KR100528315B1 - Method for repairing a floating semisubmerged drilling platform - Google Patents

Abstract

The present invention relates to shipbuilding, and more particularly to self-floating structures, in particular floating semi-submersible drilling platform (1). The platform 1 of the present invention is an anchor position keeping system, process equipment connected to a well during a work process, and a lower buoyancy separated into watertight compartments. It consists of lower pontoons and stabilized columns. A method of repairing a floating semisubmerged drilling platform, comprising examining and then repairing a compartment by accessing the compartment through an existing passageway, by alternately emptying groups of waterproof compartments. investigation and repair of the platform at sea during the course of the operation, without interrupting the well and platform connections; Continue to maintain the platform's acceptable design criteria of intact and damage stability, strength and trim, providing platform safety under severe storm and working conditions The individual compartments of the waterproof compartments are accessible through additionally formed passageways within the bulkheads in the compartments for inspection and repair, and the additional passages are closed after completing the repair.

Description

How to repair a floating semi-submersible drilling platform {METHOD FOR REPAIRING A FLOATING SEMISUBMERGED DRILLING PLATFORM}

FIELD OF THE INVENTION The present invention relates to shipbuilding, and more particularly to a method for repairing a self-suspending structure, in particular a floating semisubmerged drilling platform.

Methods of repairing floating structures, particularly floating semisubmerged platforms by docking, are no. 148953, IPC B63 C 1/00, 1981. Although the method described above is effective for repairing a platform, it is necessary for the platform to stop working and docking, which is one of the most expensive shipbuilding processes due to the high cost of docking facilities.

In addition, several methods are known for repairing floating structures, in particular floating semi-submersible platforms, by floating on water without docking.

One of the well-known methods for repairing a floating structure, mainly the floating semi-submersible platform, is described in detail when the damaged part of the hull is removed and newly welded and installed in place of the damaged part without docking. Interrupt the connection between the and the wells, interrupt the work of the platform, and disconnect the mooring lines (see SU 1625764, IPC B63B 9/04, 1988).

However, the approach as described above is to repair only the respective structural components of the platform, in particular the components above the surface, and repair other essential components such as lower pontoons below the surface. It cannot be used to do so.

The method described in WO 99/55011, IPC B63B 35/44, 29/04/1999 is directed to lower pontoons and anchor positioning systems subdivided into fixed columns, watertight compartments. semisubmerged drilling vessels by accessing any compartment through existing passageways for inspection and repair, using anchor position keeping systems and process equipment associated with specific wells during production. ) Is to rebuild.

Since the existing passageway in the lower buoyancy wall allows access only to compartments with thrusters, the vessel must be docked for inspection and repair of ballast tanks, and therefore You must stop.

The above mentioned docking is one of the most expensive drainage processes. Prior to docking, the operations under water break and disconnect the wells and move the platform away from the anchor station. To return to the production process, the platform must be anchored, and the platform must be activated and reconnected to the platform. In addition, the platform is not productive during repair time. The cost of work associated with losses due to interruption of production is higher than the cost of docking.

1 is a perspective view of a floating semisubmerged drilling platform repaired in accordance with the present invention;

2 shows an outline of a platform without process equipment, anchor system and product pipelines, FIG.

3 is a cross-sectional view of A-A of FIG. 2 (a top view of one lower pontoon, the second being symmetrically positioned),

4 is a cross-sectional view of B-B of FIG. 2 (a top view of one lower buoyancy device, the second being symmetrically positioned),

5 is a schematic diagram of a watertight compartment location (ballast tank location) in the lower section of the lower pontoons and stabilized columns, FIG.

6-11 illustrate stages in accordance with an embodiment of the present invention.

The technical result according to the invention is to repair the platform from the water surface without docking, without interrupting the connection with the wells, without interrupting the working state of the platform and without breaking the mooring lines. It becomes possible.

It is a stabilized column; Lower pontoons subdivided into watertight compartments; Process equipment connected to a well during production; And a semisubmerged drilling platform consisting of an anchor position keeping system. The anchor position maintenance system makes the platform workable, maintains connection with the anchor, and connects the anchoring rope, making it accessible to specific compartments through existing passageways for inspection and repair without docking.

For this purpose, groups of waterproof compartments are tolerated such as strength, intact and damage stability, and trim required to provide platform safety in operation and severe storm conditions. The platform remains emptied while remaining within the range of possible design parameters. Additional passages are installed to access specific watertight compartments, which are formed in bulkheads subdividing the compartments, which are accessible for repair and removed after completion of the repair.

In addition, technical results such as those described above may be reached by preliminary deballasting of the platform to a state when buoyant to have a minimum allowable operating draft, at which time the platform and Definition Well ties remain connected. It is possible to repair any groups of waterproof compartments. This is accomplished by installing additional passageways, such as manholes, in the waterproof compartment.

For a full understanding of the problem, the code for Construction and Equipment of Mobile Drilling Units (MODU Code), International Maritime Organization, London, 1989 is listed below.

Chapter 3, subparagraph 3.4.1: Units must have sufficient freeboard, watertight decks and bulkheads to provide sufficient buoyancy and safety. Should be subdivided by

delete

Chapter 4, subpargraph 4.9.1: The unit has sufficient pumping to ballast or deballast any ballast tank under normal working and changing conditions. A pumping system must be provided, optionally, allowing for controlled gravity ballasting.

Chapter 4, subparagraph 4.9.2: The ballast system is subjected to severe storm draft at maximum normal draught while in intact conditions. must provide the capability to bring the unit up to a severe storm draught.

Chapter 4, subpatagraph 4.11.1: anchoring arrangements fixed as a single means for position keeping shall be provided with sufficient elements for safety and all design conditions. Should be designed to hold the unit above the station.

Chapter 14-Operating requirements

14.1.1 In order to ensure the safe operation of the unit for both standard and observed emergency conditions, guiding work manuals are provided on board and should be readily available for all relevant purposes.

 14.1.2 The work manual shall include:

      1 unit description and details,

      Design data limitations for each mode of operation, including 3 drafts, air gap, and wave height,

      5 location of waterproofing and waterproof boundaries,

  6 Locations, types and quantities of permanent ballast installed on the unit,

      10 Resilience information based on intact and damage criteria

14.1.3 The working manual shall also include:

14.1.3.4 For vertically fixed units, descriptions, guidance and schematic diagrams for the operation of the ballasting system and other means of ballasting system operation ...

14.1.3.7 Procedures for changing the mode of operation, 14.1.3.8 Guide to severe storm conditions .... and any inherent working limits.

The floating semisubmerged drilling platform (1), which is repaired according to the repair method of the present invention, includes two lower pontoons (2), eight fixed columns (3), and process equipment ( a system of upper hulls 4 and bracings 5 integrated with the process equipment.

The platform 1 is connected to FPSO (not shown) through wells in water and pipelines 6 produced with flexible. The platform itself is an anchor system 7 which is held in position above the operating point. The lower buoyancy devices 2 of the platform 1 have separate waterproof compartments subdivided into vertical and horizontal waterproof bulkheads 8, 9. Most of the waterproof compartments of the lower buoyancy device 2 are ballast tanks 10. The ballast tank 11 is in the lower section of the fixed column 3. The port (P / S) and starboard (S / S) of the ballast tank 10 of the lower buoyancy device 2 range from 10 ₁ (P / S and S / S) to 10 ₁₀ (P / S and S / S), the numbers of the ballast tanks 11 of the pillars 3 have from 11 ₁ (P / S and S / S) to 11 ₄ (P / S and S / S). To empty and fill the tanks 10, 11, the platform 1 is provided with a ballasting system comprising valved pipelines and pumps (not shown in the figure).

During operation, the platform 1 submerges in particular to a draught d, the operating minimum draught being dmim. At this draft, the lower buoyancy unit 2 and the lower section of the column 3 are below the sea level. The ballast tanks 10 and 11 are filled with seawater. Buoyant compartments 12 are provided with passage manholes 13 for access to the ballast tanks 11 of the columns 3. Existing passage-deck manholes 14 have a structure that allows easy access to the ballast tank 10 of the buoyancy device 2 under a fixed column 3. The ballast tank 10 of the lower buoyancy device 2 outside the area of the fixed column 3 is accessible through the current manholes 15. However, during operation, these manholes will be below the water, 9m to 11m deep. Therefore, in order to reach the ballast tank 10 outside the area of the fixed column 3, an additional passage must be provided in the partition wall 8 or partition wall 9 which subdivides the tank during the repair process. This additional passage is formed as the manholes 16.

The method for repairing a floating semi-submersible drilling platform according to the invention is carried out in the following order.

 The platform is under working condition. The connection between the platform and the wells is not broken and the anchor system 7 is in working condition. All ballast tanks 10 and 11 are inspected and the results are recorded.

First stage of repair work

For example, ballast tanks such as 10 ₅ , 11 ₁ , 11 ₂ , and 11 ₄ (P / S and S / S) are emptied as well as ballast tanks 10 ₁₀ , S / S. After opening the current manholes 13 from the buoyant compartment 12 of the pillars 3 to the ballast tank 11 of the pillars 3, ventilation and temporary illumination (not shown) are provided to provide a temporary ladder. Ladders are installed when necessary and safety and precautions are followed during repair work (eg, Subparagraph 10.9 of Prepatation of water and ballast tanks for repair in Safety regurations for commercial vessesls, Reklaminformbureau of Maritime Ministry, Moscow, 1975, pp. See 171-172) and then inspect and repair these tanks, if necessary (see FIG. 6). Then, after opening the deck manholes 14, the ballast tanks in the lower buoyancy device 2 are replaced with 11 ₂ (P / S), 11 ₂ (S / S) and 11 ₄ (S / S). Accessible through the same ballast tank, inspect and repair ballast tanks such as 10 ₅ (P / S), 10 ₅ (S / S) and 10 ₁₀ (S / S) (see FIG. 6). If necessary, safety precautions are provided with ventilation, temporary lighting and temporary ladders.

2nd step of repair work

The tanks, 10 ₆ (P / S) and 10 ₆ (S / S), are drained using a ballasting system. This is in accordance with the platform work instructions. At the same time,

Proceed in advance what is needed to meet specific safety criteria such as intact and damage stability, strength and reliability of the anchor position keeping system. To obtain a draft draught, some tanks of the platform may be deballasted to have a draft d _min or ballasted to others, and the platform may be heeled or trimmed. no trim).

Additional passages such as manholes 16 are installed in the transverse partition walls 9 in common for the tank 10 ₆ (P / S) and the tank 10 ₆ (S / S), thus providing an empty tank. (10 ₅ (P / S) and 10 ₅ (S / S)) into these genes. Thereafter, the tanks 10 ₆ (P / S) and 10 ₆ (S / S) are examined and repaired (see FIG. 7). As soon as the repair process is completed, the manhole 16 is closed or removed with the removal of the cutout.

 The platform returns to its previous state by debaling.

Ballast tanks, 10 ₄ (P / S) and 10 ₄ (S / S), 10 ₇ (P / S) and 10 ₇ (S / S) are removed by the ballasting system. The aforementioned tasks are also suitable for platform operating instructions.

3rd step of repair work

The ballast tanks, 10 ₄ (P / S) and 10 ₄ (S / S), 10 ₇ (P / S) and 10 ₇ (S / S) are cleaned by the ballasting system. This task sequence is also consistent with platform operating instructions.

Previous draughts are taken to advance what is needed to meet specific safety criteria such as intact and damage stability, reliability, and strength of the anchor position maintenance system. It may deballast several tanks of the platform to provide or ballast others, and the platform is free of heel and trim.

In order to test and repair the tank of the lower buoyancy device 2 (see FIG. 8), the drained ballast tank, 11 ₂ (P / S), 11 ₂ (S / S) and tank 11 ₃ (P / S), Access through the manhole 14 of 11 ₃ (S / S).

 The platform 1 is returned to its previous position by the reballast.

4th step of repair work

The ballast tanks, 10 ₂ (P / S) and 10 ₂ (S / S), as well as tanks 10 ₁₀ (P / S) are emptied by using a ballasting system. This work order is also consistent with the platform work instructions. Tank, 10 ₂ (P / S) and 10 ₂ (S / S), as well as the tank ₁₀ 10 (P / S) is empty ballast tank through a manhole _{(14), 11 1 (P} / S), 11 1 (S / S), and 11 ₄ (P / S) (see FIG. 9).

5th step of repair work

The ballast tanks, 10 ₁ (P / S), 10 ₁ (S / S) and 10 ₉ (P / S), 10 ₉ (S / S) are drained by using a ballasting system. The tanks, 10 ₉ (P / S) and 10 ₉ (S / S), have manholes 14 in the empty ballast tanks of fixed columns 3, 11 ₄ (P / S) and 11 ₄ (S / S). Can be reached through.

As soon as the fourth stage of the repair is completed, the tank, 10 ₂ (P / S) and 10 ₂ (S / S) are left empty, where additional manholes 16 are installed in the horizontal partition wall 9 To provide access to tanks 10 ₁ (P / S) and 10 ₁ (S / S) (see FIG. 10).

After repairing the tank, 10 ₁ (P / S) and 10 ₁ (S / S), the manhole 16 is removed and the platform 1 is rebalanced.

6th step of repair work

Ballast tanks, 10 ₃ (P / S), 10 ₃ (S / S) and 10 ₈ (P / S), 10 ₈ (S / S) are cleaned by the ballasting system. In order to gain access to the tank, neighboring tanks such as 10 ₉ (P / S) and 10 ₉ (S / S) as well as 10 ₅ (P / S) and 10 ₅ (S / S) must be emptied.

To enter tanks such as 10 ₅ (P / S), 10 ₅ (S / S), 10 ₈ (P / S), and 10 ₈ (S / S), add an additional manhole 16 to 10 ₅ (P / S). S), 10 ₅ (S / S), 10 ₃ (P / S), 10 ₃ (S / S), 10 ₉ (P / S), 10 ₉ (S / S), 10 ₈ (P / S) And in a transverse waterproof partition wall 9 common to the tank, such as 10 ₈ (S / S) (see FIG. 11). The tank to be accessible is irradiated with subsequent closure of the manhole 16 and Environmental conditions, work order recommendations, and work experience considerations, several different sequences of repair work, progress conditions from ballasting and deballasting, are selected for each specific loading of the platform. Can lose.

By using the present invention, internal inspection and repair of ballast compartments and their equipment can be docked without interrupting the operation of the platform and connection to the wells by the most efficient and time-consuming easy way. It can be done at sea without.

The rough economic effect of the application of the present invention to the repair of one AKer H-3 type semi-submersible platform amounts to about 5,000,000 USD.

Claims (3)

Anchor position keeping system, process equipment connected to the well during operation, lower buoyons separated by watertight compartments, and fixed A method of repairing a floating semisubmerged drilling platform consisting of stabilized columns, the method comprising investigating and subsequently repairing the compartment by accessing the compartment through an existing passageway. In Inspecting and repairing the platform at sea during the course of operation, without interrupting wells and platform connections by alternately emptying the groups of waterproof compartments; The platform is continuously maintained with acceptable design criteria of intact and damage stability, strength and trim to ensure platform safety under severe storm and working conditions. Provide, Individual compartments of the waterproof compartments are accessible through additionally formed passageways within the bulkheads in the compartments for inspection and repair, And closing the additional passage after completing the repair. The method of claim 1, The platform is suspended until a minimum possible operating draught is reached without interrupting the connection with the tablet, and is pre-deballasted to repair the group of waterproof compartments. How to repair a semi-submersible drilling platform. The method of claim 1, And the additional passageway is formed as manholes in watertight compartments.