KR20140125916A - Flexible Riser System and Method for Adjusting Buoyancy of Flexible Riser Using The Same - Google Patents

Abstract

The present invention relates to a flexible riser system and a flexible riser buoyancy adjusting method using the same. A ballast chamber is formed to be capable of providing liquid into a floating structure or recollecting the liquid and combined to a riser to adjust the level of buoyancy and a buoyancy applied position by adjusting the supply or recollection of liquid. Accordingly, even if the gravity of the riser is changed during oil extracting, the state of the riser underwater can be stably maintained. In addition, each ballast chamber of multiple floating structures which are connected to each other can selectively provide and recollect liquid, thus, the entire buoyancy and the buoyancy applied positions of the multiple floating structures can be adjusted. Therefore, the state of the riser underwater can be more stably maintained.

Description

Technical Field [0001] The present invention relates to a flexible riser system and a flexible riser buoyancy adjusting method using the flexible riser system.

The present invention relates to a flexible riser system and a flexible riser buoyancy control method using the flexible riser system. More particularly, the present invention relates to a method of forming a ballast chamber by forming a ballast chamber in a form capable of supplying or recovering a liquid into the inside of a buoyant body and bonding the ballast chamber to the riser, So that even if the specific gravity of the riser changes during the production of the crude oil, the seabed condition of the riser can be maintained stably and continuously, and a plurality of buoyant bodies can be connected to each other to supply liquid to the ballast chambers of the respective buoyant bodies The size of the buoyant force and the acting position of the buoyant force can be adjusted through the whole of the plurality of buoyant bodies and the flexible riser system and the flexible riser buoyancy adjusting method capable of more stably maintaining the submarine arrangement state of the riser .

Floating crude oil storage facility (hereinafter referred to as "FPSO") or floating liquid storage gas storage facility (hereinafter referred to as "LNG FPSO") is a floating storage facility in the form of a ship or a barge. Of these, FPSO is currently being used to produce crude oil from oilfields, and LNG FPSO has been actively developed in recent years due to depletion of oilfields and increased demand for clean fuels.

FPSO or LNG FPSO is a floating marine refinery capable of refining, storing and transporting crude oil or natural gas while floating in the sea.

Such a floating storage facility is equipped with a riser to move oil, gas, etc. from the oil well at the bottom of the seabed to the storage facility. Typically, a riser is used to transport a crude oil product that is a mixture of oil, gas, and water from an oil well (or gas well) to a process plant on the hull, Means a tube that serves as a passageway for filling.

In this case, since the floating storage facility changes its position due to the influence of waves and algae, the riser is formed in a flexible form so as to cope with such a change in position. In particular, Since the motion is relatively large, the motion of the floating storage device can be absorbed in a wider range by using a separate buoyant body or the like so that the arrangement of the risers forms an "S "

1 is a schematic view schematically showing an installation structure of a conventional flexible riser system according to the prior art.

As shown in FIG. 1, the riser 30 is formed to have flexibility so as to connect the well head 21 of the wellhead with the floating hull 10. A conventional riser system according to the prior art is, for example, And a separate buoyant body (40) is coupled to an intermediate portion of the riser (30). By the buoyancy generated by the buoyant body 40, the riser 30 is arranged in an approximately "S " -jar curve shape, and through this arrangement it is possible to absorb the movement of the hull 10 in a relatively wider range have.

Also, although not shown, a system in which a buoyancy tank or the like is installed on the bottom of the sea bed so that the configuration of the riser 30 is continuously formed in an "S" curve shape is generally applied to the riser system.

When the crude oil is produced at sea, the production operation is interrupted. Depending on the situation, the inside of the riser (30), which is a crude oil passage, may be emptied. When there is no gas or gas inside the riser 30, the weight of the riser 30 decreases and buoyancy increases, so that there is a high possibility that the riser 30 rises in the water surface direction and collides with the floating hull 10. Particularly, when the water depth is low, the possibility of collision between the riser 30 and the hull 10 is further increased because the distance between the bottom of the sea bottom and the hull 10 is considerably lower than the deep water depth.

In order to prevent this, the weight of the riser 30 may be increased or the buoyant body 40 of low buoyancy may be used. However, when the production work of the crude oil is started, The weight of the riser 30 increases, and the possibility that the riser 30 will collide with the undersurface increases.

That is, it is very difficult to maintain the stable arrangement of the riser 30 during the production of crude oil, because the buoyancy acting on the riser 30 changes due to the specific gravity of the fluid flowing in the riser 30, ) Is also very difficult to calculate.

Prior art is Korean Patent Registration No. 10-835713.

SUMMARY OF THE INVENTION The present invention has been made to solve the problems of the prior art, and it is an object of the present invention to provide a ballast chamber in which a liquid can be supplied or recovered in a buoyant body, It is possible to control the buoyancy size of the buoyant body through the supply of the liquid or the regeneration amount of the liquid and thereby to keep the seabed condition of the riser steady even if the specific gravity of the riser changes during the production of crude oil, Thereby providing a flexible riser buoyancy adjustment method.

Another object of the present invention is to connect a plurality of buoyant bodies formed with a ballast chamber to each other and to selectively supply and recover the liquid to and from the ballast chambers of the buoyant bodies, And the position of the buoyancy can also be adjusted, so that a flexible riser system and a flexible riser buoyancy adjusting method capable of more stably maintaining the submarine arrangement state of the riser are provided.

The present invention relates to a flexible riser system for use in marine oilfield development, comprising: a flexible riser connected from a floating floating hull to an oil well top of a seabed bottom; And a buoyant body having a ballast chamber formed therein to allow the inflow and outflow of liquid and to be connected to the riser to provide buoyancy to the riser, Wherein the buoyant force is controlled by adjusting the buoyancy of the flexible riser system.

At this time, the ballast chamber and the floating hull can be connected to each other through a separate umbilical line capable of transferring the liquid so as to supply or recover the liquid from the floating hull to the ballast chamber of the buoyant body.

In addition, a separate ballast pump may be mounted on the floating hull so as to be connected to the umbilical line so as to supply or recover the liquid to the ballast chamber.

In addition, a plurality of buoyant bodies may be disposed, and a plurality of buoyant bodies may be connected to each other through separate transfer lines so that the respective ballast chambers communicate with each other and liquid can be transferred.

Also, any one of the plurality of buoyancy bodies may be connected to the umbilical line, and the remainder may be sequentially connected from the buoyancy body connected to the umbilical line through the transfer line.

The transfer line may be provided with an opening / closing valve for opening / closing the transfer line.

In addition, a plurality of the buoyant bodies may be arranged, and each of the plurality of buoyant bodies may be connected to the respective umbilical lines of the respective ballast chambers.

Further, the umbilical line may include a main line connected to the ballast pump of the floating hull, and an auxiliary line branched from the main line and connected to the plurality of buoyant bodies, respectively.

The auxiliary line may be provided with an on-off valve capable of opening and closing the auxiliary line.

In addition, the buoyant body may be formed in a pillar shape having a center hole formed in the central portion so that the riser passes therethrough and having a donut shape in cross section.

In addition, the ballast chamber may be formed in a circumferential direction along an outer circumference of the center hole.

In addition, the buoyant body may be divided into a first body and a second body symmetrically formed along the radial direction, and the ballast chamber may be formed independently of the first body and the second body.

In addition, the first and second bodies may be independently configured to supply or recover liquid to and from the ballast chambers independently of the first body and the second body.

In the meantime, the present invention provides a flexible riser buoyancy adjusting method, wherein buoyancy provided to the riser is adjusted using the flexible riser system.

According to the present invention, the ballast chamber is formed in such a form as to be capable of supplying or recovering the liquid inside the buoyant body, and by connecting the ballast chamber to the riser, the buoyancy of the buoyant body Therefore, even if the specific gravity of the riser changes during the production of crude oil, it is possible to maintain the seabed condition of the riser continuously and stably.

In addition, by connecting a plurality of buoyant bodies formed with the ballast chambers to each other, and selectively supplying and recovering the liquid to and from the ballast chambers of the buoyant bodies, the buoyancy can be adjusted through the plurality of buoyant bodies, In addition, the operation position of the buoyant force can be adjusted, so that the seabed position of the riser can be maintained more stably.

1 is a schematic view schematically showing an installation structure of a conventional flexible riser system according to the prior art,
FIG. 2 is a schematic view schematically showing an installation structure of a flexible riser system according to an embodiment of the present invention;
FIGS. 3 and 4 conceptually illustrate the structure of a buoyant body according to an embodiment of the present invention;
5 and 6 are views schematically showing an installation form of a buoyant body according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the drawings, the same reference numerals are used to designate the same or similar components throughout the drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

FIG. 2 is a schematic view schematically showing an installation structure of a flexible riser system according to an embodiment of the present invention. FIG. 3 and FIG. 4 conceptually show the structure of a buoyant body according to an embodiment of the present invention And FIGS. 5 and 6 are views schematically showing an installation form of the buoyant body according to an embodiment of the present invention.

The flexible riser system according to an embodiment of the present invention is used for marine oil field development and has a flexible structure which is connected to the well head 21 at the top of the oil well 20 at the bottom of the sea floor from the floating floating hull 10 A riser 30 and a buoyant body 40 coupled to the riser 30 to provide buoyancy to the riser 30.

The ballast chamber (50) is formed in the buoyant body (40) in such a form that the liquid can flow in and out. When the liquid is discharged from the ballast chamber 50 and the ballast chamber 50 is filled with air, the buoyancy of the buoyant body 40 is maximally increased. On the contrary, when the liquid flows into the ballast chamber 50, , The buoyancy of the buoyant body (40) is reduced to the minimum.

Such a buoyant body 40 is formed so that liquid can flow into or out of the ballast chamber 50 and thus the buoyant force of the buoyant body 40 can be controlled through the flow of the liquid to and from the ballast chamber 50.

When the buoyant force of the buoyant body 40 is adjusted, buoyancy to be provided to the riser 30 can be adjusted according to the state of the riser 30, so that the riser 30 can be always maintained in a stable arrangement state.

The buoyant body 40 may be formed in various forms such that the ballast chamber 50 is formed therein. For example, in the buoyant body 40, as shown in FIG. 3, And the ballast chamber 50 may be formed in a circumferential direction along the periphery of the center hole 41. The ballast chamber 50 may be formed in the shape of a column having a donut shape in cross section. 3B is a cross-sectional view taken along the line AA shown in FIG. 3A, and FIG. 3C is a cross-sectional view taken along the line BB shown in FIG. to be. The buoyant body 40 thus formed may be provided with a liquid flow hole 51 communicating with the ballast chamber 50 at one side thereof to allow the liquid to flow into and out of the ballast chamber 50.

4, the buoyant body 40 may be divided into a first body 40a and a second body 40b symmetrically formed along the radial direction. At this time, the ballast chamber 50 may be divided into a first body 40a and a second body 40b, May be independently formed on the first body 40a and the second body 40b. In this case, the liquid flow holes 51 are communicated with the respective ballast chambers 50 so that liquid can be flowed into and out of the ballast chambers 50 formed in the first body 40a and the second body 40b, respectively Two can be formed.

As described above, the buoyant body 40 is divided into the first body 40a and the second body 40b, and the ballast chambers 50 are independently formed in the respective bodies, thereby separately supplying liquid to the respective ballast chambers 50 The size of the buoyant force generated through one buoyant body 40 can be adjusted more precisely as well as stepwise more variously.

4B is a cross-sectional view taken along the line AA shown in Fig. 4A, and Fig. 4C is a cross-sectional view taken along the line BB shown in Fig. to be. The first body 40a and the second body 40b may be detachably coupled to each other through a separate coupling device 60 as shown in FIG. 4 (b).

The operation of supplying or recovering the liquid to or from the ballast chamber 50 of the buoyant body 40 is performed by the ballast chamber 50 and the floating hull 10 so that the ballast chamber 50 and the floating hull 10 can carry the liquid And can be connected via a separate umbilical line (71).

At this time, a separate ballast pump 80 may be mounted on the floating hull 10 so as to be connected to the umbilical line 71 so as to supply or recover the liquid to the ballast chamber 50.

Therefore, when the ballast pump 80 of the floating hull 10 is operated to supply liquid to the ballast chamber 50 through the umbilical line 71, the buoyancy of the buoyant body 40 is reduced in size , So that the upward movement force by the buoyancy of the riser 30 also decreases. Conversely, when the ballast pump 80 is operated to recover liquid from the ballast chamber 50 through the umbilical line 71, the buoyancy of the buoyant body 40 increases in size, The buoyant force of buoyancy also increases.

By this operation method, the arrangement state of the riser 30 can be stably maintained. That is, depending on the specific gravity of the fluid flowing into the riser 30 in the course of producing the crude oil, the buoyant force and weight of the riser 30 itself may change and the riser 30 may be raised or lowered. The flexible riser system according to the present invention adjusts the buoyancy of the buoyant body 40 in such a manner that the liquid is supplied to or recovered from the ballast chamber 50 in accordance with the change in the state of the riser 30, .

2, 5 and 6, the buoyant body 40 can be coupled to the riser 30 at a plurality of locations, wherein a plurality of buoyant bodies 40 are disposed in each of the ballast chambers 50 may be connected through a separate transfer line 72 so as to communicate with each other.

5, one of the plurality of buoyant bodies 40 is connected to the umbilical line 71 and the rest is connected to the transfer line 40 from the buoyant body 40 connected to the umbilical line 71, (72). ≪ / RTI > For connection using the transfer line 72, a separate connection hole 52 should be formed in the buoyant body 40 in addition to the liquid flow hole 51 communicating with the ballast chamber 50.

According to such a structure, the liquid can be supplied or recovered only to a part of the buoyant body 40 of the plurality of buoyant bodies 40, so that the size of the buoyant force can be controlled through the whole of the plurality of buoyant bodies 40. That is, when liquid is supplied from the ballast pump 80 to one of the buoyant bodies 40 through the umbilical line 71, the other buoyant body 40 is sequentially transferred from the corresponding buoyant body 40 through the transfer line 72 The supply amount or the recovery amount of the liquid to the whole of the plurality of buoyant bodies 40 can be adjusted by adjusting the amount of liquid supplied or recovered through the ballast pump 80. [ Therefore, it is possible to adjust the size of the buoyant force with respect to the entire number of the buoyant bodies 40, thereby keeping the arrangement state of the riser 30 stable.

At this time, the transfer line 72 connecting the plurality of buoyant bodies 40 may be provided with an on-off valve 73 for opening and closing the transfer line 72. Accordingly, it is possible to selectively restrict the supply range of the liquid to the plurality of buoyant bodies 40 in which the liquid is sequentially supplied, thereby more precisely and conveniently controlling the supply amount of the liquid, have.

6, the plurality of buoyant bodies 40 may be configured such that each of the ballast chambers 50 is connected to the umbilical line 71, respectively. 6, each of the umbilical lines 71 may be connected to one main line (not shown). However, as shown in FIG. 6, the umbilical line 71 may be connected to one main line 71-1 and a plurality of auxiliary lines 71-2 branched from the auxiliary lines 71-1 and 71-2, respectively, so that the buoyant bodies 40 are connected to the respective auxiliary lines 71-2.

That is, the umbilical line 71 includes a main line 71-1 connected to the ballast pump 80 of the floating hull 10 and a plurality of auxiliary lines 71 branched from the main line 71-1 -2), and the plurality of buoyant bodies 40 are connected to the plurality of auxiliary lines 71-2, respectively.

At this time, an opening / closing valve 73 capable of opening / closing the auxiliary line 71-2 may be mounted on each of the auxiliary lines 71-2. Accordingly, by selectively opening and closing some of the plurality of on-off valves 73, liquid can be supplied to or recovered from only the specific buoyant body 40, Can be adjusted. In addition, the position of the buoyancy acting on the riser 30 through the supply or recovery of liquid to the specific buoyant body 40 can also be adjusted in various forms.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas falling within the scope of the same shall be construed as falling within the scope of the present invention.

10: Floating hull 20: Oil well
30: riser 40: buoyant body
50: ballast chamber 51: liquid flow hole
52: connection hole 60: coupling device
71: Umbilical line 71-1: Main line
71-2: auxiliary line 72: transfer line
73: opening / closing valve 80: ballast pump

Claims (14)

In a flexible riser system used for offshore field development,
A flexible riser connected from the floating hull of the sea to the top of the wellhead at the bottom of the seabed; And
A ballast chamber is formed therein in such a form as to allow the inflow and outflow of liquid, and a buoyancy chamber, which is coupled to the riser to provide buoyancy to the riser,
Wherein the buoyancy of the buoyant body is controlled through the inflow and outflow of liquid to and from the ballast chamber. The method according to claim 1,
Characterized in that the ballast chamber and the floating hull are connected to each other through a separate umbilical line capable of transferring the liquid so as to supply or recover the liquid from the floating hull to the ballast chamber of the buoyant body. Riser system. 3. The method of claim 2,
Wherein the floating hull is equipped with a separate ballast pump connected to the umbilical line so as to supply or recover the liquid to the ballast chamber. The method of claim 3,
Wherein a plurality of buoyant bodies are arranged and a plurality of buoyant bodies are connected through separate transfer lines so that the respective ballast chambers communicate with each other and liquid can be transferred. 5. The method of claim 4,
Wherein one of the plurality of buoyant bodies is connected to the umbilical line and the remainder is sequentially connected from the buoyancy body connected to the umbilical line through the transfer line. 5. The method of claim 4,
Wherein the transfer line is provided with an opening / closing valve for opening / closing the transfer line. The method of claim 3,
Wherein the plurality of buoyant bodies are arranged such that each of the plurality of buoyant bodies is connected to the respective umbilical line of the respective ballast chambers. 8. The method of claim 7,
The Umbilical line
A main line connected to the ballast pump of the floating hull and an auxiliary line branched from the main line and connected to the plurality of buoyant bodies, respectively. 9. The method of claim 8,
Wherein the auxiliary line is equipped with an on-off valve capable of opening and closing the auxiliary line. 10. The method according to any one of claims 1 to 9,
Wherein the buoyant body has a central hole formed at a central portion thereof so as to penetrate the riser, and the buoyant body is formed in a column shape having a donut shape in cross section. 11. The method of claim 10,
Wherein the ballast chamber is formed in a circumferential direction along an outer circumference of the center hole. 12. The method of claim 11,
Wherein the buoyant body is divided into a first body and a second body symmetrically formed along the radial direction, and the ballast chamber is formed independently of the first body and the second body. 13. The method of claim 12,
Wherein the first and second bodies are independently formed to independently supply or recover liquid to and from the ballast chamber formed independently of the first body and the second body. A flexible riser buoyancy regulating method comprising regulating buoyancy provided to the riser using the flexible riser system of claim 1.

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