A towed three-component fiber optic streamer and method of marine seismic data acquisition

Abstract

This invention provides a towed three-component fiber optic submarine cable and a method for acquiring marine seismic data, relating to the field of seismic exploration and acquisition technology. The towed three-component fiber optic submarine cable has a Y-axis along its length and X and Z axes perpendicular to the Y-axis. The cable includes an outer armor, within which optical fibers and several three-component structures fixed to the inner wall of the outer armor are disposed. Each three-component structure includes three cylinders, arranged sequentially along the X-axis, Z-axis, and Y-axis, with respect to the cylinder's axial direction. The optical fibers pass through the three-component structures by winding around the outer surfaces of the three cylinders. The towed three-component fiber optic submarine cable provided by this invention achieves three-component acquisition by winding the optical fibers, and utilizes the characteristics of ultra-long sensing distance, ultra-high sampling density, strong inter-channel consistency, low cost, and wide response bandwidth of optical fibers to obtain information with longer offset distances and lower frequencies.

Description

Technical Field

[0001] This invention relates to the field of seismic exploration and acquisition technology, specifically to a towed three-component fiber optic submarine cable and a method for acquiring marine seismic data. Background Technology

[0002] Currently, marine seismic exploration primarily uses towed cables or OBS (OBN / OBC) for data acquisition, with moving-coil geophones remaining the core technology. To address issues such as low signal-to-noise ratio, narrow bandwidth, incomplete information, and even distortion caused by insufficient azimuth, low coverage, severe ghost wave frequency trapping, and limited offset, marine exploration is moving towards high-specification seismic acquisition operations, such as multi / wide azimuth towed cables, "two wide and one high" or "two wide and two high" acquisition methods. While this has significantly improved data quality, it has also led to a sharp increase in operational costs. The high acquisition cost has become one of the major factors restricting the large-scale application of high-quality marine seismic exploration technology. Summary of the Invention

[0003] Based on the above analysis, the present invention aims to provide a towed three-component fiber optic submarine cable and a method for acquiring marine seismic data, which uses a towed method to acquire marine seismic exploration data, thereby replacing the traditional moving-coil geophone submarine cable acquisition equipment.

[0004] The objective of this invention is mainly achieved through the following technical solutions:

[0005] In a first aspect, the present invention provides a towed three-component optical fiber submarine cable, the three-component optical fiber submarine cable having a Y-axis along its length direction and an X-axis and a Z-axis perpendicular to the Y-axis. The three-component optical fiber submarine cable includes a submarine cable armor, within which optical fibers and a plurality of three-component structures fixed to the inner wall of the submarine cable armor are disposed. The three-component structure includes three cylinders, which are arranged sequentially along the X-axis, Z-axis and Y-axis, with respect to the axial direction of the cylinders. The optical fibers pass through the three-component structure by wrapping around the outer surface of the three cylinders.

[0006] Preferably, the two ends of the cylinders arranged along the X-axis and along the Z-axis are embedded into the inner wall of the submarine cable outer armor for fixation.

[0007] Preferably, the inner wall of the submarine cable outer armor is provided with a plurality of fixing posts, and the outer wall of the cylinder arranged along the Y-axis is engaged with the fixing posts.

[0008] Preferably, the cylinders in the three-component structure have the same or different dimensions, with each cylinder having a height of 5-10 cm and a diameter of 5-10 cm.

[0009] Preferably, the spacing between adjacent three-component structures is 1-10m.

[0010] Preferably, the length of the optical fiber wound on the outer surface of each cylinder is 0.5m-1m; the diameter of the optical fiber is 0.3-0.7mm.

[0011] Secondly, the present invention provides a towed marine seismic data acquisition device, including the aforementioned three-component fiber optic cable and a depth positioning auxiliary device, wherein the depth positioning auxiliary device is snapped onto the outer surface of the outer armor of the cable, and the position of the depth positioning auxiliary device corresponds to the position of the three-component structure.

[0012] Preferably, the depth positioning auxiliary device includes a water depth positioning unit and a fixing buckle. The fixing buckle is disposed on the upper surface of the water depth positioning unit and is engaged with the water depth positioning unit. The depth positioning auxiliary device is engaged with the outer surface of the submarine cable armor by the fixing buckle.

[0013] Preferably, the marine seismic data acquisition device further includes a mobile device connected to one end of the three-component fiber optic submarine cable.

[0014] Thirdly, the present invention provides a method for acquiring marine seismic data, utilizing the aforementioned marine seismic data acquisition equipment, comprising the following steps:

[0015] Step 1: Place the three-component fiber optic submarine cable and the depth positioning auxiliary equipment fixed to it into the seawater;

[0016] Step 2: The marine seismic data acquisition equipment is moved to acquire seismic data.

[0017] Beneficial effects:

[0018] The towed three-component fiber optic submarine cable provided by this invention uses a wound fiber optic cable to achieve three-component acquisition. It utilizes the characteristics of the fiber, such as ultra-long sensing distance (100km), ultra-high sampling density (0.1m), strong inter-channel consistency, low cost, and wide response bandwidth (0.001Hz-50kHz), to obtain information with longer offset distance and lower frequency, thereby achieving low-cost and high-efficiency marine seismic exploration. Attached Figure Description

[0019] Figure 1 A side view of the towed three-component optical fiber submarine cable structure provided by the present invention;

[0020] Figure 2 A top view of the towed three-component optical fiber submarine cable structure provided by the present invention.

[0021] Figure 3 A schematic diagram of the structure of the depth positioning auxiliary device provided by the present invention;

[0022] Figure 4 A schematic diagram of the structure of the towed marine seismic data acquisition device provided by the present invention;

[0023] Among them, 100-three-component fiber optic submarine cable; 1-first cylinder; 2-second cylinder; 3-third cylinder; 4-submarine cable outer armor; 5-fiber optic cable; 6-fixed post; 200-depth positioning auxiliary equipment; 210-water depth positioning unit; 220-fixed buckle; 300-moving device; 310-cable reel; 400-water bird. Detailed Implementation

[0024] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of the present invention and, together with the embodiments of the present invention, serve to illustrate the principles of the present invention.

[0025] This invention provides a towed three-component fiber optic submarine cable and a method for acquiring marine seismic data. It uses a wound fiber optic cable to acquire three-component data and uses a towed vessel to acquire marine seismic exploration data, thus replacing the traditional moving-coil geophone submarine cable acquisition equipment.

[0026] Distributed fiber optic sensing technology has been widely applied in well seismic exploration, demonstrating strong development momentum in various application scenarios such as fracturing monitoring, production profile monitoring, and joint well-to-surface 3D acquisition. The ultra-long sensing distance (100km), ultra-high sampling density (0.1m), strong inter-channel consistency, low cost, and wide response bandwidth (0.001Hz-50kHz) of fiber optics allow it to combine the advantages of both towed cables and OBNs, obtaining information with longer offset distances and lower frequencies. Furthermore, it overcomes the problems of insufficient coverage and low signal-to-noise ratio when using towed cables alone, as well as the insufficient spatial sampling caused by using sparse seabed nodes alone.

[0027] Firstly, referring to Figure 1-2 This invention provides a towed three-component fiber optic submarine cable 100. The three-component fiber optic submarine cable 100 has a Y-axis along its length and X-axis and Z-axis perpendicular to the Y-axis. The three-component fiber optic submarine cable 100 includes a submarine cable outer armor 4, which is cylindrical and hollow inside. An optical fiber 5 and several three-component structures fixed to the inner wall of the submarine cable outer armor 4 are disposed inside the submarine cable outer armor 4. Each three-component structure includes three adjacent cylinders. Taking the axial direction of the cylinders, the three cylinders are arranged sequentially (in the direction of the submarine cable from above water to underwater) along the X-axis, Z-axis, and Y-axis. The optical fiber 5 is wound around the surface of the three cylinders. In the three-component fiber optic submarine cable 100, the optical fiber 5 wound around the surface of all cylinders is the same optical fiber. That is, the same optical fiber 5 is wound around all cylinders in the three-component structure.

[0028] In a specific embodiment of the present invention, the three cylinders may include a first cylinder 1, a second cylinder 2, and a third cylinder 3 that are adjacent to each other, wherein the first cylinder 1 is arranged along the X-axis, the second cylinder 2 is arranged along the Z-axis, and the third cylinder 3 is arranged along the Y-axis, and the optical fiber 5 is wound around the surface of the first cylinder 1, the second cylinder 2, and the third cylinder 3.

[0029] In some embodiments of the present invention, the two ends of the cylinders arranged along the X-axis and Z-axis are embedded in the inner wall of the submarine cable outer armor 4 for fixation. Preferably, the two ends of the first cylinder 1 and the second cylinder 2 are embedded in the inner wall of the submarine cable outer armor 4 for fixation.

[0030] In some embodiments of the present invention, the inner wall of the submarine cable outer armor 4 is provided with a plurality of fixing posts 6, and the outer wall of the cylinder arranged along the Y-axis is engaged with the fixing posts 6. The number of fixing posts 6 is 4-8. Preferably, the third cylinder 3 is engaged with the fixing posts 6.

[0031] In some embodiments of the present invention, the cylinders in the three-component structure have the same or different dimensions, each being independently 5-10 cm in height and 5-10 cm in diameter.

[0032] In some embodiments of the present invention, in the three-component optical fiber submarine cable 100, the number of three-component structures n = total cable length / spacing, and the spacing of the three-component structures is 1-10m, for example 1, 2, 3, 4, 5, 6, 7, 8, 9, 10m.

[0033] In some embodiments of the present invention, the cylinders in the three-component structure are made of the same or different materials, each independently selected from high Poisson's ratio materials, such as rubber.

[0034] In this invention, the length of the optical fiber 5 wound on each cylinder is 0.5m-1m, and the diameter of the optical fiber 5 is 0.3-0.7mm, preferably 0.5mm.

[0035] The towed three-component fiber optic submarine cable provided by this invention introduces optical fiber as a vibration sensing unit into the towed submarine cable, and realizes three-component acquisition by winding in different directions, replacing the moving coil detector in the current electronic towed cable.

[0036] The towed three-component fiber optic submarine cable provided by this invention differs from conventional micro-towed submarine cable acquisition. The spatial sampling density of this invention can be reduced from the conventional 12.5m sampling interval to the 1m level or even lower, the length of a single cable can be increased from 12km to more than 50km, and the frequency band range can be extended from 5-200Hz to 0.001Hz-20kHz, resulting in a significant improvement in overall data quality.

[0037] Secondly, the present invention provides a towed marine seismic data acquisition device, including a three-component fiber optic cable 100 and a depth positioning auxiliary device 200. The depth positioning auxiliary device 200 is snapped onto the outer surface of the towed three-component fiber optic cable 100 and its position corresponds to the position of the three-component structure. The depth positioning auxiliary device 200 is used to sink the three-component fiber optic cable 100 to a set depth in the ocean.

[0038] In some embodiments of the present invention, the depth positioning auxiliary device 200 includes a water depth positioning unit 210 and a fixing buckle 220 disposed on the upper surface of the water depth positioning unit 210. The fixing buckle 220 is engaged with the water depth positioning unit 210 to realize its fixing and disassembly on the three-component fiber optic submarine cable 100. A space is left between the fixing buckle 220 and the water depth positioning unit 210 for fixing the towed three-component fiber optic submarine cable 100.

[0039] In some specific embodiments of the present invention, the Z-axis of the depth positioning auxiliary device 200 is in the same direction as the cylinder set along the Z-axis in the three-component structure. Specifically, the depth positioning unit 210 can be cuboid in shape, and the length direction of the depth positioning unit 210 is along the length direction (Y-axis direction) of the submarine cable. The three-component fiber optic submarine cable 100 is fixed on the upper surface of the depth positioning unit 210, and the cylinder set along the Z-axis in the three-component structure is perpendicular to the upper surface of the depth positioning unit 210.

[0040] In some embodiments of the present invention, the towed marine seismic data acquisition device further includes a mobile device 300, which can be a work vessel. A cable reel 310 can be installed on the mobile device 300, wherein a three-component fiber optic submarine cable 100 is wound on the cable reel 310 of the mobile device 300.

[0041] In this invention, when the cable reel 310 releases the three-component fiber optic submarine cable 100 into the sea, the depth positioning auxiliary device 200 is fixed to the outer surface of the three-component fiber optic submarine cable 100 by the fixing buckle 220. The depth positioning auxiliary device 200 can be disassembled when the three-component fiber optic cable 100 emerges from the water.

[0042] In this invention, the three-component fiber optic submarine cable 100 needs to be used in conjunction with the depth positioning equipment 200. Since the cylinders set along the X and Z axes are embedded in the outer armor 4 of the submarine cable during manufacturing, they have a distinct tactile difference and are clearly marked at that position. When assembling with the depth positioning auxiliary equipment 200, it is necessary to ensure that the cylinders of the submarine cable 100 set along the Z axis coincide with the Z axis of the depth positioning auxiliary equipment 200. After entering the water, the attitude is adjusted to ensure that the Z axis coincides with the Z axis of the ground to achieve the requirement of data fidelity.

[0043] In some embodiments of the present invention, the marine seismic data acquisition device also includes a waterbird 400, which is disposed at the free end of the three-component fiber optic cable 100 and is used to adjust the attitude of the three-component fiber optic cable 100 so that the three-component fiber optic cable is as straight as possible.

[0044] The towed marine seismic data acquisition device provided by this invention uses a wound optical fiber to achieve three-component acquisition. It is mounted on a work vessel and towed to acquire marine seismic exploration data, obtaining high-density, high signal-to-noise ratio raw seismic exploration data that meets the needs of processing and interpretation.

[0045] Thirdly, the present invention provides a method for acquiring marine seismic data, comprising the following steps:

[0046] Step 1: Place the three-component fiber optic submarine cable 100 and the depth positioning auxiliary device 200 fixed to it into the seawater;

[0047] Step 2: Move the marine seismic data acquisition equipment to collect seismic data.

[0048] In some embodiments of the present invention, the specific steps of the marine seismic data acquisition method provided by the present invention are as follows:

[0049] Step 1a: Connect the tail end of the three-component fiber optic submarine cable 100 fixed on the cable reel 310 of the work vessel 300 to the seabird 400 and put it into the seawater, and start releasing the three-component fiber optic submarine cable 100 at a uniform speed.

[0050] Step 1b: During the release process, a depth positioning auxiliary device 200 is added to the outside of the cable at each three-component structure;

[0051] Step 2: After being released to the designed length, the work vessel moves forward at a constant speed of 300, and the air gun source begins to be activated according to the construction design.

[0052] The following detailed description of preferred embodiments of the present invention illustrates the principles of the invention and is not intended to limit the scope of the invention.

[0053] Example 1

[0054] (1) Towed three-component fiber optic submarine cable:

[0055] The length of a single three-component fiber optic submarine cable 100 is 2km and the diameter is 10cm; the spacing of the three-component structure is 5m and the number is 400; the diameter of the three cylinders is 10cm and the height is 9cm; the diameter of the optical fiber is 0.5mm and 1m is wound on each cylinder.

[0056] (2) Specific steps of marine seismic data acquisition methods:

[0057] Step 1a: After connecting the tail end of the fiber optic towing cable fixed on the cable reel of the work vessel to the waterbird, put it into the seawater and start releasing the fiber optic towing cable at a constant speed.

[0058] Step 1b: During the release process, a depth positioning device is added to the outside of the cable at each three-component structure, and the sinking depth is set to 1m;

[0059] Step 2: After being released to the designed length, the work vessel moves forward at a constant speed, and the air gun source begins to be activated according to the construction design.

[0060] Example 2

[0061] (1) Towed three-component fiber optic submarine cable:

[0062] A single three-component fiber optic submarine cable 100 is 1km long and 10cm in diameter; the three-component structure is spaced 2m apart and consists of 500 components; the three cylinders are 10cm in diameter and 9cm in height; the optical fiber is 0.5mm in diameter and is wound 1m long around each cylinder.

[0063] (2) Specific steps of marine seismic data acquisition methods:

[0064] Step 1a: After connecting the tail end of the fiber optic towing cable fixed on the cable reel of the work vessel to the waterbird, put it into the seawater and start releasing the fiber optic towing cable at a constant speed.

[0065] Step 1b: During the release process, a depth positioning device is added to the outside of the cable at each three-component structure, and the sinking depth is set to 2m;

[0066] Step 2: After being released to the designed length, the work vessel moves forward at a constant speed, and the air gun source begins to be activated according to the construction design.

[0067] Example 3

[0068] (1) Towed three-component fiber optic submarine cable:

[0069] The length of a single three-component fiber optic submarine cable 100 is 3km and the diameter is 10cm; the spacing between the three components is 5m and the number of components is 600; the diameter of the three cylinders is 10cm and the height is 9cm; the diameter of the optical fiber is 0.5mm and 1m is wound around each cylinder.

[0070] (2) Specific steps of marine seismic data acquisition methods:

[0071] Step 1a: After connecting the tail end of the fiber optic towing cable fixed on the cable reel of the work vessel to the waterbird, put it into the seawater and start releasing the fiber optic towing cable at a constant speed.

[0072] Step 1b: During the release process, a depth positioning device is added to the outside of the cable at each three-component structure, and the sinking depth is set to 6m;

[0073] Step 2: After being released to the designed length, the work vessel moves forward at a constant speed, and the air gun source begins to be activated according to the construction design.

[0074] Example 4

[0075] (1) Towed three-component fiber optic submarine cable:

[0076] The length of a single three-component fiber optic submarine cable 100 is 1km and the diameter is 10cm; the spacing between the three components is 1m and the number is 1000; the diameter of the three cylinders is 10cm and the height is 9cm; the diameter of the optical fiber is 0.5mm and 1m is wound around each cylinder.

[0077] (2) Specific steps of marine seismic data acquisition methods:

[0078] Step 1a: After connecting the tail end of the fiber optic towing cable fixed on the cable reel of the work vessel to the waterbird, put it into the seawater and start releasing the fiber optic towing cable at a constant speed.

[0079] Step 1b: During the release process, a depth positioning device is added to the outside of the cable at each three-component structure, and the sinking depth is set to 3m;

[0080] Step 2: After being released to the designed length, the work vessel moves forward at a constant speed, and the air gun source begins to be activated according to the construction design.

[0081] Example 5

[0082] (1) Towed three-component fiber optic submarine cable:

[0083] The length of a single three-component fiber optic submarine cable 100 is 4km and the diameter is 10cm; the spacing between the three components is 10m and the number is 400; the diameter of the three cylinders is 10cm and the height is 9cm; the diameter of the optical fiber is 0.5mm and 1m is wound around each cylinder.

[0084] (2) Specific steps of marine seismic data acquisition methods:

[0085] Step 1a: After connecting the tail end of the fiber optic towing cable fixed on the cable reel of the work vessel to the waterbird, put it into the seawater and start releasing the fiber optic towing cable at a constant speed.

[0086] Step 1b: During the release process, a depth positioning device is added to the outside of the cable at each three-component structure, and the sinking depth is set to 4m;

[0087] Step 2: After being released to the designed length, the work vessel moves forward at a constant speed, and the air gun source begins to be activated according to the construction design.

[0088] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A towed three-component optical fiber submarine cable, characterized in that, The three-component fiber optic submarine cable has a Y-axis along its length and an X-axis and a Z-axis perpendicular to the Y-axis. The three-component fiber optic submarine cable includes a submarine cable armor (4). An optical fiber (5) and several three-component structures fixed to the inner wall of the submarine cable armor (4) are disposed inside the submarine cable armor (4). The three-component structure includes three cylinders. The three cylinders are arranged sequentially along the X-axis, Z-axis and Y-axis, with the cylinder axis as the reference. The optical fiber (5) passes through the three-component structure by wrapping around the outer surface of the three cylinders.

2. The optical fiber submarine cable according to claim 1, characterized in that, The two ends of the cylinders set along the X-axis and along the Z-axis are embedded into the inner wall of the submarine cable outer armor (4) for fixation.

3. The optical fiber submarine cable according to claim 1 or 2, characterized in that, The inner wall of the submarine cable outer armor (4) is provided with several fixing posts (6), and the outer wall of the cylinder arranged along the Y axis is engaged with the fixing posts (6).

4. The optical fiber submarine cable according to claim 1 or 2, characterized in that, The cylinders in the three-component structure may have the same or different dimensions, with each cylinder having a height of 5-10 cm and a diameter of 5-10 cm.

5. The optical fiber submarine cable according to claim 1 or 2, characterized in that, The spacing between adjacent three-component structures is 1-10m.

6. The optical fiber submarine cable according to claim 1 or 2, characterized in that, The length of the optical fiber (5) wound around the outer surface of each cylinder is 0.5m-1m; And / or, the diameter of the optical fiber (5) is 0.3-0.7 mm.

7. A towed marine seismic data acquisition device, characterized in that, The cable includes a three-component fiber optic submarine cable as described in any one of claims 1-6 and a depth positioning auxiliary device (200), wherein the depth positioning auxiliary device (200) is engaged on the outer surface of the outer armor (4) of the submarine cable, and the position of the depth positioning auxiliary device (200) corresponds to the position of the three-component structure.

8. The device according to claim 7, characterized in that, The depth positioning auxiliary device (200) includes a water depth positioning unit (210) and a fixing buckle (220). The fixing buckle (220) is disposed on the upper surface of the water depth positioning unit (210) and is engaged with the water depth positioning unit (210). The depth positioning auxiliary device (200) is engaged with the outer surface of the submarine cable outer armor (4) by the fixing buckle (220).

9. The device according to any one of claims 7-8, characterized in that, The marine seismic data acquisition equipment also includes a mobile device (300) connected to one end of the three-component fiber optic submarine cable.

10. A method for acquiring marine seismic data, characterized in that, Performed using the device according to any one of claims 7-9, comprising the following steps: Step 1: Place the three-component fiber optic submarine cable and the depth positioning auxiliary equipment (200) fixed to it into the seawater; Step 2: The marine seismic data acquisition equipment is moved to acquire seismic data.

Images