually automated by an ROV operator. The disclosed system may be coupled to a ROV navigation system. The node identification system tracks the position of each seismic node (associated with a unique identification number) within each tray or other node holder at all times, whether the tray is located on board a surface vessel, within an ROV, within a subsea basket, or on the seabed. The identification system is configured to track, select, deploy, and recover a particular seismic node by its unique identification number.

US 2016214694 A1 describes an apparatus for deploying and retrieving seismic nodes comprises a towing connection connecting the apparatus to a towing cable running from a towing vessel; vertical control means for adjusting a height over the seafloor by means of the towing cable; horizontal control means for adjusting a horizontal position according to the desired path and deployment and retrieval means for deploying and receiving nodes connected to a wire at predetermined intervals along the path. The deployment means are preferably configured to deploy the nodes without substantial pull from the previously deployed wire.

Summary of the invention

In a first aspect the invention describes a system for deploying seismic ocean bottom nodes from a ship. The system comprises at least one ROV crane, which is a standard active heave compensated ROV Launch and Recovery Systems (LARS) comprising a load carrying umbilical and a Tether Management System (TMS) for launching and recovering a ROV, wherein the LARS is positioned on the ship. The system further comprise at least one ROV with a skid designed for handling ocean bottom nodes and having a hydraulic system for external power use, and wherein the ROV is connected to the mentioned at least one standard ROV LARS. The system further comprise at least one basket crane, which is a ROV Launch and Recovery Systems (LARS) positioned on the ship at a distance from the ROV LARS to avoid entanglement and a node basket attached to the basket crane. One or both of the ROV and basket must comprise a locking system for coupling the basket and the ROV and transfer means for transferring the nodes from the basket to the ROV and back again, and wherein the basket crane is active heave compensated (AHC) and directly attached to the basket, or the crane is attached to a TMS, which in turn is attached to the basket, thus enabling the basket to remain relatively still in the water independent of vertical wave heave action.

In a second aspect the invention describes a method according to claim 6 for deploying and recovering seismic ocean bottom nodes from a ship using the system according to claim 1.

Short description of drawings

For better understanding of the invention the device will be described with reference to the figures. Like numerals describe like parts in the different figures. The figures illustrate examples of the invention.

Figure 1 shows the system with a ROV and a basket in crane with AHC. Figure 2 shows the system with a ROV and a basket in a crane with a TMS. Figure 3 shows the system with the ROV coupled to the basket for transfer of nodes.

Detailed description

The invention describes a system for deploying seismic ocean bottom nodes 7 from a ship 9 for the purpose of seismic surveying. In order to ease the language we use the terms ‘ROV crane 5’ and ‘basket crane 10’. The two terms are defined in the text below.

The basic idea is to use existing ROV handling cranes already on the ship and to couple a basket to a ROV handling crane and coupling a basket to a ROV in the water column. If this is done, all the modifications needed is done on the basket and ROV, which means that it is not necessary to hire the entire survey vessel for extended time when modifying the equipment. In addition we increase the efficiency of the distribution itself, further reducing costs, mainly in the form of hire of vessel and labor cost.

Especially at greater depth the savings on process efficiency can be significant because the ROV do not have to wait for the basket, but are able to meet the basket on its way down and due to the proximity of the launch points and similar drag characteristics they arrive at similar in lnline and crossline locations.

The system comprises at least one ROV crane 5, which is a standard active heave compensated ROV Launch and Recovery Systems (LARS) 5 comprising a load carrying umbilical 6 and a Tether Management System (TMS) 4 for launching and recovering a ROV 1, wherein the LARS is positioned on the ship 9. The system further comprises at least one ROV with a skid 2 designed for handling ocean bottom nodes and having a hydraulic system for external power use, and wherein the ROV is connected to the mentioned at least one standard ROV LARS 5.

The system further comprises at least one basket crane 10, which is a ROV Launch and Recovery System (LARS) 10 positioned on the ship at a distance from the ROV crane 5 to avoid entanglement. The system also comprises a node basket 3 attached to the basket crane 10, wherein one or both of the ROV and node basket comprises a locking system 11 for coupling the node basket to the ROV and transfer-means for transferring the nodes from the node basket 3 to the ROV 1 and back again. Preferably the basket crane 10 is active heave compensated (AHC) and the basket is equipped with positioning means and attached to a TMS hanging from the basket crane 10. This will enable the basket to remain vertically still in the water independent of wave heave action. The reason for this is that the ROV must encounter a reasonably steady node basket in order to be able to couple the ROV and the basket. In one embodiment the TMS is used for powering the basket using hydraulic or electrical power and provide electrical control and communication to cameras and sensors. Preferably the basket is connected to the TMS by an industry standard docking bullet.

In one embodiment the transfer means for transferring the nodes is a travelling gantry with suction tools attached. Other embodiments include use of a conveyor or a moving arm with a suction tool. Many options are found in the market and will not be described in detail.

In one embodiment the locking system 11 for coupling the basket to the ROV is an arm fastened to the ROV with a releasable click-on structure 11 at the outer end and a mating structure on the basket. Again, many options are found in the market and will not be described in detail.

In a preferred embodiment the ROV is powered by DC electrical batteries driving electrical thrusters. When the ROV is powered by batteries, the ROV may be attached to the TMS with a small diameter tether with digital communication for video, control and survey peripherals only, saving the weight of the relatively heavy power conductors.

In another embodiment the ROV is powered by AC electrical power driving an electro/hydraulic system to provide fluid power to hydraulic thrusters.

In order to operate the system we describe a method for deploying seismic ocean bottom nodes from a ship using the system described. The method comprises the following steps:

a) loading a first set of nodes into the skid of the ROV attached to a standard active heave compensated ROV Launch and Recovery Systems (LARS) comprising a load carrying umbilical and a Tether Management System (TMS) for launching and recovering the ROV. Here we define ‘a set’ as the set of nodes that are loaded into the skid of the ROV or the basket.

b) lowering the ROV to working depth,

c) launching the ROV from the TMS when working depth is achieved,

d) loading the basket with a further set of nodes on deck,

e) lowering the basket to a transfer depth of the ROV,

f) coupling the ROV to the basket when the prior set of nodes is distributed, wherein the coupling is carried out with aid of the locking system 11,

f) transferring the nodes from the basket to the skid of the ROV by aid of the transfer means and disconnect when transfer is complete,

g) hoisting the basket to the deck and repeat from c) with further sets while the ROV is deploying the nodes on the ocean floor,

h) recovering nodes after completion of survey,

i) connecting the ROV to the basket and transfer the nodes from the ROV to the basket when the basket has a full or partial load and disconnect when transfer complete,

j) hoisting the basket to the deck and unload while the ROV returns to step h if recovery is not complete.

In one embodiment the basket may be powered from the ROV by engaging a hot stab hydraulic connection to power the basket from the ROV hydraulic system.

It is also conceivable that the basket has a spare charged battery for the main power for the ROV and that the transfer means also has a system for exchanging the batteries such that the depleted battery can be returned to the surface and be recharged as a part of the Node transfer operation.

Inventory

1 ROV

2 Skid

3 Node basket

4 TMS

5 ROV crane

6 Load carrying umbilical

7 Seismic nodes

8 Node storage

9 Survey ship

10 Basket crane

11 Locking system

Claims

1. System for deploying seismic ocean bottom nodes (7) from a ship (9) comprising:

at least one ROV crane (5), which is a standard active heave compensated ROV Launch and Recovery Systems (LARS) (5) comprising a load carrying umbilical (6) and a Tether Management System (TMS)(4) for launching and recovering a ROV (1), wherein the LARS is positioned on the ship (9),

at least one ROV with a skid (2) designed for handling ocean bottom nodes and having a hydraulic system for external power use, and wherein the ROV is connected to the mentioned at least one standard ROV LARS (5),

at least one basket crane (10), which is a ROV Launch and Recovery Systems (LARS) (10) positioned on the ship at a distance from the ROV LARS (5) to avoid entanglement,

a node basket (3) attached to the basket crane (10),

wherein one or both of the ROV and basket must comprise:

a locking system (11) for coupling the basket and the ROV, transfer means for transferring the nodes from the basket (3) to the ROV (1) and back again, and

wherein the basket crane (10) is active heave compensated (AHC) and directly attached to the basket, or the crane (10) is attached to a TMS ,which in turn is attached to the basket, thus enabling the basket to remain relatively still in the water independent of vertical wave heave action.

2. System according to claim 1, wherein the means for transferring the nodes is a travelling gantry with suction tools attached.

3. System according to claim 1, wherein the locking system (11) for coupling the basket to the ROV is an arm fastened to the ROV with a releasable click-on structure at the outer end and a mating structure on the basket.

4. System according to claim 1, wherein the ROV is powered by DC electrical batteries driving electrical thrusters.

5. System according to claim 1, wherein the ROV is powered by AC electrical power driving a electro/hydraulic system to provide fluid power to hydraulic thrusters.

6. System according to claim 5, wherein the ROV is attached to the TMS with a small diameter tether with digital communication for video, control and survey peripherals.

7. Method for deploying and recovering seismic ocean bottom nodes (7) from a ship using the system according to claim 1, wherein the system comprises the steps:

a) loading a first set of nodes (7) into the skid (2) of the ROV (1),

b) launching the ROV from a standard active heave compensated ROV Launch and Recovery Systems (LARS) comprising a load carrying umbilical (6) and a Tether Management System (TMS) (4) for launching and recovering a ROV,

c) loading the basket (3) with a second set of nodes (7) on deck,

d) lowering the basket to the working depth of the ROV,

e) connecting the ROV (1) to the basket (3) when the first set of nodes (7) is distributes wherein the connection is carried out with aid of the locking system (11),

f) transferring the nodes (7) from the basket (3) to the skid (2) of the ROV (1) by aid of the transfer means and disconnect when transfer is complete,

g) hoisting the basket (3) to the deck and repeat from c) with further sets while the ROV is deploying the nodes (7) on the ocean floor,

h) recovering nodes (7) after completion of survey,

i) connecting the ROV to the basket and transfer the nodes from the ROV to the basket when the basket has a full or partial load and disconnect when transfer is complete,

8. Method according to claim 7 characterized in that step e) is followed by the step of engaging a hot stab hydraulic connection to power the basket from the ROV Hydraulic system.