JPS6217216A - J-shaped ocean oil production riser - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention This invention relates to a method and apparatus for conveying hydrocarbon fluids from subsea manifolds and wellheads to production vessels, and more particularly to risers for flowing hydrocarbon fluids.

BACKGROUND OF THE INVENTION Vertical risers have been used to transport hydrocarbon fluids, such as oil and natural gas, from subsea manifolds and wellheads to offshore production vessels. Vertical risers used for this purpose have the fundamental problem of holding in place the production vessel connected to the riser. Additionally, vertical production risers must be tensioned to prevent the risers from breaking due to buckling or bending, which is especially necessary in deep water. The tensions acting on the vertical risers need to be relatively high, reaching 600 hi:p in stormy weather.

Furthermore, the relatively high tensions require vertical compensators, requiring frequent inspection and replacement of riser segments due to fatigue.

Another problem with the use of vertical production risers is the problem of wear on the joints connecting the risers to the subsea manifold.

In the event of an emergency such as rough weather, it is often necessary to separate the riser at a connection near the seabed. This can cause bending and rebound of the riser, causing damage to the tube and production vessel at the top of the riser.

Another issue with the use of vertical risers is that semi-submersible vessels are recommended to reduce wave-induced motion on production vessels, but the payload capacity is reduced.

Increasing the length of the riser increases the need to keep the production vessel within a limited range of motion. A storage tanker in close proximity to a production vessel requires precise control to prevent lateral loading due to the presence of the production vessel and the storage tanker on the riser.

US Pat. No. 8,266,256 is a document related to a method of laying an underwater pipeline.

SUMMARY OF THE INVENTION In view of the above-mentioned drawbacks, the present invention provides a new structure and configuration for a riser for conveying hydrocarbon fluids from a subsea manifold to an offshore production vessel.

SUMMARY OF THE INVENTION A new production riser system according to the present invention couples a subsea manifold to an offshore production vessel. The device has one or more risers, the number of risers being determined by the number of supply lines in the subsea manifold where the device is used. Each riser of the device forms a J-shape, with the horizontal section resting on the seabed and the outer end connected to a coupling device on the subsea manifold. A slack or bend is formed between the horizontal section and the offshore production vessel coupling upright section.

The horizontal section of a riser or one or more risers of a multi-riser system frictionally engages the seabed to resist the tendency of the horizontal section to move due to frictional forces between the horizontal section and the seabed. The length of the horizontal section is selected such that the frictional forces absorb at least a majority of the horizontal pulling forces on the riser by the production vessel. The vessel is maintained in position by at least one of a dynamic thrust system and a tether.

While stationary in this position, the vessel applies a horizontal pull on the riser to face upwind while hydrocarbon fluid is conveyed from the manifold through the riser to the production vessel. The riser of the present invention eliminates the need for known vertical production risers to be kept within tight confines by the vessel to prevent failure due to buckling or bending, especially in deep water.

A riser arrangement formed by one or more risers according to the invention couples the collection section of a subsea manifold or wellhead to an offshore production vessel, with each riser being J-shaped to form a horizontal section and an upright section. The horizontal portion of a single riser or one or more risers of a multi-riser system frictionally engages the seabed and the upright portion is coupled to the production vessel. Horizontal tensile forces acting on the riser from a ship facing upwind are absorbed by the frictional forces of the riser in frictional engagement with the seabed, so the vessel does not have problems holding in place and the riser has minimal tensile force and no overbending. No stress occurs.

The riser device in combination with a subsea manifold and a production vessel according to the present invention is such that while the hydrocarbon fluid is conveyed from the manifold through the riser device to the production vessel, the riser device has a horizontal section, and the riser device acts on the riser device from the production vessel. Horizontal forces are absorbed by the frictional force between the seabed and the horizontal part.

The method of installing a J-type riser device according to the present invention allows the riser device to be installed on the seabed efficiently, with minimal cost, and with little possibility of damage to the manifold structure on the seabed.

Embodiments and drawings illustrating the present invention will be described.

Embodiment A first embodiment of the J-type offshore gold production riser apparatus 8 according to the present invention uses one riser 10 to connect a subsea manifold 12 to a vessel 14 on the water surface, and transports hydrocarbon fluid, etc. from the manifold to the vessel. send to

The riser 10 is suitable for deep sea applications, such as offshore applications of about 10,000 ft (approximately 8000 fi). Further, the riser is suitable for use on frozen water, and the riser 10 of the device 10 can be placed on the seabed to provide a remote location for ships when ice forces are strong.

The riser IO is a string of tubes joined together at their ends by welding, screwing, or the like. The diameter of the pipe is arbitrary, but as a standard it is 12<n (approximately 800 am) or larger and carries mixed product from several oil wells.

The riser 10 has a slack portion 16 between its ends, one end being connected to a manifold and the other end being connected to a watercraft 14. The horizontal portion 18 of the riser 10 is coupled to the slack portion 16;
It is on the seabed 20 and comes into frictional contact. A second upright portion 22 extends upwardly from slack portion 16 and couples to vessel 14 . The entire suspension part of the riser is a reinforced catenary. The upper end 24 of the upright portion 22 remains vertical or near vertical and extends vertically from a vertical motion restriction device 26 mounted on the vessel, as shown in FIGS. 1-8. A turret or rotating turntable allows the vessel to rotate relative to the riser. As another example, the connection between the riser and the vessel may be a gimbaled derrick or pivot ramp, also combined with a turret or rotating turntable.

Manifold 12 is of the required known design.

The manifold rests on the seabed 20 and has a connecting box 28 connecting the ends of the horizontal section 18.

In use, the riser lO conveys hydrocarbon fluids, including oil and natural gas, from the manifold 12 to the surface vessel 14. Typically, natural gas is separated from oil in a vessel 14 and injected back into the ocean floor 20 to be used as fuel gas or flare;
The oil is sent to a tanker (not shown) connected to the vessel 14 by a locking mechanism or the like.

Another method is to pump up and store in one vessel,
or sending hydrocarbons via undersea pipelines to other ships or to shore.

While conveying hydrocarbon fluid through riser 10, surface vessel 14 maintains a fixed y position relative to manifold 12 and tie line 30. In the event of inclement weather, one or more power thrust devices 32 are used by the vessel 14 to provide horizontal pulling forces on the vessel. The horizontal pulling force by the tether 30 or thrust device 32 is between 1 and 150 kips. Thus, using the riser 10 of the present invention, the basic problem of maintaining a fixed position of a vessel on the surface of the water is eliminated and the tension required on the riser 10 is minimized. Tension is primarily obtained using frictional forces between the seabed and the horizontal portion 18 of the riser 10, and the horizontal tension between the manifold and riser connections is eliminated. This action protects the connection between the riser 10 and the manifold 12 so that the vessel 14 remains stationed and exerts a horizontal pull on the riser, pointing in the direction of the waves and directing the hydrocarbon fluid from the manifold to the riser. After that, it is transported to a ship.

In forming the riser 10, a vertical rigid tube made of a plurality of tubes joined by welding, screwing, etc. is vertically lowered from the watercraft 14 into the coupling box 28 of the manifold 12. The tube sections are then added and the vessel is moved from its position directly above the manifold as shown in FIG. As shown in FIG. 2, as the pipe length increases, a slack portion is created in the riser, and the vessel 14 is at an intermediate position in the lateral direction from the position immediately above the manifold 12. At this stage, the riser is under top tension. Adding further tube sections to the riser increases the length of the riser, and due to its inherent flexibility, a portion of the riser forms a horizontal section 18 that in turn seats on the seabed.

The length of the horizontal portion 18 is calculated so that at least a large portion of the horizontal pulling force acting on the vessel 140 is absorbed by the frictional force between the sea bed and the horizontal portion 18. At this point, the vessel maintains its stopping position by extending the heavy superstructure 30 between the vessel and the seabed attachment position. In rough weather, the thrust device 32 is used in conjunction with a heavy lift. The J-type riser shown in Figure 3 is maintained in the state shown for a required period of time, during which time hydrocarbons are transported through the riser
The vessel supports some of the weight of the riser and contents, maintaining horizontal tension.

Another technique for assembling the present riser is to attach the lower end of the riser to the seabed or manifold by a cable to form a J-shape of the riser. The riser is then pulled horizontally and installed as described above. The lower end of the riser is pulled to secure it to the manifold, and then a further tube is laid on the seabed to a length where the required horizontal pulling force is absorbed by the frictional force with the seabed.

The above-described technique is illustrated in FIGS. 4-6 in which a surface vessel 14 lowers a cable 84 to the seabed 20 and attaches the lower end of the cable to a manifold on the seabed by any necessary means. For example, to attach the cable to the seabed 20, a holding pulley 36 or the like is used, which is attached to a pile that is driven into the seabed. One end of the cable is connected to a buoy 38 floating on the water surface, and the other end of the cable is connected to a buoy 38 floating on the water surface.
Install it on 4.

In another embodiment, the cables are routed through the junction box 28 of the manifold 12. The coupling box 28 does not need to be rotatable as in FIGS. 1-3. Therefore, if the techniques shown in FIGS. 4-6 are used, structural problems such as bearings in the coupling box will not occur.

As the vessel 14 moves in the direction of arrow 40, the tube is continuously pulled out to follow the cable. This requires increased cable length. If the vessel 14 moves further, the horizontal portion 42 will be on the seabed. At this point, the cable is separated from the buoy 38 and connected to another vessel 44.

Vessel 44 moves in the opposite direction as shown by arrow 46 to pull and couple the riser to coupling box 28 . The cable is then separated from the vessel 14 and wound onto the vessel 44. After this, the riser is continued to be laid down by the vessel 14, and the required length of riser contacts the seabed to create the required frictional force and absorb the pulling force of the vessel 14.

Comparing the operating characteristics of the J-type riser according to the present invention to a conventional vertical riser, the riser 10 provides many advantages not available with vertical risers.

For example, a vertical riser requires 600 kips of tension to prevent the riser from buckling in inclement weather. If the riser 10 uses a heavy overhead line 30 or a thrust device, the horizontal tensile force will be 1=140&ff1p in rough weather.
It's nothing more than that. To compensate for heave motion, ships using vertical risers require a tensioning system with active heave compensation. On the other hand, if the riser 10 is used, such a tensioning device is not required.

Using vertical risers of known design, relatively large tension forces are continuously applied to the riser itself.

Because of this, it is often necessary to inspect the riser and replace sections of the riser that are close to their fatigue limits.

In contrast, the riser 10 is not subjected to high continuous tension. In riser 10, the stress point is sag 16. One or more segments of the riser may be replaced or removed on the vessel 14 over time.

With the use of known vertical risers, the problem of wear of the articulation or ball joints of subsea manifolds often arises. If the riser 10 is used, no problem will arise. This is because the horizontal portion of the riser 10 is in frictional contact with the seabed and does not move. That is, there is no relative movement between the horizontal portion 18 of the riser 10 and the manifold 12, and there is no wear problem that occurs with known vertical riser ball joints.

With known vertical risers, it is necessary to separate the lower end of the riser from the manifold in case of inclement weather, etc. This creates a dangerous situation in deep water as the riser is suspended below the vessel on the water. Separation can cause the riser to bounce back and cause damage to the vessel, with problems with suspended pipes hanging off the vessel.

No suspension problems arise with the J-type riser 10 of the present invention. The riser is installed on the seabed and does not need to be separated from the manifold in the event of rough weather or ice.

The use of known vertical risers limits the capacity of vessels to which the risers are attached, and a semi-submersible type is usually used to reduce the movement of the vessel in each direction.

This results in a reduction in load capacity, and the upper limit for a typical semi-submersible type is 6,000 to 7,000 tons.

A ship 14 using the J-type riser 10 of the present invention can have a maximum capacity as a normal ship-type hull. Capacity is 100,00
0 tons or more.

Using normal vertical risers, the vessel's possible lookout circle is small. The longer the length of the riser and the greater the depth to which the riser is extended, the greater the restrictions on the vessel's range of motion in order to avoid significantly higher lateral loads on the riser. By using the riser 10 of the present invention, the riser l
The above problem does not occur because O can withstand relatively large lateral movements associated with lateral loads and also has dynamic stability against lateral tension.

With known vertical risers, there are precise control requirements regarding the position of the storage tanker relative to the production vessel to which the vertical riser is coupled. When the storage tanker "b1" is modeled on a production vessel, precise requirements are placed on the tanker's control system to avoid lateral loads between the production vessel and the riser.If the riser IO of the present invention is used, the production vessel By relating the lateral forces acting on the riser and the horizontal movement of the production vessel, the control of the tanker is simplified.The riser 10 therefore minimizes both equipment and labor costs and controls the tanker. control over production vessels can be ensured.

Production is not possible during template well inspection using known vertical risers. With the riser 10 of the present invention, production can continue under conditions where another vessel performs the inspection and does not interfere with transporting the hydrocarbon fluid to the production vessel.

A production multi-riser apparatus 50 is shown in FIGS. 7-10 and has a plurality of risers 52 formed similarly to riser 10. Each riser 52 may be coupled to other risers 52 in groups, such as supporting members 52 at multiple locations along the length of the riser.
4 will be provided. For example, the set of risers 52 has the shape shown in FIG. 8.9.

In the illustrated example, a central riser 52 is surrounded by a group of risers 52 . In the illustrated example, it is formed by nine risers 52.

The lower end of the riser 52 is inserted into a coupling device 56 shown in FIG. 7 of the subsea manifold. To this end, coupling device 56 is pivotally mounted on a shaft 60 projecting laterally from manifold 58 . A hole 64 is provided in the distribution member 62 of the coupling device 56, into which the lower end of the riser 52 is inserted. A tube 66 connected to each hole 64 communicates with a respective subsea well to receive hydrocarbons from the well. - the coupling device 56 is rotatable about the longitudinal axis of the shaft 60; in the normal position, the member 62 is at the upper end and the open end of the hole 64 corresponds vertically to the respective riser 52; When the riser is lowered from a vessel on the water, the riser will open each hole 6.
4 and communicates with the respective pipes 66. Tubes 66 connect to respective offshore oil fields. If the vessel to which the riser 52 is coupled moves in a direction relative to the manifold 58, the coupling device 56 will rotate relative to the manifold 58. Figures 1-3 show a vessel on the water moving from directly above the manifold to sideways and upwards of the manifold.

In use of device 50, coupling device 56 is initially in the position shown in FIG. As the riser 52 is formed from the vessel, it is lowered and the lower end of the riser enters a respective hole 64 and connects to a respective tube 64. The vessel then moves laterally relative to manifold 58 and the riser tilts as shown in FIG. Finally, the riser is in the position shown in FIG. 10, with a portion 52α being horizontal and the other portion 52b being slanted and extending upwards to reach the vessel. At least a portion of the horizontal portion 52α is in frictional contact with the seabed as shown in FIG.
The tendency to move the horizontal portion 52α is resisted by the frictional force between the horizontal portion 52α and the seabed.

The length of the horizontal portion in contact with the seabed is selected such that the frictional forces absorb at least a large portion of the horizontal tensile forces. A tensile force is applied to the riser from the ship.

The ship is maintained in a stationary position by the excitation thrust system, the heavy overhead line, or both. The vessel exerts a horizontal pull on the riser 52 during the standstill, with the bow pointing upwind, and hydrocarbon fluid is conveyed from the manifold through each riser to the production vessel.

Effects of the Invention The riser installation according to the present invention provides the above-mentioned advantages.

[Brief explanation of drawings]

Figure 1 shows one production riser extended downward from a ship on the water and connected to a subsea manifold, showing the first stage of forming the J-type production riser of the present invention, and Figure 2 shows the length of the riser. Side view showing the second stage of increasing inclination, No. 8
Figure 4 is a side view showing the operating position of the J-type production riser; Figure 4 is a side view showing the first stage of another technique for joining the riser to the subsea manifold; Figure 5 is the second stage of Figure 4. 6 is a side view of the J-type riser connected to the manifold; FIG. 7 is a perspective view of the multi-riser device inserted into the submarine manifold; FIG. 8 is a perspective view of the upper end of the riser of the multi-riser device; FIG. 9 is a plan view of the upper end of the riser in FIG. 7.8, and FIG. 1θ is a partial side view of the riser of the multi-riser device after it is formed into a J shape. 8.50 J type production riser device 10.52
Riser 12.58 Subsea manifold 14.44
Surface vessel 16 Slack part 18.42.52α Horizontal part 20 Seabed 22 Upright part 28.56 Coupling device 30 Heavy superstructure 32 Thrust device 34 Cable 38 Buoy 60 shaft 62 Distribution member 64 holes (5 people outside)

Claims (1)

[Claims] 1. A device for conveying hydrocarbon fluid from a subsea well head or manifold to a production vessel, which includes a riser having a horizontal section, an upright section, and a slack section, and the riser is connected to the subsea well in the horizontal section. It has a device for attaching to the manifold, the upper end of the upright has a device for coupling the upright to a watercraft, the slack part forms a smooth transition between the horizontal part and the upright part, and the horizontal part A hydrocarbon fluid conveying device characterized by frictional contact with the seabed. 2. The apparatus of claim 1, wherein said riser comprises a plurality of interconnected tube segments and said slack portion is curved. 3. A combination device of a submarine manifold having a connecting device, a ship on the sea, and a J-type riser device including a riser extending between the manifold and the ship, the riser having a connecting device connected to the manifold. A combination device of a manifold, a ship, and a riser, characterized by having a horizontal part placed in frictional engagement with the seabed adjacent to the manifold. 4. The device according to claim 3, wherein the riser has a curved slack portion connecting the horizontal portion and the upright portion. 5. The device according to claim 3, wherein the riser device includes a plurality of risers and a device for combining the risers into a bundle. 6. The apparatus of claim 5, wherein the subsea manifold includes a connecting device rotatably attached to the manifold and having a plurality of holes for receiving the lower end of each riser. 7. The apparatus according to claim 3, wherein the marine vessel is equipped with a device that supports the upper end of the upright portion of the riser and allows the vessel to rotate relative to the riser. 8. A method for coupling a submarine fluid manifold having a coupling device to a marine vessel, the method comprising: forming a riser device extending downward from the marine vessel; coupling the lower end of the riser device to the coupling device of the submarine manifold; increasing the length of the riser device while coupled to the coupling device and moving the vessel laterally, characterized in that a portion of the riser device is laid down on the seabed while the vessel moves into position relative to the manifold; How to connect a subsea manifold to a ship. 9. The method according to claim 8, characterized in that a bend is formed in the riser device when a portion of the riser device is placed on the seabed. 10. The method according to claim 8, wherein the upper end of the riser device is supported on a ship so that the ship can rotate relative to the riser device.