CN112119006B - Offshore facility and method of constructing the same - Google Patents

Abstract

The invention provides an offshore operation facility which can perform stable operation even in deep water and improve operation efficiency. An offshore operation facility comprising: three legs 10, a hull 20 supported to be movable up and down with respect to the legs 10, and a crane 30 mounted on the hull 20. The hull 20 is constructed as a floating structure, and includes a main hull portion 21 and a first suspended portion 22 formed to be suspended from the main hull portion 21. The crane 30 is mounted on the first overhanging portion 22. The offshore operation facility is constructed by adding the first suspended section 22 and the crane 30 to the jack-up rig from which the drilling equipment and the cantilever have been removed. The first overhang portion 22 is added to the main hull portion 21 using a cantilevered support structure.

Description

Offshore facility and method of constructing the same

Technical Field

The present invention relates to an offshore working facility which can be used for constructing an offshore facility such as an offshore wind power plant, and a method of constructing the same.

Background

Offshore wind power generation has attracted attention from the viewpoint of efficient use of natural energy.

In order to build offshore wind power plants, offshore working facilities such as self-elevating platforms (SEPs) are often used. A self-elevating platform generally has a plurality of legs and a hull supported by the legs so as to be vertically movable (patent documents 1 and 2). A crane for working is mounted on the hull and the offshore wind power plant is assembled using the crane. The hull can also be used as cargo handling space for parts of an offshore wind power plant.

List of citations

Patent document

Patent document 1: japanese patent laid-open No. 2015-37925

Patent document 2: japanese patent laid-open No. 2016-215937.

Disclosure of Invention

Technical problem

In recent years, high-output offshore wind power plants of, for example, 6MW or more have been developed as offshore wind power plants. Along with this, the size of offshore wind power generation facilities itself has become larger, and floating facilities are also being developed and put into practical use in addition to the landing type. As described above, the hull of the offshore working facility is equipped with a crane for work, and is also used as a cargo handling space for each section. Therefore, in order to construct a large offshore wind power plant, an offshore working facility having a larger hull is required. Further, in order to construct a floating wind power generation facility, it is necessary to have an offshore facility that can stably operate even in an ocean having a water depth of more than 90 m.

Existing self-elevating platforms cannot be used for offshore construction in waters with depths exceeding 90 m. Therefore, although a large floating crane is generally used, the floating crane is susceptible to waves, and the operation standby time is likely to occur, which reduces the operation efficiency. On the other hand, offshore operating facilities with large hulls cause a reduction in the towing speed from a harbor to the sea area where the offshore facility is constructed. The reduction in towing speed results in a longer construction cycle of the offshore plant.

Accordingly, it is an object of the present invention to provide an offshore facility and a method of constructing the same, which can perform stable work and improve work efficiency even in a deep sea area.

Solution to the problem

The offshore operation facility according to the present invention is an offshore operation facility comprising:

three or more legs;

a hull constructed as a floating structure and supported to be movable up and down with respect to the legs; and

a crane mounted on the hull;

wherein the hull includes a main hull portion in which the legs are arranged and an overhanging portion formed by overhanging from the main hull portion;

the offshore operation facility is constructed by adding a suspended section and a crane to an existing jack-up rig having a main hull section and legs;

adding a suspended portion to the main hull portion by using a support structure of a cantilever of an onboard drilling equipment installed on an existing jack-up rig; and

the crane is mounted on the overhanging portion.

A method of constructing an offshore facility, comprising:

preparing a jack-up rig, the jack-up rig comprising: three or more legs, a main hull section in which the legs are arranged and supported to be movable up and down relative to the legs, a cantilever supported to the main hull section by a support structure, and drilling equipment arranged on the cantilever;

removing the cantilever and drilling equipment from the jack-up rig;

adding an overhanging portion formed by overhanging from the main hull portion to the main hull portion using a support structure; and

the crane is mounted on the overhanging portion.

Advantageous effects of the invention

According to the present invention, it is possible to provide an offshore facility that can operate stably and efficiently even in a deep sea area. Further, according to the method of constructing an offshore facility of the present invention, the offshore facility can be constructed in a short time and at low cost.

Drawings

Fig. 1 is a schematic side view of an offshore operation facility according to an embodiment of the invention.

Fig. 2 is a schematic plan view of the offshore working facility shown in fig. 1.

Fig. 2A is a view showing an internal structure of a hull in the offshore operation facility shown in fig. 2.

Fig. 3 is a diagram showing the working range of the crane when the crane is arranged in the area enclosed by the legs.

Fig. 4 is a schematic side view of an offshore operation facility in which a hull has a multi-layered structure according to another embodiment of the present invention.

Fig. 5 is a view showing an example of a use form of the offshore operation facility shown in fig. 1.

Detailed Description

Referring to fig. 1 to 3, an offshore operation facility 1 according to one embodiment of the present invention is shown having legs 10, a hull 20 supported by the legs 10, and a crane 30 mounted on the hull 20. The offshore working facility 1 may be used for the construction of offshore equipment, such as an offshore wind power plant. The hull 20 is constructed as a floating structure, and when the offshore facility 1 is used to construct an offshore facility, the offshore facility 1 is towed by a towing vessel such as a tug boat to the sea area where the offshore facility is constructed.

During offshore operations performed by the offshore operation facility 1, the legs 10 support the hull 20 above sea level. Therefore, the leg 10 has a length capable of supporting the hull 20 above the sea surface in a state where the lower end portion of the leg 10 is disposed on the sea bottom. In order to stably support the hull 20, the offshore operation facility 1 has three or more legs 10. The structure of the leg 10 may be arbitrary as long as the leg 10 can perform the above-described function, and a known structure may be employed, for example, a structure of a leg for a self-elevating platform, which is an offshore working facility 1 or a self-elevating drilling platform. Although the length of the leg 10 is not particularly limited, it is preferable that the length of the leg 10 is long enough to allow the leg 10 to reach the bottom even when the construction is performed in a sea area exceeding 90m and stably perform the construction without being affected by waves. The sectional shape of the leg 10 is not particularly limited, and may be any shape such as a circle or a polygon.

The hull 20 is supported by a lifting mechanism (not shown) so as to be vertically movable relative to the support legs 10. As the elevating mechanism, any mechanism such as a rack and pinion mechanism may be used. When towing the offshore unit 1, the lift mechanism is operated to raise the legs 10 relative to the hull 20 so that the legs 10 do not reach the sea floor. Since the hull 20 is constructed as a floating structure, the offshore operation facility 1 floats above the sea surface by raising the legs 10, and the offshore operation facility 1 can be towed in this state.

The hull 20 has a deck 20a, a bottom 20b and an outer shell 20c, whereby the hull 20 is constructed as a floating structure in which a closed inner space is formed. As shown in fig. 2A, the inner space of the hull 20 is divided into a plurality of sections by at least one partition 20d as a reinforcing member, thereby ensuring sufficient mechanical strength so that the upper surface of the hull 20 can be used as a work space and a part storage space of the offshore equipment to be constructed.

As shown in fig. 2, the hull 20 has a main hull portion 21, a first overhang portion 22, and a second overhang portion 23. In the illustrated embodiment, the hull 20 has one first overhang portion 22 and two second overhang portions 23. However, the number of the first overhanging portions 22 and the number of the second overhanging portions 23 may be arbitrary. Of the main hull portion 21, the first suspended extension portion 22, and the second suspended extension portion 23, the main hull portion 21 is a portion having the largest area as viewed from above, and the leg 10 is arranged at an outer edge portion of the main hull portion 21. Therefore, a large part of the upper surface of the main hull part 21 can be used as a working space and a part storage space of the offshore facility to be constructed. When the offshore unit is an offshore wind power plant, the hull 20 preferably has a space in which components for an offshore wind power plant can be placed, for example. The planar shape of the main hull portion 21 may be arbitrary.

The first suspended portion 22 has a shape suspended from the main hull portion 21 in a convex shape with respect to a side connecting two adjacent legs 10 when viewed from above. Further, it is preferable that the upper surface of the first overhang portion 22 is in the same plane as the upper surface of the main hull portion 21. Therefore, the work space and the component storage space on the upper surface of the hull 20 can be sufficiently expanded.

The crane 30 is mounted on the first overhanging portion 22. The crane 30 may be stationary or crawler mounted. However, since work is usually performed on the first overhang portion 22 without moving, the stationary crane 30 is basically sufficient. Furthermore, the stationary crane 30 is advantageous in that it occupies a smaller area on the hull 20 than a crawler crane, and can ensure a larger space on the hull 20.

By mounting the crane 30 on the first overhanging portion 22, the crane 30 is positioned outside the area surrounded by all the legs 10 (three legs 10 in this embodiment) supporting the hull 20.

Therefore, as shown in fig. 2, by mounting the crane 30 on the first overhanging portion 22 and positioning it outside the region surrounded by the outriggers 10, the working range θ 1 of the crane 30 (the range of rotation about the rotation center O of the crane 30) can be extended to a range exceeding 180 °. On the other hand, as shown in fig. 3, when the crane 30 is mounted on the main hull part 21, the crane 30 will be positioned in the area between two legs 10, since the legs 10 are usually arranged at corner portions of the main hull part 21. Therefore, the working range θ 2 of the crane 30 is less than 180 °. By extending the operating range of the crane 30, the degree of freedom of operation of the crane 30 can be improved.

As long as the hull 20 is configured as a floating structure as a whole, the first suspended portion 22 itself may or may not be configured as a floating structure. When first overhang portion 22 is configured as a floating structure, first overhang portion 22 may have a deck, a bottom, and an outside shell that forms an inner space in first overhang portion 22, like main hull 21. The first overhanging portion 22 may also have a partition, if necessary.

The second suspended portion 23 is formed at a position different from the first suspended portion 22 so as to be suspended from the main hull 21 in a shape not exceeding the width of the main hull portion 21. The second overhanging portion 22 may also have a convex shape overhanging from the main hull portion 21 with respect to the side connecting two adjacent legs 10, similar to the first overhanging portion 22, when viewed from above. The second overhanging portion 23 is constructed as a floating structure. Thus, like the main hull section 21, the second overhanging section 23 may have a deck, a bottom and an outer shell, which form an inner space in the second overhanging section 23. The second overhanging portion 23 may also have a partition if necessary.

By adding the second overhang portion 23 to the main hull portion 21, the space above the hull 20 is expanded and at the same time the stability of the offshore construction facility 1 during towing is improved. Further, since the second overhang portion 23 has a shape not exceeding the width of the main hull portion 21, an increase in resistance during towing can be suppressed. Therefore, the offshore operation facility 1 can be towed efficiently by suppressing a decrease in towing speed. In order to further suppress the drag during towing, when the offshore operation facility 1 is disposed to be towed in the white arrow direction shown in fig. 2A, it is preferable that the second overhanging portion 23 is formed in the following shape: in this shape, the main hull section 21 and the second overhang section 23 are combined, and the shape is boat-shaped, with the width widening in the direction from the bow side to the stern side.

Although the case where the hull 20 has a single layer has been described above, the hull 20 may have a multi-layered structure. Fig. 4 shows a schematic side view of an offshore operation facility with a multi-layer hull. In the following description of the offshore operation facility shown in fig. 4, the same components as those of the offshore operation facility described above are denoted by the same reference numerals as those in the drawings of fig. 1 and the like, and the description thereof is omitted.

In the offshore operation facility 1 shown in fig. 4, the hull 20 includes: a second deck 120a disposed above the deck 20a and having a space with respect to the deck 20 a; a second outer case 120c and a second partition (not shown) supporting the second deck 120a and having a space with respect to the deck 20 a. Thus, the hull 20 has a double-layered structure. By means of the deck 20a, the second deck 120a, the second outer casing 120c and the second bulkheads, the structure arranged above the deck 20a is constructed as a floating structure in which an inner space divided into a plurality of sections is formed. Therefore, even if structures such as the second deck 120a, the second outside housing 120c, and the second bulkhead are added to the deck 20a, the hull 20 can ensure buoyancy necessary to allow the offshore operation facility to be towed.

The second deck 120a and the second outside housing 120c may be disposed at positions corresponding to at least the main hull portion 21 among the main hull portion 21 (see fig. 2), the first suspended portion 22 (see fig. 2), and the second suspended portion (see fig. 2). That is, it is not necessary that all areas of the hull 20 have a double-layered structure. However, in order to effectively utilize the upper surface of the hull 20, the second deck 120a and the second outboard casing 120c are preferably arranged so that all regions of the main hull portion 21, the first overhang portion 22, and the second overhang portion 23 have a double-layer structure.

Since the hull 20 has a double-layered structure, the mechanical strength of the hull 20 can be improved, and a heavy object can be mounted on the hull 20. Accordingly, when the component is transported from a construction site for offshore facility construction to a sea area of the construction site, more or heavier objects can be transported using the offshore operation facility. Although the case where the hull 20 has a double-layered structure has been described herein, the hull 20 may be constructed to have three or more layers.

Next, a method of constructing an offshore facility using the offshore operation facility 1 of the present embodiment will be described by taking as an example that the offshore facility is an offshore wind power generation facility.

First, various components such as wind turbine components of the offshore wind power plant and the offshore working facility 1 are moved from a construction site for construction to a sea area as a construction site. The offshore operation facility 1 is moved by towing the offshore operation facility 1 with a tug boat in a state where the legs 10 are raised with respect to the hull 20 and the hull 20 floats on the sea surface. At this time, the components of the offshore wind power generation facility are mounted on the hull 20. If the hull 20 has space and mechanical strength for mounting components of an offshore wind power plant, a ship for transporting the components is not required to move the components of the offshore wind power plant.

When the movement of the offshore wind power plant and the components of the offshore operation facility 1 is completed, the legs 10 of the offshore operation facility 1 are lowered with respect to the hull 20, and the legs 10 are disposed on the seabed. At this point, the legs 10 are lowered until the hull 20 is above the sea surface, as shown in figure 1. Thus, the offshore wind power plant can be constructed without being affected by sea conditions.

After the legs 10 are arranged on the seabed, the components on the hull 20 are suspended by the crane 30, and the offshore wind power plant is assembled by the crane 30. Since the hoist 30 is mounted on the first overhang portion 22, and the working range of the hoist 30 is further expanded, the assembly can be smoothly performed.

After the offshore wind power plant is assembled, the legs 10 are raised again with respect to the hull 20 and the offshore operation facility 1 is returned to the construction site by means of a tugboat.

It is also possible to connect a plurality of offshore working facilities 1 and use them as a construction site for constructing an offshore facility to load and assemble components of the offshore facility. Fig. 5 shows a plan view of a construction site using a plurality of offshore working facilities 1.

The construction site shown in fig. 5 is constructed by connecting three offshore facilities 1, so that parts of the offshore facility can be loaded and assembled on the hull 20. Since the crane 30 is installed on the first overhang portion 22, a wider hull space can be secured. Further, by arranging the offshore operation facility 1 such that the cranes 30 are positioned alternately, even if a plurality of cranes 30 are operated simultaneously, it is possible to prevent interference with each other.

A construction site may be installed for each project. By using the offshore operation facility 1 as a construction site, when work at the site is completed, the offshore operation facility 1 can be moved to a construction area for offshore equipment to construct the offshore equipment. The construction site may also be used as permanent equipment. Therefore, by using the offshore facility 1 as a construction site, the offshore facility can be used as a substitute for a port facility of an offshore facility, and the construction site can be installed at low cost and in a short time.

The invention has been described above by way of an exemplary embodiment. The offshore operation facility 1 according to the present invention can be constructed by adding the first suspended section 22 and the crane 30, and further adding the second suspended section 23 as needed to an existing offshore operation facility having the main hull section 21 and the legs 10, such as a self-elevating platform or a self-elevating drilling platform. The "existing offshore facility" refers to an offshore facility that has been assembled and has the intended function of the offshore facility, and the offshore facility 1 according to the present embodiment can be constructed by modifying such an offshore facility.

In general, conventional offshore working facilities such as a jack-up platform and a jack-up rig include self-elevating legs and a platform (corresponding to the main hull part 21 in the above-described offshore working facility 1 of the present embodiment) supported so as to be able to move up and down with respect to the legs.

Therefore, by constructing the offshore operation facility according to the present invention using (modifying) the existing offshore operation facility, the legs 10 and the main hull section 21 can be constructed using the legs and the platform of the existing offshore operation facility, respectively. Consequently, the offshore facility can be obtained more easily and with a shorter construction period, and therefore a significant cost reduction of the offshore facility can be achieved. In particular, by constructing the offshore operation facility 1 using the existing jack-up type drilling platform, the offshore operation facility can be obtained more easily and with a shorter construction period, which can be stably constructed without being affected by waves by disposing the legs on the seabed in a water depth of more than 90m during the offshore construction.

Further, the jack-up type drilling platform has onboard drilling equipment so that drilling work of oil and gas can be performed in a state of being disposed on the sea bottom. The shipborne drilling equipment is arranged on a cantilever arranged on the platform. However, the cantilever is moved on the platform by a drive mechanism and drilling work is performed at a position cantilevered with respect to the platform. In order to support the load of the entire cantilever including the drive mechanism and the onboard drilling equipment, the platform has inside it strength members, such as bulkheads, as a support structure, which have the necessary strength.

The present embodiment focuses on this, utilizing the support structure of the cantilever of an existing jack-up rig in forming the first suspended section 22. That is, the first suspended portion 22 is supported by a support structure of a cantilever and suspended from the main hull portion 21. Here, the "support structure of the cantilever" is a support structure provided on the platform to support the load of the entire cantilever including the above-described drive mechanism and the onboard drilling equipment, and particularly, the support structure of the cantilever is a strength member having a strength required to support the entire cantilever, such as a bulkhead. As described above, by using the support structure originally provided in the existing jack-up rig, the first overhanging portion 22 having mechanical strength sufficient to install the crane 30 that can hoist a heavy structure such as a nacelle of an offshore wind power plant can be easily added according to the originally provided strength member without newly adding the strength member. Thus, a significant reduction in the cost of the offshore operation facility is achieved.

When the first suspended portion 22 is constructed by using the support structure for the cantilever of the jack-up rig as described above, the cantilever of the jack-up rig and the onboard drilling equipment are removed, the first suspended portion 22 is formed on the support structure of the cantilever, and the crane 30 is installed thereon. The offshore unit 1 is therefore no longer used as a drilling platform.

In addition, when the hull 20 has a multi-layered structure to improve the mechanical strength of the hull 20, it is generally considered to replace the originally provided deck with a deck having a higher mechanical strength. However, various structures such as electric wires and water supply/drainage pipes are generally attached to the lower surface of the deck. Therefore, when changing decks, these structures need to be changed together. Therefore, as shown in fig. 4, by keeping the deck 20a as it is and disposing the second deck 120a above the deck 20a, it is possible to utilize the electric wires and the water supply/drainage pipes which are originally provided. Therefore, it is possible to shorten the construction period of the offshore operation facility 1 and suppress an increase in construction cost.

Description of the symbols

1. Offshore working facility

10. Supporting leg

20. Boat hull

20A deck

20b bottom

20c outer casing

20d partition board

21. Main hull part

22. A first overhang part

23. A second overhang portion

30. Crane with a movable crane

120a second plate

120c outer housing.

Claims (7)

1. An offshore operation facility, comprising:

three or more legs;

a hull configured as a floating structure and supported to be movable up and down relative to the legs; and

a crane mounted on the hull;

wherein the hull includes a main hull portion in which the legs are arranged and an overhanging portion formed by overhanging from the main hull portion;

the main hull section and the legs are constructed from a jack-up rig having the main hull section and the legs and having drilling equipment and a cantilever for installing the drilling equipment removed;

adding the overhanging portion to the main hull portion by using a support structure of the cantilever; and

the crane is mounted on the overhanging portion.

2. The offshore operation facility of claim 1, wherein the hull further comprises a second overhanging portion configured as a floating structure.

3. An offshore operation facility, according to claim 2, wherein the second overhang portion is formed to overhang the main hull portion in a shape not exceeding the width of the main hull portion.

4. An offshore operation facility, according to claim 2 or 3, wherein the second overhanging section is formed by overhanging from the main hull section in a shape: the shape combined with the main hull part is formed in a boat shape in which the width widens in a direction from the bow side to the stern side.

5. The offshore facility as claimed in claim 1, the hull having a deck, a bottom, an outer shell and a bulkhead, an interior space being formed in the hull by the deck, the bottom and the outer shell and being divided into a plurality of sections by the bulkhead.

6. The offshore facility as claimed in claim 5, further comprising: a second deck disposed above the deck, and a second outer case and a second barrier supporting the second deck and having a space with respect to the deck.

7. A method of constructing an offshore facility, the method comprising the steps of:

preparing a jack-up rig, the jack-up rig comprising: three or more legs, a main hull part in which the legs are arranged and which is supported so as to be movable up and down relative to the legs, a cantilever which is supported to the main hull part by a support structure, and a drilling apparatus arranged on the cantilever;

removing the cantilever and the drilling equipment from the jack-up rig;

adding an overhang portion formed by overhanging from the main hull portion to the main hull portion using the support structure; and

a crane is mounted on the overhanging portion.

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