Seismic node and method for making seismic node

Abstract

Described herein is a seismic node comprising: at least one seismic sensor; a pressure resistant structure having a first wall, a second wall, and one or more support elements extending between the first wall and the second wall to define one or more cavities for receiving a pressure sensitive component; and a separate waterproof sealing skin surrounding the pressure resistant structure and the at least one seismic sensor. Also described herein is a method for making a seismic node.

Description

[0001] The present invention relates to a seismic node and in particular to a seabed node suitable for offshore seismic exploration and having a compact profile. The present invention also relates to a method for making a seismic node.

[0002] Seismic exploration techniques are an important tool for studying the Earth's subsurface structure. The information obtained from such exploration has broad scientific significance and can be used to study the Earth's composition and history, as well as to locate and access underground reservoirs based on hydrocarbon fossil fuels. Seismic exploration uses sound sources, such as air guns or marine vibrators in the case of offshore seismic exploration, which are configured to emit sound energy at selected frequencies and then propagate through the surface and underground. The sound waves are reflected or refracted at the boundaries between different materials within the underground structure and travel back toward a sensor positioned close to the surface. The sensor converts the received acoustic signal into an electrical signal, which is then sent to a processor for analysis. The collected signal carries information about the materials on either side of the different boundaries and the location of the boundaries themselves.

[0003] To survey underground structures, sensors are typically located in one or more streamers towed behind an oceanographic survey vessel or positioned at specific locations on the earth's surface (such as on the seabed), and the sensors may be located in nodes or along cables. The invention described herein is particularly useful when used as a seabed node, but may also be used as a land-based node or even as a node or device in a streamer or seabed cable if desired.

[0004] The seismic sensor itself may include one or more of a variety of different types of devices capable of detecting seismic waves within the surrounding material (air, water, or the material of the node itself). These may include pressure sensors (such as hydrophones) and motion sensors (such as geophones or accelerometers (e.g., MEMS accelerometers)). The node may also include additional sensors for measuring node position, orientation, temperature, for locating the node, and for monitoring other parameters.

[0005] The seabed nodes may be connected together via cables or ropes, which facilitates deployment and placement of the nodes on the seabed, retrieval, or in some cases sending signals to and receiving data from the nodes during use. The nodes may be autonomous, meaning that they do not require any external control signals to record seismic data while on the seabed. In this case, no data connection needs to be established with the nodes during the survey. The nodes can simply be turned on and left on the seabed in the desired configuration (via their attachment to ropes or cables, using ROVs or by other means) for subsequent collection. Once the nodes are returned to the seismic survey vessel, the data recorded by the nodes can be retrieved.

[0006] In order to be suitable for use as an offshore seismic node (which will be located on the seabed, which may be several kilometers away from the surface), the shell of the node must be able to withstand the high pressure of the seabed and protect the internal electrical components from being exposed to water. Traditionally, this is achieved by means of an external shell, which is both sealed to prevent water from entering the internal cavity and pressure-resistant to prevent damage to the internal components. Therefore, usually, the node includes one or more waterproof shells, which accommodate seismic sensors, power sources, control devices, clocks and other sensors for orientation and positioning, formed as a relatively thick metal shell. This type of seabed node is described in EP1805533B1. Here, the disc-shaped shell not only protects the internal components from the influence of the external pressure environment, but also seals the node to prevent water intrusion.

[0007] US-A-14 / 821471 describes a seabed node having an internal pressurized waterproof shell, which is preferably formed of cast titanium. A non-watertight external structure is arranged around part of the shell. Components such as hydrophones are exposed to the water and are not covered by this external structure. The internal pressurized shell can be disassembled into two or more pieces (i.e., a cover and a tray) to access the internal components. The external structure, which may be formed of rubber, metal, carbon fiber or plastic, covers only part of the node and acts as a shock absorber, thereby providing additional shock protection and allowing the node to be attached to wires for deployment and handling, and thereby achieving effective stacking of nodes.

[0008] The requirement that the node housing be both pressure resistant and sealed imposes some restrictions on the types of materials that can be used and the minimum weight and size of the node. Obviously, the efficiency and cost of the process depend to a large extent on these factors, and therefore, it is desirable to reduce size and weight as well as improve functionality.

[0009] According to a first aspect of the present invention, a seismic node is provided, which includes: at least one seismic sensor; a pressure-resistant structure having a first wall, a second wall, and one or more supporting elements, the one or more supporting elements extending between the first wall and the second wall to define one or more cavities for accommodating pressure-sensitive components; and a separate waterproof sealing skin, which surrounds the pressure-resistant structure and at least one seismic sensor.

[0010] The waterproof sealed skin shields the internal pressure-resistant structure and at least one seismic sensor from the influence of water (ie, seawater when the node is deployed on the seabed).

[0011] One or more of the walls may be formed integrally with the support elements of the internal structure. Therefore, the wall may not necessarily be removed from the rest of the structure, but may represent its external surface. Typically, at least a portion of one of the walls of the internal structure (which may include all or part of the first wall, the second wall, the sidewall, or the front wall or the rear wall) will be removable to access one or more cavities and the pressure sensitive components therein. The node will typically be cubic or cylindrical (i.e., disc-shaped), so the first wall and the second wall are rectangular, square or circular, but any shape may be used for the node. A spherical node may include two dome wall segments connected by a support element. A spherical node may include a removable wall segment or may include a detachable hemispherical portion to allow access to one or more cavities.

[0012] Pressure sensitive components represent components that need to be protected from the external pressures experienced on the seabed so that these parts are not damaged and can continue to operate. The pressure-resistant structure may include an enclosure for containing the pressure-resistant components. The enclosure may completely surround the pressure-resistant components.

[0013] The sealing skin is a covering that contains and surrounds the internal structure and other node components. The internal structure and the seismic sensors are surrounded by the skin together. Both can be located in the same cavity or void formed by the outer skin, or the sensors can be fully or partially embedded in the sealing skin, as described below. In either case, the layers of the sealing skin will completely surround the internal structure and the seismic sensors together with other components supported in one or more cavities.

[0014] The term "pressure-resistant" as used herein refers to the ability of the internal structure to maintain its shape without any external support under the pressures typically experienced on the seabed during exploration. These pressures can represent pressures higher than about 2 Bar and up to about 300 Bar (about 3 km depth) or even higher pressures for exploration at greater depths. In this way, the skin surrounding the node is not pressure-resistant. Therefore, without the support of the internal structure, it cannot maintain its container-like shape, and without such additional support, it will collapse inward under the pressure of ocean exploration. This does not mean that the material itself will degrade or be damaged under these pressures. The single piece of material (i.e., plastic material) used to form the surrounding skin will withstand the seabed pressure without damage, but the entire skin formed into a suitable shape to accommodate and surround the internal structure and components of the node cannot maintain this shape on the seabed in the absence of the internal structure. Therefore, the shape of the node in use is defined by the shape of the outer range of the internal structure. This means that, although the pressure structure ensures that the node maintains its shape, assuming that no internal structure is present and the sealed skin is placed on the seabed, the container formed by the skin will not be able to maintain its shape and will be crushed or collapsed. The internal pressure structure alone may not be waterproof, i.e., water may enter the cavity of the internal pressure structure in the absence of a sealed skin.

[0015] The sealing skin is typically thin and soft or flexible compared to the outer shell of a typical seismic node. The terms "waterproof" and "sealed" used in connection with the skin refer to the fact that the skin acts as a waterproof jacket or cover and completely seals the node to prevent water intrusion. Due to the presence of the skin, water cannot enter the closed chamber formed by the skin and containing the internal structure and seismic sensors from the outside of the node. Therefore, these internal parts are protected or shielded from water by the surrounding sealing skin.

[0016] The skin completely surrounds the internal pressure-resistant structure and other components and can represent a completely uninterrupted surface that accommodates and encloses these components. The first wall and the second wall can be referred to as the bottom wall and top wall of the node, respectively. These bottom walls and top walls can be larger than the side walls, front wall and rear wall (if present) and are therefore more suitable for being placed closest to the seabed when in use. In use, there can only be a waterproof skin (and possibly some PCBs or other components) between the bottom wall / top wall of the internal structure and the seabed. The support element can include a central block, in which a cavity is provided, and the support element can be integrated with the top wall and the bottom wall, as mentioned above, so that the top wall and the bottom wall represent the upper external surface and the lower external surface of the central block. The support element can include side walls and / or front walls and rear walls, some or all of which can also be integrated with the central block, so that they represent the front surface, rear surface, and side surface of the internal structure. Alternatively, one or more walls in the wall or parts thereof can be removable to allow access to one or more cavities of the cavity of the internal structure.

[0017] Components such as hydrophones and antennas for wireless communication and / or charging can be mounted on the exterior surface of the internal structure or located outside the exterior surface, such as, positioned in a recess on the exterior surface of the structure. The components can be simply placed on the surface to be mounted or in some cases can be fixed to the surface before applying the sealing skin. Here, these components can be protected from water damage by the sealing skin without affecting the acoustic coupling or the transmission of wireless signals or charging signals to the components. This is because the components are separated from the surrounding water only by the skin, which must be waterproof and sealed (i.e., it must prevent water intrusion), but it cannot itself keep the node in its shape. Therefore, the sealing skin can represent only a relatively thin waterproof cover or overmolding, rather than a thicker metal shell, so that the hydrophone and antenna can operate when positioned in a compartment housed by the sealing skin. The same is true for other components mounted on or outside the exterior surface of the internal structure, but located inside (between) the surrounding sealing skin. Some components (including seismic sensors) may be partially or fully embedded within the skin, but in this case they will still be surrounded by the sealing skin and have an additional layer of sealing skin material between them and the internal structure.

[0018] The pressure structure is also protected by a sealed skin from salt water corrosion due to exposure, which means that there are more choices in the materials used for these underlying structural components of the node. The internal structure can be formed in whole or in part from a metal or metal alloy (such as aluminum). The aluminum used to form the pressure structure can be corrosion resistant or not. Aluminum is lightweight and easy to form, but in certain forms it may be susceptible to corrosion and require anodizing to be used as a sealed shell for the node. Here, the internal pressure structure is not exposed to the external seawater, so there is no need to treat the aluminum or other metals for corrosion protection (although it is possible).

[0019] Unlike previous node designs, the seismic node of the present invention comprises two distinct, separate components to provide the required pressure resistance and watertight seal.

[0020] The node may comprise two or more modules of the type described above, each of which is sealed with a waterproof sealing skin. The modules may each comprise an internal pressure resistant structure formed by a first wall and a second wall and one or more support elements extending between the first wall and the second wall. Different components of the node may be housed in different modules, which are connected together by mechanical means or by wiring extending between the two. If wiring connects two modules of the node, a seal may be provided around any entry point of the line to maintain the waterproof properties of the outer skin. The mechanical connection means may be positioned on the outside of the sealing skin.

[0021] In an embodiment, the sealing skin is molded over or onto the pressure-resistant structure. In this case, the skin will be bonded to the exterior surface of the internal structure and will conform to the shape of the structure and any components of the node mounted outside of it. This can help to improve the functionality of the external components, as described below. The sealing skin can be formed as a single integral piece (i.e., without holes or seams), and in some cases, can be formed as a single polyurethane layer molded over and thereby bonded to the internal structure. This approach enables the production of smaller, more compact nodes, which can be manufactured at a lower cost. The frictional connection or bonding between the sealing skin and the internal structure helps to transmit seismic signals into the node.

[0022] In an embodiment, the support element includes at least one additional wall, and the walls of the internal pressure-resistant structure form a substantially continuous external surface to support the surrounding sealing skin. The external surface includes the external surfaces of the first wall and the second wall and the external surfaces of one or more side walls. If the node is cylindrical, one side wall can extend all the way around the node to provide a continuous external surface. If the node is cubic, there may be two side walls, a rear wall and a front wall. When the sealing skin is overmolded onto the internal structure, these walls prevent the molten material of the skin from seeping into the cavity of the internal structure. There may be small holes, such as those used to fix any removable sections to the rest of the internal structure, but these holes will be small enough that the material of the sealing skin will not penetrate through them at the pressure and temperature used for molding. As mentioned above, there may be components positioned outside the internal structure, in which case the external surface of the internal structure will support these parts in certain areas, thereby supporting the sealing skin. The sealing skin can be bonded to these parts and the internal structure across the rest of its external surface.

[0023] In an embodiment, the sealing skin is formed of a non-metal. In an embodiment, the sealing skin is formed of a plastic material. Plastic is an inexpensive, lightweight, flexible material that can be molded at relatively low temperatures. The thin plastic skin does not interfere with the operation of the components of the node. In an embodiment, the plastic material is polyurethane. The sealing skin may be formed of epoxy, polyester, vinyl ester resin, or silicone. In an embodiment, the sealing skin is formed of rubber.

[0024] In an embodiment, the sealing skin comprises an integral single piece of material. This can be achieved, for example, by molding the skin onto and over the underlying structure, and ensures that there are no seams or holes in the skin that could lead to unwanted leakage through the skin.

[0025] In an embodiment, the pressure-resistant structure is a metal structure or frame. In an embodiment, the pressure-resistant structure is an aluminum frame. The frame may be formed partially or entirely of aluminum. Aluminum is light, easy to process, and inexpensive. The frame may be treated (i.e., by anodizing) to improve corrosion resistance, but this may not be necessary because the internal structure is protected from water by the sealed skin.

[0026] In an embodiment, the sealing skin has a thickness of between 2 mm and 10 mm. In an embodiment, the sealing skin has a thickness of between 2 mm and 10 mm at least in the region of the skin extending beyond the first wall and the second wall, and preferably across the entire extent of the skin. Thus, the skin is relatively thin, which may aid in the attachment and operation of the antenna and the hydrophone.

[0027] In an embodiment, one or more cavities in the internal structure include at least one data logger, at least one power source, and at least one circuit board supporting a clock circuit.

[0028] In an embodiment, one or more seismic sensors include at least one hydrophone. This may be positioned external to the internal structure. In an embodiment, the hydrophone is received in a cavity in the external surface of the internal structure. The recess may be, for example, cylindrical, which is a convenient shape for machining into the internal structure. However, the recess may be of any shape and will at least partially accommodate a hydrophone positioned therein and provide a degree of protection for the hydrophone positioned therein.

[0029] In an embodiment, the hydrophone is embedded in the sealing skin in whole or in part. The hydrophone can be received on the internal pressure-resistant structure or in the cavity of the internal structure so that it is exposed to the surrounding sealing skin. The hydrophone can be completely embedded in the surrounding sealing skin. Therefore, the hydrophone can be protected from damage caused by impact. At the same time, its function will not be hindered, in part because there are no air pockets or materials between the hydrophone and the seawater around the node except for the sealing skin. The hydrophone can be positioned in the cavity before the skin is overmolded. This can be achieved by using a spacer, a small piece of glue, or a small sample of the same material used to form the skin. The skin is then overmolded over the internal structure and the hydrophone so that the hydrophone is suspended in the skin. Therefore, the hydrophone does not necessarily contact the internal structure and is not necessarily mounted directly to the internal structure, but can still be accommodated in the cavity to protect it.

[0030] In an embodiment, the one or more seismic sensors include at least one pressure sensor and at least one motion sensor. The sensors may include one or more of at least one accelerometer and at least one geophone. Including an additional seismic sensor allows the seismic field to be correctly characterized, particularly if a hydrophone is present as one of the sensors.

[0031] In an embodiment, the seismic node includes at least one antenna positioned between the outer surface of the internal structure and the sealing skin. The antenna, which can be configured for wireless communication or for charging the node, can be positioned on the outer surface of the internal structure, such as on the outer surface of the first wall or the second wall, or can be received in a recess in the pressure-resistant structure so that it faces the surrounding sealing skin and is generally in contact with the surrounding sealing skin. Similarly, the function of the antenna in receiving the wireless signal of the node is not hindered by the sealing skin covering them, but the sealing skin does provide protection for the antenna and will protect them from water damage. One or more of these antennas can be used as a charging coil to wirelessly charge the node. Therefore, the node does not require any physical connection for charging or data communication, which is a huge advantage over previous designs. Existing antennas can include one or more of Bluetooth antennas, RFID antennas, charging coils, and GNSS antennas.

[0032] In an embodiment, the seismic node includes at least one antenna located behind a window in an exterior surface of the internal pressure hull. The window may be formed of a material that allows radiation to pass through the window to the antenna. In some cases, the window may be formed of a material other than the metal that forms the pressure hull.

[0033] In an embodiment, the seismic node comprises: a panel embedded in or positioned on a sealing skin to attach a handle to the node; and at least one antenna located behind a window in the panel. The handle is attached to the node via the panel.

[0034] In an embodiment, the node is a seabed seismic node. The node may be externally powered, or may use an internal power source, or both.

[0035] According to a second aspect of the present invention, a method for making a seismic node is provided, the method comprising: providing a pressure-resistant structure, the pressure-resistant structure comprising a first wall, a second wall and one or more supporting elements, the one or more supporting elements extending between the first wall and the second wall to define one or more cavities between the first wall and the second wall for accommodating pressure-sensitive components; positioning at least one seismic sensor relative to the structure; and applying a separate waterproof sealing skin so that it accommodates and surrounds the pressure-resistant structure and the seismic sensor.

[0036] In an embodiment, the method comprises applying a sealing skin layer onto the structure by overmolding the sealing skin layer onto an exterior surface of the structure.

[0037] In an embodiment, the method includes positioning one or more pressure sensitive components within a cavity of the internal structure prior to applying the sealing skin.

[0038] According to a third aspect of the invention, there is provided a seismic node comprising: at least one seismic sensor; an internal pressure-resistant structure defining one or more cavities for accommodating pressure-sensitive components; and a separate waterproof sealing skin overmolded on an outer surface of the internal pressure-resistant structure to surround the internal structure and at least one seismic sensor. In an embodiment, the skin may be formed of a plastic material such as polyurethane. The overmolded skin may be bonded to and supported on an outer surface of the pressure-resistant structure. The outer surface of the internal structure may represent a substantially continuous surface.

[0039] According to a fourth aspect of the present invention, a seismic device is provided, which includes: an internal pressure-resistant structure, which defines one or more cavities for accommodating pressure-sensitive components; and a separate waterproof sealing skin, which is molded onto the outer surface of the internal pressure-resistant structure to surround the internal structure and the pressure-sensitive components.

[0040] In an embodiment, the device may be a seismic node. The node may include a seismic sensor and a sealing skin may be applied to surround the seismic sensor, the internal pressure-resistant structure, and the pressure-sensitive component. The overmolded skin may be formed of a plastic material such as polyurethane. The overmolded skin may be bonded to and supported on an external surface of the pressure-resistant structure. The external surface of the internal structure may represent a substantially continuous surface.

[0041] According to a fifth aspect of the present invention, a monitoring device is provided, which includes: at least one sensor; a pressure-resistant structure having a first wall, a second wall and one or more supporting elements, the one or more supporting elements extending between the first wall and the second wall to define one or more cavities for accommodating pressure-sensitive components; and a separate waterproof sealing skin, which surrounds the pressure-resistant structure and at least one sensor.

[0042] The sealing skin may be an overmolded skin. The overmolded skin may be formed of a plastic material such as polyurethane. The overmolded skin may be bonded to and supported on the outer surface of the pressure-resistant structure. The outer surface of the internal structure may represent a substantially continuous surface.

[0043] Embodiments of the present invention will now be described by way of example only with reference to the following figures, in which:

[0044] Figure 1A seabed node including a waterproof sealing skin is shown;

[0045] Figure 2 Shows Figure 1 an upper side portion of a node with a cutout showing a portion of the internal pressure-resistant structure;

[0046] Figure 3 An overmolded or sealed skin is shown with an internal pressure-resistant structure and other components not shown;

[0047] Figure 4 Shown in exploded view and without sealing skin Figure 1 and Figure 2 Nodes; and

[0048] Figure 5 A seabed node is shown, comprising a waterproof sealing skin and a handle.

[0049] Figure 1 An example of a seabed node 1 is shown in , which comprises an outer sealing skin 2 surrounding an inner pressure-resistant structure or frame 4 . Figure 2 The sealing skin is shown partially removed to illustrate possible locations for certain components mounted on the internal structure. The internal structure includes a number of cavities, recesses, or mounting points through which various components can be fitted into or placed on the structure. Recesses can represent recessed areas of the external surface of the internal structure (such as the upper wall) that are sized and shaped to correspond to the components. Recess 5 ( Figure 4 ) is present on the upper wall of the internal structure, for example for receiving a correspondingly shaped PCB 7 ( Figure 2 and Figure 4 ), PCB 7 includes electronics related to wireless communication of the node and charging of the node. Components can be positioned within recesses for mounting thereof, which will help to hold the components in place, at least during application of the outer sealing skin. The recesses can provide space for more delicate electronic components that require a greater degree of protection from the seabed pressure to which the outward facing surface of the PCB 7 is exposed. Components such as PCBs can protrude above the outer surface of the internal structure or can be completely contained within the outer surface of the internal structure. The mounting point may include a coupling device by which the component can be attached to the internal structure with or without a corresponding recess.

[0050] The internal structure itself can be formed from many separate pieces, e.g. Figure 4As shown in , these pieces can be connected together in any suitable manner (such as by bolting, locking, screwing, or clamping) using fastening devices. The internal structure includes at least an upper wall 6 and a lower wall 8, each of which extends across most of each of the upper and lower surfaces of the internal structure (if not all or substantially all). These walls can be removed from the rest of the internal structure as shown or can be integrated with the rest of the internal structure. Then, the wall will generally extend from one side of the internal structure to the other side, from the front of the internal structure to the back, but may include holes, recesses, cutout portions, etc., so as to allow the internal structure to be assembled and to allow parts to be installed above or below the wall. Except for these attachment points or cutouts that may exist in some cases, the panel extends across and substantially forms the entire upper and lower surfaces of the internal structure, and thereby provides a surface that can support the thin sealing skin 2 on. As mentioned, the sealing skin can be applied to the internal structure by an overmolding process.

[0051] The overmolding may be achieved by pouring a fluid mixture (eg, a fluid plastic mixture, which may be based on a polyurethane mixture) into a casting mold, the casting mold comprising Figure 4 The complete internal pressure-resistant assembly and the components mounted thereon will be formed by the fluid mixture hardening into a skin that is bonded to the internal structure and any components on the exterior of the structure, thereby providing a sealed skin. After the hardening of the skin is complete, the mold is removed and a sealed node is obtained. This process can be repeated for subsequent nodes, thereby reusing the same mold.

[0052] The node can be box-shaped and can have a width and depth that are both larger than the height of the node, thereby providing a relatively low profile and a relatively large bottom / top surface to connect to the seabed. The node can be used with either of the largest surfaces (top surface and bottom surface) facing downward. This is another advantage of this special design. Seismic sensors (e.g., hydrophones) and any light source or signal source that is optionally used to locate the node can be located on the side surfaces so that the function is the same when either of the largest surfaces of the node faces downward to the seabed when in use. In an embodiment, the hydrophone or sensor is located on one of the front surface, rear surface, or side surface of the node. In the example shown, the hydrophone is located in a cavity on the rear surface of the internal structure of the node. Typically, one of the larger top or bottom surfaces will be the location for the charging coil and communication electronics (see below), and this will typically be referred to as the "top surface" of the node, even if the node is still able to operate with the surface facing downward toward the seabed. In the example shown in the figure, the node 1 comprises large rectangular top and bottom surfaces 44, 46, and smaller left side surfaces 48, right side surfaces 50, front surfaces 52, and rear surfaces 54, which together form a box shape. The internal structure 4 defines the shape and extent of the node and is therefore also box-shaped, although it may be provided with various recesses, cavities, or openings as explained above. The internal structure forms a generally box-shaped shell over which a waterproof sealing skin 2 is provided.

[0053] The front surface 52 of the node shown in the figure is provided with a handle or coupling device 14 (in Figure 5 ) surface, while the rear surface 54 is the surface in which or behind which the cavity 12 for the hydrophone 10 is arranged. Obviously, the shape and configuration of the node can be adjusted and different components can be provided on different surfaces, but the rectangular box shape provides a particularly compact configuration for the entire node and provides a relatively large surface for contacting the seabed when in use. The handle 14 is shown, which is located on the front surface 52 of the node, and the hydrophone 10 is located on or behind the rear surface 54, however, if desired, they can also be located on another surface of the node.

[0054] The sealing skin itself is generally not strong enough to withstand the pressures at the exploration depth, and therefore an internal structure is required to define the shape of the node, as mentioned. The presence of the upper and lower walls, thanks to the fact that the internal structure once assembled generally also provides a largely uninterrupted left side surface, right side surface, front surface, and rear surface, means that the pressure-resistant structure defines a solid shape on which the sealing skin can be supported and overmolded without penetrating the internal cavity and the delicate components therein. In the example shown, the shape is a rectangular cube, which facilitates the stacking and handling of the nodes, and also helps to ensure effective connection with the seabed. However, if desired, the nodes can be manufactured to have another overall shape, such as square, hexagonal, disc-shaped, spherical, triangular, conical, cylindrical, etc. Regardless of the overall shape of the node, the internal pressure structure is manufactured from one or more pieces that can be fitted together to provide a substantially continuous exterior surface to which a sealing skin can be applied, and which form a number of cavities, recesses and / or mounting points that allow components of the node to be supported within or connected to the internal structure.

[0055] The sealing skin is preferably applied to the internal structure via an overmolding process, which involves applying one or more layers of resin material to the outer surface of the internal structure. This material is then allowed to harden to form the skin. The skin can be formed by overmolding without holes or seams, which can represent areas where water may be more likely to leak through the skin. The material forming the sealing skin can be polyurethane or a similar plastic material. The outer skin can be overmolded onto the internal structure using the material to be applied at around room temperature, which helps prevent damage to electronic components and connection points within and connected to the internal structure. A certain degree of preheating can be used to assist in applying the skin, provided that the electronic devices are separated from the coating by portions of the internal structure to avoid contact, or are able to resist damage at the relevant temperatures.

[0056] For example, the outer sealing skin can be applied using injection molding, which is a specific overmolding method. If injection molding is used, the outer shell is applied to the outer surface of the internal pressure-resistant structure in molten, liquid or semi-liquid form using an external mold that defines the shape of the sealing skin. Once the skin material is introduced into the mold, it can be allowed to harden so that it takes the shape of the mold and adheres to the outer surface of the internal structure. The mold is then removed. Other methods for applying the sealing skin are also conceivable. For example, the skin can be molded separately into two or more sections, which can be joined together at a sealed interface to cover the structure. However, this will introduce weaknesses that can make the skin more susceptible to leaks.

[0057] The sealing skin may represent a continuous, uninterrupted cover formed by a single piece of material that completely surrounds the internal structure. There may be no holes, seams or openings in the skin through which water may leak into the internal structure, and the skin may represent the outermost surface of the node across its entire range. However, in some cases, additional components (such as handles 14) may be connected to the node so as to be positioned near the outer surface of the skin. In some cases, these components may be connected via screws or other attachment devices, which extend partially through the skin. In the example shown in the figure, the handle is attached by a panel (i.e., a metal panel) embedded in the sealing skin. Before or during the sealing skin is applied to the node, the panel can be positioned relative to the internal structure and positioned slightly apart from the internal structure. During the molding process, the panel can be fixed in place with a small piece of glue or a temporary fixture or a piece of material used to form a sealing skin about the hydrophone. Alternatively, a sealing skin may be applied over the internal structure, the panels placed over it, and then the remainder of the sealing skin 2 applied over the panels. Bolts or other attachment means for the handles may be pre-attached to the panels and may extend to the outside of the sealing skin to facilitate attachment of the handles. The internal structure is still protected from water intrusion due to the sealing skin between the panels and the internal structure 4. Even if water is able to leak into the opening through which the bolts / attachment means extend, the water will not be able to continue to flow to the internal structure 4 and the node components supported thereon, and will be prevented from doing so by the sealing skin therebetween.

[0058] If applicable, the panel supporting the handle and the handle itself may include a window 42 (e.g. Figure 5 ) as shown to expose the sealing skin underneath. This can be used to allow an antenna positioned on an exterior surface of the node's internal structure and behind a panel to receive signals and / or send signals. Positioning the handle 14 and one or more antennas on the same surface of the node is advantageous for transmitting signals used to synchronize the node during retrieval. When the node is pulled out of the water and its front surface 52 faces upward, the node will hang downward from the handle. Therefore, placing the antenna on the front wall of the internal structure allows signals to be efficiently transmitted to and / or received from the node via the antenna. The antenna can be used to receive signals used to synchronize the node clock.

[0059] The skin will also completely surround and shield from the environment all components supported directly within or on the internal structure. The fact that the material of the pressure portion of the node is protected from water by the outer sealing skin means that there is greater flexibility in which material can be used to form that portion. Aluminum or aluminum alloys can be used for this purpose and are easy to process, inexpensive, and lightweight. Aluminum may or may not be treated (such as anodizing) to reduce the likelihood of corrosion and wear.

[0060] Figure 3 One possible shape of the sealing skin 2 is shown if the configuration of the internal structure and the placement of the node components are as shown in the other figures. The sealing skin alone cannot maintain its box-like shape under the range of pressures expected at the depth of investigation, and without the internal support provided by the internal pressure-resistant structure, the container formed by the skin will collapse inwardly under these pressures. The skin is adapted within the shape of the cavity 12 and conforms to this shape to receive the hydrophone (forming a shaped part of the skin 27). The charging antenna / coil and some communication electronics are located on the external surface of the internal structure when in use.

[0061] All internal components are also protected from water damage and to a certain extent contact damage by the sealing skin. The same applies to one or more hydrophones of the node, which are traditionally located outside the pressure-resistant and sealed metal shell and exposed to seawater. The reason for positioning the hydrophones on the outside is to allow them to detect pressure waves in the surrounding water, as this function would be severely hindered if the hydrophones were located inside the metal pressure shell of a traditional node. Therefore, the hydrophones and other external components of the seabed node were previously susceptible to physical damage. The present invention uses an external sealing skin that does not provide and does not need to provide any pressure resistance, and can therefore be formed as a relatively soft / thin shell over the internal structure. The hydrophone can be positioned within the cavity of the internal structure so that it can detect pressure changes in the water, and only the material of the sealing skin is between it and the surrounding environment. In this way, the hydrophone is protected from damage, is not exposed to seawater, and can detect surrounding sound waves as effectively as the hydrophones of previous seabed node designs that have been made.

[0062] Figures 1 to 4 The node shown includes a cavity 12 within the central portion of the internal structure, which is designed for placement of a hydrophone 10 therein. If overmolding is used to apply the sealing skin 2, the hydrophone and other components of the node will be placed within or on the internal structure 4 before the skin itself is applied. This enables the skin to follow the shape of the cavity and the hydrophone itself (as shown in the figure), thereby ensuring effective attachment and performance of the hydrophone. Once applied, the hydrophone will typically be at least partially embedded within the skin, allowing for effective acoustic coupling.

[0063] A handle or coupling mechanism 14 may be provided on the node 1 to facilitate transportation, handling and storage of the node. In the example shown in the figure, this is provided on the outside of the sealing skin 2 and is coupled to a support panel embedded in the sealing skin. The coupling or attachment of the handle to the support panel may be achieved by bolts extending through the outer portion of the sealing skin, but not all of it, as described above. Alternatively, the handle 14 may be coupled to an internal structure or the handle 14 may form part of the internal structure, and an outer skin may be applied so as to also surround the handle. If so, the skin will completely surround all components of the node.

[0064] Figure 5 One possible design of a handle 14 is shown, which is designed to facilitate manual handling of the node or handling by an ROV. This type of node can be provided with more than one handle or coupling device, and these handles or coupling devices can be of different types. The handle can also be shaped for attachment to a deployment cable. Obviously, the specific configuration of the handle shown is not limited, and the shape and position of these components can be adjusted according to how the node is intended to be deployed and used.

[0065] The sealing skin 2 may include protrusions 24 on its outer surface, which are useful when stacking nodes one on top of another for storage, particularly in combination with the rectangular shape of the node defined by the internal structure, and may be used to enhance the connection with the seabed. In a preferred example, the top surface 44 of the node is provided with a protrusion at each corner, and the bottom surface 46 is provided with a groove at each corner (which itself may be in an additional protrusion) to receive the protrusion 24 of the upper surface of a similar node stacked below. Obviously, the grooves can be evenly arranged on the upper surface and the protrusions can be evenly arranged on the lower surface, or some protrusions and some recesses can be arranged on each surface. As long as these nodes correspond and interlock with adjacent nodes, some support will be provided for the stacked equipment. The node may also include grooves or patterns on its top and / or bottom surfaces to improve the connection of the node to the seabed and the detection of acoustic radiation reflected from underground structures.

[0066] exist Figure 4As can be seen most clearly in the exploded view shown in , the internal structure can be formed of three main sections, namely the upper wall 6, the lower wall 8 and the central block 26, which forms the side walls, the front wall and the rear wall or can be adapted to the side walls, the front wall and the rear wall. In this case, the central block includes two cavities 28, which accommodate battery packs 30 or power sources for the node. These battery packs can provide sufficient power to allow the node to operate for a period of time and can allow the node to operate for about 120 days or more without providing any external energy source. The battery packs themselves can each be formed as a solid metal block, preferably a metal (i.e. aluminum or another metal) block, which includes an opening, each of which is positioned with a pack including a plurality of batteries. In the example shown, two such battery packs are included in the node, and two corresponding cavities are provided in the central block 26, however, in some embodiments more than two or more battery packs may be included. The connecting portion then provides a connection between the individual cells within each battery pack.

[0067] The central block 26 also includes a cavity 12 for receiving the hydrophone 10, which in this case is located on the rear surface 54. The cavity can be cylindrical in shape as shown or can be any other shape. One or more components (such as a PCB with wireless communication / charging electronic devices 7) are located in a recess on the top of the upper wall together with a charging coil 36, which can be used to wirelessly charge the batteries of the battery pack. The main printed circuit board 38 (which includes additional electronic devices required for the node) is located on the right side of the node in this case and is protected by a removable side wall 40 that forms part of the internal structure. In some cases, there may be additional circuit boards and additional removable protective side walls extending across the left side of the node. The main PCB 38 is then housed in a cavity in the internal structure, which is substantially closed when in use by adapting the side wall 40 to cover it. In some cases, the side walls may be integral with the central block and the circuit board may be inserted into a cavity behind the side walls, which cavity may then be closed by attaching a top wall or by a cover that is integral with the circuit board itself.

[0068] The node 1 may include antennas on one or more surfaces. For example, antennas may be present on two or more sides of the node, and preferably on three or more sides of the node. These antennas will be positioned outside the internal structure, and these antennas may be positioned within recesses in the internal structure. In some cases, the antennas may be located behind windows through the internal structure. This is to allow electromagnetic signals to reach the antennas, which can easily pass through the sealed skin but cannot pass through the metal internal structure. The example shown in the figure includes antennas on both sides, including an antenna on the right side connected to the main PCB 38 and an antenna behind the handle 14 at the front of the node. It may also be an antenna on a separate PCB 7 located on the upper wall.

[0069] As mentioned above, and as Figure 5 As can be seen most clearly in FIG. 1 , the panel supporting the handle and the handle itself 14 may include a window 42 in which the antenna is located. An additional window 43 (eg, Figure 2 and Figure 4 As shown in the figure, the window 43 may also provide an opening behind which the antenna is located. The beacon may also be located behind one of the windows 42 or 43 or the beacon may be located behind a separate window in the exterior surface of the internal structure (i.e., the left wall, right wall, front wall, rear wall, top wall, or bottom wall). The beacon may be a light (such as an LED or another lighting device, an acoustic transducer) or an electromagnetic source (such as an electromagnetic coil). The beacon may be used to help locate the node on the seafloor. Additional beacons and / or additional windows may be provided in the node so that additional lights, sources, or antennas may be located around the node. In the figure, the second window 43 includes an opening in the side wall 40 of the internal structure that is adapted to a cover of transparent material that acts as a light guide and provides additional protection for the beacon. Similar transparent material or light guides may be provided in any of the other windows. Because the sealed skin is thin, the beacon light or source located behind the window is waterproof and visible through the skin. If an antenna is present, the material covering the window can be any material as long as the signal can be sent from the antenna located behind (i.e., these window covers will not be formed of metal). In order to view the light behind the window, it is preferred that the cover is also transparent or translucent to allow at least most of the light to pass through.

[0070] The internal structure may include any number of these windows which allow the node to detect light or other signal sources when in use or provide access to the node's antenna. These windows may be located anywhere on the internal structure, but in the example shown in the figure, there are two windows and they are located in the side wall 40 and behind the handle as mentioned above. The windows may each include an additional covering portion (which will also help prevent the skin from penetrating into the inner portion of the internal structure during molding), or the windows may simply represent openings in the outer surface of the internal pressure-resistant structure. The window on the front of the node may be located only in the handle portion, and if present, the plate is located behind the handle and the signaling light is positioned on the outer surface of the internal structure.

[0071] Electromagnetic signals are able to easily pass through the skin and reach any antennas located on or outside the exterior surface of the internal structure but within the sealed skin. For example, positioning a charging coil for a battery beneath the sealed skin but on or outside the exterior surface of the internal structure allows for efficient wireless charging of the node by induction. Typically, the thin sealed skin protects the components from water damage without impeding the functionality of those components as previous metal node housings necessarily did. This is an important feature of the nodes described herein and has particular utility when it comes to the protection and functionality of one or more of wireless antennas, beacon sources, and hydrophones for communications and / or charging.

[0072] The main circuit board 38 of the node may support at least the control / microcontroller chip (logic) and other electronics required for the node. Where an optical beacon is included, and if the light source is not located at the surface of the node, the node may also include an additional light guide to transmit light from the beacon light to a window at the surface of the node's internal structure so that the light is visible from the outside for use in locating the node by an ROV or the like.

[0073] The seismic sensors themselves may include one or more sensors that measure velocity, displacement, and / or acceleration. Geophones may be used for this purpose, but preferably at least one or some of the seismic sensors of the node will be accelerometers, such as MEMS accelerometers. Additional node sensors may include one or more of a heading sensor (such as a compass), a tilt sensor, and a temperature sensor, and a static pressure sensor. These sensors may be located in additional cavities or recesses formed in the central block of the internal structure.

[0074] As mentioned above, the node may include a charging coil 36 and one or more of one or more wireless antennas located outside the supporting internal structure but inside the outer sealed skin. The node can be configured for wireless communication by mounting the required components on the outer surface of the internal pressure-resistant structure. The PCB 7 in the example shown in the figure supports at least some of the wireless communication electronics required for the node. Due to the need for electrical components to be protected from water corrosion and the need for thick metal sealed housings to house these components, functional solutions for wireless communication with seabed nodes or wireless charging of such nodes have not been proposed as part of previous node designs. These metal shells prevent signals from reaching or being sent to and from the node, and these metal shells prevent the use of magnetic charging devices to generate current in the charging coil.

[0075] The use of an internal pressure resistant structure and an external sealed skin that is not pressure resistant and non-metallic but fits around the internal structure to form a waterproof cover means that components such as wireless antennas and charging coils can be located very close to the external surface of the node without thick or metal walls between them and the surrounding environment. Instead, there is only a relatively thin layer of material (such as plastic) that does not prevent: signals / data from being transmitted to and from the node, viewing beacon lights or receiving beacon signals, or charging the coil by an external device. Charging via the coil can include charging the node's power source (such as batteries in one or more battery packs). The node is able to transmit and receive data, be programmed, and be charged without opening the node and without the need for external connectors. This is obviously very beneficial when the node is designed to stay on the seabed for a long time because it reduces the possibility of leakage and damage to internal components.

[0076] In order to make a node, the internal pressure-resistant structure 4 must first be made. This can be achieved by machining the various parts of the internal structure with metal. Optionally, aluminum can be used for the internal structure because it is particularly light, cost-effective, and easy to form. The internal structure can be composed of an upper wall 6, a lower wall 8, and a left wall and a right wall (preferably including one or more covers, such as cover 40). One or more of these walls may include: a recess for receiving electronic devices and other components; or a hole for attaching the various parts of the internal structure together using bolts or other attachment devices. The internal structure may also include a central block 26, in which a cavity for accommodating larger components (such as an electric power source) is provided. The central block will generally represent the heaviest part of the node housing and will provide most of the pressure resistance required for the internal structure. As mentioned above, one or more of the walls can be integral with the central block so that they do not represent removable panels and cannot be separated from the central block. The components of the node are then placed in their assigned cavities or recesses, or are secured to or placed in desired locations on the interior structure prior to application of the exterior skin.

[0077] The step of applying the outer skin 2 may include applying the skin by an overmolding process, which may involve applying a resin substance to the outer surface of the inner structure (on the upper wall, lower wall, front wall, rear wall, right wall and left wall, where rectangular shapes are used for the nodes). The resin substance is allowed to harden to form a sealing skin. As mentioned above, the skin may be formed of a plastic material such as polyurethane. If desired, additional components (such as handles 14) may be fixed to the nodes on the outside of the skin, or they may be integrated into the sealing skin and formed by the mold used to form the skin. For example, a raised portion for overlapping and connecting may be integral with the sealing skin and formed during the molding process.

[0078] The material used to form the outer skin (particularly where the node is used as a seabed node and the skin is to be applied by overmolding) should preferably be heat resistant, should provide good acoustic coupling, should be mouldable at low temperatures, should be a low wear material, and should be fire resistant, UV resistant etc. Plastic materials such as polyurethane are a good choice for a sealed shell.

[0079] In some cases, rather than using a skin that is formed as a single portion by molding to be applied to a surface of an internal structure, a sealed skin comprising more than one portion may be used. Two or more sections of the skin may be joined together via a sealed connection so that once assembled, the skin is waterproof and prevents water from intruding into the internal components of the node. Again, the skin does not provide any pressure resistance or any actual structural support to the node, and therefore can be thin and formed from a material such as plastic. This composite skin will function in the same manner as the overmolded skin described above, in that it will provide a sealing function to protect the internal components from water intrusion, but will not interfere with the performance of components such as hydrophones, charging coils, and wireless communication devices. Again, internal structure is required to define the shape of the node when the node is subjected to pressure in use.

[0080] Although the nodes described herein are designed for use as seismic nodes, and therefore include seismic sensors as sensors, the same principles may be used to make another type of sensing node. Thus, in any of the above embodiments, the seismic sensor may be replaced with another sensor to monitor the characteristics of the node's surroundings. As described, the sensor may be housed in a pressure hull within a sealed skin.

Claims

1. A seismic node (1), comprising: at least one seismic sensor; an internal pressure-resistant structure (4), the internal pressure-resistant structure (4) comprising a first wall (6), a second wall (8), and one or more support elements extending between the walls to define one or more cavities for accommodating pressure-sensitive components; as well as A separate waterproof sealing skin (2) surrounds the internal pressure-resistant structure and the at least one seismic sensor.

2. The seismic node (1) according to claim 1, wherein: The sealing skin (2) is molded onto the pressure-resistant structure (4).

3. A seismic node (1) according to any one of claims 1 and 2, wherein: The support element comprises at least one additional wall, and the walls of the internal pressure-resistant structure (4) together form a substantially continuous outer surface for supporting the surrounding sealing skin (2).

4. The seismic node according to any one of claims 1 to 3, wherein: The sealing skin (2) is formed from a plastic material.

5. The seismic node according to claim 4, wherein: The plastic material is polyurethane.

6. The seismic node according to any one of claims 1 to 5, wherein: The sealing skin (2) comprises a single piece of material.

7. The seismic node according to any one of claims 1 to 6, wherein: The pressure-resistant structure (4) is a metal frame.

8. The seismic node according to claim 7, wherein: The pressure-resistant structure (4) is an aluminum frame.

9. The seismic node according to any one of claims 1 to 8, wherein: The thickness of the sealing skin (2) is between 2 mm and 10 mm.

10. The seismic node according to any one of claims 1 to 9, wherein: One or more of the seismic sensors comprises at least one hydrophone (10) received in a cavity (12) in an outer surface of the pressure structure (4).

11. The seismic node according to claim 10, wherein: The hydrophone (10) is embedded in the sealing skin (2).

12. The seismic node according to any one of claims 1 to 11, wherein: One or more of the seismic sensors include at least one motion sensor and at least one pressure sensor.

13. The seismic node according to any one of claims 1 to 12, comprising at least one antenna positioned between the outer surface of the internal pressure structure (4) and the sealing skin (2).

14. The seismic node of any one of claims 1 to 12, comprising at least one antenna located behind a window in an exterior surface of the internal pressure structure.

15. The seismic node according to any one of claims 1 to 12, comprising: a panel embedded in or positioned on the sealing skin to attach a handle to the node; and at least one antenna located behind a window in the panel.

16. A seismic node according to any one of claims 1 to 15, wherein: The seismic node (1) is a seabed seismic node.

17. A method for making a seismic node (1), the method comprising: A pressure-resistant structure (4) is provided, the pressure-resistant structure (4) comprising a first wall (6), a second wall (8), and one or more support elements, the one or more support elements extending between the first wall and the second wall to define one or more cavities between the first wall and the second wall for accommodating a pressure-sensitive component; positioning at least one seismic sensor relative to the structure; as well as A separate waterproof sealing skin (2) is applied to the node such that the separate waterproof sealing skin (2) contains and surrounds the pressure-resistant structure and the seismic sensors.

18. Method according to claim 17, comprising applying the sealing skin (2) onto the pressure-resistant structure (4) by overmolding the sealing skin (2) onto the outer surface of the pressure-resistant structure (4).

19. A method according to any one of claims 17 and 18, comprising positioning one or more pressure sensitive components within the cavity of the pressure resistant structure (4) prior to applying the sealing skin (2).

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