Hollow cylindrical floating production oil storage and discharge device

Abstract

The invention discloses a hollow cylindrical floating oil production, storage and offloading device which is composed of a lower floating body, an upper module and a mooring rope, the lower floating body comprises a main deck, the upper module is arranged on the main deck, and the mooring rope is arranged on the upper module. An outer floating deck box, an upper hollow annular cylindrical barrel, a circular-truncated-cone-shaped transition section, a lower hollow annular cylindrical barrel and a heaving body are sequentially arranged on the side, away from the upper module, of the main deck so that the lower floating body can be arranged in a cylindrical shape. A mooring cable is connected to the lower floating body, the near end of the mooring cable is fixed to the heaving body through an anchoring groove, and the far end of the mooring cable is fixed to the seabed; the upper module is connected with a steel catenary vertical pipe, and the steel catenary vertical pipe penetrates through the lower floating body to be connected with a seabed wellhead. According to the hollow cylindrical floating type oil production, storage and unloading device, the large-size moon pool penetrating up and down is arranged in the lower floating body, so that the waterline area of in-place design draft of the platform is effectively reduced, the heaving natural period of the platform is prolonged, and the main energy period range of waves is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of marine oil and gas development, and in particular relates to a hollow cylindrical floating production storage and unloading oil device. Background Art

[0002] At present, FPSO (Floating Production Storage and Offloading Unit) is one of the main equipment for offshore oil and gas field development. Among them, the cylindrical FPSO is an overall central axis symmetrical structure. Because of its isotropic hydrodynamic characteristics, it is insensitive to environmental directionality and can adopt an extended mooring system to avoid the use of a single-point mooring system. Compared with the ship-shaped FPSO, the cylindrical FPSO has a compact structure, and the mid-sag and mid-arch effects are not obvious. The symmetrical floating body and simple structure are more suitable for modular design and construction. The cylindrical FPSO usually uses a large-diameter heave tank at the bottom to increase the motion added mass and damping to improve the hull motion performance.

[0003] However, like the ship-shaped FPSO, the cylindrical FPSO also has a larger waterplane area, and its natural period of movement is still not enough to avoid the wave energy period range under typhoon sea conditions. Its movement performance under sea conditions is not as good as that of a semi-submersible, and it also cannot adapt to the suspension requirements of steel catenary risers (SCRs).

[0004] Therefore, there is an urgent need to design a hollow cylindrical floating production storage and offloading device to solve the above-mentioned problems. Summary of the invention

[0005] In order to solve the technical problem mentioned in the background technology that the movement performance of a cylindrical FPSO under sea conditions is not as good as that of a semi-submersible FPSO and cannot meet the suspension requirements of a steel catenary riser, a hollow cylindrical floating production storage and offloading device is provided to solve the problem of oil storage demand and steel catenary riser suspension requirements.

[0006] To achieve the above-mentioned purpose, the specific technical scheme of the hollow cylindrical floating production storage and offloading device of the present invention is as follows: A hollow cylindrical floating production storage and offloading device is composed of a lower buoy, an upper assembly and a mooring cable. The lower buoy includes a main deck, on which the upper assembly is arranged. An outer buoy deck box, an upper hollow annular cylinder, a truncated cone transition section, a lower hollow annular cylinder and a heave body are arranged in sequence on the side of the main deck away from the upper assembly, so that the lower buoy is arranged in a cylindrical shape; a mooring cable is connected to the lower buoy, the proximal end of the mooring cable is fixed to the heave body through an anchor groove, and the distal end of the mooring cable is fixed to the seabed; the upper assembly is connected to a steel catenary riser, and the steel catenary riser passes through the lower buoy and is connected to a seabed wellhead.

[0007] Furthermore, the process deck of the upper assembly is supported and arranged on the main deck, and a wind-permeable and wave-breaking wall is arranged between the process deck and the main deck.

[0008] Furthermore, the outer buoyancy deck box, the upper hollow annular cylindrical cylinder, the truncated cone transition section, the lower hollow annular cylindrical cylinder and the heave body are sequentially connected to form an annular column type closed structure with non-uniform diameters, and the internal hollow part is a moon pool that passes through from top to bottom.

[0009] Furthermore, a plurality of anchoring slots are provided on the heave body, and a mooring cable passes through each anchoring slot.

[0010] Furthermore, the horizontal cross-section of the lower hollow annular cylindrical body is annular, and one end of the lower hollow annular cylindrical body away from the truncated cone-shaped transition section is butted against the heave body.

[0011] Furthermore, a plurality of steel catenary risers are arranged in the moon pool.

[0012] Furthermore, a plurality of radial bulkheads and annular bulkheads are provided inside the lower buoy, and the ballast water tank and the crude oil tank are separated by the radial bulkheads and the annular bulkheads.

[0013] Furthermore, the ballast water tank is provided with two circles, inner and outer circles, and is arranged symmetrically in a circular shape inside the lower buoy to protect the crude oil tank.

[0014] Furthermore, the crude oil tank is arranged in a ring shape between the inner and outer ballast water tanks above the heave body, and the outer ballast water tank is provided with an anchor chain locker in a ring shape.

[0015] Furthermore, a diesel tank and a fresh water tank are symmetrically arranged on one side of the inner ballast water tank close to the moon pool; and a dirty oil water tank and a chemical tank are symmetrically arranged on one side of the inner ballast water tank away from the moon pool.

[0016] The hollow cylindrical floating production storage and offloading device of the present invention has the following advantages: (1) By setting a large-sized moon pool that runs vertically through the lower buoy, the water plane area of ​​the platform's in-situ design draft is effectively reduced, which can increase the platform's natural heave period and avoid the main wave energy period range compared to traditional cylindrical FPSOs. The seawater movement in the moon pool of the present application is coupled with the movement of the buoy, which can provide a significant damping effect, making the overall movement performance of the platform significantly improved compared to cylindrical floating production storage and offloading units; (2) The large-volume heave body and damping plate design at the bottom of the platform increase the additional mass and damping during the platform's movement, which can further enhance the platform's motion performance, effectively improve the platform's self-floating stability and reduce the empty ship's draft. This is conducive to the overall construction and joint commissioning of the upper module and the lower buoyancy body at construction sites with limited water depth at docks and waterways, and reduces the water depth requirements for the waterway during towing. (3) The large-sized moon pool design has a certain shielding effect on the external seawater, and can be used for the layout of steel catenary risers or drilling and workover risers and related equipment, reducing the risk of damage and failure of related facilities due to external seawater impact or ship collision; (4) The lower buoy is equipped with a ballast water tank, crude oil tank, ballast water tank and moon pool, forming a double hull and double bottom protection for the internal crude oil tank, avoiding the risk of crude oil leakage caused by collision between the external oil tanker or drilling and workover equipment and riser and the lower buoy; (5) The compact circular deck can adopt a small, modular upper module structure, further reducing the module weight and facilitating modular construction and assembly integration. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of the hollow cylindrical floating production storage and offloading device of the present invention; Figure 2 It is a schematic diagram of the division of the internal compartments below the main deck of the hollow cylindrical floating production storage and offloading unit of the present invention; Figure 3 It is a schematic diagram of the division of the internal compartments of the lower hollow annular cylindrical body of the hollow cylindrical floating production storage and offloading device of the present invention; Figure 4 It is a schematic diagram of a middle longitudinal section of the lower buoy of the hollow cylindrical floating production storage and offloading device of the present invention; Figure 5 for Figure 4 Cross-sectional view at the AA position.

[0018] Description of the markings in the figure: 1. Lower buoyancy body; 2. Upper assembly; 3. Outer buoyancy deck box; 4. Upper hollow cylindrical cylinder; 5. Cone-shaped transition section; 6. Lower hollow cylindrical cylinder; 7. Heave body; 8. Process deck; 9. Wind-permeable wave-breaking wall; 10. Main deck; 11. Mooring line; 12. Steel catenary riser; 13. Moon pool; 14. Anchor groove; 15. Ballast water tank; 16. Crude oil tank; 17. Slop water tank; 18. Chemical tank; 19. Diesel tank; 20. Chain locker; 21. Fresh water tank; 22. Damping plate; 23. Radial bulkhead; 24. Annular bulkhead. DETAILED DESCRIPTION

[0019] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work are within the scope of protection of the present invention.

[0020] Those skilled in the art will appreciate that, although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present invention and form different embodiments. For example, in the claims, any one of the claimed embodiments may be used in any combination.

[0021] Please refer to the attached Figure 1 To Attachment Figure 5 The hollow cylindrical floating production storage and offloading unit of the present invention is described.

[0022] like Figure 1 As shown, the hollow cylindrical floating production storage and offloading device in the present invention is composed of a lower buoy 1, an upper module 2 and a mooring cable 11. The lower buoy 1 includes a main deck 10, on which the upper module 2 is arranged. The main deck 10 is provided with an outer buoy deck box 3, an upper hollow annular cylinder 4, a truncated cone transition section 5, a lower hollow annular cylinder 6 and a heave body 7 in sequence on the side away from the upper module 2, so that the lower buoy 1 is arranged in a cylindrical shape; the lower buoy 1 is connected with a mooring cable 11, the proximal end of the mooring cable 11 is fixed to the heave body 7 through an anchor groove 14, and the distal end of the mooring cable 11 is fixed to the seabed; the upper module 2 is connected with a steel catenary riser 12, and the steel catenary riser 12 passes through the lower buoy 1 and is connected to the seabed wellhead.

[0023] By setting a large-sized moon pool 13 that runs vertically through the lower buoy 1, the water plane area of ​​the platform's in-situ design draft is effectively reduced, and the platform's natural heave period can be increased compared to the traditional cylindrical FPSO to avoid the main wave energy period range. The seawater movement in the moon pool 13 of the present application is coupled with the movement of the buoy, which can provide a significant damping effect, so that the overall movement performance of the platform is greatly improved compared to the cylindrical floating production storage and offloading unit.

[0024] Further, if Figure 1 As shown, the process deck 8 of the upper assembly 2 is supported and arranged on the main deck 10, and a wind-permeable wave-blocking wall 9 is arranged between the process deck 8 and the main deck 10; the outer buoyancy deck box 3, the upper hollow annular cylindrical cylinder 4, the truncated cone transition section 5, the lower hollow annular cylindrical cylinder 6 and the heave body 7 are sequentially connected to form a non-uniform diameter annular column type closed structure, and the internal hollow part is a moon pool 13 that passes through from top to bottom; the heave body 7 is provided with an anchor groove 14, and the mooring cable 11 passes through the anchor groove 14.

[0025] In this embodiment, preferably, the lower buoy 1 adopts a ring-column closed structure with unequal diameters at the top and bottom, a moon pool 13 is formed in the center, the bottom is connected to the mooring cable 11, and the top supports the upper assembly 2. The heave body 7 is located at the bottom of the lower buoy 1, and is an annular closed structure with a boss shape in vertical section, and its outer side, inner side and bottom are adjacent to the external seawater.

[0026] Several groups of anchoring grooves 14 can be provided on the outer side of the heaving body 7 according to the requirements of the mooring cables 11. In the present embodiment, the mooring cables 11 are composed of three groups of anchoring systems, one group includes five mooring cables, and three anchoring grooves 14 are provided on the heaving body 7 for facilitating the arrangement of the mooring cables 11; preferably, the anchoring grooves 14 are connected to the upper part of the lower buoy 1 by means of an installation chain, and the anchoring grooves 14 are connected to the seabed through the mooring cables 11.

[0027] Further, if Figures 1 to 3 As shown, the horizontal cross-section of the lower hollow annular cylinder 4 is annular, and the end of the lower hollow annular cylinder 6 away from the truncated cone transition section 5 is connected to the heave body 7; a plurality of steel catenary risers 12 are arranged in the moon pool 13; a plurality of radial bulkheads and annular bulkheads are arranged inside the lower buoy 1, and the ballast water tank 15 and the crude oil tank 16 are separated by the radial bulkheads and the annular bulkheads.

[0028] In this embodiment, preferably, the horizontal cross-section of the lower hollow annular cylinder 6 is annular, and its bottom is connected to the heave body 7; the hollow truncated cone transition section 5 is installed on the lower hollow annular cylinder 6; the upper hollow annular cylinder 4 is installed on the hollow truncated cone transition section 5; the outer side and inner side of the outer floating deck box 3 are inclined toward the outer side and the center side of the platform respectively, forming a closed annular structure with an inverted convex cone shape in vertical cross-section, the bottom of which is connected to the upper hollow annular cylinder 4, and the top is provided with a main deck 10.

[0029] The process deck 8 of the upper assembly 2 is supported and installed on the main deck 10. A windproof wave-breaking wall 9 is arranged on the side between the process deck 8 and the main deck 10. The windproof wave-breaking wall 9 can protect the deck facilities from the impact of waves and provide natural ventilation for the space between the main deck 10 and the process deck 8.

[0030] As a preferred embodiment, the lower buoy 1 is a hollow non-uniform diameter annular column closed structure, and its hollow part forms a moon pool 13 that passes through from top to bottom. A steel catenary riser 12 is arranged in the moon pool 13. The steel catenary riser 12 is used to connect the oil and gas processing system of the upper module 2 with the wellhead located on the seabed. The steel catenary riser 12 is a production riser. The upper module 2 is arranged on the process deck 8. Small modular facilities such as oil and gas processing process facilities, public facilities, drilling and repair facilities, flare arms, external transmission systems and living buildings can be arranged on the upper module 2 according to the functional requirements of the platform.

[0031] Further, if Figures 3 to 5As shown, the ballast water tanks 15 are provided with two circles, inner and outer circles, and are symmetrically arranged in a ring shape inside the lower floating body 1 to protect the crude oil tank 16; the crude oil tank 16 is arranged in a ring shape between the inner and outer circle ballast water tanks 15 above the heaving body 7, and the outer circle ballast water tank 15 is provided with a chain locker 20 in a ring shape; the diesel tank 19 and the fresh water tank 21 are symmetrically arranged on the side of the inner circle ballast water tank 15 close to the moon pool 13; the dirty oil water tank 17 and the chemical tank 18 are symmetrically arranged on the side of the inner circle ballast water tank 15 away from the moon pool 13.

[0032] In this embodiment, preferably, the overall space of the lower floating body 1 is separated by a plurality of radial bulkheads 23 and annular bulkheads 24 to form a ballast water tank 15 and a crude oil tank 16; the ballast water tank 15 is provided with two circles, inner and outer circles, and is arranged symmetrically in a circular shape inside the lower floating body 1, so as to realize double hull and double bottom protection for the crude oil tank 16.

[0033] The crude oil tank 16 is arranged in a ring shape between the inner and outer ballast water tanks 15 above the heave body 7; the chain locker 20 is arranged in a ring shape in the outer ballast water tank 15; the diesel tank 19 and the fresh water tank 21 are symmetrically arranged on the side of the inner ballast water tank 15 close to the moon pool 13; the dirty oil water tank 17 and the chemical tank 18 are symmetrically arranged on the side of the inner ballast water tank 15 away from the moon pool 13, forming double hull protection.

[0034] As a preferred embodiment, the FPSO design in-situ draft is located at the upper hollow annular cylindrical body 4, and the design draft is about 65%-78% of the FPSO mold depth. At the design in-situ draft, the diameter of the moon pool 13 is about 60% of the outer diameter of the upper hollow annular cylindrical body 4; in the lower hollow annular cylindrical body 6, the diameter of the moon pool is about 45% of the outer diameter of the lower hollow annular cylindrical body. The outer diameter of the upper hollow annular cylindrical body 4 is about 75% of the maximum outer diameter of the bottom of the heave body 7.

[0035] The design of the closed structure of the upper and lower non-equal diameter ring column allows the FPSO to have a smaller waterline area within the designed draft range to improve the movement performance, while still having a large displacement to meet the requirements of the oil storage function; the movement of seawater in the moon pool 13 is coupled with the movement of the floating body, which can produce a significant damping effect and greatly improve the overall movement performance of the platform.

[0036] In addition, the design of the large-volume heave body 7 at the bottom of the platform and the trumpet-shaped opening and damping plate 22 at the bottom of the moon pool 13 further increases the additional mass and damping during the movement of the platform, which can further improve the movement performance of the platform.

[0037] Tank model test studies have shown that the platform can control the heave motion within 5 meters and the sway motion within 7 degrees under extreme conditions, which can meet the suspension requirements of the steel catenary riser SCR and realize the functional expansion of conventional FPSO. The design of the large-volume heave body 7 effectively improves the self-floating stability of the platform and reduces the draft of the empty ship, which is conducive to the overall construction and joint commissioning of the upper module 2 and the lower floating body 1 at the construction site with limited water depth at the dock and channel, and reduces the channel depth requirements during towing.

[0038] The arrangement of the steel catenary riser 12 or drilling and workover riser and related equipment in the moon pool 13 can form shielding protection for related facilities and reduce the risk of damage and failure of related facilities due to external seawater impact or ship collision.

[0039] Based on the hollow cylindrical floating production storage and offloading device, a large-sized moon pool 13 is set up in the lower floating body 1, which effectively reduces the water plane area of ​​the platform's in-situ design draft, and can increase the platform's heave natural period and avoid the wave main energy period range compared to the traditional cylindrical FPSO. The seawater movement in the moon pool 13 of the present application is coupled with the movement of the floating body, which can provide a significant damping effect, so that the overall movement performance of the platform is greatly improved compared to the cylindrical floating production storage and offloading device.

[0040] Obviously, the above embodiments of the present invention are merely examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the embodiments here. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the claims of the present invention.

Claims

1. A hollow cylindrical floating production storage and offloading unit, consisting of a lower buoy, an upper assembly and a mooring cable, characterized in that: The lower floating body includes a main deck, on which an upper assembly is arranged. An outer buoyant deck box, an upper hollow cylindrical cylinder, a truncated cone transition section, a lower hollow cylindrical cylinder and a heave body are sequentially arranged on the side of the main deck away from the upper assembly, so that the lower floating body is arranged in a cylindrical shape; a mooring cable is connected to the lower floating body, the proximal end of the mooring cable is fixed to the heave body through an anchor groove, and the distal end of the mooring cable is fixed to the seabed; the upper assembly is connected to a steel catenary riser, and the steel catenary riser passes through the lower floating body and is connected to the seabed wellhead.

2. The hollow cylindrical floating production storage and offloading unit according to claim 1, characterized in that: The process deck of the upper module is supported and arranged on the main deck, and a wind-permeable and wave-blocking wall is arranged between the process deck and the main deck.

3. The hollow cylindrical floating production storage and offloading unit according to claim 1, characterized in that: The outer buoyancy deck box, the upper hollow annular cylindrical cylinder, the truncated cone transition section, the lower hollow annular cylindrical cylinder and the heave body are sequentially connected to form an annular column type closed structure with unequal diameters, and the inner hollow part is a moon pool which is connected from top to bottom.

4. The hollow cylindrical floating production storage and offloading unit according to claim 3, characterized in that: A plurality of anchoring slots are arranged on the heave body, and a mooring cable passes through each anchoring slot.

5. The hollow cylindrical floating production storage and offloading unit according to claim 1, characterized in that: The horizontal cross section of the lower hollow annular cylindrical cylinder is annular, and one end of the lower hollow annular cylindrical cylinder away from the truncated cone transition section is butted against the heave body.

6. The hollow cylindrical floating production storage and offloading unit according to claim 2, characterized in that: There are several steel catenary risers in the moon pool.

7. The hollow cylindrical floating production storage and offloading unit according to claim 1, characterized in that: A plurality of radial bulkheads and annular bulkheads are arranged inside the lower buoy, and the ballast water tank and the crude oil tank are separated by the radial bulkheads and the annular bulkheads.

8. The hollow cylindrical floating production storage and offloading unit according to claim 7, characterized in that: The ballast water tanks are provided with two circles, inner and outer circles, and are arranged symmetrically in a circular shape inside the lower buoy to protect the crude oil tanks.

9. The hollow cylindrical floating production storage and offloading unit according to claim 8, characterized in that: The crude oil tank is arranged in a ring shape between the inner and outer ballast water tanks above the heave body, and the outer ballast water tank is arranged in a ring shape with an anchor chain locker.

10. The hollow cylindrical floating production storage and offloading unit according to claim 9, characterized in that: The diesel tank and the fresh water tank are symmetrically arranged on the side of the inner circle ballast water tank close to the moon pool; the dirty oil water tank and the chemical tank are symmetrically arranged on the side of the inner circle ballast water tank away from the moon pool.

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