JP2013521170A - Tension mooring platform with improved hydrodynamic performance - Google Patents

Abstract

A stable tension mooring platform with a mooring district integrated deck without the use of temporary stability modules or special installation techniques. The floating structure preferably comprises four radially arranged vertical corner columns connected to four central annular pontoon sections. The vertical column is fixed to the outer periphery of the central pontoon. The column is characterized by a main radial axis and a short transverse axis. The mooring system includes a tendon that is supported directly by a tendon pouch at the corners of the outer bottom of the four columns, without the addition of a radially extending tendon support structure.
[Selection] Figure 3

Description

  The present invention relates generally to tension mooring platforms, such as for offshore oil and gas drilling production, and more specifically, assembling superstructures in a mooring area without the use of temporary stability modules or other special equipment. The invention relates to a tension mooring platform that has sufficient intrinsic stability to allow the assembled floating structure and upper deck to be pulled and installed at the installation site.

  In the offshore oil and gas industry, floating structures such as tension and mooring platforms (TLP) for drilling and / or production are common. TLP is a floating platform of the type used for drilling and production in relatively deep water. The structure of a typical TLP floating structure consists of one, three or four vertical columns and three or four pontoons connecting the columns below the surface of the water. Columns and pontoons are typically rectangular or cylindrical in cross section. An upper structure is installed at the top of the column, and the upper structure includes an upper deck production facility, a drilling system, a production riser, and a residential area. In an installed draft, the TLP pontoon dives and the column extends from below the surface to above the surface.

  The TLP mooring system includes a steel pipe member called a tendon (also called a tether), which is connected to a diving or partially submerged floating platform floating structure to provide strong tension. Receive (tension). The high stiffness of tendons reduces the vertical natural period of the mooring system to a level well below the natural period of the main wave energy. As a result, there is little dynamic amplification of vertical motion and the platform has limited ups and downs, rolls and pitches. In a strongly tensioned tendon system, horizontal movement is limited to only a small percentage of the water depth.

  FIG. 1 is a plan view (in a horizontal section along a column) of a floating structure of a conventional TLP 200 of the prior art. Four columns 212 are arranged, and the center line VC of each column 212 forms a square corner to form a square. Four respective pontoons 214 form each side of the square. The pontoon 214 is typically arranged such that its center line HC is aligned in a straight line between the column center lines VC. A tendon pouch 220 is mounted directly on the outer corner of the column 212 for connection to a mooring tendon.

  FIG. 2 is a plan view (in a horizontal section along the column) of a prior art new generation TLP 300, known as an extended tension mooring platform (ETLP). Similar to the prior art TLP 200 of FIG. 1, in ELTP 300 of FIG. 2, column 312 is arranged so that the vertical centerline VC of corner column 312 intersects the axial centerline HC of pontoon 314 connected to column 312. Is done. Compared to the conventional TLP 200 of FIG. 1 having a similar sized footprint, the ETLP of FIG. 2 differs in that the column 312 and the pontoon 314 are located more inside to form a small square. Four tendon support structures 330 are mounted on the outer corners of column 312 at keel height. A tendon pouch 320 is provided at the distal end of the tendon support structure 330 for connection to a mooring tendon.

  Because the column 312 is located near the center C of the platform, a simplified deck structure can be used, resulting in a greater structural weight efficiency than the TLP 200 of FIG. Smaller ring-shaped pontoon structures 314 contribute to greater structural weight efficiency, simplify the structure, reduce support spans and cantilevers, and provide improved hydrodynamic performance of the platform. That is, a larger load can be supported with respect to a given combined load of the floating structure and the superstructure. Furthermore, the ETLP 300 of FIG. 2 with a simplified superstructure allows for more economical upper deck assembly in the mooring area, or eliminates the need for installation of heavy load carriers or float over decks.

  In both TLP200 and ETLP300, the interior of the column and pontoon is partitioned with structural dividers for damage management, strengthening the structure, and various devices (eg, anchors, chains, propulsion mechanisms, etc.) Provides a sealed space for storing and storing liquids such as fuel water and hydrocarbon products and stabilizing them with ballast.

  Depending on the structure, the stability of the TLP (conventional or extended) may be insufficient during installation. When TLP is stabilized with ballast between an initial free floating draft (eg, a floating towing or floating draft) and a fixed draft (draft where the TLP begins to be fixed to the tendon), the draft where the stability of the TLP is compromised The TLP may become unstable or it may be fixed to the tendon and barely stable before the ballast ends.

  There are many ways to address this stability issue when passing through the installation draft before fixing and finishing the ballast. Many prior art installation techniques rely on the use of expensive special installation equipment. For example, one method is to install the upper deck deck offshore after the floating structure is connected to the tendon. Installing the deck offshore is an expensive and high-risk task, usually requiring installation techniques for a heavy-duty carrier or float-over deck. Furthermore, a fairly long period of fine weather is necessary. Thus, if possible, it is generally preferable to assemble the superstructure in the mooring area and tow the completed platform to the installation site.

  Another method uses an upward hook load on the assembled TLP from a larger installation support vessel. The hook load has the advantage that the tendon can be tensioned quickly after fixation without waiting for the process of finishing the slow ballast. However, there are very few ships in the world that can provide the hook load required by normal size TLPs.

  Yet another way to improve stability during platform installation is to use a temporary buoyancy module that avoids floating structures from overturning before the floating structures are secured to the mooring tendon and subsequently finished ballasting. . For example, US Pat. No. 6,503,023 issued January 7, 2003 to Huang et al. Discloses an ETLP that uses a temporary stability module located outside a column on a tendon support structure. In the method of Huang et al., The TLP structure including the platform, deck and equipment is built upright and towed to the installation site, allowing the TLP structure or temporary stability module to be stably installed with ballast. In the arrangement of Huang et al., After the ETLP is fixed and the ballast is finished, the surface area of the structure at the surface of the water will be increased and the ETLP will be exposed to a larger wave in the wave area at the surface of the sea. Should be removed.

  U.S. Pat. No. 5,551,802 issued to Wybro on September 3, 1996, and U.S. Pat. No. 7,044,685 issued to Wybro et al. On May 16, 2006 include lines that are pushed down or pulled down at each corner of the TLP ( Alternatively, a TLP installation method is disclosed that prevents the TLP from overturning before being secured to the tendon using a chain. The line to be pushed down or pulled down is fixed at the lower end to the top of the installed tendon. The line passes through the tendon pouch followed by a ratchet gripper member or winch located on the tendon pouch. As the TLP draft increases to accept the tendon into the tendon pouch, the gripper or winch maintains line tension, thus preventing the TLP from falling to either side.

  As an alternative to these special installation techniques, the TLP can be designed to have the essential stability required for towing and installation. Stability may be improved by using a combination of design changes that increase the metacenter height of the platform, such as wider spacing between columns and / or lowering the large columns or the center of gravity. For example, the conventional TLP structure of FIG. 1 has inherently greater stability than the ETLP structure of FIG. 2, which is otherwise the same. Since the design of complex systems requires a trade-off between competing requirements, the conventional TLP design of FIG. 1 is larger than the ETLP design of FIG. 2 at the expense of structural weight efficiency and hydrodynamic performance. Get stability.

  US Patent Application No. 2002/0090270 by Malcolm et al. Discloses a column stable semi-submersible offshore platform. The Malcolm et al platform uses a triangular annular pontoon structure located inside three corner columns. In particular, the longitudinal centerlines of the three pontoon members are inside the sides of the triangle defined by being located at the corner of the vertical centerline of the column. However, since the pontoon is only inside the column, the sides of the geometric triangle pass through the pontoon just by passing outside the centerline of the pontoon.

  US Pat. No. 7,140,317 issued to Wybro et al. Also discloses a semi-submersible platform with improved stability. The platform of the Wybro et al. 7,140,317 patent uses four columns and a rectangular annular pontoon structure located inside the columns. That is, the sides of the square determined by positioning the vertical center lines of the four columns at the four corners of the square are completely outside and outside the pontoon. The pontoon of Wybro et al.'S 7,140,317 patent is located inside the column, so the platform is simplified construction with reduced support spacing and cantilever and each pontoon is centered between the columns at both ends Is characterized by improved hydrodynamic performance over

  Each semi-submersible platform described in Malcolm's patent application 2002/0090270 and Wybro et al.'S 7,140,317 patent is moored with a plurality of suspended mooring lines extending radially to the outer perimeter of the platform. For this reason, these platforms are not constrained up and down like TLP. Thus, an up-and-down restrained tension mooring platform that uses a wide column spacing for enhanced stability but has a small pontoon structure located inside the column for improved structural efficiency and hydrodynamic performance. It is desirable to have.

  A first object of the present invention is a tension mooring platform for offshore applications, such as for offshore oil and gas drilling production, having a plurality of columns and a central pontoon structure located inside the columns And to provide a tension mooring platform that simplifies the structure, reduces support spacing and cantilever, and provides improved hydrodynamic performance of the platform.

  Another object of the present invention is to have a floating structure having a rectangular column that is correctly positioned in the radial direction and a central pontoon structure that is disposed inside the column and is substantially formed of a flat plate structure. It is to provide a tension mooring platform that simplifies.

  A further object of the present invention is to have a vertical column of rectangular cross-section with a main axis correctly positioned radially outward from the center of the floating structure, the vertical column provides deck support and is required for conventional TLP deck support It is an object of the present invention to provide a tension mooring platform that reduces the support interval and cantilever of a simple deck structure.

  A further object of the present invention is to have an integrated central pontoon structure located inside a vertical column, with a central moon pool opening or completely enclosed, to improve the hydrodynamic performance of the platform compared to a conventional annular pontoon. It is an object of the present invention to provide a tension mooring platform that is improved and has a simple structure, light weight and easy support for steel suspension and flexible risers.

  It is a further object of the present invention to have a floating structure with a rectangular column correctly positioned in the radial direction and a central pontoon structure with a moon pool, the pontoon structure being located inside the column and centrally supporting the flexible riser. It is to provide a tension mooring platform that can be inside or outside of the pontoon structure.

  The above objects and other advantages and features of the present invention are incorporated into a tension mooring platform for offshore applications such as for offshore oil and gas drilling production, the tension mooring platform being a vertical support column, at the lower end of the column, inside it. A floating structure structure including a central pontoon structure disposed and a deck structure supported on the upper end of the column. The structure is connected to the outer surface of the column at the keel height and secured with a vertical tension leg that extends vertically downward to the sea floor. The vertical mooring tendons are connected by tendon pouches that are placed directly on the columns without the use of extended tendon support structures.

  The vertical column and pontoon structure are preferably constructed of substantially flat plates. The vertical column is adjacent to the outer periphery of the central pontoon and has a cross-sectional shape with a main axis that faces radially outward from the center point of the floating structure, with the central vertical axis at a position away from the outer periphery of the pontoon. Have.

  The riser is supported inside or outside the pontoon and extends to the deck. The central pontoon and outer column structure simplify construction, reduce support spacing and cantilevers, and provide improved hydrodynamic performance of the platform.

  The invention will be described in detail below on the basis of embodiments shown in the attached drawings.

FIG. 1 is a plan view in cross section of a prior art conventional TLP floating structure showing pontoons disposed between vertical columns and connecting the vertical columns. FIG. 2 shows a vertical column with reduced lateral spacing (compared to the conventional TLP floating structure of FIG. 1 having the same mooring footprint), a pontoon arranged between the vertical columns and connecting the vertical columns; FIG. 2 is a plan view in cross section of a prior art extended TLP (ETLP) floating structure showing a tendon support structure extending radially outward from the column. FIG. 3 is a perspective view of a tension mooring platform according to a preferred embodiment of the present invention showing vertical columns connected together by an annular pontoon located inside the column. 4 is a plan view of the floating structure (column and pontoon) of the tension mooring platform of FIG. 3 in a cross section taken along line 4-4 of FIG. FIG. 5 is a perspective view of a floating structure (column and pontoon) of a tension mooring platform according to an alternative embodiment of the present invention, where the central pontoon structure has no central opening and a large separation inside the column. And touch the column by extending the rectangle. FIG. 6 shows a tension mooring according to another alternative embodiment of the present invention, similar to the embodiment of FIG. 5, except that the vertical column has a substantially trapezoidal cross section with a wide inner wall and a narrow outer wall. It is a perspective view of the floating structure (column and pontoon) of a type platform.

  US Pat. No. 7,140,317 issued to Wybro et al. On Nov. 28, 2006 and entitled “Central Pontoon Semisubmersible Floating Platform” is hereby incorporated by reference in its entirety.

  3 and 4 illustrate a tension mooring platform 10 according to a preferred embodiment of the present invention for use in offshore applications such as offshore oil and gas drilling and production. The platform 10 has a floating structure 11 that includes a vertical support column 12 and a central pontoon structure 14 disposed inside the lower end of the column. The TLP 10 includes a deck structure 13 supported on the upper end of the column 12.

  The interior of the column 12 and the pontoon 14 is preferably separated by structural partitions (not shown), strengthening the structure and storing various devices (eg, anchors, chains, propulsion mechanisms, etc.). It provides a sealed space and provides a plurality of separate tanks for ballasting floating structures and for storing various fluids and other materials and products in wells that may or may be needed during drilling.

  The TLP 10 is fixed by a plurality of vertical or substantially vertical mooring tendons 17 connected to a tendon pouch 18 at the lower end of the outer surface of the column 12. Each column 12 is designed to couple with at least one, usually two or more tendons 17. The tendon pouch is located near the keel height and includes a connection sleeve (not shown) that houses and secures the upper end of the tendon 17. The connecting sleeve may be annular with the vertical entrance of the tendon 17 or may be formed with a slot into which the tendon 17 passes.

  Various types of risers 19 can be supported by the floating structure 11 and include a generally vertical top tension riser (TTR), flexible riser, or steel tube suspended riser (SCR). A flexible riser or steel pipe suspended riser (SCR) can be supported inside or outside the central pontoon structure 14 and extends to the deck 13 with a single length member or piping supported on a floating structure. The upper tension riser (TTR) can be supported by the deck 13 and can be supported laterally at the height of the pontoon by a riser keel joint (not shown).

  Although any suitable shape may be used, the central pontoon structure 14 is preferably octagonal and has four orthogonal side portions 14A, the side portion 14A having four diagonal corner portions 14B. The corner portions 14B are connected to the pontoon structure 14 to form an integrated structure centered about the central vertical axis C of the platform. In the embodiment shown in FIGS. 3 and 4, the central pontoon structure 14 includes a central moon pool opening 14C, which is illustrated as an octagonal opening, but may have other suitable shapes. Good. The side portions 14A and the corner portions 14B are preferably characterized by a substantially rectangular cross section surrounding the central horizontal axis or the horizontal central axis HC, respectively.

Each vertical column 12 has a lower end 12A and an upper end 12B. Column 12 preferably has a quadrilateral transverse (horizontal) cross section, the cross section being generally rectangular or trapezoidal. 3 and 4 show the column 12 having a cross-sectional shape with a main axis A ₁ radially outward from the center point C of the floating structure 11 as a rectangle. Specifically, the column 12 defines a rectangular cross section formed by two parallel wide lateral walls 12C that connect to a narrow inner wall 12D and an outer wall 12E, respectively. Thus, each vertical support column 12 defines a main axis _{A 1} and the minor axis _{A 2} extending between the two lateral walls 12C extending between the inner wall 12D and the outer wall 12E. Each vertical support column 12 defines the vertical longitudinal axis or vertical centerline VC at the intersection of the main axis A ₁ and the minor axis A _2. Spindle A ₁ of each vertical support column 12 is preferably from the center C of the platform is a radially outwardly. The lower portion of the inner wall 12D of each vertical support column 12 is adjacent to and connected to the diagonal corner portion 14B of the pontoon structure 14.

The vertical support column 12 is disposed substantially outside the central pontoon structure 14. The vertical axis VC of each column 12 is a distance D ₁ outward from the outer periphery of the corner portion 14B of the pontoon structure 14 and a distance D ₂ outward from a central horizontal axis or horizontal centerline HC extending through the pontoon corner portion 14B. Placed in. Therefore, in the floating structure structure of the present invention, the central pontoon structure 14 is located inside the vertical support column 12, and the line S defined between the vertical center lines VC of the two adjacent columns 12 is the pontoon side portion. It is located outside the horizontal center line HC, more preferably outside the outer periphery of the pontoon structure 14. This design feature allows prior art tension mooring platform designs (e.g., with individual pontoons in the middle between columns where the vertical centerline of the support column intersects the horizontal centerline of adjacent pontoons, e.g. 1 and 2).

  FIG. 5 illustrates a TLP floating structure 11A according to an alternative embodiment of the present invention. Similar to the TLP floating structure 11 of the embodiment of FIGS. 3 and 4, the floating structure 11A has a central pontoon structure 114 located inside the column 12, but unlike the TLP 10 of FIGS. The pontoon structure 114 does not have a central moon pool opening. Further, the outer periphery of the pontoon structure is spaced a large distance radially inward from the vertical support column 12 (ie, the outer periphery of the pontoon 114 is close to the platform centerline C). In the present embodiment, the lower part of the inner wall 12D of each vertical support column 12 is provided and fixed to a diagonal corner 114B of the pontoon structure 114 by a rectangular extension 15, and the rectangular extension 15 is fixed to the corner of the pontoon and the column. Twelve inner walls 12D are fixed to form an integrated structure.

  FIG. 6 illustrates a TLP floating body structure 11B according to a third embodiment of the present invention. In this alternative embodiment, each vertical support column 112 has a lower end 112A and an upper end 112B and a wide inner wall interconnected in parallel spaced relationship by two non-parallel laterally spaced walls 112C. 112D and the narrow outer wall 112E define a generally trapezoidal cross section.

  According to various embodiments of the present invention, including the embodiments of FIGS. 3-6 and variations thereof, stability is improved by increasing the column spacing, and the central pontoon structure 14, 114 is attached to the vertical support columns 12, 112. Arranging radially inward improves the hydrodynamic performance of the platform and reduces support spacing and cantilevers. Columns 12, 112 and pontoons 14, 114 are preferably not cylindrical, so they can be constructed of substantially steel flat plates (except for corners provided for simple radius curves and sharp corners). This feature simplifies the construction of floating structures.

  The gist of this disclosure has been written only to provide the United States Patent and Trademark Office and society in general with a quick way to quickly determine the nature and spirit of a technical disclosure and is representative of the preferred embodiment. It does not represent the full essence of the present invention.

  Although several embodiments of the invention have been described in detail, the invention is not limited to the illustrated embodiments. Those skilled in the art will recognize modifications and adaptations of the above-described embodiments. Such modifications and adaptations fall within the spirit and scope of the invention as specified herein.

Claims (20)

Floating structure (11, 112) comprising a plurality of vertical columns (12, 112) and a pontoon structure (14, 114) disposed inside the column and connected to the column at the lower end (12A, 112A) of the column 11A, 11B), each column having a horizontal cross-sectional shape defining a principal axis (A ₁ ) radially outward from a center point (C) of the floating structure (11, 11A, 11B);
A deck (13) supported by the upper ends (12B, 112B) of the column;
A plurality of tensioned and connected between the column and the seabed to maintain the tension mooring platform on a desired seabed position and substantially restrain the tension mooring platform from vertical up and down swinging. With tendon (17);
Tension mooring platform (10). The column (12, 112) and the pontoon structure (14, 114) are constructed of substantially flat plates;
The tension mooring platform (10) of claim 1. Each of the plurality of columns (12, 112) has a polygonal cross-section;
The tension mooring platform (10) of claim 1. Each of the plurality of columns (12, 112) has a quadrilateral cross section;
The tension mooring platform (10) of claim 1. Each of the plurality of columns (12, 112) is defined by an inner wall (112D) and an outer wall (112E) interconnected in a parallel spaced relationship by two non-parallel laterally spaced walls (112C). The outer wall (112E) is wider than the inner wall (112D), and the main axis (A ₁ ) extends between the inner wall and the outer wall;
Tension mooring platform (10) according to claim 4. Each of the plurality of columns (12, 112) is interconnected in a parallel spaced relationship by two parallel laterally spaced walls (12C) and approximately the same inner wall (12D) and outer wall (12E). The two parallel and laterally spaced walls (12C) are wider than the inner wall (12D) and the outer wall (12E), and have a substantially horizontal horizontal cross section defined by ₁ ) extends between the inner wall and the outer wall;
Tension mooring platform (10) according to claim 4. The pontoon structure (14, 114) is octagonal;
The tension mooring platform (10) of claim 1. Each of the columns (12, 112) is joined to a corner portion (14B, 114B) of the pontoon structure (14, 114) by an extension member (15);
The tension mooring platform (10) of claim 7. The pontoon structure (14) includes a central moon pool opening (14C) formed in a vertical direction;
The tension mooring platform (10) of claim 1. The pontoon structure (14) includes four orthogonal side portions (14A) interconnected by four diagonal corner portions (14B);
Each of the side portion (14A) and the corner portion (14B) is substantially rectangular in cross section and defines a horizontal axis (HC);
The tension mooring platform (10) of claim 9. Each of the columns (12, 112) is joined to a corner portion (14B) of the pontoon structure (14) by an extension member (15);
The tension mooring platform (10) of claim 9. A floating structure (11) including a pontoon structure (14, 114) having an outer periphery surrounding a central vertical axis (C) and a vertical column (12, 112) connected to the outer periphery of the pontoon structure by a lower end (12A, 112A) , 11A, 11B) wherein the pontoon structure is disposed inside the column, each of the columns being spaced from the outer periphery of the pontoon structure by a first non-zero distance (D ₁ ) from the central vertical axis (C Floating structure (11, 11A, 11B) defining a vertical column axis (VC) located radially outward from);
A deck (13) supported by the upper ends (12B, 112B) of the column;
In order to maintain the tension mooring platform on the desired seabed position and to substantially restrain the tension mooring platform from vertical up and down swinging, it is directly tensioned to the column (12, 112) at the upper end. A tendon (17) connected to the column by a provided tendon pouch (18) and connected to the sea floor at the lower end;
Tension mooring platform (10). Each of the columns (12, 112) has a cross-sectional shape having a horizontal main axis (A ₁ ) radially outward from the central vertical axis (C);
Tension mooring platform (10) according to claim 12. The pontoon structure (14) includes a vertical central opening (14C) therethrough;
The pontoon structure (14) includes four orthogonal side portions (14A) separated by four diagonal corner portions (14B);
Each of said side portion (14A) and corner portion (14B) has a polygonal vertical cross section and defines a horizontal longitudinal axis (HC);
Each vertical column axis (VC) of each column (12, 112) is radiused by a _second non-zero distance (D ₂ ) from the horizontal longitudinal axis (HC) of the adjacent corner portion (14B) of the pontoon structure (14). Located outside in the direction;
The tension mooring platform (10) of claim 13. Each of said columns (12, 112) has a polygonal cross section;
The tension mooring platform (10) of claim 13. Each of the plurality of columns (12, 112) is wider than an inner wall (112D) and an inner wall (112D) interconnected in a parallel spaced relationship by two non-parallel laterally spaced walls (112C). Having a generally trapezoidal cross section formed by a narrow outer wall (112E);
The tension mooring platform (10) of claim 15. Each of the plurality of columns (12, 112) is interconnected in a parallel spaced relationship by two parallel laterally spaced walls (12C) and approximately the same inner wall (12D) and outer wall (12E). The two parallel and laterally spaced walls (12C) are wider than the inner and outer walls;
The tension mooring platform (10) of claim 15. An overhead line (S) extending between the vertical column axes (VC) of two adjacent columns (12, 112) is located outside the outer periphery of the pontoon structure;
Tension mooring platform (10) according to claim 12. The overhead line (S) extending between the vertical column axes (VC) of the two adjacent columns (12, 112) is a horizontal longitudinal axis (14A) of the side portion (14A) positioned between the two adjacent columns. HC) outside;
Tension mooring platform (10) according to claim 14. An annular pontoon structure (14) formed of a plurality of portions (14A, 14B) surrounding a central opening (14C) and defining a horizontal centerline (HC) in a transverse cross section;
Vertical columns (12, 112) connected to the outside of the pontoon structure (14) at lower ends (12A, 112A), respectively, wherein the pontoon structure is disposed inside the column, each of the columns being the horizontal A central vertical longitudinal axis (VC) disposed radially outward from the center (C) of the platform by a distance (D ₂ ) from the axial center line (HC), the central vertical longitudinal axis being defined as the horizontal axis center line; Vertical columns (12, 112) to avoid crossing;
A vertical mooring tendon (17) connecting the column and the seabed;
Tension mooring platform (10).

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