KR20100127460A - Floating marine structure having a riser assembly and method for attaching the riser assembly - Google Patents

Abstract

PURPOSE: A floating marine structure and a method for setting a riser assembly are provided to improve the heat exchange efficiency of a heat exchanger since deep water is absorbed and used as cooling water. CONSTITUTION: A floating marine structure(1) comprises a riser assembly(10) and a heat exchanger. The riser assembly absorbs deep water wherein multiple risers(11) are arranged in parallel. The heat exchanger enables heat exchange using cooling water. The deep water is used as cooling water in the heat exchanger. The risers are supported by a reinforcing member(12) at fixed intervals and are maintained in parallel. The riser assembly comprises a first connection loop(13) and a second connection loop(14).

Description

FLOATING MARINE STRUCTURE HAVING A RISER ASSEMBLY AND METHOD FOR ATTACHING THE RISER ASSEMBLY}

The present invention relates to a floating offshore structure that can be used while mooring offshore, and more particularly to a floating offshore structure with a riser assembly for sucking deep water that can be used as cooling water. The invention also relates to a method of installing the riser assembly in the floating offshore structure.

Natural gas is transported in a gaseous state through onshore or offshore gas piping, or to a distant consumer while stored in an LNG carrier in the form of liquefied liquefied natural gas (LNG). Liquefied natural gas is obtained by cooling natural gas to cryogenic temperature (approximately -163 ℃), and its volume is reduced to about 1/600 than natural gas in gas state, so it is very suitable for long distance transportation through sea.

Recently, the demand for floating offshore structures such as LNG Floating, Production, Storage and Offloading (FPSO) or LNG Floating Storage and Regasification Unit (FSRU) is increasing. These floating offshore structures are also installed with storage tanks installed on LNG carriers or LNG RVs, and are equipped with devices for liquefying or reliquefying natural gas or regasifying LNG as necessary.

LNG FPSOs are floating offshore structures that are used to liquefy the produced natural gas directly from the sea and store it in storage tanks and, if necessary, to transport LNG stored in the storage tanks to LNG carriers. In addition, LNG FSRU is a floating offshore structure that stores LNG unloaded from LNG carriers in a storage tank at sea far from the land, and then vaporizes LNG as needed to supply land demand.

Thus, floating offshore structures, such as LNG FPSO and LNG FSRU, which store liquid cargo, such as LNG, are generally used while being moored by a one-point mooring system such as a turret or yoke mooring.

LNG FPSO (or Oil FPSO) is a gas well (or oil well) after draining gas (or oil) to use seawater as a heat exchange medium for cooling the heat exchanger included in a mounted natural gas liquefaction facility. In order to inject seawater into the oil well, a large amount of seawater is sucked from the sea chest located at the vessel bottom of the structure. At this time, the inhaled seawater is surface water near the surface of the seawater, so that the seawater is heated by sunlight or the like and is generally hotter than deep water.

In addition, in case of LNG FSRU, an evaporative gas reliquefaction facility may be installed. In order to use seawater as a heat exchange medium for cooling the heat exchanger included in the reliquefaction facility, a large amount of water may be provided from the seawater inlet located at the bottom of the structure. Inhale sea water.

However, conventionally, since the surface water near the surface of the seawater is directly sucked from the seawater inlet located at the bottom of the structure, the temperature of the seawater is relatively high, and there is a problem that the temperature of the seawater changes severely with climate change. In addition, the algae or marine debris is often inhaled to block the inlet of the seawater, which caused a lot of effort and time for maintenance.

In order to solve this problem, some shipbuilders in Korea have proposed a method of sucking the seawater by lowering the cylindrical pipe from the bottom to a certain depth, but this method is applied to a conventional ship and open the door formed on the bottom only when the seawater is sucked into the cylindrical pipe. Was put into the seawater to inhale seawater, and when the seawater is not inhaled, the cylindrical pipe was pulled back into the engine room for storage.

Therefore, the method described above could not be applied to floating offshore structures such as LNG FPSO or LNG FSRU, which must be continuously supplied with constant temperature seawater.

In addition, since the length of the cylindrical pipe used in the above-described method was too short, the pipe end did not reach the deep water, so the surface water directly below the sea surface could be sucked, so that the seawater at a sufficiently low temperature and a constant temperature could not be sucked. There was no significant improvement in efficiency.

That is, according to the method described above, the effect of not inhaling seaweeds or marine debris suspended near the surface of the sea was inevitably satisfied.

When surface water is sucked and used as a heat exchange medium in this manner, the surface water is heated by sunlight or the like as described above, so the heat exchange efficiency in the heat exchanger is low, and a large amount of sea water has to be sucked in. Accordingly, there has been a problem that equipment sizing and power consumption are increased.

In addition, in floating offshore structures such as LNG FPSO and LNG FSRU, which require continuous supply of seawater at a constant temperature, facilities such as heat exchangers that require seawater as a heat exchange medium can be operated while solving the above problems. In this case, a structure capable of continuously inhaling seawater without cumbersome additional work such as opening and closing the bottom is required.

Accordingly, the present invention is to solve the problems of the prior art, an object of the present invention is to equip the riser assembly for sucking the deep water so that the deep water can be used as the cooling water at a lower temperature than the surface water and the temperature is kept constant. To provide a floating offshore structure.

It is still another object of the present invention to provide a method of installing a riser assembly manufactured by arranging a plurality of risers in parallel in parallel on land, in a floating offshore structure which is anchored at sea.

According to an aspect of the present invention for achieving the above object, a floating offshore structure used to be anchored in the sea, the riser assembly is formed in which a plurality of risers are arranged in parallel parallel to the intake of deep water; A heat exchanger performing heat exchange using cooling water; And a deep water sucked through the riser assembly is used as cooling water in the heat exchanger.

It is preferable that the plurality of risers arranged in parallel are supported by reinforcing members provided at regular intervals to maintain a parallel state with each other.

The riser assembly preferably includes a first connecting ring formed at one side of the reinforcing member, and a second connecting ring formed at the center of the reinforcing member located at one end of the riser assembly.

The riser assembly preferably includes a buoy member attached to an outer circumferential surface of the riser to provide buoyancy.

The riser assembly is installed to extend in a vertical direction to the bottom of the floating offshore structure, the floating offshore structure, the bottom of the floating offshore structure pending the riser assembly that has been manufactured and transported onshore Preferably, the wire passage further includes a wire passage through which a wire for lifting the riser assembly can be installed.

Preferably, the floating marine structure further includes a plurality of deep water passages formed in the floating marine structure to supply the deep water sucked through the plurality of risers to the heat exchanger.

Preferably, the wire passage is one of a plurality of deep water passages.

The floating offshore structure is preferably any one of LNG FPSO and LNG FSRU.

According to another aspect of the invention, the riser assembly is installed on the bottom of the floating offshore structure for sucking deep water, a plurality of risers arranged in parallel in parallel, and constant so that the risers can be in parallel with each other Provided is a riser assembly comprising reinforcement members spaced apart.

According to yet another aspect of the present invention, a method of installing a riser assembly in a floating offshore structure in which a plurality of risers are arranged in parallel and arranged in parallel to suck deep water, the method comprising the steps of: manufacturing the riser assembly on land; ; Transferring the completed riser assembly to a point at which the floating offshore structure is pending; Attaching the riser assembly that has been transferred to the floating offshore structure; There is provided an installation method comprising a.

In the conveying step, it is preferable that two or more tug boats cooperate with each other to convey the riser assembly suspended in water.

The attaching step may include: sending the wire into the water through a wire passage formed through the upper deck to the bottom of the floating offshore structure; connecting the wire, which is brought into the water, to a connection ring formed at one side of the riser assembly; And pulling up a wire to closely contact one side of the riser assembly to the bottom of the floating offshore structure, and coupling one side of the tight riser assembly to the bottom of the floating offshore structure.

As described above, the present invention provides a floating offshore structure equipped with a riser assembly for sucking deep water. Accordingly, according to the floating offshore structure of the present invention, since the deep water that is lower than the surface water is sucked in and used as the cooling water, the heat exchange efficiency in the heat exchanger is improved, and the heat exchange required by the seawater with a smaller amount than the surface water is used. Efficiency can be achieved.

Furthermore, according to the floating offshore structure of the present invention, since a small amount of seawater is sucked compared to the prior art, equipment capacity and power consumption can be reduced, and inflow of seaweed or marine debris near the sea surface can be prevented at the source. have.

According to the present invention, there is also provided a method of installing a riser assembly produced by arranging a plurality of risers in parallel in parallel on land, in a floating offshore structure which is anchored at sea. As a result, compared to the installation method of connecting each short riser for each one at sea while descending to the water, the work time can be shortened and the process can be simplified.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a perspective view schematically showing a deep water intake riser assembly mounted to a floating offshore structure according to a preferred embodiment of the present invention, and FIGS. 2 to 5 show a deep water intake riser assembly mooring at sea. A drawing for sequentially explaining a method of installing in a floating offshore structure is shown.

As shown in FIG. 1, the deep water suction riser assembly 10 mounted to the floating offshore structure according to the present invention includes a plurality of risers 11 arranged in parallel in parallel.

Although eight risers 11 are arranged in parallel in FIG. 1, the number of risers 11 arranged in parallel or the diameter of each riser may be arbitrarily changed in design. The diameter of the plurality of risers 11 may all be the same, or may differ from each other.

In addition, the plurality of risers 11 arranged in parallel are supported by a plate-shaped reinforcing member 12 provided at regular intervals so as to maintain a parallel state with each other.

In FIG. 1, a plurality of risers 11 are shown to be kept in a parallel state by a rectangular reinforcing member 12. Oval, triangular, polygonal, etc. may have a shape. In addition, the reinforcing member 12 does not necessarily have a plate shape as long as the risers 11 can be kept in a parallel state by maintaining a constant distance between the plurality of risers 11.

Riser assembly 10 is composed of alternating riser and reinforcing member to have a length of about 150 to 200m. One long overall riser is made by connecting the ends of each relatively short unit riser coupled between the reinforcing member 12 and the reinforcing member 12 adjacent to each other.

One side of the reinforcing member 12 is formed with a first connecting ring 13 that can be used when the riser assembly 10 is manufactured or moved.

In addition, in the center of the reinforcing member 12 located at one end of the riser assembly 10, when the riser assembly 10 is later installed in the floating offshore structure 1 or the completed riser assembly 10 is transported at sea. When the second connection ring 14 can be used.

Each riser 11 includes a buoy member 15 attached to an outer circumferential surface to provide buoyancy to the riser 11. The buoy member 15 allows the riser assembly 10 to have a constant buoyancy, thereby facilitating the transfer operation when transported offshore, or with the floating offshore structure being mounted on the floating offshore structure. Inclination by the load of 10 can be alleviated.

Hereinafter, a method of installing the above riser assembly 10 in a floating offshore structure will be described with reference to FIGS. 2 to 5.

After fabrication is completed on land, the riser assembly 10 is transported by the tug boat 20 to the position where the floating offshore structure 1 is moored, as shown in FIG. 2. In the transfer of the riser assembly 10, a wire extending from the tug boat 20 to the first connecting ring 13 or the second connecting ring 14 formed in the reinforcing member 12 of the riser assembly 10 ( The riser assembly 10 can be suspended from the tug boat 20 by connecting 21.

At this time, since the buoy member 15 is included in the riser assembly 10 located in the water as described above, the load in the vertical direction due to the weight of the riser assembly 10 can be reduced.

Depending on the length of the riser assembly 10, it is preferable that two or more tug boats 20 for conveying the riser assembly 10 cooperate with each other to convey the riser assembly 10.

As shown in FIG. 3, when the riser assembly 10 arrives at a position where the floating offshore structure 1 is moored, the wire 21 connected to the second connecting ring 14 on one side of the riser assembly 10. All but the other wires are disconnected so that the riser assembly 10 can stand vertically underwater.

On the other hand, as shown in Figure 4, in the position where the riser assembly 10 of the floating offshore structure 1 is to be installed, the deep water passage of the same number and diameter to communicate with the riser 11 of the riser assembly 10 (5) is formed. The deep water passage 5 is a passage for transferring the deep water sucked through the riser assembly 10 to the upper equipment (eg, a heat exchanger, etc.) of the floating offshore structure 1, and the upper portion of the floating offshore structure 1. It is preferably formed to extend vertically from the deck 2 to the bottom 4.

In the center of the deep water passages 5 is formed a wire passage 6 through which a wire 7 for raising the riser assembly 10 passes. The wire passage 6 may be provided separately or any one of the plurality of deep water passages 5 may be used as the wire passage.

In the floating offshore structure 1, a weight and a small buoy 8, such as a sandbag, is provided at the end of the wire 7 to connect the wire 7 to the second linkage 14 of the riser assembly 10. Is suspended through the wire passageway 6 of the floating offshore structure.

The wire 7 can be lowered or raised into the sea water by winding or unwinding by the winch device of the crane 3 installed on the floating offshore structure 1. The weight connected to the wire 7 is connected via a hydraulic pressure releaser.

In this way, since a heavy body such as a sandbag is suspended at the end of the wire 7, when the winch device of the crane 3 is released, the wire 7 can be sent down to the sea through the wire passage 6.

At this time, the hydraulic pressure release device interposed between the end of the wire and the weight body reaches a predetermined depth and when the water pressure rises above the set value, the connected weight body is separated. When the weight is separated, as shown in FIG. 4, the end portion of the wire 7 floats to sea level by buoyancy of the small buoy 8 attached to the wire 7.

The wire 7 floated to sea level is hooked up by the worker onto the deck of the tug boat 20 using a hook or the like and connected to another wire connected to the second link 14 of the riser assembly 10, or the diver It can be directly connected to the second link 14 of the riser assembly 10 in water.

Thus, by connecting the riser assembly 10 to the wire 7 wound around the winch device of the crane 3 installed on the deck of the floating offshore structure 1, the wire 7 is wound using this winch device. It is possible to lift the riser assembly 10 suspended in the water standing upright.

At this time, the wire 21 between the riser assembly 10 and the tug boat 20, as shown in FIG. 5, before the riser assembly 10 is coupled to the bottom 4 of the floating offshore structure 1. It is preferred to be separated by divers.

The winch device of the crane 3 lifts the riser assembly 10 until the riser assembly 10 is completely adjacent to the bottom 4 of the floating offshore structure 1. When the riser assembly 10 is pulled up to a position adjacent the bottom 4 of the floating offshore structure 1, the diver engages the riser assembly 10 to the bottom 4 of the floating offshore structure 1.

When the installation of the riser assembly 10 to the bottom 4 of the floating offshore structure 1 is completed, disconnect the wire 7 connected to the second linkage 14 and wind the wire 7. All work is done by raising.

As described above, according to the present invention, a riser assembly manufactured by arranging a plurality of risers in parallel to each other on land is transported and installed to a floating offshore structure that is anchored at sea, whereby each connection for short length is used. Compared to the installation method in which the risers are connected one by one from the sea and lowered into the water, the work time can be shortened and the process can be simplified.

In the present invention, the floating offshore structure 1 is constructed from LNG FPSO or onshore, which is used to directly liquefy the produced natural gas in the sea, store it in a storage tank, and transfer LNG stored in the storage tank to an LNG carrier, if necessary. It may be an LNG FSRU that stores LNG, which is unloaded from an LNG carrier in a distant sea, in a storage tank, and then vaporizes LNG as needed to supply land demand.

In addition, the floating offshore structure 1 according to the present invention may be any one of all kinds of offshore structures used as a heat exchange medium for cooling by sucking seawater while being fixed or mooring at a fixed position.

Although not shown in the drawings, the floating offshore structure 1 is provided with a storage tank (not shown) for storing cargo such as LNG therein, and the upper deck 2 is required according to the use of the floating offshore structure. Various facilities may be provided, and arrangement or kind of these facilities does not limit the present invention.

In addition, the floating offshore structure 1 of the present invention can be used while mooring on the sea at a fixed position by mooring lines. For mooring the floating offshore structure 1, a turret or spread type mooring means may be provided, and the type, installation position, etc. of the mooring means do not limit the present invention.

According to the present invention, there is no need to install the opening and closing door in particular on the bottom, and since the floating offshore structure 1 of the present invention is used while mooring at a certain point on the sea, it is not necessary to perform cumbersome preliminary work such as opening the opening and closing door. It is possible to inhale deep water and supply it to a heat exchanger or the like by simply driving a pump when it is necessary to inhale sea water without performing it.

As described above, according to the floating marine structure 1 of the present invention, deep water may be sucked through the riser assembly 10 by suction force generated from the pump. Inhaled deep water is used as a heat exchange medium in a heat exchanger installed in the floating offshore structure 1.

For example, using a nitrogen heat exchanger that exchanges nitrogen and seawater with each other, lowering the nitrogen temperature of 60 ° C. to 40 ° C. under certain conditions (nitrogen pressure: 15.45 bar, nitrogen flow rate: 7.008e + 005 ton / d) Comparing the hourly circulation of seawater required for When performing heat exchange using surface water of approximately 32 ° C. as conventionally, about 24,058 tons of sea water per hour is required. However, when performing heat exchange using deep water of approximately 10 ° C. according to the present invention, approximately 5,154 ton sea water per hour is used. need.

As described above, according to the present invention, the circulation amount of the seawater can be reduced by about 80% compared to the conventional conditions under the above-described conditions, and thus the equipment capacity and power consumption can be reduced because the seawater is inhaled in comparison with the conventional water. In addition, deep water has almost no temperature change due to climate change, so that the inlet temperature of the heat exchanger can be kept constant.

On the other hand, compared to surface water near sea level, the inflow of algae or marine debris can be prevented at the source, which is advantageous for maintenance.

While the invention has been described above with reference to specific embodiments, various modifications, changes or modifications may be made in the art within the spirit and scope of the appended claims, and thus, the foregoing description and drawings It should be construed as illustrating the present invention, not limiting the technical spirit of the present invention.

1 is a perspective view schematically showing a riser assembly for deep water intake mounted to a floating offshore structure according to a preferred embodiment of the present invention; and

2 to 5 are views for sequentially explaining a method for installing a deep water intake riser assembly to a floating offshore structure that is anchored at sea.

<Description of Symbols for Main Parts of Drawings>

1: floating offshore structure 2: upper deck

3: crane 4: bottom

5: deep water passage 6: wire passage

7: wire 8: small buoy

10 riser assembly 11 riser

12: reinforcing member 13: the first connecting ring

14: second link 15: buoy member

20: tug boat 21: wire

Claims (12)

Floating offshore structures used for mooring at sea, A riser assembly in which a plurality of risers are arranged in parallel and arranged in parallel to suck deep water; A heat exchanger performing heat exchange using cooling water; Including; And use deep water sucked through said riser assembly as cooling water in said heat exchanger. The method according to claim 1, The plurality of risers arranged in parallel is a floating offshore structure, characterized in that supported by reinforcing members are installed at regular intervals to maintain a parallel state with each other. The method according to claim 2, The riser assembly includes a first connecting ring formed at one side of the reinforcing member, and a second connecting ring formed at the center of the reinforcing member located at one end of the riser assembly. . The method according to claim 1, The riser assembly includes a buoy member attached to an outer circumferential surface of the riser to provide buoyancy. The method according to claim 1, The riser assembly is installed to extend perpendicular to the bottom of the floating offshore structure, And further comprising a wire passage through which a wire for lifting the riser assembly passes, so that the riser assembly manufactured after being transported on land can be installed at the bottom of the floating marine structure mooring at sea. Eclipse Nautical Structures. The method according to claim 1, And a plurality of deep water passages formed in the floating offshore structure to supply the deep water sucked through the plurality of risers to the heat exchanger. The method according to claim 5, And a plurality of deep water passages formed in the floating offshore structure to supply the deep water sucked through the plurality of risers to the heat exchanger, wherein the wire passage is one of the plurality of deep water passages. Eclipse Nautical Structures. The method according to claim 1, The floating offshore structure is a floating offshore structure, characterized in that any one of LNG FPSO and LNG FSRU. A riser assembly installed on the bottom of a floating offshore structure for sucking deep water, And a plurality of risers arranged in parallel and parallel to each other, and reinforcement members installed at regular intervals to maintain the risers in parallel with each other. A method of installing a riser assembly in a floating offshore structure, in which a plurality of risers are arranged in parallel and arranged in parallel to suck deep water, Fabricating the riser assembly on land; Transferring the completed riser assembly to a point at which the floating offshore structure is pending; Attaching the riser assembly that has been transferred to the floating offshore structure; Installation method characterized in that it comprises a. The method according to claim 10, In the conveying step, two or more tug boats cooperate with each other to transport the riser assembly suspended in the water. The method according to claim 10, The attaching step may include: sending the wire into the water through a wire passage formed through the upper deck to the bottom of the floating offshore structure; Pulling up a wire to bring one side of the riser assembly into close contact with the bottom of the floating offshore structure, and coupling one side of the tight riser assembly with the bottom of the floating offshore structure; Way.

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