Top-tensioned riser and offshore oil and gas production system

Abstract

The present application relates to the field of oil exploitation, provide a kind of top tension type riser and offshore oil and gas exploitation system, including riser main body, buoyancy cylinder assembly and limiting component, buoyancy cylinder assembly is set in the top outer side of riser main body, and the top of buoyancy cylinder assembly and the top of riser main body are connected with dry Christmas tree, the buoyancy of seawater that buoyancy cylinder assembly receives is transferred to riser main body by dry Christmas tree, provides the tension of upward for riser main body.Buoyancy cylinder assembly is subjected to the buoyancy that it can provide tension for riser main body, need not be connected with dry tree cylinder platform, therefore, buoyancy cylinder assembly can adapt to the characteristics of vertical amplitude of dry tree cylinder platform.Limiting component set on buoyancy cylinder assembly is also used to limit the top of dry tree cylinder platform to float between the bottom of dry Christmas tree and the top of buoyancy cylinder main body, prevent dry tree cylinder platform from colliding with dry Christmas tree or buoyancy cylinder main body when floating.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of oil exploitation, and particularly relates to a top-tensioned riser and offshore oil and gas exploitation system. BACKGROUND

[0002] At present, when a dry tree platform is used to exploit oil, a top-tensioned riser is usually selected to connect the platform and a subsea wellhead, and the top of the top-tensioned riser provides tension through a hydraulic tensioning system.

[0003] When the dry tree platform is a dry tree cylinder platform, one end of the hydraulic tensioning system needs to be connected with the dry tree cylinder platform, and the other end is connected with the top-tensioned riser. However, the vertical motion amplitude of the floating body of the dry tree cylinder platform is large, and the extension distance of the hydraulic tensioning system is limited, which leads to the fact that the hydraulic tensioning system cannot adapt to the characteristics of the large vertical motion amplitude of the dry tree cylinder platform. SUMMARY

[0004] The present application aims to at least solve one of the problems in the prior art. To this end, the present application provides a top-tensioned riser and offshore oil and gas exploitation system, which aims to solve the problem that the hydraulic tensioning system is connected between the dry tree cylinder platform and the top-tensioned riser, and due to the limited extension distance of the hydraulic tensioning system, the hydraulic tensioning system cannot adapt to the characteristics of the large vertical motion amplitude of the dry tree cylinder platform.

[0005] The present application provides a top-tensioned riser, comprising:

[0006] a riser body, a top of the riser body being used to pass through a moon pool of a dry tree cylinder platform upwardly and connect with a dry tree located above the dry tree cylinder platform, and a bottom of the riser body being used to connect with a wellhead;

[0007] a buoyancy cylinder assembly, the buoyancy cylinder assembly comprising at least a buoyancy cylinder body and a top connecting rod, a bottom of the top connecting rod being connected with a top of the buoyancy cylinder body, and a top of the top connecting rod being used to connect with the dry tree, the buoyancy cylinder body and the top connecting rod being sleeved outside the top of the riser body;

[0008] a limiting assembly, the limiting assembly being arranged on the buoyancy cylinder assembly, and the limiting assembly being used to limit the top of the dry tree cylinder platform to float between a bottom of the dry tree and a top of the buoyancy cylinder body.

[0009] According to the top-tensioned riser provided by the present application, at least one cabin is arranged in the buoyancy cylinder body, and a gas interface and a liquid interface are arranged on each cabin.

[0010] The top-tensioned riser provided by the application is characterized in that a reinforcing keel joint is connected to the riser body, and the reinforcing keel joint is located at a pipe section of the riser body within a bottom stroke range of the dry tree cylinder platform.

[0011] The top-tensioned riser provided by the application is characterized in that the reinforcing keel joint has an inner diameter equal to that of the riser body, an outer diameter gradually decreasing from the middle to the two ends, and an outer diameter at the two ends equal to that of the riser body.

[0012] The top-tensioned riser provided by the application is characterized in that the buoyancy cylinder assembly further comprises a bottom connecting rod, a top of the bottom connecting rod being connected to the buoyancy cylinder body, and a bottom of the bottom connecting rod being used for sleeving outside the reinforcing keel joint.

[0013] The top-tensioned riser provided by the application is characterized in that the limiting assembly is arranged outside the top connecting rod, the bottom connecting rod and / or the buoyancy cylinder body.

[0014] The top-tensioned riser provided by the application is characterized in that the limiting assembly comprises an upper deck stopper and a lower deck stopper arranged outside the top connecting rod, the upper deck stopper being located close to the bottom of the dry tree, the lower deck stopper being arranged close to the top of the buoyancy cylinder body, and a top deck of the dry tree cylinder platform being located between the upper deck stopper and the lower deck stopper.

[0015] The top-tensioned riser provided by the application is characterized in that a reinforcing stress joint is further arranged at a bottom end of the riser body, and one end of the reinforcing stress joint away from the riser body is connected to the wellhead.

[0016] The top-tensioned riser provided by the application is characterized in that the reinforcing stress joint is a conical stress joint, the conical stress joint has an inner diameter equal to that of the riser body, an outer diameter gradually increasing from top to bottom, and an outer diameter at the top equal to that of the riser body.

[0017] The application further provides an offshore oil and gas exploitation system comprising a dry tree cylinder platform and the top-tensioned riser as described above, and a top of the top-tensioned riser being located within a moon pool of the dry tree cylinder platform.

[0018] The application has the following advantages due to the above technical solutions.

[0019] The top-tensioned riser provided by the application comprises a riser body, a buoyancy cylinder assembly and a limiting assembly. The top of the riser body is used to pass through the moon pool of the dry tree cylinder platform upwardly, and is connected with the bottom of the dry tree above the dry tree cylinder platform. The bottom of the riser body is used to be connected with the subsea wellhead. The buoyancy cylinder assembly comprises at least a buoyancy cylinder body and a top connecting rod. The bottom of the top connecting rod is connected with the top of the buoyancy cylinder body. The top of the top connecting rod is used to be connected with the dry tree. The buoyancy cylinder body and the top connecting rod are sleeved outside the top of the riser body. In this way, the buoyancy cylinder body interacts with seawater, and the buoyancy thereof provides a supporting force for the dry tree, so that the dry tree is located above the dry tree cylinder platform. The top of the riser body is connected with the bottom of the dry tree and is hung at the bottom of the dry tree. The buoyancy of the buoyancy cylinder body provides an upward tension force for the riser body through the dry tree. The top-tensioned riser provided by the application can provide sufficient tension force for the riser body by the buoyancy cylinder assembly itself, and does not need to be connected with the dry tree cylinder platform. Therefore, the dry tree cylinder platform can perform a large vertical movement. The limiting assembly is arranged on the buoyancy cylinder assembly and is used to limit the top of the dry tree cylinder platform to float between the bottom of the dry tree and the top of the buoyancy cylinder body. In this way, the dry tree cylinder platform can be prevented from colliding upwardly with the dry tree and downwardly with the buoyancy cylinder body when floating upwardly and downwardly, so that the dry tree and the buoyancy cylinder body can be effectively protected.

[0020] Further, in the offshore oil and gas exploitation system provided by the application, the top-tensioned riser is arranged, and the advantages are the same as those of the above-mentioned top-tensioned riser. BRIEF DESCRIPTION OF DRAWINGS

[0021] In order to more clearly illustrate the technical solutions in the application or the prior art, the following will briefly introduce the drawings needed in the embodiments or the prior art description. Obviously, the drawings in the following description are some embodiments of the application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0022] Figure 1 is a top structure schematic view of the top-tensioned riser provided by an embodiment of the application;

[0023] Figure 2 is Figure 1 is an enlarged view of A in FIG. 1;

[0024] Figure 3 is Figure 1 is an enlarged view of B in FIG. 1;

[0025] Figure 4 is a bottom structure schematic view of the top-tensioned riser provided by an embodiment of the application.

[0026] Reference Signs:

[0027] 100: dry tree cylinder platform; 110: moon pool; 200: riser body; 210: buoyancy cylinder body; 220: top connecting rod; 230: bottom connecting rod; 300: dry Christmas tree; 400: wellhead; 500: reinforced keel joint; 610: upper deck stopper; 620: lower deck stopper; 700: reinforced stress joint. DETAILED DESCRIPTION

[0028] In order to make the objects, technical solutions and advantages of the present application clearer, the technical solutions in the present application will be described clearly and completely below in conjunction with the drawings in the present application. Obviously, the described embodiments are only some of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0029] In the description of the present application, it should be understood that the orientation or positional relationship indicated by the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", "axial", "radial", "circumferential" and the like is based on the orientation or positional relationship shown in the drawings, and is only for the purpose of facilitating the description of the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation on the present application.

[0030] In addition, the terms "first", "second", "third" and the like are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the technical features indicated. Therefore, the features defined with "first", "second" and the like can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "plurality" is two or more, unless otherwise explicitly specified and limited.

[0031] In the present application, unless otherwise explicitly specified and limited, the terms "mounting", "connection", "connection", "fixing" and the like should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral; it can be mechanical connection, or electrical connection; it can be directly connected, or indirectly connected through an intermediate medium; it can be the internal communication of two elements or the interaction relationship between two elements. For those of ordinary skill in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0032] In the present application, unless otherwise explicitly specified and limited, the first feature is "on" or "under" the second feature can be that the first and second features are in direct contact, or the first and second features are in indirect contact through an intermediate medium. Moreover, the first feature is "above", "over" and "on" the second feature can be that the first feature is directly above or obliquely above the second feature, or simply means that the first feature is horizontally higher than the second feature. The first feature is "under", "below" and "under" the second feature can be that the first feature is directly below or obliquely below the second feature, or simply means that the first feature is horizontally lower than the second feature.

[0033] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "an example", "a specific example", or "some examples" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any suitable manner in any one or more embodiments or examples. In addition, the skilled person in the art can combine and combine the different embodiments or examples described in the present application and the features of the different embodiments or examples without contradiction.

[0034] The present application provides a top-tensioned riser, comprising a riser body, a buoyancy cylinder assembly and a limiting assembly, the buoyancy cylinder assembly is sleeved outside the top of the riser body, and the top of the buoyancy cylinder assembly and the top of the riser body are connected with a dry Christmas tree, the buoyancy of the sea water acting on the buoyancy cylinder assembly is transmitted to the riser body through the dry Christmas tree to provide upward tension to the riser body. The buoyancy acting on the buoyancy cylinder assembly itself can provide tension to the riser body, and it is not necessary to be connected with the dry Christmas tree cylinder platform, therefore, the buoyancy cylinder assembly can adapt to the characteristics of large vertical amplitude of the dry Christmas tree cylinder platform. The limiting assembly arranged on the buoyancy cylinder assembly is also used to limit the top of the dry Christmas tree cylinder platform to float between the bottom of the dry Christmas tree and the top of the buoyancy cylinder body, so as to prevent the dry Christmas tree cylinder platform from colliding with the dry Christmas tree or the buoyancy cylinder body when floating.

[0035] The top-tensioned riser and offshore oil and gas exploitation system of the present application will be described below in combination with Figures 1 to 4 The top-tensioned riser and offshore oil and gas exploitation system of the present application will be described below in combination with

[0036] The embodiment of the present application provides a top-tensioned riser, comprising a riser body 200, a buoyancy cylinder assembly and a limiting assembly.

[0037] The top of the riser body 200 extends upwardly and passes through the moon pool 110 in the middle of the dry tree cylinder platform 100, and the top end of the riser body 200 is connected to the bottom of the dry production tree 300 above the dry tree cylinder platform 100, and the bottom of the riser body 200 is used to be connected to the wellhead 400. In this way, the riser can transport the oil under the well to the dry tree cylinder platform 100.

[0038] The buoyancy cylinder assembly at least includes a buoyancy cylinder body 210 and a top connecting rod 220, the bottom of the top connecting rod 220 is connected to the top of the buoyancy cylinder body 210, and the top of the top connecting rod 220 is used to be connected to the bottom of the dry production tree 300, and the buoyancy cylinder body 210 and the top connecting rod 220 are both sleeved outside the top of the riser body 200. The buoyancy of the sea water received by the buoyancy cylinder assembly can be transmitted to the riser body 200 through the dry production tree 300 to provide an upward tension to the riser body 200.

[0039] The limiting assembly is arranged on the buoyancy cylinder assembly, and is used to limit the top of the dry tree cylinder platform 100 to float between the bottom of the dry production tree 300 and the top of the buoyancy cylinder body 210. In this way, the dry tree cylinder platform 100 and the dry production tree 300 and the buoyancy cylinder body 210 can be prevented from colliding.

[0040] Specifically, the riser body 200 is a production riser, which is used to connect the wellhead 400 and the dry production tree 300 to transport the oil under the well to the dry tree cylinder platform 100. For the dry tree cylinder platform 100, the center thereof is provided with a moon pool 110 penetrating the dry tree cylinder platform 100 in the vertical direction, and the top of the riser body 200 passes through the moon pool 110 to extend upwardly above the dry tree cylinder platform 100. The dry production tree 300 is located above the dry tree cylinder platform 100, and thus the top end of the riser body 200 is connected to the bottom of the dry production tree 300.

[0041] The buoyancy cylinder assembly includes a buoyancy cylinder body 210 and a top connecting rod 220, the top connecting rod 220 is arranged coaxially with the buoyancy cylinder body 210 in the up-down direction, the bottom of the top connecting rod 220 is connected to the top center of the buoyancy cylinder body 210, and the top of the top connecting rod 220 is used to be connected to the bottom of the dry production tree 300, for example, in the form of a flange. The center of the top connecting rod 220 and the center of the buoyancy cylinder body 210 are both provided with a through hole penetrating itself in the axial direction, and the top of the riser body 200 is located in the through hole, so that the buoyancy cylinder assembly can be sleeved outside the riser body 200.

[0042] The buoyancy of the sea water received by the buoyancy cylinder body 210 can be transmitted to the dry production tree 300 through the top connecting rod 220, and then transmitted to the riser body 200 by the dry production tree 300 to provide an upward tension to the riser body 200.

[0043] Because the buoyancy cylinder assembly itself can provide upward tension to the riser main body 200, and does not need to be connected with the dry tree cylinder platform 100, the characteristics of the large vertical movement amplitude of the dry tree cylinder platform 100 can be adapted.

[0044] However, the dry tree cylinder platform 100 cannot move upward or downward unlimitedly, but only needs to float within the stroke range of the riser main body 200. If the dry tree cylinder platform 100 floats upward too far, the top of the dry tree cylinder platform 100 will collide with the dry tree 300 above, and if the dry tree cylinder platform 100 floats downward too far, the top of the dry tree cylinder platform 100 will collide with the buoyancy cylinder main body 210 in the moon pool 110.

[0045] Therefore, a limiting assembly is further arranged on the buoyancy cylinder assembly, and the limiting assembly is used to limit the floating of the top of the dry tree cylinder platform 100 between the bottom of the dry tree 300 and the top of the buoyancy cylinder main body 210, so as to protect the dry tree 300 and the buoyancy cylinder main body 210.

[0046] In some embodiments of the present application, at least one cabin is arranged in the buoyancy cylinder main body 210, and a gas interface and a liquid interface are arranged on the cabin. When the buoyancy cylinder main body 210 needs to descend, the gas outside can be discharged through the gas interface to release pressure, and when the seawater pressure is greater than the pressure in the cabin, the seawater enters the cabin through the liquid interface. At this time, the gravity of the buoyancy cylinder increases, and the density increases, and the buoyancy cylinder main body 210 descends. When the buoyancy cylinder main body 210 needs to ascend, the cabin can be inflated through the gas interface, for example, nitrogen can be introduced into the cabin. When the air pressure in the cabin is greater than the seawater pressure, the seawater in the cabin is discharged through the liquid interface. At this time, the weight of the buoyancy cylinder decreases, and the density decreases, and the buoyancy cylinder main body 210 ascends.

[0047] The horizontal movement amplitude of the dry tree cylinder platform 100 is large, and during the horizontal movement, the riser main body 200 near the bottom of the dry tree cylinder platform 100 will bear a large bending moment, so the pipe section at this position needs to be specially considered.

[0048] In the top-tensioned riser provided by the embodiments of the present application, a reinforcing keel joint 500 is arranged at the pipe section where the riser main body 200 is located within the stroke range of the bottom of the dry tree cylinder platform 100, so as to ensure that the structural strength at this position meets the use requirements.

[0049] Specifically, the inner diameter of the reinforced keel joint 500 is equal to the inner diameter of the riser body 200, and the outer diameter of the reinforced keel joint 500 gradually decreases from the middle to the two ends, forming a structure similar to a spindle or a double cone. The outer diameter of the two ends of the reinforced keel joint 500 is equal to the outer diameter of the riser body 200. When connected, the two end portions of the reinforced keel joint 500 can be connected with the riser body 200 by welding.

[0050] In some embodiments of the present application, the buoyancy cylinder assembly further comprises a bottom connecting rod 230, the top of the bottom connecting rod 230 is connected with the bottom of the buoyancy cylinder body 210, and the bottom of the bottom connecting rod 230 is used to be sleeved on the outside of the reinforced keel joint 500.

[0051] Specifically, the bottom connecting rod 230 is hollow inside, and the inner diameter can be equal to or slightly larger than the outer diameter of the middle section of the reinforced keel joint 500. The top of the bottom connecting rod 230 is coaxially arranged above and below the buoyancy cylinder body 210, and the top of the bottom connecting rod 230 is connected with the bottom of the buoyancy cylinder body 210. The bottom connecting rod 230 extends downward and is sleeved on the outside of the reinforced keel joint 500. In this way, the reinforced keel joint 500 can be protected, and the influence of external force generated by fluid on the reinforced keel joint 500 can be reduced.

[0052] In some embodiments of the present application, the limiting assembly can be arranged on the outside of the top connecting rod 220, the outside of the bottom connecting rod 230, or the outside of the buoyancy cylinder body 210.

[0053] For example, the limiting assembly is arranged on the outside of the top connecting rod 220, and at this time the limiting assembly interacts with the top deck of the dry tree cylinder platform 100. The limiting assembly can include an upper deck stopper 610 and a lower deck stopper 620, the upper deck stopper 610 is located near the bottom end of the dry production tree 300 and below the bottom end of the dry production tree 300, and the lower deck stopper 620 is located near the top of the buoyancy cylinder body 210 and inside the top deck of the buoyancy cylinder body 210 of the dry tree cylinder platform 100, the inside edge of the top deck of the buoyancy cylinder body 210 is located between the upper deck stopper 610 and the lower deck stopper 620.

[0054] When the dry tree cylinder platform 100 floats upward and before the top deck hits the dry production tree 300, it will first contact the upper deck stopper 610 to limit the dry tree cylinder platform 100 from continuing to move upward, thereby protecting the dry production tree 300. When the dry tree cylinder platform 100 moves downward and before the top deck hits the buoyancy cylinder body 210, it will first contact the lower deck stopper 620 to limit the dry tree cylinder platform 100 from continuing to move downward, thereby protecting the buoyancy cylinder body 210.

[0055] During work, the bottom of the riser body 200 and the wellhead 400 connection will bear a large bending moment, so the pipe section also needs special consideration.

[0056] In the embodiment of the application, a reinforced stress joint 700 is arranged at the bottom of the riser body 200, and the end of the reinforced stress joint 700 away from the riser body 200 is connected with the wellhead 400.

[0057] Specifically, the reinforced stress joint 700 is a tapered stress joint, the inner diameter of the tapered stress joint is equal along the axial direction and equal to the inner diameter of the riser body 200, and the wall thickness of the tapered stress joint gradually increases from top to bottom, that is, the outer diameter of the tapered stress joint gradually increases from top to bottom. The tapered stress joint made of tapered thick wall casting can make the bending moment and axial force it bears smoothly transition to the wellhead 400.

[0058] The embodiment of the application also provides a marine oil and gas exploitation system, which comprises a dry tree cylindrical platform 100 and a top-tensioned riser as described above, and the top of the top-tensioned riser is located in the moon pool 110 of the dry tree cylindrical platform 100. Since the top-tensioned riser as described above is arranged, the same advantages as described above are achieved, and details are not repeated here.

[0059] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the application, and not to limit them; although the application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement to part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the application, and they should be covered in the scope of the claims and the description of the application. Especially, as long as there is no structural conflict, each technical feature mentioned in each embodiment can be combined in any way. The application is not limited to the specific embodiments disclosed in the text, but includes all technical solutions falling within the scope of the claims.

Claims

1. A top-tensioned riser, characterized in that, include: The riser body (200) has its top for passing upward through the moon pool (110) of the dry tree cylindrical platform (100) and connecting to the dry tree (300) located above the dry tree cylindrical platform (100), and its bottom for connecting to the wellhead (400). A buoyancy cylinder assembly, comprising at least a buoyancy cylinder body (210) and a top connecting rod (220), the bottom of which is connected to the top of the buoyancy cylinder body (210), and the top of which is used to connect to the dry tree (300). The buoyancy cylinder body (210) and the top connecting rod (220) are sleeved on the top outer side of the riser body (200). The buoyancy cylinder body (210) has at least one compartment, and each compartment is provided with a gas interface and a liquid interface. A limiting component is disposed on the buoyancy cylinder assembly. The limiting component is used to restrict the top of the dry tree cylinder platform (100) from floating between the bottom of the dry tree (300) and the top of the buoyancy cylinder body (210). The limiting component includes an upper deck block (610) and a lower deck block (620) disposed outside the top connecting rod (220). The upper deck block (610) is located near the bottom of the dry tree (300), and the lower deck block (620) is located near the top of the buoyancy cylinder body (210). The top deck of the dry tree cylinder platform (100) is located between the upper deck block (610) and the lower deck block (620).

2. The top-tensioned riser according to claim 1, characterized in that, The riser body (200) is connected to a reinforcing keel joint (500), which is located in the pipe section within the bottom stroke range of the riser body (200) and the dry tree cylindrical platform (100).

3. The top-tensioned riser according to claim 2, characterized in that, The inner diameter of the reinforcing keel joint (500) is equal to the inner diameter of the riser body (200), the outer diameter of the reinforcing keel joint (500) gradually decreases from the middle to both ends, and the outer diameters of both ends of the reinforcing keel joint (500) are equal to the outer diameter of the riser body (200).

4. The top-tensioned riser according to claim 2 or 3, characterized in that, The buoyancy cylinder assembly also includes a bottom connecting rod (230), the top of which is connected to the buoyancy cylinder body (210), and the bottom of which is used to be sleeved on the outside of the reinforcing keel joint (500).

5. The top-tensioned riser according to claim 4, characterized in that, The limiting component is located on the outside of the top connecting rod (220), the bottom connecting rod (230) and / or the buoyancy cylinder body (210).

6. The top-tensioned riser according to claim 1, characterized in that, The bottom end of the riser body (200) is also provided with a reinforcing stress joint (700), and the end of the reinforcing stress joint (700) away from the riser body (200) is connected to the wellhead (400).

7. The top-tensioned riser according to claim 6, characterized in that, The reinforced stress joint (700) is a tapered stress joint. The inner diameter of the tapered stress joint is equal to the inner diameter of the riser body (200). The outer diameter of the tapered stress joint gradually increases from top to bottom, and the outer diameter of the top of the tapered stress joint is equal to the outer diameter of the riser body (200).

8. An offshore oil and gas extraction system, characterized in that, It includes a dry tree cylindrical platform (100) and a top-tensioned riser as described in any one of claims 1 to 7, wherein the top of the top-tensioned riser is located within the moon pool (110) of the dry tree cylindrical platform (100).

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