JP2014058275A - Semi-submersible type floating structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semi-submersible type floating structure that achieves an increased loadage and improved stability performance.SOLUTION: A semi-submersible type floating structure 1 includes a deck 2 and a plurality of columnar members 3 extending downward from the deck 2. The semi-submersible type floating structure 1 includes a lower hull 4 connected to end portions of the plurality of columnar members 3. The lower hull 4 has a cavity therein. The lower hull 4 also has a water inlet 11 for taking seawater into the interior of the lower hull 4.

Description

  The present invention relates to a semi-submersible floating structure used for oil drilling at sea and a marine base.

  Conventionally, a semi-submersible floating structure (Semi-Submersible, hereinafter referred to as a semi-sub) is used as a platform for excavating natural gas, oil, or the like on the seabed.

  FIG. 3 shows an outline of a conventional semi-sub. The semi-sub 1X includes a deck 2 on which a drilling rig or the like is installed, a plurality of columnar members 3X extending downward from the deck 2, and a lower hull 4X installed at the lower end of the columnar member 3X. The deck 2 has a deck through hole 7 for allowing a drill pipe or the like extended from the drilling rig to pass therethrough. The size of the semi-sub 1X is, for example, about 80 m × 80 m in length and width and about 100 m in height.

  Next, the operation of the semi-sub 1X will be described. The semi-sub 1X maintains a state where the deck 2 and a part of the columnar member 3X are exposed and floated on the ocean, and is moored on the seabed by a mooring line or the like. On the deck 2, an oil drilling rig or the like is installed.

  With the above configuration, the semi-sub 1X can suppress swinging. This is because the cross-sectional area of the structure when cut at the sea surface is smaller than that of boat-shaped FPSO or the like, and is not easily affected by waves.

  In addition, a configuration is disclosed in which the columnar members are doubled so that each columnar member can move up and down independently (see, for example, Patent Document 1). With this configuration, the semi-sub swing can be suppressed. This is because the kinetic energy of the waves can be absorbed and the kinetic energy acting on the semi-sub can be suppressed by the vertical movement of each columnar member.

  However, the above semisubs have several problems. First, there is a problem that the load (payload) is small. This is because the semi-sub 1X has less buoyancy than the boat-shaped FPSO. Therefore, when performing deep drilling that requires a large amount of drill pipes, etc., these equipments must be transported separately.

  Second, the semi-sub 1X has a long overall height (vertical length) and a large wind speed acting on the load on the deck, so it is difficult to suppress swinging and further improve the stability performance. There is a problem that there is. The semi-sub columnar member 3X is designed to have such a length that the wave does not collide with the bottom surface of the deck 2, and thus it is difficult to shorten the overall height of the semi-sub.

  Thirdly, the semisub described in Patent Document 1 has a problem that its construction cost increases. This is because the structure of the columnar member is complicated and the semi-sub construction process is complicated.

JP-A-6-144362

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a semi-sub that has an increased load capacity and improved stability performance in a semi-submersible floating structure (semi-sub). .

  In order to achieve the above object, a semi-submersible floating structure (semi-sub) according to the present invention is a semi-submersible floating structure having a deck and a plurality of columnar members extending downward from the deck. The type floating structure has one lower hull connected to ends of a plurality of columnar members, and the lower hull has a cavity inside.

  With this configuration, the load capacity of the semi-submersible floating structure (semi-sub) can be increased. This is because the lower hull can be enlarged and its buoyancy can be increased. Further, the semi-sub swing can be suppressed and the stability performance can be improved. This is because the vertical movement of the waves under the deck is remarkably suppressed by one lower hull connected to all the columnar members, and the columnar members can be configured to be short.

  In the semi-submersible floating structure (semi-sub), the lower hull has a water intake for introducing seawater therein. With this configuration, the seawater introduced into the lower hull acts as a damping mass and can suppress the semisub oscillation.

  In the semi-submersible floating structure (semi-sub), the lower hull has a pressure adjusting mechanism that adjusts the pressure of the air in the lower hull, and the pressure adjusting mechanism It has the structure which controls the quantity of the seawater in the said lower hull by adjustment.

  With this configuration, it is possible to control the performance and buoyancy that suppress the swing of the semi-sub. This is because the amount of seawater in the lower hull can be adjusted.

  In the semi-submersible floating structure (semi-sub), the lower hull has a plurality of anti-vibration tanks formed by dividing an internal cavity by an isolation wall, and the isolation wall is the anti-vibration tank. It has a communication port for seawater that enables movement of seawater between and an air communication port that enables movement of air.

  With this configuration, it is possible to suppress the swing of the semi-sub and improve the stability performance. This is because the responsiveness of the seawater in the anti-vibration tank is improved with respect to the semi-sub oscillation.

  According to the semi-submersible floating structure (semi-sub) according to the present invention, it is possible to provide a semi-sub with increased loading capacity and improved stability performance.

It is the figure which showed the outline of the semi-submersible floating body structure of embodiment which concerns on this invention. It is the figure which showed the outline of the vibration reduction tank of the semi-submersible floating body structure of embodiment which concerns on this invention. It is the figure which showed the outline of the conventional semi-submersible type floating structure.

Hereinafter, a semi-submersible floating structure (semi-sub) according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows an outline of a semi-submersible floating structure (semi-sub 1). The semi-sub 1 includes a deck 2, a plurality of columnar members 3 extending downward from the deck 2, and a single lower hull 4 connected to the ends of the plurality of columnar members 3.

  The lower hull 4 is one member connected to all the columnar members 3 and has a cavity inside. Further, the lower hull 4 has at least one water intake 11 for introducing seawater therein, and a plurality of anti-vibration tanks 13 formed by dividing an internal cavity by a separating wall 12. The vibration reduction tank 13 is surrounded by the isolation wall 12 and the inner wall surface of the lower hull 4.

  Here, the lower hull 4 is desirably formed in a rectangular parallelepiped shape as shown in FIG. 1, but may have other shapes such as a columnar shape or a spherical shape.

  When installing an oil drilling rig on the upper surface of the deck 2 of the semi-sub 3, the drill pipe passes through the deck through hole 7 formed in the deck 2 and the lower hull through hole 5 formed in the lower hull 4. It extends to the sea floor.

  With the above configuration, the semi-sub 1 of the present invention can obtain the following effects. First, the load capacity of the semi-sub 1 can be increased. This is because a large lower hull can be installed in the semi-sub 1 and its buoyancy can be increased. For this reason, it is possible to mount all the equipment required for deep drilling, which requires a large amount of drill pipes, etc., in the semi-sub 1.

  Secondly, the stability performance of the semi-sub 1 can be improved. This is because the vertical movement of the waves under the deck 2 is remarkably suppressed by one lower hull 4 connected to all the columnar members 3, and the columnar members 3 can be configured to be short. The semi-sub 1 that employs the columnar member 3 that is shorter than the conventional one has a reduced overall height, so that the stability performance at sea is improved and the swinging can be suppressed.

  In addition, the stability of the semi-sub 1 can be further improved by the configuration in which the water intake 11 is installed in the lower hull 4. This is because the seawater introduced into the lower hull 4 acts as a vibration control mass that moves according to the swing of the semi-sub 1 and can suppress the swing of the semi-sub 1.

  Thirdly, the semi-sub 1 having high stability performance can be provided without increasing the construction cost. This is because the semi-sub 1 of the present invention does not require a complicated mechanism or a complicated construction process.

  Even if the semi-sub 1 does not have the intake port 11, if a fluid such as seawater is introduced into the lower hull 4, stability performance can be improved. This is because the fluid in the lower hull 4 moves freely in the lower hull 4 and acts as a damping mass that moves so as to automatically cancel the swing of the lower hull 4.

  Next, details of the lower hull 4 will be described. FIG. 2 shows a partially enlarged view of the lower hull 4. The lower hull 4 has a plurality of anti-vibration tanks 13 formed by dividing an internal cavity by a plurality of isolation walls 12. The anti-vibration tank 13 has a sea water communication port 14 that enables movement of sea water between the vibration reduction tanks 13 and an air communication port 15 that enables movement of air.

Further, the lower hull 4 has a pressure adjustment mechanism 16 constituted by a blower or the like for adjusting the pressure of air in the lower hull 4. The pressure adjustment mechanism 16 has a configuration for controlling the amount of seawater in the lower hull 4 by adjusting the pressure of air in the lower hull 4. In addition, the white arrow has illustrated the moving direction of air and seawater, 17 has shown the water surface 17 of the seawater introduced into the inside of the lower hull 4. FIG.

  Next, the function of the lower hull 4 will be described. First, when increasing the amount of seawater in the lower hull 4, the pressure adjustment mechanism 16 depressurizes the air in the lower hull 4 (decompression step). Seawater flows into the lower hull 4 from the water intake 11 due to the pressure reduction of the air. At this time, the seawater flows into each anti-vibration tank 13 through the seawater communication port 14 formed in the isolation wall 12. Thereafter, when the pressure outside the intake port 11 and the pressure inside the lower hull 4 are balanced, the inflow of seawater automatically stops. In addition, the water intake 11 is comprised so that a normally open state may be maintained.

  Next, when reducing the amount of seawater in the lower hull 4, the air in the lower hull 4 is pressurized by the pressure adjustment mechanism 16 (pressurization step). Due to this increase in air pressure, seawater flows out of the lower hull 4 from the water intake 11. At this time, the seawater is sent from each anti-vibration tank 13 to the water intake 11 via the seawater communication port 14 formed in the isolation wall 12. Thereafter, when the pressure outside the intake port 11 and the pressure inside the lower hull 4 are balanced, the inflow of seawater automatically stops.

  With the above configuration, the semi-sub 1 of the present invention can obtain the following effects. First, it becomes possible to adjust the buoyancy of the semi-sub 1. Therefore, the buoyancy of the semi-sub 1 can be controlled according to the weight of the load mounted on the semi-sub 1, and the height from the sea surface to the deck can be easily controlled.

  Secondly, the stability performance of the semi-sub 1 can be further improved. This is because seawater is introduced into the large lower hull 4 and used as a damping mass. That is, since the area of the water surface 17 can be ensured large and the mass of the fluid (seawater) can be increased, the damping performance by the damping mass is improved.

  Further, the stability performance of the semi-sub 1 can be further improved by installing the isolation wall 12 and dividing the cavity inside the lower hull 4 into a plurality of decompression tanks 13. This is because the response performance as the damping mass is improved by the configuration in which the movement range of the seawater (fluid) is limited by the isolation wall 12. This is particularly effective when the semi-sub 1 swings with a short period.

  Thirdly, the semi-sub 1 can easily control the amount of sea water in the lower hull 4 with at least one pressure adjustment mechanism 16 by the configuration in which the sea water communication port 14 and the air communication port 15 are formed. . Therefore, the configuration of the semi-sub 1 can be simplified and an increase in construction cost can be suppressed.

  In addition, it is good also as a structure which installs an opening-and-closing control valve etc. in the communication port 14 for seawater, and the communication port 15 for air. With this configuration, the amount of seawater in each anti-vibration tank 13 can be controlled independently. Therefore, although the semi-sub construction cost increases, the stability performance of the semi-sub can be further improved.

Further, it is desirable to determine the size of the anti-vibration tank 13 and the amount of seawater to be introduced with reference to the following formula.

Here, T indicates the natural period (sec) of the primary mode on the water surface 17 of the vibration reducing tank 13. L (L1, L2, L3, etc.) indicates the length (m) of the vibration reducing tank 13, and H indicates the water depth (m) in the vibration reducing tank 13 (see FIG. 2). Note that the length L is the length of the anti-vibration tank 13 in the swing direction of the semi-sub 1. The size of the anti-vibration tank 13 and the amount of seawater to be introduced may be determined so that the natural period T (sec) obtained by the above formula is equal to or less than the period T ₀ of the target wave in the sea area where the semi-sub is installed. desirable.

  Moreover, it can also comprise so that the quantity of the seawater in the lower hull 4 may be controlled with a ballast pump etc. instead of the pressure adjustment mechanism 16. FIG.

1 Semi-submersible floating structure (semi-sub)
2 Deck 3 Columnar member 4 Lower hull 11 Water intake 12 Isolation wall 13 Anti-vibration tank 14 Seawater communication port 15 Air communication port 16 Pressure adjustment mechanism

Claims (4)

In the semi-submersible floating structure having a deck and a plurality of columnar members extending downward from the deck,
The semi-submersible floating structure has one lower hull connected to ends of a plurality of columnar members,
The semi-submersible floating structure, wherein the lower hull has a cavity inside.   The semi-submersible floating structure according to claim 1, wherein the lower hull has at least one water intake for introducing seawater therein. The lower hull has a pressure adjusting mechanism for adjusting the pressure of air in the lower hull;
The semi-submersible floating body according to claim 1 or 2, wherein the pressure adjusting mechanism has a configuration that controls the amount of seawater in the lower hull by adjusting the pressure of air in the lower hull. Structure. The lower hull has a plurality of anti-vibration tanks formed by dividing an internal cavity by an isolation wall;
The said isolation wall has the communicating port for seawater which enables the movement of seawater between the said anti-vibration tanks, and the communicating port for air which enables the movement of air. 4. The semi-submersible floating structure according to any one of 3 above.

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