A method of installing a small seastar tension leg platform

Abstract

The application provides a small star-shaped tension leg platform installation method, which comprises the following steps: S1, transporting a lower floating body to a work sea area and connecting the lower floating body with a suction anchor pre-installed on a seabed; the lower floating body is submerged to a preset depth and balanced; S2, dry towing an upper floating body to the work sea area; connecting the upper floating body and a towing boat through a temporary mooring cable; inflating an air bag to make the upper floating body float on the water surface; S3, slowly floating the lower floating body and aligning a first sleeve, a second sleeve and a third sleeve on the upper floating body with a first guide pile, a second guide pile and a third guide pile on the lower floating body in sequence, slowly transferring the weight of the upper floating body to the lower floating body until the air bag is completely floated out of the water surface; S4, tensioning an anchor chain, discharging the gas in the air bag and completing the installation; in the whole installation process, a large floating crane is not needed, the installation cost is reduced, the docking difficulty is effectively reduced and the docking efficiency is improved by adopting the way of sequentially docking and positioning the guide piles and the sleeves.

Description

Technical Field

[0001] This invention belongs to the field of offshore oil platform engineering technology, specifically relating to an installation method for a small starfish-type tension leg platform. Background Technology

[0002] The SeaStar Tension-Leg Platform (SeaStar TLP) is a floating structure commonly used in the development of deep-sea oil and gas resources. It consists of an upper module and a lower floating body. The lower floating body comprises a vertically positioned central cylinder and three horizontal buoys positioned on the outer circumference of the lower end of the central cylinder. These three buoys are located in the same horizontal plane and are distributed at a 120° angle. The central cylinder supports the upper module via a jacket structure. At the end of each horizontal buoy is a tension leg mooring system (consisting of two anchor chain deployment / retraction devices; each tension leg consists of two anchor chains, and the deployment / retraction devices are used to deploy and retrieve the corresponding anchor chains). The released tension leg extends to the seabed and is secured to the anchoring foundation, thus achieving near-rigid out-of-plane movement of the tension leg platform. The small starfish-shaped tension leg platform is small in size, lightweight in structure, easy to move and install, highly flexible, and can withstand the effects of harsh environments. It is mainly suitable for water depths of about 150 meters and can realize the rapid rolling development of small and medium-sized marginal oil and gas fields.

[0003] However, the current installation of starfish-type tension leg platforms involves constructing the upper module and lower floating body separately on land, then towing them separately to the designated operating area by dry or wet towing. A large floating crane then lifts and launches them into the water, assists in righting and docking, and performs offshore welding and installation operations. This offshore installation method requires the use of large floating cranes and other equipment, resulting in high installation costs. It is not conducive to the economical and effective development of small and medium-sized marginal oil and gas fields. Furthermore, the upper module lifting operation has high requirements for the construction environment and weather, resulting in poor lifting stability, long installation time, and high operational difficulty. Summary of the Invention

[0004] In view of the shortcomings of the prior art, the purpose of this invention is to provide another installation method for a small starfish-type tension leg platform, which uses an airbag floating installation method for the upper module to replace the existing large floating crane hoisting method, effectively reducing installation costs. In addition, since the heights of the first guide pile, the second guide pile, and the third guide pile decrease sequentially, when the upper module is docked with the lower floating body, the docking positioning is achieved by sequentially docking the guide piles and the sleeve, which effectively reduces docking difficulty and improves docking efficiency.

[0005] To achieve the above and other related objectives, the present invention provides a method for installing a small starfish-type tension leg platform, the method comprising the following steps:

[0006] S1. Transport the completed lower floating body to the operating sea area and let it float on the water surface; then, release the anchor chain through the anchor chain release and release device at the end of the upper floating box of the lower floating body, and connect the released anchor chain to the suction anchor pre-installed on the seabed of the operating sea area; finally, inject ballast water into the ballast tank in the upper floating box of the lower floating body through the ballast pump, so that the lower floating body submerges to the preset depth, and tighten the anchor chain through the anchor chain release and release device to make the lower floating body reach a balanced state at the preset depth;

[0007] S2. Install an uninflated airbag at the bottom of the upper module to form an upper float. Dry-tow the upper float to the operating area using a semi-submersible barge. Connect the upper module of the upper float to the tugboat using a temporary mooring cable. Then, submerge the semi-submersible barge and inflate the airbags simultaneously, causing the upper module to float on the water surface under the action of the airbags and separate from the semi-submersible barge. When the distance between the semi-submersible barge and the upper module reaches the second preset distance, depart from the semi-submersible barge.

[0008] S3. The ballast water in the ballast tank of the float box is discharged by the ballast pump, and the anchor chain is released to allow the lower float to rise slowly. The docking position of the upper module is adjusted by the tugboat so that the first sleeve, second sleeve, and third sleeve on the upper module are aligned with the first guide pile, second guide pile, and third guide pile on the central cylinder of the lower float in sequence. During this process, the lower float continues to rise, so that the weight of the upper module is slowly transferred to the lower float until the airbag of the upper float is completely above the water surface. The height of the first guide pile, second guide pile, and third guide pile decreases in sequence.

[0009] S4. Tension the anchor chain and release the gas from the airbag to complete the installation of the small starfish-type tension leg platform.

[0010] Preferably, in step S1, after the completed lower floating body is towed to the operating sea area by a semi-submersible barge, the semi-submersible barge needs to be submerged first, so that the lower floating body floats on the water surface under the action of the buoy and separates from the semi-submersible barge; when the distance between the semi-submersible barge and the lower floating body reaches the first preset distance, the barge is driven away from the semi-submersible barge, and then the connection between the anchor chain and the suction anchor on the lower floating body is completed.

[0011] Preferably, the airbag includes a plurality of first airbag assemblies and a plurality of second airbag assemblies; the first airbag assemblies and the second airbag assemblies are arranged alternately to form a quadrilateral central open area; the first sleeve, the second sleeve, and the third sleeve are located within the central open area.

[0012] Preferably, the central open area is square or rectangular.

[0013] Preferably, both the first airbag assembly and the second airbag assembly are square, and the first airbag assembly is composed of four square first airbags spliced ​​together, and the second airbag is composed of four square second airbags spliced ​​together; among the airbags, 2 to 4 first airbags, 2 to 4 second airbags, or a combination of 2 to 4 first airbags and second airbags are spare airbags.

[0014] Preferably, one first sleeve and one first guide pile are provided, two second sleeves and two second guide piles are provided, and one third sleeve and one third guide pile are provided; one first sleeve, two second sleeves and one third sleeve are respectively located at the four corner positions of the central open area.

[0015] Preferably, three pontoons are evenly distributed on the outer circumference of the lower end of the central cylinder; the three pontoons are located at the same level, and the included angle between two adjacent pontoons is 120°; each pontoon is provided with multiple ballast tanks radiating from the inside out.

[0016] Preferably, the three pontoons have an equal number of ballast tanks, and the ballast tanks located on the same radial circle are simultaneously filled with or drained water.

[0017] Preferably, the preset depth is not less than 10m.

[0018] Preferably, the first preset spacing and the second preset spacing are 1m.

[0019] As described above, the installation method of the small starfish-type tension leg platform of the present invention has the following beneficial effects:

[0020] This invention eliminates the need for a large floating crane; simply pre-installing an airbag at the bottom of the upper module allows for its floating installation. This not only reduces installation costs but also mitigates the impact of adverse sea conditions and weather, thus lowering installation difficulty. Furthermore, since the heights of the first, second, and third guide piles decrease sequentially, the upper module can be positioned by sequentially connecting the guide piles and the sleeve during docking with the lower floating body, effectively reducing docking difficulty and improving docking efficiency. Attached Figure Description

[0021] Figure 1 This is the front view of the starfish-type tension leg platform.

[0022] Figure 2 This is a three-dimensional view of the lower floating body.

[0023] Figure 3 This is a schematic diagram showing the arrangement of ballast tanks in each pontoon of the lower floating body.

[0024] Figure 4 This is a top view of the airbag.

[0025] Figure 5 This is a schematic diagram of the first airbag assembly.

[0026] Figure 6 This is a schematic diagram of the second airbag assembly.

[0027] Figure 7 This is a process diagram (i.e., the implementation diagram of step S1) for transporting the lower floating body to the designated location.

[0028] Figure 8 This is a process diagram for transporting the upper module to the docking position (i.e., the implementation diagram of step S2).

[0029] Figure 9 This is a diagram showing the process of docking and installing the upper module with the lower floating body (i.e., the implementation diagram of steps S3 to S4).

[0030] Figure 10 This is a flowchart illustrating the installation of the starfish-type tension leg platform according to the present invention.

[0031] Explanation of reference numerals in the attached figures

[0032] Upper float 1, upper module 11, airbag 12, first airbag assembly 121, first airbag 121a, second airbag assembly 122, second airbag 122a, first sleeve 131, second sleeve 132, central open area 14, lower float 2, central cylinder 21, float box 22, ballast tank 1 221, ballast tank 222, ballast tank 3 223, ballast tank 4 224, ballast tank 5 225, ballast tank 6 226, first guide pile 231, second guide pile 232, third guide pile 233, anchor chain 24, suction anchor 3, semi-submersible barge 4, temporary mooring cable 5. Detailed Implementation

[0033] The following specific embodiments illustrate the implementation of the present invention. Those skilled in the art can easily understand other advantages and effects of the present invention from the content disclosed in this specification.

[0034] Please see Figures 1 to 10It should be understood that the structures, proportions, sizes, etc., illustrated in the accompanying drawings are merely for illustrative purposes to aid those skilled in the art and to facilitate understanding and reading. They are not intended to limit the scope of the invention and therefore have no substantial technical significance. Any modifications to the structure, changes in proportions, or adjustments to size, without affecting the effectiveness and purpose of the invention, should still fall within the scope of the technical content disclosed in this invention. Furthermore, the terms such as "upper," "lower," "left," "right," "middle," and "one" used in this specification are merely for clarity and not intended to limit the scope of the invention. Changes or adjustments to their relative relationships, without substantially altering the technical content, should also be considered within the scope of the invention's implementation.

[0035] like Figure 1 and Figure 4 As shown, the starfish-type tension leg platform includes an upper float 1 and a lower float 2.

[0036] The upper float 1 includes an upper module 11 and an airbag 12 located at the bottom of the upper module 11. The airbag 12 includes multiple first airbag assemblies and multiple second airbag assemblies, which together form a quadrilateral central open area 14. The upper module 11 has four sleeves embedded in the central open area. The four sleeves are located at the four corners of the central open area 14. The four sleeves include one first sleeve 131, two second sleeves 132, and one third sleeve (not shown in the figure).

[0037] The lower floating body 2 includes a vertically arranged central cylinder 21 and three floating boxes 22 evenly arranged on the outer circumference of the lower end of the central cylinder 21. The three floating boxes 22 are located in the same horizontal plane and are distributed at an angle of 120°. Each floating box 22 is provided with multiple ballast tanks radiating from the inside out. The central cylinder 21 is provided with four guide piles that cooperate with four sleeves on the upper module 11 to support the upper module 11. The four guide piles include a first guide pile 231 that cooperates with the first sleeve 131, a second guide pile 232 that cooperates with the second sleeve 132, and a third guide pile 233 that cooperates with the third sleeve. The heights of the first guide pile 231, the second guide pile 232, and the third guide pile 233 decrease sequentially. Two anchor chain retrieval devices are provided at the ends of the floating boxes 22 for retrieving and releasing the corresponding anchor chains 22, so that the anchor chains 24 extend to the seabed and connect with the suction anchor 3.

[0038] Furthermore, the central open area 14 is parallelogram-shaped.

[0039] It is understandable that, in order to reduce the difficulty of arranging the airbag 12, the central open area 14 is square or rectangular; in order to ensure that the airbag has sufficient buoyancy, this embodiment preferably makes the central open area 14 square.

[0040] like Figures 4 to 6 As shown, both the first airbag assembly 121 and the second airbag assembly 122 are square in shape, and the first airbag assembly 121 is composed of four square first airbags 121a spliced ​​together, and the second airbag assembly 122 is composed of four square second airbags 122a spliced ​​together.

[0041] It is understood that the number of the first airbag assembly 121 and the second airbag assembly 122, as well as the specifications of the first airbag 121a and the second airbag 122a, can be determined according to the actual situation and are not limited thereto. In this embodiment, the specifications of the first airbag 121a are preferably set to 5m×5m×6m, and the specifications of the second airbag 122a are preferably set to 5m×7m×6m; both the first airbag assembly 121 and the second airbag assembly 122 are set to 4 units.

[0042] Understandably, in order to ensure the stability of the upper module 11, the airbag 12 can also be divided into working airbag and backup airbag according to its function. The backup airbag is a combination of multiple first airbags 121a, multiple second airbags 122a, or multiple first airbags 121a and second airbags 121a. The backup airbag is not inflated or deflated under normal circumstances. It is only used when the working airbag is accidentally damaged and the buoyancy is insufficient.

[0043] Understandably, there are 2 to 4 spare airbags.

[0044] like Figure 3 As shown, ballast tanks 221, 222, 223, 224, 225, and 226 are arranged radially from the inside out on the pontoon 22. Each ballast tank 221 forms one group of ballast tanks, each ballast tank 222 forms two groups of ballast tanks, each ballast tank 223 forms three groups of ballast tanks, each ballast tank 224 forms four groups of ballast tanks, each ballast tank 225 forms five groups of ballast tanks, and each ballast tank 226 forms six groups of ballast tanks. The ballast water injection sequence is ballast tank 1, ballast tank 2, ballast tank 3, ballast tank 4, ballast tank 5, and ballast tank 6. The ballast water discharge sequence is the exact opposite of the ballast water injection sequence, so that each ballast tank in the same group is simultaneously filled or drained.

[0045] Understandably, to ensure stability, ballast tanks with the same number are located on the same radiation zone.

[0046] like Figure 10As shown, a method for installing a small starfish-type tension leg platform includes the following steps:

[0047] S1. Transport the completed lower floating body 2 to the operating sea area and make it float on the water surface; then, release the anchor chain 24 through the anchor chain retrieval device at the end of the upper floating box 22 of the lower floating body 2, and connect the released anchor chain 24 to the suction anchor 3 pre-installed on the seabed of the operating sea area; finally, inject ballast water into the ballast tank in the upper floating box 22 of the lower floating body 2 through the ballast pump, so that the lower floating body 2 submerges to the preset depth, and tension the anchor chain 24 through the anchor chain retrieval device, so that the lower floating body 2 reaches a balanced state at the preset depth;

[0048] It is understood that the preset depth can be determined according to the actual situation and is not limited thereto, as long as the lower floating body 2 does not interfere with the upper module 1 and the semi-submersible barge 4 that transports the upper module 1. In this embodiment, the preset depth is preferably set to 10m.

[0049] It is understood that the lower float 2 can be transported by dry towing or wet towing, and there is no limitation on this. In this embodiment, dry towing is preferred, and the dry towing method is as follows:

[0050] like Figure 7 As shown, after the completed lower floating body 1 is towed to the operating sea area by the semi-submersible barge 4, the semi-submersible barge 4 needs to be submerged first, so that the lower floating body 1 floats on the water surface under the action of the buoy 22 and separates from the semi-submersible barge 4; when the distance between the semi-submersible barge 4 and the lower floating body 1 reaches the first preset distance, the barge 4 is driven away, and then the connection between the anchor chain 24 and the suction anchor 3 on the lower floating body 1 is completed.

[0051] It is understood that the first preset distance can be determined according to the actual situation and is not limited thereto, as long as it ensures that the semi-submersible barge 4 does not interfere with the lower floating body 2 when it leaves; in this embodiment, the first preset distance is preferably set to 1m.

[0052] S2, such as Figure 2 As shown, an uninflated airbag 12 is installed at the bottom of the upper module 11 to form an upper float 1. The upper float 1 is towed to the operating sea area by a semi-submersible barge 4. The upper module 11 of the upper float 1 is connected to the tugboat by a temporary mooring cable 5. Then, the semi-submersible barge 4 is submerged while the airbag 12 is inflated, so that the upper module 11 floats on the water surface under the action of the airbag 12 and separates from the semi-submersible barge 4. When the distance between the semi-submersible barge 4 and the upper module 11 reaches the second preset distance, the barge departs from the semi-submersible barge 4.

[0053] Understandably, inflation stops when the buoyancy generated by the airbag 12 equals the weight of the upper module 11.

[0054] It is understood that the second preset distance can be determined according to the actual situation and is not limited thereto, as long as it ensures that the semi-submersible barge 4 does not interfere with the upper module 11 and the lower floating body 2 when it leaves; in this embodiment, the second preset distance is preferably set to 1m.

[0055] S3, such as Figure 9 As shown, the ballast water in the ballast tank of the float 22 is discharged by the ballast pump, and the anchor chain 24 is released, causing the lower float 2 to slowly rise. The docking position of the upper module 11 is adjusted by the tugboat, so that the first sleeve 131, the second sleeve 132, and the third sleeve on the upper module 11 are aligned with the first guide pile 231, the second guide pile 232, and the third guide pile 233 on the central cylinder 21 of the lower float 2 in sequence. During this process, the lower float 2 continues to rise, so that the weight of the upper module 11 is slowly transferred to the lower float 2 until the airbag 12 of the upper float 1 is completely floating on the water surface, completing the docking of the upper module 11 and the lower float 2. The heights of the first guide pile 231, the second guide pile 232, and the third guide pile 233 decrease in sequence.

[0056] By first aligning and fitting the first sleeve 131 with the first guide pile 231, and then aligning and fitting the second sleeve 132 with the second guide pile 132, the difficulty of docking is greatly reduced and the docking efficiency is improved.

[0057] It is understood that the height difference between the first guide pile 231 and the second guide pile 232 can be determined according to the actual situation and is not limited thereto. In this embodiment, the height difference between the first guide pile 231 and the second guide pile 232 is preferably set to 2m.

[0058] S4. Tension the anchor chain 24 and release the gas from the airbag 12 to complete the final installation of the small starfish-type tension leg platform.

[0059] It is understood that the airbag 12 that discharges gas can be removed from the upper module 11 or not, and there is no limitation on this. In this embodiment, it is preferred to remove the airbag 12.

[0060] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A method for installing a small starfish-type tension leg platform, characterized in that, The method includes the following steps: S1. Transport the completed lower floating body to the operating sea area and let it float on the water surface; then, release the anchor chain through the anchor chain release and release device at the end of the upper floating box of the lower floating body, and connect the released anchor chain to the suction anchor pre-installed on the seabed of the operating sea area; finally, inject ballast water into the ballast tank in the upper floating box of the lower floating body through the ballast pump, so that the lower floating body submerges to the preset depth, and tighten the anchor chain through the anchor chain release and release device to make the lower floating body reach a balanced state at the preset depth; S2. Install an uninflated airbag at the bottom of the upper module to form an upper float. Dry-tow the upper float to the operating area using a semi-submersible barge. Connect the upper module of the upper float to the tugboat using a temporary mooring cable. Then, submerge the semi-submersible barge and inflate the airbags simultaneously, causing the upper module to float on the water surface under the action of the airbags and separate from the semi-submersible barge. When the distance between the semi-submersible barge and the upper module reaches the second preset distance, depart from the semi-submersible barge. S3. The ballast water in the ballast tank of the float box is discharged by the ballast pump, and the anchor chain is released to allow the lower float to rise slowly. The docking position of the upper module is adjusted by the tugboat so that the first sleeve, second sleeve, and third sleeve on the upper module are aligned with the first guide pile, second guide pile, and third guide pile on the central cylinder of the lower float in sequence. During this process, the lower float continues to rise, so that the weight of the upper module is slowly transferred to the lower float until the airbag of the upper float completely floats out of the water, completing the docking of the upper module and the lower float. The heights of the first guide pile, second guide pile, and third guide pile decrease in sequence. S4. Tension the anchor chain and release the gas from the airbag to complete the installation of the small starfish-type tension leg platform.

2. The installation method of a small starfish-type tension leg platform according to claim 1, characterized in that, In step S1, after the completed lower floating body is towed to the operating sea area by a semi-submersible barge, the semi-submersible barge must first be submerged so that the lower floating body floats on the water surface under the action of the buoy and separates from the semi-submersible barge. When the distance between the semi-submersible barge and the lower floating body reaches the first preset distance, the barge is driven away from the semi-submersible barge, and then the connection between the anchor chain and the suction anchor on the lower floating body is completed.

3. The installation method of a small starfish-type tension leg platform according to claim 1 or 2, characterized in that, The airbag includes multiple first airbag components and multiple second airbag components, and the multiple first airbag components and multiple second airbag components together form a quadrilateral central open area; the first sleeve, the second sleeve and the third sleeve are located within the central open area.

4. The installation method of a small starfish-type tension leg platform according to claim 3, characterized in that, The central open area is square or rectangular.

5. The installation method of a small starfish-type tension leg platform according to claim 3, characterized in that, Both the first airbag assembly and the second airbag assembly are square in shape, and the first airbag assembly is composed of four square first airbags spliced ​​together, and the second airbag is composed of four square second airbags spliced ​​together; the airbag may contain multiple first airbags, multiple second airbags, or multiple combinations of first airbags and second airbags as spare airbags.

6. The installation method of a small starfish-type tension leg platform according to claim 4, characterized in that, One first sleeve and one first guide pile are provided, two second sleeves and two second guide piles are provided, and one third sleeve and one third guide pile are provided; one first sleeve, two second sleeves and one third sleeve are respectively located at the four corner positions of the central open area.

7. The installation method of a small starfish-type tension leg platform according to claim 1, characterized in that, Three pontoons are evenly distributed on the outer circumference of the lower end of the central cylinder; the three pontoons are located at the same level, and the included angle between two adjacent pontoons is 120°; each pontoon is equipped with multiple ballast tanks radiating from the inside out.

8. The installation method of a small starfish-type tension leg platform according to claim 7, characterized in that, The three pontoons have an equal number of ballast tanks, and the ballast tanks located on the same radial circle are simultaneously filled with or drained water.

9. The installation method of a small starfish-type tension leg platform according to claim 1, characterized in that, The preset depth is not less than 10m.

10. The installation method of a small starfish-type tension leg platform according to claim 2, characterized in that, The first preset spacing and the second preset spacing are 1m.

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