BACKGROUND OF THE INVENTION

Technical Field

An autonomous data acquisition node, system and method are disclosed. The data may be marine or more particularly submarine data, including but not limited to one or more of seismic data and other data.

Description of the Related Technology

The genesis of the disclosed node, system and method stems from considering the quality and cost of acquiring marine seismic data. The acquisition of marine seismic data (also known as marine seismic surveying) is a critical initial phase in the exploration of offshore energy or mineral reserves.

One marine seismic surveying technique involves the use of a marine survey vessel to tow a seismic source and sensors through a body of water over a survey area whilst actuating the seismic source at selected intervals of time. The seismic source generates seismic waves which travel through the body of water and the subsurface generating reflection and refractions at interfaces associated with geological layers and formations. The reflected waves are detected by the sensors being towed by the vessel. Thus, there is a hydraulic coupling of the seismic energy from the seabed and underlying geology to the sensors.

In an alternate technique, seismic sensors are physically laid on the seabed to detect seismic energy which emanated from a controlled source and is subsequently reflected by the seabed and underlying geology. In this method there is a mechanical coupling of the seismic energy propagating through the seabed.

The mechanical coupling of sensors provides better quality data than hydraulic coupling. However, a drawback with the mechanical coupling is the difficulty and thus cost of placing and positioning the sensors on the seabed and subsequently moving them multiple times to cover a designated survey area. This is much easier and cheaper when sensor streamers are towed behind a vessel and reside in or near the water plane.

GB2541189 (Autonomous Robotics Limited) describes an autonomous underwater vehicle (AUV) that can be used for recording seismic signals during a marine seismic survey. The AUV is described as having a passive buoyancy system where a bladder holds a gas which is compressed by hydrostatic pressure as the AUV descends under the power of a thruster. Therefore, there is no ability to actively control or vary the buoyancy of the AUV. A propeller or thruster is used to both drive the AUV to the seafloor and also for recovery from the seafloor.

This specification is totally silent on the issues of navigation of the AUV and acoustic communication between the AUV and surface vehicles.

U.S. Pat. No. 9,417,351B2 (CGG Services SA) describes a system and method for conducting marine seismic surveys. This uses two clusters of AUVs each associated with an unmanned surface vessel (USV) to conduct marine survey. The USV follow paths independent of each other. A central control vessel controls the USVs. The AUV do not land on the seabed to acquire seismic data, rather they acquire their data while travelling through the water. This document does mention that an AUV can be “parked” on the ocean bottom if its depth is no more than a few hundred metres and the ocean bottom currents are not too strong. Then when a new survey needs to be performed the AUV may be awakened by a corresponding USV. The awakened AUV then operated in all manner to acquire data while in transit through the water rather than when on the seabed.

This document describes the use of an acoustic underwater positioning and navigation system installed on the USVs to communicate with the AUVs. This uses super Short Baseline (SSBL) or Ultra Short Baseline (USBL) communication. Each UV also described as optionally having a Wi-Fi communication system. This is to enable data transfer between an AUV and USV, and also for the purposes of obstacle avoidance.

U.S. Pat. No. 6,951,138B1 (Jones) describes a multi component ocean bottom seismometer (MOBS) that can be deployed from a vessel and swim to a location on the seabed to acquire seismic data, then either swim back to the vessel or to a second location on the seabed. The MOBS uses fins to dig into sea bottom to improve coupling. The fins also form part of a propulsion system that may optionally also include one or more propellers.

The MOBS a buoyancy system which essentially comprises a fixed volume ballast tank41they can be emptied or filled to provide a required buoyancy.

The MOBSs can swim to a new survey location after a completed survey. The navigation is provided by acoustic transponders46,50,52that must be installed on the seabed prior to commencing a survey. While the surface support ship48, MOBSs and seabed acoustic transponders to a navigation system can communicate with each other this document does not describe any particular method of acoustic communications.

US2013/0083624A1 (CGGVERITAS Services SA) describes a system and method for conducting marine seismic surveys similar to that in U.S. Pat. No. 9,417,351B2, except that the AUVs navigate to the seabed where they acquire seismic data. The buoyancy system134and this document has a number of chambers that can be flooded with water to modify the buoyancy of the AUV. Is further disclosed that an accumulative holding compressed gas can be provided on the AUV to expel water from the chambers. The communications system is very rudimentary and limited, essentially mimicking that in U.S. Pat. No. 9,417,351B2.

US2017/0137098A1 (Seabed Geosolutions BV) describes an AUV for acquiring seismic data from the seabed. A buoyancy control system134is provided for controlling the AUV depth. The ability to vary the buoyancy is described at [0035] by releasing a degradable weight on the bottom of the ocean. The possibility of one or buoyancy tanks that can be flooded with air or water to assist in vertical navigation is also described.

The AUVs in this specification can communicate with other subsea devices or a surface vessel using USBL, SSBL or SBL (short base length) systems.

Any discussion of the background art throughout this specification should in no way be considered as an admission that such background art is prior art, nor that such background art is widely known or forms part of the common general knowledge in the field in Australia or worldwide.

While the above background is cast in relation to marine seismic surveying, embodiments of the disclosed method, system and nodes are not limited in application to acquisition of seismic data and may alternately or additionally sense or measure other characteristics or physical attributes including but are not limited to: water temperature, density, chemical characteristics such as salinity, pH, oxygen content, carbon dioxide content, phosphate content; sulphur content; oceanographic conditions including ocean current velocity and hydrostatic pressure; gravitational field strength; magnetic field strength and orientation; gamma radiation; acoustic characteristics; optical characteristics; bathymetry; and aspects of the benthic zone.

SUMMARY

In one aspect there is disclosed a submersible autonomous data acquisition node comprising:buoyancy system enabling variation of the node buoyancy between positive buoyancy and negative buoyancy, the buoyancy system including at least one inflatable external bladder and at least one internal reservoir containing a liquid wherein the liquid can be transferred between the at least one inflatable external bladder and the internal reservoir to vary node buoyancy by changing total displacement of the node.

In one embodiment the buoyancy system is operable as a buoyancy propulsion system enabling the node to transit between two submarine locations, wherein the buoyancy system is arranged to vary node buoyancy between a positive buoyancy and a negative buoyancy to maintain the node within a transit envelope below the water surface and above a seabed to facilitate the node traversing along an oscillating path from a first submarine location to a second submarine location.

In one embodiment the submarine locations are landed locations on the seabed and wherein the buoyancy system is operable upon the node landing at a seabed location to increase the negative buoyancy of the node to thereby increase contact pressure between the node and the seabed.

In one embodiment the node is configured when landed on the seabed in manner wherein the negative buoyancy of the node is substantially evenly distributed over contact locations between the node and the seabed.

In one embodiment the buoyancy system comprises a pump system having at least one pump operable to transfer liquid from the reservoir to the at least one inflatable external bladder to thereby increase total node buoyancy, and a bleed path operable to selectively allow the liquid to flow from the at least one inflatable external bladder to the reservoir by action of a difference in pressure acting on liquid in the reservoir and in the at least one inflatable external bladder, to thereby decrease total node buoyancy.

In one embodiment the reservoir includes a pneumatic region separated from a hydraulic region containing the liquid, and wherein the pneumatic region is at a negative pressure with respect to atmospheric or hydrostatic pressure acting on the at least one inflatable external bladder.

In one embodiment the bleed path includes a one-way valve operable to enable fluid to flow only in a direction from the at least one external inflatable bladder to the reservoir, the valve being switchable between an opened state wherein liquid is able to flow from the at least one external inflatable bladder to the reservoir, and a closed state in which the liquid is blocked from flowing through the bleed path.

In one embodiment the pump system comprises a single pump capable of pumping liquid from the reservoir to the at least one inflatable external bladder.

In one embodiment the pump system comprises a transit pump and a lift-off pump, wherein the transit pump is arranged to pump liquid between the reservoir and the bladder at a first flow rate and first pressure, and the lander buoyancy system comprises a lander pump which pumps liquid between the reservoir and the bladder and a second flow rate and second pressure wherein the first flow rate is higher than the second flow rate and the second pressure is higher than the first pressure.

In one embodiment the node is selectively operable to broadcast acoustic communications packets to facilitate; and capable of receiving and processing acoustic communications packets to facilitate one-way travel time positioning when the node is repositioning between two submarine locations.

In one embodiment the node comprises a top mounted transducer for broadcasting the acoustic communications packets and a downward facing receiver for receiving acoustic communications packets transmitted by another node.

In one embodiment the node is arranged to communicate with a surface marine vessel using USBL, SBL or SSBL acoustic communications.

In one embodiment the node comprises a surface communications system enabling a node to communication when on a water surface with the or another surface vessel and/or a land-based station.

In one embodiment the node comprises a GPS receiver.

In one embodiment the node comprises a thruster arranged to automatically operate when speed of a node derived from operation of the buoyancy propulsion system is less than a threshold speed.

In a second aspect there is disclosed an autonomous seismic data acquisition node comprising the node according to the first aspect and one or more seismic sensors supported on the node for acquiring seismic data.

In one embodiment the node comprises one or more other sensors.

In a third aspect there is disclosed an autonomous ocean data acquisition node comprising the node according to the first aspect and one or more sensors capable of sensing one or more oceanographic characteristics or properties.

In a fourth aspect there is disclosed marine data acquisition system comprising a plurality of nodes according to the first aspect.

In a fifth aspect there is disclosed a marine seismic data acquisition system comprising:one or more surface vessels,a plurality of autonomous nodes capable of acquiring seismic data at one or more seabed locations, each node having a buoyancy propulsion system enabling each node to reposition between respective landed seabed locations without surfacing by variation of the node buoyancy between positive buoyancy and negative buoyancy;a first acoustic positioning system operable between one of the surface vessels and the nodes; anda second acoustic positioning system operable between respective submerged nodes.

In one embodiment the first acoustic positioning system is a USBL, SSBL or SBL system.

In one embodiment the second acoustic positioning system comprises a one-way travel time positioning system.

In one embodiment the one or more surface vessels comprise a node mothership having a command and control system arranged to provide centralised communication, control and monitoring of the nodes and other surface vessels.

In one embodiment the system comprises a wireless mesh communications network for enabling communication between the command and control system and the nodes via acoustic modems associated with at least the first acoustic positioning system.

In one embodiment the system comprises an acoustic doppler current profiler installed on the node mothership for providing real time water current velocity profile data to the command and control system.

In one embodiment the command control system is arranged to process and utilise the real-time current profile data to exert navigation control and scheduling of the nodes.

In one embodiment the system comprises a multibeam echo sounder installed on the node mothership and arranged acquire and provide bathymetric information in real-time to the command and control system.

In one embodiment the system comprises one or more containerised node docking systems located on a deck of node mothership wherein each containerised node docking system comprises a container having a plurality of docks, wherein each dock is arranged to house a corresponding node.

In one embodiment each containerised node docking system comprises a power distribution system arranged for electrically charging nodes when in their respective docks.

In one embodiment each containerised node docking system comprises a communications network arranged to enable communication and data transfer between a node in its dock and the command and control system.

In one embodiment each containerised node docking system comprises an automated handling system arranged to transfer a node into and out of a dock.

In one embodiment the node mothership comprises a launch and recovery system arranged to transfer a node from a first of the containerised node docking systems to a launch location on the node mothership, and transfer a node from a recovery location on the node mothership to the first or another one of the containerised node docking system.

In a sixth aspect there is disclosed a method of conducting a marine seismic survey comprising:transmitting seismic energy from a seismic source vessel;autonomously landing a plurality of nodes on a seabed at respective first locations to form an array of nodes;using the landed nodes to acquire seismic data at the first locations;varying the buoyancy of at least some of the nodes between a positive buoyancy and a negative buoyancy to facilitate transit of the nodes from their respective first locations to respective second landed seabed locations without the nodes surfacing; andusing the landed nodes to acquire seismic data at the second locations.

In one embodiment varying the buoyancy between positive and negative buoyancy comprises controlling flow of a liquid between an inflatable bladder external of a body of the node and a reservoir internal of the body of the node.

In one embodiment the controlling flow of the liquid comprises: utilising a pressure differential to allow a liquid to bleed from the bladder to the reservoir to reduce a total displacement of the node thereby reducing the buoyancy of the node; and pumping liquid from the reservoir to the bladder to increase the total displacement of the node.

In one embodiment utilising a first acoustic positioning system operable between one or more surface vessels and the nodes to position the nodes at their respective first and second landed locations; andutilising a second acoustic positioning system operable between respective submerged nodes to navigate the transiting nodes from their first locations to their second locations.

In one embodiment the first acoustic positioning system comprises using USBL, SSBL, or SBL acoustic positioning.

In one embodiment the method comprises configuring respective groups of the nodes to have a same USBL, SSBL, or SBL beacon address and activating nodes in each group in a manner wherein no two nodes with the same USBL, SSBL, or SBL beacon address actively communicate via an associated USBL, SSBL, or SBL modem at the same time.

In one embodiment the method comprises utilising a second acoustic positioning system comprises using a one-way travel time acoustic positioning.

In one embodiment the method comprises operating a set of nodes at their respective first landed locations to operate as one-way travel time beacons and broadcast acoustic communication packets.

In one embodiment the method comprises enabling the transiting nodes to receive and use the broadcast an acoustic communication packets to navigate from their first landed location to a second landed location.

In a seventh aspect there is disclosed a method of conducting a marine seismic survey comprising:transmitting seismic energy from a seismic source vessel;positioning a plurality of nodes having seismic sensors to respective first landed locations on a seabed using a first acoustic positioning system;acquiring seismic data at the respective first landed locations using the seismic sensors of the landed nodes;transiting at least some of the nodes from their respective first landed locations toward respective second landed locations using a second acoustic positioning system operable between a set of the landed nodes and transiting nodes; andpositioning the at least some of the nodes at their respective second landed position utilising the first acoustic positioning system.

In one embodiment using a first acoustic positioning system comprises using USBL, SSBL, or SBL acoustic positioning.

In one embodiment the method comprises configuring respective groups of the nodes to have a same USBL, SSBL, or SBL beacon address and activating the nodes in each group in a manner wherein no two nodes in that group with the same USBL, SSBL, or SBL beacon address actively communicate via an associated USBL, SSBL, or SBL modem at the same time.

In one embodiment utilising a second acoustic positioning system comprises using a one-way travel time acoustic positioning.

In one embodiment the method comprises activating a set of nodes at their respective first landed locations to operate as one-way travel time beacons and broadcast acoustic communication packets.

In one embodiment the method comprises enabling the transiting nodes to receive and use the broadcast an acoustic communication packets to navigate from their first landed location to a second landed location.

In one embodiment the method comprises acquiring bathymetric data during the survey in real-time and modifying an associated survey plan on the basis of the acquired bathymetric data.

In an eight aspect there is disclosed a method of remotely conducting an ocean survey comprising:varying buoyancy of one or more ocean data acquisition submersible between a positive buoyancy and a negative buoyancy to facilitate transit of the one or more nodes from a deployment location to a first submersed survey location, wherein each node includes one or more ocean data sensors;while transiting, enabling one or more nodes to autonomously navigate from the deployment location to the first submersed survey location; andusing the one or more ocean data sensors when at the first survey location to acquire ocean data.

In one embodiment the method comprises autonomously landing the one or more nodes on a seabed at the first survey location wherein the ocean data is acquired while the one or more nodes are landed on the seabed.

In one embodiment the method comprises triggering the one or more nodes landed on the seabed to transit for reposition to a second survey location wherein the transit is performed, or assisted, by variation of the buoyancy of the node.

In one embodiment the triggering is performed on the basis of: an effluxion of time; or, in response to information collected by the one or more ocean data sensors.

In one embodiment the method comprises causing a node to surface during transit from the first survey location to the second survey location and, while surfaced, enabling the node to (a) acquire GPS data, or (b) transfer sensed ocean data to another node, or (c) wirelessly transfer sensed ocean data to a remote location, or any two or more of (a), (b) and (c).

In one embodiment the method comprises transporting the one or more nodes to the deployment location on a manned or an unmanned surface vessel.

In a ninth aspect there is disclosed a method of remotely conducting an ocean survey comprising:transiting one or more nodes accordance with the first aspect from a deployment location to a first submersed survey location, wherein each node includes one or more ocean data sensors;while transiting, enabling one or more nodes to autonomously navigate from the deployment location to the first submersed survey location; andusing the one or more ocean data sensors when at the first survey location to acquire ocean data.

In one embodiment the first survey location is a landed location on a seabed.

In one embodiment the ocean data includes water temperature, density, chemical characteristics such as salinity, pH, oxygen content, carbon dioxide content, phosphate content; sulphur content; oceanographic conditions including ocean current velocity and hydrostatic pressure; gravitational field strength; magnetic field strength and orientation; gamma radiation; acoustic characteristics; optical characteristics; bathymetry; and aspects of the benthic zone.

