Hybrid seismic data acquisition apparatus and corresponding methods

Abstract

A seismic data acquisition apparatus (400) is proposed for placement on the sea floor, the seismic data acquisition apparatus (400) comprising a polymer housing (412) defining a chamber accommodating at least a portion of a data acquisition system (440, 444, 445) and a metal arrangement (414) in which the polymer housing (412) is captured, the metal arrangement (414) comprising two metal beams (4141, 4142) extending on opposite sides of the polymer housing (412). A method for assembling such an apparatus and a corresponding method for sea bed seismic data acquisition are also proposed.

Description

Technical Field

[0001] The embodiments of the subject matter disclosed herein generally relate to methods and apparatus for seismic acquisition of the seabed, and more specifically to ocean bottom nodes. Background Technology

[0002] Seismic data acquisition and processing can be used to generate profiles (images) of geophysical structures beneath the surface (subsurface). While these profiles do not provide the precise location of oil and gas reservoirs, they suggest to those trained in the field the presence or absence of such reservoirs. Therefore, providing high-resolution subsurface images is important, for example, for those who need to determine the location of oil and gas reservoirs.

[0003] For ocean imaging, such high-resolution images can be obtained using the seismic acquisition systems currently being discussed. For example... Figure 1 As shown, the seismic acquisition system 100 includes multiple seabed nodes 102, which are distributed on the seabed 101 by various means. Each seabed node 102 includes, for example, a hydrophone 104 for detecting pressure waves, a processor 106 for processing the detected waves, a memory 108 for storing seismic data, and a power supply 110 for providing power to these components. A vessel 120 tows one or more seismic sources 122, which are located at a specific depth in the water relative to the sea surface 121. The seismic sources 122 are configured to generate seismic waves 124. The seismic waves 124 propagate into the subsurface 126 and are reflected and / or refracted at various interfaces 128 in the subsurface. The reflected waves 130 are then detected by the hydrophone 104 and recorded in the memory 108 of the seabed node 102.

[0004] Traditional subsea nodes are designed based on the water depth at which they operate and the required autonomy. Generally, shallow water depths, where deployment methods such as the node-on-a-rope technique described in U.S. Patent No. 6,024,344, require lower autonomy. However, deep-water applications, where nodes are typically deployed and positioned by remotely operated vehicles, require longer autonomous nodes, thus necessitating greater battery capacity. To address these two different requirements, most existing nodes are designed with two distinct configurations, one for shallow water and one for deep water, which involves different battery capacities, sizes, and volumes.

[0005] Shallow sea bottom nodes comprise, in addition to hydrophones, geophones for detecting seismic waves. Nodes used in water less than 300 meters deep are considered shallow sea bottom nodes. Geophone sensors are particle motion sensors and detect the velocity of water particles if implemented as geophones or the acceleration if implemented as MEMS and can be omnidirectional or unidirectional. Depending on the node configuration, a shallow sea bottom node can integrate one or more particle motion sensors and one hydrophone. Due to the inherent limitations of gimbal mounted geophones, it is preferable to integrate a 3C particle motion sensor.

[0006] For deep water seismic acquisition, most often from 700 meters to 3,000 meters, high battery autonomy is required as the nodes need to be placed on the sea floor for a long period of time. The housing for such nodes also needs to be heavy and robust, often made of titanium material to avoid corrosion and housing deformation due to high hydrostatic pressure. The node design is also oversized by using reinforcing elements for high pressure resistance. Such nodes are therefore very expensive.

[0007] For shallow sea water depths, the use of titanium material and oversized shapes is not necessary. Therefore, as OBN for shallow sea water depths are deployed at shallower depths and for shorter time operations, cheaper materials can be used for the housing, for example, polymer materials. However, it is observed that even for deployment depths less than 100 meters, polymer housings for shallow sea OBN also deform and water penetrates into the housing, compromising the contained electronic devices. In addition, in some cases, the weight of the polymer housing is too light and the shallow sea OBN can not achieve good contact with the seabed.

[0008] Therefore, there is a need to design an improved OBN for shallow water operations that has a better trade-off between weight, cost, compactness and reliability. SUMMARY

[0009] According to an embodiment, there is provided a seismic data acquisition device, also called a bottom node and for placement on the sea floor, comprising:

[0010] - a polymer housing defining a cavity that houses at least part of a data acquisition system; and

[0011] - a metal device in which the polymer housing is captured, the metal device comprising two metal beams extending on opposite sides of the polymer housing.

[0012] The subsea node will thus combine a polymer-based inner shell with a metal outer device to hold the electronics to be used for seismic data acquisition. Due to this configuration of the node, it is not necessary to manufacture the shell comprising the seismic acquisition system in an expensive material, titanium. The arrangement of the metal device around the polymer shell enables the node to resist the hydrostatic pressure and corrosive environment that increases with water depth.

[0013] In addition, the metal outer device increases the dead weight of the subsea node (OBN) to provide a good coupling of the node to the seabed.

[0014] The beams of the metal outer device increase the mechanical resistance of the polymer inner shell and thus enable the polymer inner shell to reliably resist the hydrostatic pressure. The assembly of the metal outer device around the polymer inner shell prevents bending and collapse of the polymer inner shell.

[0015] This hybrid solution allows to increase the mechanical resistance of the OBN to withstand the external hydrostatic pressure compared to an equivalent product relying only on plastic parts and, on the other hand, avoids having to manufacture the OBN in a fully metal material.

[0016] According to an embodiment, the metal outer device extending around the polymer inner shell comprises through passages or openings, so that it is possible to limit the amount of metal material used to manufacture the metal outer device reinforcing the polymer inner shell.

[0017] According to an embodiment, the metal outer device presses the two polymer halves against each other, thereby increasing the mechanical resistance and waterproofness of the assembled polymer inner shell.

[0018] According to an optional feature, the metal device further comprises two joining parts joining the metal beams to form a metal band encircling the polymer shell, preferably the metal band encircling the polymer shell in a middle region of the polymer shell.

[0019] According to an optional feature, the metal device further comprises metal arches extending laterally from one metal beam to another metal beam, preferably to form a grid on opposite lateral portions of the polymer shell.

[0020] According to an optional feature, the metal device has two halves attached to each other in a detachable manner by a fixing system, for example by screws, each half of the metal device having a metal beam element forming, together with a corresponding beam element of the other half, said metal beam of the metal device.

[0021] According to an optional feature, the polymer shell has two halves.

[0022] According to an optional feature, each half of the polymer housing has an external collar element adapted to contact a corresponding external collar element of the other half when the two halves of the polymer housing are assembled to form said external collar of the polymer housing.

[0023] According to an optional feature, a through hole is machined through the external collar element and a threaded hole is machined in at least one of the metal beam elements, the halves of the metal outer device being connected to each other by a screw (436) passing through the through hole of the external collar element to attach the beam elements together while sandwiching the external collar elements in between.

[0024] According to an optional feature, the through hole machined in the external collar element is not threaded, such that a screw extends from the beam element through the external collar element without being secured to the external collar element to cooperate with a corresponding threaded hole machined in the other corresponding beam, such that the external collar elements are held against each other by the pressure exerted by the beam elements sandwiching said external collar elements in between.

[0025] According to an optional feature, the seismic data acquisition device comprises a protective bumper fixed to the metal outer device, preferably to the metal beams, the protective bumper covering a portion of the polymer inner housing.

[0026] According to an optional feature, the protective bumper has two halves separated by the metal beams of the metal outer device.

[0027] According to an optional feature, the protective bumper has a hole enabling water to enter the protective bumper.

[0028] According to an optional feature, the polymer housing is made of polyurethane, polypropylene, polyethylene or polyamide.

[0029] According to an optional feature, the polymer housing is reinforced by glass fibers incorporated in the polymer.

[0030] According to an optional feature, the metal device is made of a copper alloy, in particular bronze.

[0031] According to an optional feature, the seismic data acquisition device comprises a hydrophone attached to the polymer inner housing to be in electrical communication with the electronic devices embedded in the polymer inner housing.

[0032] According to an optional feature, said at least a portion of the data acquisition housed in the polymer inner housing comprises a management card configured to communicate through a port with a power supply and / or a data server on shore, the port being closed with a cap to prevent water from reaching any electrical contacts when the node is deployed in water.

[0033] According to a particular embodiment, the metal device is dimensioned such that the arches extend within corresponding recesses of the polymer housing.

[0034] According to another embodiment, a method for assembling a seismic data acquisition device, also referred to as a seabed node and for being placed at the seabed, is provided, the method comprising:

[0035] - providing a data acquisition system and a polymer housing accommodating at least a part of the data acquisition system; and

[0036] - providing a metal device comprising two metal beams adapted to extend over opposite sides of the polymer housing; and

[0037] - binding the polymer housing in the metal device.

[0038] According to another embodiment, a method for seabed seismic data acquisition, preferably for water depths between 100 and 700 meters, is provided, the method comprising the steps of providing a seismic data acquisition device as described above; and placing the seismic data acquisition device at the seabed. BRIEF DESCRIPTION OF DRAWINGS

[0039] For a more complete understanding of the present application, reference is now made to the following description taken in conjunction with the accompanying drawings in which:

[0040] Figure 1 is a schematic view of a seismic data acquisition system using seabed nodes as known in the background art;

[0041] Figure 2 shows an exploded view of a hybrid seabed node having an inner polymer housing and an outer metal device according to an embodiment of the application;

[0042] Figure 3 shows a hybrid seabed node of Figure 2 having an additional bumper component;

[0043] Figure 4 shows a hybrid seabed node of Figure 3 according to another view;

[0044] Figure 5 shows a hybrid seabed node of Figure 4 in an assembled state; and

[0045] Figure 6 shows a hybrid seabed node having an inner polymer housing and an outer metal device according to another embodiment of the application, showing the situation after the halves of the outer metal housing have been attached to each other such that the halves of the inner polymer housing are also joined to each other by the metal outer device;

[0046] Figure 7 An exploded view of a hybrid seabed node according to another embodiment of the present invention is shown. Figure 6 The nodes have an internal polymer shell and an external metal device, and further have protective buffers;

[0047] Figure 8 The assembly state is shown. Figure 7 The hybrid seabed node, in which half of the protective buffer is attached to half of the external metal device;

[0048] Figure 9 Another embodiment of a hybrid seabed node is shown, in which a pinger can be attached to a protective buffer of the hybrid seabed node;

[0049] Figure 10 This is a flowchart of a method according to an embodiment of the present invention, used for assembling a hybrid subsea node having an internal polymer shell and an external metal device, such as... Figures 2 to 9 Any node in the graph. Detailed Implementation

[0050] The following description of the embodiments refers to the accompanying drawings. The same reference numerals in different drawings identify the same or similar elements. The following detailed description does not limit the invention. Rather, the scope of the invention is defined by the appended claims. For simplicity, the following embodiments are discussed with respect to shallow seabed nodes that record seismic data. However, the embodiments discussed below are not limited to shallow seabed nodes that record seismic data, and can be applied to other nodes that collect different data.

[0051] Throughout this specification, references to "an embodiment" or "an embodiment" mean that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the disclosed subject matter. Therefore, the phrases "in one embodiment" or "in an embodiment" appearing in various places throughout the specification do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0052] According to embodiments, most of the electronics of a new shallow sea bottom node configured to record seismic data are housed in an internal polymer housing. The internal polymer housing is made of two or more parts and the parts are configured to fit together to form a watertight internal chamber. A metal outer device is configured to enclose the internal polymer housing and to ensure that the parts of the internal polymer housing remain in close contact with each other, thereby maintaining watertightness. In addition, the mass of the metal outer device is selected so that the entire bottom node has negative buoyancy, so that the node achieves firm contact with the sea floor. According to embodiments, the outer metal housing is configured to surround the internal polymer housing. The internal polymer housing is watertight, while the outer metal housing is preferably not watertight.

[0053] With reference to the drawings, a seismic data acquisition apparatus 400, also referred to as an ocean bottom node (OBN), is presented, which is intended to be placed on the sea floor and used for acquisition of seismic data.

[0054] The seismic data acquisition apparatus 400 comprises a polymer internal housing 412, which houses at least a part of a data acquisition system. The seismic data acquisition system comprises a battery 440 and electronics 444 for seismic data acquisition. The electronics 444 can comprise a processor, a memory and at least one seismic sensor, such as a particle motion sensor 445. The at least one seismic sensor can comprise a MEMS sensor or a geophone.

[0055] As will be described below, the seismic data acquisition system can further comprise a hydrophone 470, which is connected to the electronics 444, but extends outside the polymer internal housing 412 to be submerged in water, so as to measure water pressure variations.

[0056] In the illustrated embodiment, the polymer internal housing 412 has two internal halves 412A, 412B, which are intended to be joined together, so as to prevent water from entering inside a chamber defined by the halves 412A, 412B, which chamber comprises said at least a part of the data acquisition system.

[0057] The seismic data acquisition apparatus 400 further comprises a metal device 414, which is referred to as a metal outer device 414, since it is positioned outside the polymer internal housing 412 and, in the present embodiment, it is in contact with the polymer internal housing 412. According to a particular aspect of this embodiment, a metal arch 418 (described below) of the metal outer device 414 coincides with the polymer internal housing 412. However, in embodiments where the polymer internal housing 412 is not watertight, the metal outer device 414 can be configured to enclose the polymer internal housing 412, so as to ensure that the parts of the polymer internal housing 412 remain in close contact with each other, thereby maintaining watertightness. Figure 6In another embodiment of the illustrated embodiment, the metal arch 418 that provides protection in the event of an impact does not contact the polymer inner housing 412 because the fixation of the metal outer device 414, in particular the metal band, is directly fixed to the outer lip (outer collar) of the polymer inner housing 412.

[0058] For example, in one embodiment, the polymer material can be a plastic or rubber, such as polyamide PA, polyurethane PU, polyethylene PE or polypropylene PP, which can be reinforced with glass fibers, for example, and the metal material can be an aluminum-copper alloy. Other polymer materials and / or metal materials can be used.

[0059] The metal outer device 414 can comprise two halves 414A, 414B that are positioned around the polymer inner housing 412 and are fixed to each other by a mechanical fixation means such as screws 436, such that the fixation of the halves to each other imprisons the polymer inner housing 412. The metal outer device 414 is thus attached to the polymer housing and mechanically reinforces the polymer housing 412 that is captured in the metal outer device 414.

[0060] According to an embodiment, the metal outer device 414 is coupled to the polymer inner housing by clamping or confining the polymer inner housing 412 between the two halves 414A, 414B of the metal outer device 414. Then, as illustrated in the embodiment of Figures 2 to 5 The two halves 414A, 414B of the metal outer device 414 can be attached to each other by direct contact between the two halves 414A, 414B of the metal outer device 414 with screws 436. Preferably, as illustrated in the embodiment of Figures 6 to 8 The attachment is achieved by having the halves 414A, 414B of the metal outer device 414 contact opposite sides of the outer collar (or lip) 4124 of the polymer inner housing and by passing screws through holes 4125 machined in the outer collar. Thus, the screws 436 can pass through a portion of the polymer inner housing 412 that is not in communication with the cavity defined by the polymer inner housing 412 to prevent water from being introduced into the cavity through the screws. Such a portion can be the outer collar 4124 of the polymer housing 412 that is clamped between the halves 414A, 414B of the metal device 414.

[0061] According to a particular embodiment and as illustrated in the embodiment of Figures 6 to 8 The two halves 414A, 414B of the metal outer device 414 are positioned around the polymer inner housing 412 and against the outer collar 4124 of the polymer inner housing 412. Then, the two halves 414A, 414B of the metal outer device 414 can be fixed to each other by screws passing through the outer collar 4124. In Figures 6 to 8In the illustrated embodiment, the outer collar corresponds to an assembly of two outer collar elements 4124A, 4124B of the two halves of the polymer inner housing. The two outer collar elements 4124A, 4124B are maintained against each other by the force exerted by the two halves 414A, 414B of the outer metal device 414 sandwiching the two halves 412A, 412B of the polymer inner housing. Each outer collar element 4124A, 4124B is preferably integrally formed with the half 412A, 412B of the inner polymer housing, for example by molding; a seal can be present.

[0062] As Figures 2 to 5 and Figures 6 to 8 As illustrated in the embodiment of FIG. 4, the metal outer device 414 comprises two metal beams 4141, 4142 extending on opposite sides of the polymer inner housing 412. The opposite sides on which the metal beams 4141, 4142 extend are the major surfaces of the polymer inner housing 412 corresponding to the top and bottom sides. Note that "top" and "bottom" are used with respect to the illustration: in use, the top or bottom side can face the sea bottom.

[0063] Preferably, the polymer inner housing 412 is cuboid-shaped, and the metal beams 4141, 4142 extend parallel to the longitudinal axis of the polymer inner housing 412.

[0064] The metal outer device 414 further comprises metal arches 418, each metal arch extending laterally from one metal beam 4141 to the other metal beam 4142. The arches 418 thus form a grid covering opposite lateral portions of the polymer inner housing 412. The arches 418 can be in contact with the polymer inner housing 412, thereby enabling to mechanically reinforce portions of the polymer housing 412 not covered by the beams while using a limited amount of metal, and enabling to access portions of the polymer inner housing between the arches or to access one or more elements connected to the polymer housing 412, such as the hydrophone 470 or the cap 464 closing the connection port 462 of the polymer inner housing. The operator thus does not have to remove the metal outer device 414 from the polymer inner housing 412 to access the hydrophone 470 or the cap 464.

[0065] In the illustrated embodiment, each arch 418 of the metal outer device 414 has a U-shape. The branches of the U-shape are fixed to, preferably by molding or welding to, the metal beams 4141, 4142. In the illustrated embodiment, each arch of the metal outer device 414 extends from one beam to the other, around the lateral sides of the polymer inner housing.

[0066] According to the embodiment and as illustrated in FIG. 4, the metal outer device 414 comprises two metal beams 4141, 4142 extending on opposite sides of the polymer inner housing 412. The opposite sides on which the metal beams 4141, 4142 extend are the major surfaces of the polymer inner housing 412 corresponding to the top and bottom sides. Note that "top" and "bottom" are used with respect to the illustration: in use, the top or bottom side can face the sea bottom. Figures 6 to 8As shown, the metal beams 4141, 4142 are joined to each other by metal parts 4143 to form a ring-shaped metal element, referred to as a metal band 4200. The metal band 4200 encloses a portion of the polymeric inner shell 412. In the embodiment shown, the metal band 4200 encloses a central longitudinal portion of the polymeric inner shell 412. In other words, the beams are elongated by means of the joining elements visible on the lateral sides of the polymeric shell, thereby forming a metal band. In particular, the metal band reinforces the polymeric inner shell at the region of the joining plane of the two halves 412A, 412B of the polymeric inner shell 412.

[0067] The metal band 4200 encircles the polymeric inner shell. The metal band 4200 can be formed of two metal band elements 4200A, 4200B. The two metal band elements 4200A, 4200B can be positioned from either side of the outer collar 4124 of the polymeric inner shell 412. In the embodiment shown, the two metal band elements 4200A, 4200B are positioned from the same side of the outer collar 4124 of the polymeric inner shell 412. Figures 6 to 8 In the embodiment shown, the metal band elements 4200A, 4200B are attached to each other with a screw 436 passing through the outer collar 4124 of the polymeric inner shell 412.

[0068] In other words, the metal band 4200 and more particularly the beams 4141, 4142 form a skeleton, while the arches form ribs surrounding the inner polymeric shell 412. The metal band 4200 and the arches thus form an outer shell that encloses the polymeric inner shell 412 with apertures defined between the arches. The space between the arches forming said apertures can limit the amount of material used to manufacture the metal outer device and provides easy access to some portions of the polymeric inner shell 412.

[0069] In one embodiment, the polymeric inner shell 412 is entirely made of a polymeric material, while the outer device 414 is entirely made of a metal material.

[0070] According to embodiments, each of the inner halves 412A and 412B of the polymeric inner shell 412 has one or more grooves 416 formed on the outer surface, for example as shown in Figure 2 Each of the outer halves 414A and 414B of the metal outer device has a respective one or more tongues or arches 418. Figure 2 and Figure 3The illustrated embodiment shows each interior half 412A and 412B having four grooves 416, and each metal exterior half 414A and 414B having four arches 418. However, those skilled in the art will appreciate that any number of grooves and arches can be used for a given half. According to another embodiment, the polymer interior housing 412 can not have grooves, but rather have a particular texture, such as including ribs for mechanical reinforcement of the structure of the polymer interior housing 412. The dimensions of the metal exterior device 414 can be designed such that when the exterior halves are placed on the respective interior halves, each arch 418 fits snugly within the respective groove 416, as Figure 2 illustrated.

[0071] In Figures 2 to 8 the illustrated embodiment, each half 414A, 414B of the metal exterior device 414 has a first beam element 4141A, 4142A, a second beam element 4141B, 4142B, and an arch 418 extends from the first beam element to the second beam element. The assembly of first beam elements 4141A, 4142A forms a first beam 4141, and the assembly of second beam elements 4141B, 4142B forms a second beam 4142. Thus, the arch 418 connects the two beams 4141A, 4142A to form an exterior half 414A, and the opposite arch 418 connects the two beams 4141B, 4142B to form an exterior half 414B. One of the first or second beam elements of one of the exterior halves 414A, 414B can also have a hook or loop 422, as Figure 3 illustrated, which serves as a mechanical connection when the node is deployed underwater.

[0072] The metal beam elements 4141A, 4142A, 4141B, 4142B of each half 414A, 414B of the metal device 414 include two metal beam elements that extend on opposite top and bottom sides of the polymer housing 412.

[0073] In this embodiment and as Figures 6 to 8 illustrated, for each half 414A, 414B of the metal device, the metal beam elements 4141A, 4142A, 4141B, 4142B are joined to each other by a metal part element 4143A, 4143B to form a metal band element 4200A, 4200B. When attached to each other, the metal band elements 4200A, 4200B form the metal band 4200. The metal part elements 4143A, 4143B form a metal part 4143.

[0074] Each metal band element of the half of the metal device is configured to be in contact with the outer collar element of one half of the polymer housing. Since the metal band has two halves and each half encloses one half of the polymer inner housing, while the two halves of the metal band push one half of the polymer inner housing against the other half when the two halves of the metal band are attached to each other, the metal band improves the water resistance of the two halves of the polymer housing when assembled together.

[0075] In one application, each half of the metal outer device is shaped as a band that is placed around the respective half of the polymer inner housing, and when the two metal outer halves are mechanically connected to each other, the polymer inner halves also become connected to each other without having to use any screws directly between the inner halves. In this embodiment, the two inner polymer halves are directly connected to each other due to the outer metal halves being directly connected to each other. As Figures 2 to 5 embodiments, the first and second metal outer halves can thus hold the first and second inner polymer halves together without the need for screws that extend from the first inner polymer half to the second inner polymer half. Note that in Figures 6 to 8 embodiments, the holes 4125 provided in the outer collar 4124 can be sized to simply let the screws pass through the outer collar without exerting a direct pushing force on the outer collar. The pushing forces exerted on opposite sides of the outer collar are provided by the assembly of beam elements (or respective band elements) that are connected to each other by the screws.

[0076] According to embodiments and as shown in Figures 2 to 5 and Figures 6 to 8 other than the first and second outer metal halves, nothing forces the first and second inner polymer halves to remain connected to each other. In other words, the first and second inner polymer halves are connected to each other only due to the first and second outer metal halves that are attached to each other by the screws.

[0077] As mentioned above, the first and second beam elements 4141A, 4141B and 4142A, 4142B of each of the metal outer halves 414A, 414B have holes 426 for allowing respective screws 436 to mechanically connect one of the two metal outer halves 414A and 414B to the other. By mechanically directly connecting the two metal outer halves 414A and 414B to each other, the polymer inner halves 412A, 412B are forced to mechanically abut against each other, thereby forming a first sealed inner chamber 413A within the first inner half 412A and a second sealed inner chamber 413B within the second inner half 412B. As Figure 2 and Figure 3As shown in the embodiment, the hole 426 can be formed through or in the metal beams 420A and 420B without penetrating the inner polymer housing. This provides increased mechanical strength to the OBN 400. Because the two halves of the polymer housing 412 are pressed against each other, the seal is compressed, thus improving the sealing performance. In other words, the screw 436 can pass from one beam element through at least a portion of the outer metal device to the other corresponding beam element without penetrating the inner polymer housing.

[0078] In an application, such as Figure 6 As shown, at least one screw 437 is preferably associated with at least one arched member 418. The at least one screw 437 can be used to attach, for example, an external buffer, such as... Figure 7 As shown.

[0079] according to Figures 6 to 8 In another embodiment shown, and as described above, the mechanical strength of the inner polymer housing 412 is further enhanced by providing external collar elements 4124A, 4124B for each half of the inner polymer housing 412. The collar elements 4124A, 4124B are configured to contact each other to form an external collar 4124 sandwiched between beam elements 4141A, 4141B and 4142A, 4142B. Each external collar element 4124A, 4124B extends around the body of the corresponding half of the inner polymer housing 412 and is provided with a hole 4125 that allows a screw 436 to pass from a beam element of one half of the metal exterior device through the external collar element to a corresponding beam element of the other half of the metal exterior device.

[0080] exist Figures 6 to 8 In one embodiment, the metal beam elements 4141A and 4142A of half 414A thus contact an external collar element 4124A, which extends on one side of the polymer inner shell half to which the metal beam elements of the half are applied. Another opposing metal beam element 4141B and 4142B contact another external collar element 4124B, which extends on the opposite side of the polymer inner shell half to which the other metal beam elements 4141B and 4142B are applied.

[0081] According to the embodiments and as follows Figure 2 and Figure 3Specifically shown, a battery 440 is placed in a first sealed polymer interior chamber 413A and electronics 444 (which can include a processor, memory, and a mass particle motion sensor 445, i.e., a MEMS sensor or geophone) are placed in a second sealed polymer interior chamber 413B. The two polymer chambers 413A and 413B can be separated by a strength plate 450 made of a strong material, such as titanium or any other plastic or polymer material that can be imagined that is also "hard". By being placed between the first and second interior halves 412A and 412B, the strength plate 450 provides increased structural support to the interior polymer housing. In other words, when the external pressure (hydrostatic pressure) is large, e.g., when the node is at a depth of between 75 and 100 meters from the water surface, the external pressure will not be able to bend the connecting lip of the two interior halves 412A and 412B due to the presence of the strength plate 450. In addition, the strength plate 450 serves to enable good coupling to the electronics 444 connected to the MEMS or geophone sensor. Since the strength plate is made of a strong material and does not deform, the sensor can be directly coupled to the plate. In one application, the strength plate 450 is sized to completely close the second interior chamber 413B so that there is no open passageway between the first interior chamber 413A and the second interior chamber 413B.

[0082] Other electronic components can be placed within the first and second interior chambers 413A and 413B. For example, the electronics 444 can include a power and data retrieval (management) card that can be placed within the second polymer interior chamber 413B for managing power from the battery 440 and data exchange with a base when the OBN is on shore and preparing for deployment. In this regard, the card can be configured to communicate through a port 462 with a power source (not shown) and / or a data server (not shown) on shore. The power source is used to charge the battery 440 and the data server is used to receive all recorded seismic data from the node 400. As shown, when the node is deployed in the water, the port 462 is closed off by a cap 464 to prevent water from reaching any electrical contacts. In embodiments, as further shown in Figure 3 Figure 4

[0083] Figure 2 、 Figure 4 、 Figure 6 、 Figure 7 and Figure 8 ​​​As shown, a hydrophone 470 can be attached to the second inner polymer half 412B to be in electrical communication with the electronics 444. A pressure relief valve 480 can also be attached to the second polymer inner half 412B. In the event of a battery leak, which can increase the pressure inside the node, the pressure relief valve 480 can serve as a safety element. The pressure relief valve 480 can also be used to equalize the pressure between the second inner chamber 413B and the surrounding environment after the node is retrieved onto the mother vessel.

[0084] The polymer inner housing 412 and the metal outer device 414 can be partially protected by a protective bumper 490, as shown in the embodiments of Figure 4 or Figure 7 and Figure 8 . The protective bumper 490 can have a first half bumper 490A configured to cover a portion of the first polymer inner half 412A and a portion of the first metal outer half 414A, preferably the arch 418.

[0085] The two halves 490A, 490B of the protective bumper 490 are separated from each other by the metal beams 4141, 4142 of the metal outer device 414. Each half of the protective bumper 490 covers a lateral portion of the polymer inner housing extending from either side of the metal beams. The protective bumper 490 covers the arch of the metal outer housing 414.

[0086] In the assembled state of the node, the edges define the main opening of the half bumpers 490A, 490B, which are used to cover a portion of the halves 412A, 412B of the polymer housing 412, the edges being in contact with the metal band elements 4200A, 4200B. Thus, the first half bumper 490A is configured to be positioned against the corresponding edges 4149 of the metal band elements (or metal beam elements) of the first metal outer half 414A by the edges 498, preferably the perimetrical edges. The second half bumper 490B is configured to cover a portion of the second polymer inner half 412B and a portion of the second metal outer half 414B. According to a particular aspect, the second half bumper 490B is also configured to be positioned against the corresponding edges of the metal band elements (or metal beam elements) of the second metal outer half 414B by the edges, preferably the perimetrical edges.

[0087] The protective buffer 490 can be made of an elastic material, such as thermoplastic polyurethane (TPU). One reason for using this material on a portion of the internal polymer housing that is fixed to the external metal device is to protect the MEMS sensor 445 and all electronics from unwanted impacts. Furthermore, the clock of the electronics 444 is highly sensitive and requires protection against impacts. When the node is deployed in water, impacts may occur as the node freely falls to the seabed. The elastic material is configured to absorb some of the impact.

[0088] Figure 4 and Figures 7 to 8 Further illustration shows multiple holes 492 formed through the buffer 490 to allow surrounding water to move freely into the hydrophone 470, enabling the hydrophone to come into direct contact with the water. Note that the hydrophone can only measure water pressure when it is in direct contact with a water particle.

[0089] In one application, for the purpose of stacking node 400 on top of another node and stacking other nodes on top of node 400 (when stored on a mother ship or another facility), one or more stacking features are formed in buffer 490. For example, as Figure 4 As shown, cylindrical members 494, possibly screws, are added to the first half of the buffer 490A and to the corresponding outer half, and corresponding holes 495 are added to the second half of the buffer 490B. Thus, screws from the next node (not shown) engage in the holes 495, and the holes from the next node receive the screws 494, thereby preventing the next node from slipping off the node 400. Additionally, the cylindrical members 494 secure the buffer 490 to the outer housing 414. In one application, the buffer 490 can be manufactured with a plurality of recesses 496 and a plurality of peaks 497, such that peaks from another node engage within the recesses 496, and peaks 497 engage within the recesses of another node. These features further prevent one node from slipping off another when nodes are stacked on a mother ship or ashore.

[0090] like Figure 4 As shown, and applicable to other embodiments, two inner polymer halves 412A and 412B and two outer metal halves 414A and 414B are prepared to be connected to each other to ensure a waterproof seal between the halves (i.e., no water enters the interior of the first and second inner chambers 413A and 413B), and at least one seal 610 may be provided between the inner halves. In addition to adding a first seal 610, a second seal 612 may be added to waterproof the inner chambers. According to an embodiment, the node does not have an acoustic emitter, which makes the entire node more compact.

[0091] However, as Figure 9As shown, the selection of an additional (removable) sound wave emitter is foreseen. Thus, the bumper 490 can comprise some attachment means for coupling a sound wave emitter element. The sound wave emitter 900 can be attached to the protective bumper 490 by a connection system. The connection system preferably comprises a locking rod 710 that can pass through a hole provided in the tooth 499 of the bumper 490 and a hole provided in the tooth 907 of the sound wave emitter 900. The tooth 499 of the sound wave emitter 490 interconnects with the tooth 499 of the bumper 490. This solution provides the advantage of preserving the compactness of the OBN, but other attachment means can be used.

[0092] When the screws 436 are fully engaged in the respective metal beams 420A and 420B (or metal bands 4200A, 4200B), the first and second metal outer halves 414A and 414B force the first and second polymer inner halves 412A and 412B to directly engage each other, and the metal beam elements from the first metal outer half are in direct contact with the metal beams of the second metal outer half (as shown in the embodiment of Figure 5 or indirectly contact (as shown in the embodiment of Figures 6 to 8 ) by the outer collar 4124 being sandwiched in between.

[0093] According to an embodiment, the metal outer halves 414A and 414B not only allow the user of the node to balance / stabilize the node by selecting / controlling the weight of the node, but they also encircle the polymer inner halves 412A and 412B to improve their coupling.

[0094] In addition, by having the screws 436 directly or indirectly connect (by simply passing through the hole of the outer collar instead of being screwed into said outer collar) the metal beam elements of the outer metal halves 414A and 414B, instead of having the screws connect by being screwed into the polymer material as in conventional nodes, a better and more reliable connection between the two halves 412A, 412B is achieved.

[0095] In one application, the outer metal halves 414A and 414B are dimensioned to fit tightly around the inner polymer halves 412A and 412B, such that no gap or cavity is formed between the inner surface of the metal outer halves and the outer metal surface of the inner halves. As Figure 2As noted above, the metal device has one or more spaces defined between components of the metal device. In particular, the arches 418 are spaced apart from one another, defining spaces or openings therebetween. Such spaces enable access to elements connected to the polymer housing, such as the hydrophone 470, pressure release valve 480, and / or cap 464, for example. Further, by manufacturing the outer half to have a number of arches 418 and each arch to have a desired thickness and width, the weight of the outer metal device can be controlled to ensure sufficient negative buoyancy for the node so that it freely falls to the seafloor prior to use. Moreover, the metallic nature of the outer metal device ensures good coupling (acoustic coupling) to the seafloor, which is desirable when measuring particle velocity or acceleration. Further, even if the outer metal half corrodes over time, the inner polymer half does not, which allows the overall structural integrity of the node to remain intact when used in salt water. As the outer metal half shows signs of corrosion, the outer metal half can be replaced with a new outer metal half, while keeping the inner polymer half and its electronics. Thus, the hybrid node having an inner polymer housing and outer metal device is less expensive in terms of maintenance than an all-metal node, and more reliable than an all-polymer node.

[0096] According to embodiments, as reminded above in the embodiments of Figure 6 the metal arches and the polymer inner housing. The contact between the metal device and the polymer inner housing is made at the level of the metal band and the outer collar of the polymer inner housing, and provides a corresponding reinforcement of the polymer inner housing, preferably together with a texturing of the outer surface of the polymer inner housing, for example comprising ribs.

[0097] Reference is now made to Figure 10A method for assembling the subsea node 400 will be discussed. The method includes the step 1000 of placing the battery 440 within a first inner polymer half 412A of an inner polymer housing 412 made of a polymer material, the step 1002 of placing the electronics 444 within a second inner polymer half 412B of the inner housing 412, the step 1004 of placing a first outer metal half 414A of an outer metal housing 414 made of a metal material on the first inner polymer half 412A. Preferably, a groove 416 formed in an outer surface of the first inner polymer half 412A receives a corresponding arch 418 formed in the first outer metal half 414A. The method further includes the step 1006 of placing a second outer metal half 414B of the outer metal housing 414 on the second inner polymer half 412B. Preferably, a groove 416 formed in an outer surface of the second inner polymer half 412B receives a corresponding arch 418 formed in the second outer half 414A. At step 1008, the first outer metal half 414A is positioned to contact the second outer metal half 414B such that the first inner polymer half 412A contacts the second inner polymer half 412B. The method can then include the step 1010 of attaching the first outer metal half 414A to the second outer metal half 414B, preferably directly with a screw 436 or indirectly, for example by passing the screw through a hole machined in an outer collar of the inner polymer housing without threads. The method can further include the step 1012 of placing a first outer polymer half 412A of an outer polymer housing 412 made of a polymer material on the first outer metal half 414A. Preferably, a groove 416 formed in an outer surface of the first outer polymer half 412A receives a corresponding arch 418 formed in the first outer metal half 414A. The method further includes the step 1014 of placing a second outer polymer half 412B of the outer polymer housing 412 on the second outer metal half 414B. Preferably, a groove 416 formed in an outer surface of the second outer polymer half 412B receives a corresponding arch 418 formed in the second outer half 414A. At step 1016, the first outer polymer half 412A is positioned to contact the second outer polymer half 412B such that the first outer metal half 414A contacts the second outer metal half 414B. The method can then include the step 1018 of attaching the first outer polymer half 412A to the second outer polymer half 412B, preferably directly with a screw 436 or indirectly, for example by passing the screw through a hole machined in an outer collar of the outer polymer housing without threads.

[0098] The outer metal housing 414 is not waterproof, i.e., it has holes that allow water to reach the inner housing, but the inner polymer housing is waterproof. The first and second inner polymer halves 412A, 412B are connected to each other only because the first and second outer metal halves are attached to each other by screws.

[0099] The disclosed embodiments provide a hybrid metal polymer subsea node configured to collect seismic data when deployed in a transition zone, i.e., an area of the seafloor having a depth of less than 100 meters. Although the term "sea" is used in this application, those skilled in the art will understand that the OBN can be deployed in a lake, pond, brackish water, river, etc., i.e., any body of water. It should be understood that the description is not intended to limit the application. On the contrary, the embodiments are intended to cover alternatives, modifications, and equivalents, which are included in the spirit and scope of the application as defined by the appended claims. Further, in the detailed description of the embodiments, numerous specific details are set forth in order to provide a thorough understanding of the claimed application. However, those skilled in the art will understand that the various embodiments can be practiced without these specific details.

[0100] Although features and elements are described herein in particular combinations, each feature or element can be used alone without the other features and elements or in various combinations with or without other features and elements. It will be apparent to those of ordinary skill in the art that features and / or elements can be substituted for other features and / or elements so that each feature or element can be replaced by adaptive equivalents. The scope of the disclosure is not limited to the specific examples described herein.

[0101] This written description uses examples of the disclosed subject matter to enable a person of ordinary skill in the art to practice the subject matter including making and using any devices or systems and performing any incorporated methods. The patentable scope of the subject matter is defined by the claims and can include other examples that occur to those of ordinary skill in the art. Such other examples are intended to fall within the scope of the claims.

Claims

1. A seismic data acquisition device (400), also called a seafloor node and intended to be placed on the seafloor, comprising: - a polymer housing (412) defining a chamber that houses at least part of a data acquisition system (440, 444, 445); and - a metal arrangement (414); wherein the polymer housing (412) is captured in the metal arrangement (414), the metal arrangement (414) comprising two metal beams (4141, 4142) extending on opposite sides of the polymer housing (412); wherein the metal arrangement (414) has two halves (414A, 414B) that are detachably attached to each other by a fixation system (436, 426), each half (414A) of the metal arrangement (414) has a metal beam element (4141A, 4142A) that, together with a corresponding beam element (4141B, 4142B) of the other half (414B), forms the metal beam (4141, 4142) of the metal arrangement (414).

2. The seismic data acquisition device (400) of claim 1, wherein, The metal arrangement (414) further comprises two joining parts (4143) that join the metal beams (4141, 4142) to form a metal band (4200) that encircles the polymer housing (412).

3. The seismic data acquisition device (400) of claim 1, wherein, The metal arrangement (414) further comprises a metal arch (418) that extends laterally from one metal beam (4141) to the other metal beam (4142).

4. The seismic data acquisition device (400) of claim 1, wherein, The polymer housing (412) has two halves (412A, 412B), wherein each half (412A, 412B) of the polymer housing (412) has an outer collar element (4124A, 4124B) adapted to contact a corresponding outer collar element (4124A, 4124B) of the other half (412A, 412B) to form an outer collar (4124) of the polymer housing (412) when the two halves (412A, 412B) of the polymer housing (412) are assembled.

5. The seismic data acquisition device (400) of claim 4, wherein, A through hole (4125) is machined through the outer collar elements (4124A, 4124B) and a threaded hole (426) is machined in at least one metal beam element (4141, 4142), The halves (414A, 414B) of the metal device are connected to each other by screws (436) passing through the through holes (4125) of the outer collar elements (4124A, 4124B) to attach the beam elements (4141A, 4142A, 4141B, 4142B) together while sandwiching the outer collar elements (4124A, 4124B) in between.

6. The seismic data acquisition device (400) of claim 5, wherein, The through holes (4125) machined in the outer collar elements (4124A, 4124AB) are not threaded so that the screws (436) extend from the beam elements (4141A, 4142A) through the outer collar elements (4124A, 4124AB) without being fixed to the outer collar elements (4124A, 4124AB) to cooperate with corresponding threaded holes machined in the other corresponding beam (4141B, 4142B) so that the outer collar elements (4124A, 4124B) are held against each other by the pressure exerted by the beam elements (4141A, 4141B, 4142A, 4142B) sandwiching the outer collar elements (4124A, 4124B) in between.

7. The seismic data acquisition device (400) of claim 1, wherein, The seismic data acquisition device (400) comprises a protective bumper (490) fixed to the metal device (414), the protective bumper (490) covering a portion of the polymer housing (412), wherein the protective bumper (490) has a hole (492) enabling water to enter the protective bumper.

8. The seismic data acquisition device (400) of claim 7, wherein, The protective bumper (490) has two halves (490A, 490B) separated by the metal beams (4141, 4142) of the metal device (414), wherein the protective bumper (490) has a hole (492) enabling water to enter the protective bumper.

9. A method for assembling a seismic data acquisition device (400), also called a seafloor node and intended to be placed on the seafloor, the method comprising: - providing a data acquisition system (440, 444, 445) and a polymer housing (412) housing at least part of the data acquisition system (440, 444, 445); and - providing a metal device (414) comprising two metal beams (4141, 4142) adapted to extend on opposite sides of the polymer housing (412); and - constraining the polymer housing (412) in the metal device (414); wherein the metal device (414) has two halves (414A, 414B) detachably attached to each other by a fixing system (436, 426), Each half (414A) of the metal device (414) has metal beam elements (4141A, 4142A) that together with corresponding beam elements (4141B, 4142B) of the other half (414B) form the metal beams (4141, 4142) of the metal device (414).

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