Seismic acquisition device comprising an aluminum alloy housing and corresponding manufacturing method

Abstract

The invention relates to a seismic acquisition device (1) intended to be positioned on a seabed, comprising a housing (2) comprising several housing parts (21, 22) made of aluminum alloy which can be assembled together; and screws (3) for assembling said housing parts (21, 22) by screwing. Said screws (3) are made of aluminum alloy. The invention also relates to a corresponding manufacturing method. Figure for the abstract: Fig.2B

Description

Title of the invention: Seismic acquisition device comprising an aluminum alloy housing and corresponding manufacturing method FIELD OF THE INVENTION

[0001] The present invention generally relates to seismic acquisition devices comprising an aluminum alloy housing. PREVIOUS ART

[0002] The acquisition and processing of seismic data can be used to generate a profile (image) of underground (subsurface) geophysical structures, for example for the search for natural resources. Although this profile does not provide a precise location, for example for oil and gas reservoirs, it suggests the presence or absence of such reservoirs. Thus, it is important to provide a high-resolution image of the subsurface, for example, for those who need to determine where oil and gas reservoirs are located.

[0003] For marine acquisition, such a high-resolution image can be obtained with a seismic acquisition system. An example illustrated in [Fig.l], shows a seismic acquisition system 100 which comprises several seismic acquisition devices, called ocean bottom nodes 102, or OBN (for Ocean Bottom Node in English), distributed on the seabed 101, by various means. Each seabed node 102 comprises a set of components for acquiring seismic data: for example, a hydrophone 104 for detecting a pressure wave, a processor 106 for processing the detected waves, a memory 108 for storing the seismic data and a power source 110 for providing electrical energy to these components.

[0004] A vessel 120 tows one or more seismic sources 122 at a depth in the water, relative to the ocean surface 121. The seismic source 122 is configured to generate seismic waves 124. The seismic waves 124 propagate in the subsurface 126 and are reflected and / or refracted at various interfaces 128 in the subsurface. The reflected waves 130 are then detected, and recorded in the memory 108 of the seabed node 102.

[0005] A seabed node is thus presented in the form of a box which houses electronic components which must withstand pressure and the saline environment.

[0006] Seabed knots are known whose housing is made of plastic, as for example presented in application WO2021 / 224683; this material however limits their depth of use. For greater depths / pressures, the use of the titanium to produce the case is then preferred, as for example presented in application WO2020 / 208424; the associated cost is however very high.

[0007] Aluminum, being light and inexpensive, can be considered as a material for manufacturing the case, as described in patent application US 18 / 343,079 filed in June 2023. However, closing such an aluminum case with screws is complex. Indeed, a corrosion phenomenon is observed between the aluminum case and the steel or stainless steel screws that are used to close the case.

[0008] The aforementioned patent application thus proposes using a closing clip system to lock the various elements of the housing in position, eliminating the use of screws, or to absorb the forces to which the housing is subjected, which allows the use of plastic screws. However, such a clip system implies a particular design of the housing.

[0009] The present invention aims to propose a new device and corresponding method making it possible to overcome all or part of the problems set out above. Summary of the invention

[0010] For this purpose, the invention relates to a seismic acquisition device intended to be positioned on a seabed, the seismic acquisition device comprising: - an electronic seismic acquisition assembly comprising a seismic sensor, a unit for processing the signals supplied by the seismic sensor to generate seismic data, and a power source for supplying electrical energy; - a housing housing said electronic seismic acquisition assembly and comprising several housing parts made of aluminum alloy which can be assembled together; - screws for assembling said housing parts by screwing; characterized in that said screws are made of aluminum alloy.

[0011] Such a design of the seismic acquisition device for which the housing parts to be assembled are made of aluminum alloy and the assembly screws are also made of aluminum alloy, makes it possible, on the one hand, to avoid the screws seizing in the housing; and on the other hand to ensure the braking of the screws once mounted, while responding to the mechanical constraints linked to a marine environment.

[0012] Conversely, it is noted that the use of stainless steel screws generates corrosion problems due to the galvanic couples between the aluminum and the stainless steel. In fact, aluminum will corrode in contact with stainless steel in aqueous and saline environments.

[0013] According to one embodiment, each of said screws has a layer of alumina greater than 30 microns, said layer being sealed.

[0014] According to one embodiment, the thread of each screw is provided over at least part of its length with a thread locker.

[0015] According to one embodiment, the alumina layer is covered on at least part of said screw with a fluorinated polymer, preferably polytetrafluoroethylene (PTFE).

[0016] According to one embodiment, a portion of the length of the body of each screw is free of fluoropolymer, said portion being at least partially covered with thread lock.

[0017] According to one embodiment, for each screw, the length of the body of each screw which is free of fluoropolymer is at least equal to a number of threads which is equal to the whole part of the value in millimeters of the diameter of the body of the screw, for example 6 threads for a screw with a diameter of 6 millimeters.

[0018] According to one embodiment, said screws comprise screws whose aluminum alloy is zinc-based, magnesium-based, or magnesium and silicon-based.

[0019] According to one embodiment, each of said housing parts and each of said screws is made of a category 7xxx aluminum alloy, preferably 7075 aluminum.

[0020] According to one embodiment, the housing is configured to withstand an external water pressure of at least 7*10A6 Pascals (70 Bars), preferably at least 3*10A7 Pascals (300 bars).

[0021] According to one embodiment, the seismic acquisition device comprises accessory fixing screws which cooperate with a part of the exterior of the housing to allow the fixing of an accessory on the exterior of the housing, said accessory fixing screws being of the same nature as the screws for assembling the housing parts.

[0022] The invention also relates to a method of manufacturing a seismic acquisition device housing intended for use in the ocean and under pressure, the housing comprising several housing parts made of aluminum alloy, said method comprising: - the installation of an electronic seismic acquisition assembly within at least one of the housing parts, said electronic seismic acquisition assembly comprising a seismic sensor, a unit for processing the signals provided by the seismic sensor to generate seismic data, and a power source for providing electrical energy; - assembly and fixing of the housing parts together by screws, which are made of aluminum alloy with a surface treatment.

[0023] According to one embodiment, the surface treatment comprises the following steps: - a hard anodic oxidation step, called OAD, generating an alumina layer greater than 30 microns; - a deposit or impregnation of at least part of the screw with a fluorinated polymer, preferably polytetrafluoroethylene so as to cover the alumina layer, said alumina layer having a sealed state.

[0024] The invention also relates to a method of manufacturing a seismic acquisition device housing intended for use in the ocean and under pressure, the housing comprising several housing parts made of aluminum alloy, said method comprising: - the installation of an electronic seismic acquisition assembly within at least one of the housing parts, said electronic seismic acquisition assembly comprising a seismic sensor, a unit for processing the signals provided by the seismic sensor to generate seismic data, and a power source for providing electrical energy; - the assembly and fixing of the housing parts together by screws, characterized in that said screws are made of aluminum alloy having a surface treatment.

[0025] According to one embodiment, the surface treatment comprises the following steps: - a hard anodic oxidation step, called OAD, generating an alumina layer greater than 30 microns; - a deposit or impregnation of at least part of the screw with a fluorinated polymer, preferably polytetrafluoroethylene, said layer of alumina having a sealed state.

[0026] According to one embodiment, at least a portion of the thread of the screw is free of fluoropolymer over a given length, called the relief length, a thread locker being deposited on said length of thread free of fluoropolymer, the length of the relief is at least equal to a number of threads which is equal to the whole part of the value in millimeters of the diameter of the body of the screw, for example 6 threads for a screw with a diameter of 6 millimeters.

[0027] According to one embodiment, the thread locker is deposited on at least part of the thread of each screw.

[0028] According to one embodiment, each of said screws has a surface treatment.

[0029] According to one embodiment, said screws comprise screws whose alloy Aluminum is zinc-based, magnesium-based, or magnesium-silicon-based.

[0030] According to one embodiment, each of said housing parts and each of said screws is made of a category 7xxx aluminum alloy, preferably 7075 aluminum.

[0031] According to one embodiment, each of said screws has a layer of alumina greater than 30 microns, preferably sealed. It may be provided that the layer of alumina is covered on at least part of said screw by a fluorinated polymer, preferably polytetrafluoroethylene.

[0032] According to one embodiment, a portion of the length of the body of each screw is free of fluoropolymer, while being covered with thread lock.

[0033] According to one embodiment, the thread of each screw is provided over at least part of its length with a thread locker, preferably at least over the length of the body of the screw which is free of fluoropolymer where appropriate.

[0034] According to one embodiment, the seismic acquisition device comprises accessory fixing screws which cooperate with a portion of the exterior of the housing to allow the fixing of an accessory to the exterior of the housing, said accessory fixing screws also being made of aluminum alloy.

[0035] There is also provided a method of manufacturing a seismic acquisition device housing intended for use in the ocean and under pressure, the housing comprising several housing parts made of aluminum alloy, said method comprising: - placing a seismic acquisition electronic assembly within at least one of the housing parts; said seismic acquisition electronic assembly comprising a seismic sensor, a unit for processing the signals provided by the seismic sensor to generate seismic data, and a power source for providing electrical energy; - the assembly and fixing of the housing parts together by screws, characterized in that said screws are made of aluminum alloy, each of said screws preferably having a surface treatment.

[0036] According to one embodiment, the surface treatment comprises the following steps: - a hard anodic oxidation step, called OAD, generating an alumina layer greater than 30 microns; - preferably a step of sealing the alumina layer; - a deposit or impregnation of at least part of the screw with a fluoropolymer, preferably polytetrafluoroethylene so as to cover the alumina layer.

[0037] According to one embodiment, the surface treatment comprises a sealing step between the hard anodic oxidation step and the deposition or impregnation step. Brief description of the drawings

[0038] Other characteristics and advantages of the invention will emerge from the following description, which is purely illustrative and non-limiting and must be read in conjunction with the appended drawings, in which:

[0039] - [Fig.l] [Fig.l] is a schematic view of a data acquisition system seismic, known from the state of the art which uses seabed nodes;

[0040] - [Fig.2A] [Fig.2A] is an exploded perspective view of screws relative to a housing which comprises two halves configured to be secured to each other by a portion of the screws, the other screws being usable to secure an accessory to the housing;

[0041] - [Fig.2B] [Fig.2B] is a view of the entire housing and screws of [Fig.2A] at the assembled state of the case halves with one portion of the screws, the other portion of the screws being pre-positioned on the case pending attachment of an accessory to the case;

[0042] - [Fig.2C] [Fig.2C] is a view of the housing of [Fig.2B] equipped with a set of two protective half-shells, called bumpers, fixed by screws to said case;

[0043] - [Fig.3] [Fig.3] is a schematic view of an aluminum alloy screw, according to an embodiment, which has undergone a surface treatment including hard oxidation, impregnation or deposition of a polymer, such as PTFE, and deposition of thread locker;

[0044] - [Fig.4] [Fig.4] is a schematic view of an aluminum alloy screw, according to another embodiment, which has undergone a surface treatment including hard oxidation, sealing (or plugging), and deposition of a polymer, such as PTFE, on only a portion of the body of the screw, and deposition of thread locker on the portion, called the saving zone, of the body of the screw which is free of polymer;

[0045] - [Fig.5] [Fig.5] is a flowchart of a method according to one embodiment, for assembling a seabed node housing, such as the node of Figures 2A, 2B or 2C, with aluminum alloy screws such as those of [Fig.3] or [Fig.4], DETAILED DESCRIPTION

[0046] Embodiments of the invention are described below with reference to the accompanying drawings. In the drawings, the size and relative sizes of the elements may be exaggerated for clarity. Like numerals refer to like elements throughout the drawings. However, the invention may be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein.

[0047] A reference throughout the description to "an embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment is included in at least one embodiment of the present invention. Thus, the occurrence of the expression "in an embodiment" at various locations throughout the specification does not necessarily refer to the same embodiment. Furthermore, particular features, structures, or characteristics may be combined in any suitable manner in one or more embodiments.

[0048] With reference to the figures, a seismic acquisition device 1 is shown intended to be positioned on a seabed. The seismic acquisition device 1 comprises an electronic seismic acquisition assembly (not shown) which includes a seismic sensor, a processing unit (such as a processor or microcontroller) for the signals provided by the seismic sensor to generate seismic data, and a power source, such as a battery, to provide electrical energy to the components of the assembly which need it. Preferably, said electronic assembly also comprises a memory for storing the seismic data.

[0049] Case

[0050] The electronic assembly is housed in a housing 2 which comprises several parts 21, 22 of aluminum alloy housing which can be assembled together.

[0051] As in the example illustrated in the figures, it can be provided that said housing parts form two half-shells 21, 22 which can be assembled together.

[0052] Each of the half-shells 21, 22 may comprise a peripheral element 210, 220, such as a rim, which extends around and outside the opening and intended to be positioned opposite the other peripheral rim 210, 220 to be assembled by screwing to said other peripheral rim.

[0053] The housing 2 is configured to withstand an external water pressure of at least 7*10A6 Pascals (70 Bars), preferably at least 3*10A7 bars. In other words, the housing can withstand a depth of the housing located under 700 m of water, preferably up to 3000 m of water. Advantageously, the housing is placed under partial vacuum to protect the components, preferably with an initial vacuum of the order of -0.8 bar (-8*10A4 Pascals) into which helium is injected at approximately -0.4 bar (-4*10A4 Pascals).

[0054] Aluminum alloy screw

[0055] The seismic acquisition device 1 comprises screws 3 for assembling said housing parts 21, 22 by screwing. Said screws 3 are made of aluminum alloy. The seismic acquisition device 1 may also comprise screws 3' which are used for fixing an accessory, such as a protective shell called a "bumper" on the outside of the housing and which are also made of aluminum alloy, for example an alloy such as proposed below. The protective shell may be in the form of half-shells 310, 320. In particular, it may be provided that the screws 3' are made of the same aluminum alloy as the screws 3 which are used for fixing parts of the housings together, even if the mechanical constraints imposed on them are less than for closing and maintaining the housing housing the electronic assembly.

[0056] Advantageously, the aluminum alloy used for the screws is the same as the aluminum alloy of the housing.

[0057] Preferably, the aluminum alloy is of class (also called series or category) 7075. An aluminum alloy of class 7075 has good mechanical resistance, which makes it possible to ensure the pressure resistance of the housing and the resistance to the tensile and tightening forces of the screws.

[0058] More generally, for screws, alloys of classes (or series) 7xxx, 6xxx, 5xxx can be used, which are efficient. The main composition of these alloys is presented in the table below:

[0059] Series Primary alloying element txxx ALiminLnv- 99.07¾^ pkjs 2xxx ■Copper 3xxx Manganese 4xxx Sècium 5xxx Magnesium éxxx Magnesium and siiiçj um 7xxx Zinc

[0060] It can thus be provided that the screws comprise screws whose aluminum alloy is zinc-based, magnesium-based, or magnesium and silicon-based.

[0061] Surface treatment

[0062] Each of the screws 3 has a particular surface treatment allowing the production of the housing according to the invention. The description given below can also be applied to the screws 3' for fixing accessories.

[0063] According to a preferred embodiment, each of said screws 3 has a layer of alumina greater than 30 microns, which is covered on at least part of said screw by a fluorinated polymer 32, preferably polytetrafluoroethylene PTFE.

[0064] The aluminum surfaces are covered with a layer of oxide A12O3 (alumina), here obtained by hard anodization, noted OAD, which is characterized by an alumina thickness of between 30 and 100 microns (depending on the grade of aluminum), preferably of the order of 50 microns for use according to the invention.

[0065] The thread of each screw 3 is provided over at least part of its length with a thread lock 33. In particular, at least part of the end of the screw body (opposite the head) is covered with a thread lock 33.

[0066] This treatment hardens the surface of the aluminum, improves corrosion resistance and prevents seizure when tightening and loosening. Good mechanical strength is also obtained when tightening and loosening.

[0067] The alumina layer is sealed for better corrosion resistance, preferably by a dedicated step. In fact, the alumina layer created on a substrate is porous. At the bottom of the pores, the alumina layer can therefore be very weak, and its deterioration over time can lead it to no longer perform its protective function (pitting corrosion). Sealing consists of swelling or expanding the alumina layer to close the pores and ensure better corrosion resistance. One method of carrying out this sealing consists of using hot water, by dipping the screws in it, but other methods are known to those skilled in the art.

[0068] According to one embodiment and as illustrated in [Fig. 4], a portion of the length of the body of each screw 3 is free of fluoropolymer. When it is desired that one end of the screw be free of fluoropolymer, a masking strip (also called a saving strip) can be applied to the desired area of ​​the screw in order to prevent the fluoropolymer from covering said area (called the saving zone). In this case, the portion of the screw body free of fluoropolymer is still covered with a threadlocker 33.

[0069] Advantageously, the length of the body of the screw 3 which is free of fluorinated polymer is at least equal to a number of threads which is equal to the whole part of the value in millimeters of the diameter of the body of the screw, for example 6 threads for a screw with a diameter of 6 millimeters M6.

[0070] According to a particular embodiment, the screw head is not covered with fluoropolymer, but it remains easier from an industrial point of view for the entire screw and therefore the head to be covered with fluoropolymer.

[0071] Method

[0072] The housing parts and screws presented above can be used to obtain a seismic acquisition device housing 1 intended for use in the ocean and under pressure.

[0073] Each of the screws 3 operating to close the housing housing the electronic components, and preferably each of the other screws 3', has a surface treatment.

[0074] The surface treatment also comprises a hard anodic oxidation step 510, called OAD, generating an alumina layer greater than 30 microns. The surface treatment also comprises the sealing 515 of the alumina layer. A depositing or impregnating 520 at least a portion of the screw with a fluoropolymer 32, preferably polytetrafluoroethylene (PTFE) so as to cover the alumina layer.

[0075] At least a portion of the thread of the screw is free of fluoropolymer 32 over a given length, called the relief length ZE, from its free end. Preferably, the relief length ZE is at least equal to a number of threads which is equal to the whole part of the value in millimeters of the diameter of the body of the screw, for example 6 threads for a screw with a diameter of 6 millimeters (M6).

[0076] A thread locker 33 is deposited in step 530 on at least part of the thread of each screw 3.

[0077] In step 540, an electronic seismic acquisition assembly is installed within at least a portion of the aluminum alloy housing parts 21, 22. Said electronic seismic acquisition assembly comprises a seismic sensor and a unit for processing the signals supplied by the seismic sensor to generate seismic data. In step 550, the housing parts 21, 22 are placed opposite each other by their assembly zone 210, 220 and assembled to each other by aluminum alloy screws 3. Preferably, the assembly zones 210, 220 extend around the openings of the half-shells and are advantageously pre-drilled with tapping for the passage of the screws. The housing is thus assembled and closed by said screws. Preferably, additional fixing screws are pre-positioned in corresponding holes provided in the external part of the boxes to allow one or more accessories to be added to the box.

[0078] The aluminum alloy screws can thus be treated so as to meet the constraints of their use for closing the housing used under marine pressure, with all or part of the following advantages: - limited cost; - grip-free tightening, resistance to loosening torque; - shock resistance; - reduced or even eliminated risk of corrosion; - reduced risk of loss due to vibration.

[0079] The screws resist falls of the device. The device may have a mass of more than 10 kg, for example of the order of 13 kg or 24 kg.

[0080] The invention is not limited to the embodiments illustrated in the drawings. Furthermore, the term "comprising" does not exclude other elements or steps. Furthermore, features or steps that have been described with reference to one of the embodiments set forth above may also be used in combination with other features or steps of other embodiments set forth above.

Claims

Claims

1. Seismic acquisition device (1) intended to be positioned on a seabed, the seismic acquisition device (1) comprising: - an electronic seismic acquisition assembly comprising a seismic sensor, a unit for processing the signals supplied by the seismic sensor to generate seismic data, and a power source for supplying electrical energy; - a housing (2) housing said electronic seismic acquisition assembly and comprising several housing parts (21, 22) made of aluminum alloy which can be assembled together; - screws (3) for assembling said housing parts (21, 22) by screwing; characterized in that said screws (3) are made of aluminum alloy.

2. Seismic acquisition device (1) according to claim 1, wherein each of said screws (3) has a layer of alumina greater than 30 microns, said layer being sealed.

3. Seismic acquisition device (1) according to claim 2, wherein the alumina layer is covered on at least part of said screw by a fluoropolymer (32), preferably polytetrafluoroethylene (PTFE).

4. Seismic acquisition device (1) according to claim 3, in which a part of the length of the body of each screw (3) is free of fluoropolymer, said part being covered at least partially with thread lock (33).

5. Seismic acquisition device (1) according to claim 4, wherein, for each screw (3), the length of the body of each screw (3) which is free of fluoropolymer is at least equal to a number of threads which is equal to the whole part of the value in millimeters of the diameter of the body of the screw, for example 6 threads for a screw of diameter 6 millimeters (M6).

6. A seismic acquisition device (1) according to any preceding claim, wherein said screws (3) comprise screws whose aluminum alloy is zinc-based, magnesium-based, or magnesium-silicon-based.

7. A seismic acquisition device (1) according to any preceding claim, wherein each of said parts housing and each of said screws (3) is made of a category 7xxx aluminum alloy, preferably 7075 aluminum.

8. Seismic acquisition device (1) according to any one of the preceding claims, wherein the housing (2) is configured to withstand an external water pressure of at least 7*10A6 Pascals (70 Bars), preferably at least 3*10A7 Pascals (300 bars).

9. A seismic acquisition device (1) according to any preceding claim, wherein the seismic acquisition device (1) comprises accessory fixing screws (3') which cooperate with a portion of the exterior of the housing to enable an accessory to be fixed to the exterior of the housing, said accessory fixing screws (3') being of the same nature as the screws (3) for assembling the housing portions.

10. Seismic acquisition device (1) according to any one of the preceding claims, in which the thread of each screw (3) is provided over at least part of its length with a thread locker (33).

11. A method of manufacturing a seismic acquisition device housing (1) intended for use in the ocean and under pressure, the housing comprising several housing parts (21, 22) made of aluminum alloy, said method comprising: - placing (540) a seismic acquisition electronic assembly within at least one of the housing parts (21, 22), said seismic acquisition electronic assembly comprising a seismic sensor, a unit for processing the signals supplied by the seismic sensor to generate seismic data, and a power source for supplying electrical energy; - assembling and fixing (550) the housing parts (21, 22) together by screws (3), characterized in that said screws (3) are made of aluminum alloy having a surface treatment.

12. Method according to claim 11, in which the surface treatment comprises the following steps: - a step (510) of hard anodic oxidation (31), called OAD, generating a layer of alumina greater than 30 microns; - a deposition or impregnation (520) of at least a part of the screw with a fluoropolymer (32), preferably polytetrafluoroethylene (PTFE) so as to cover the layer of alumina, said layer of alumina having a clogged state.

13. Method according to claim 12, in which at least a part of the thread of the screw is free of fluoropolymer (32) over a given length (ZE), called the saving length, a thread locker (33) being deposited (530) on said length of thread free of fluoropolymer (32), and in which the saving length is at least equal to a number of threads which is equal to the whole part of the value in millimeters of the diameter of the body of the screw, for example 6 threads for a screw with a diameter of 6 millimeters (M6).

14. A method according to claim 12 or 13, wherein the surface treatment comprises a sealing step between the hard anodic oxidation step and the deposition or impregnation step.

15. A method according to any one of claims 11 to 14, wherein a thread locker (33) is deposited (530) on at least a portion of the thread of each screw (3).

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