System and Method for Coupling a Topside to a Floating Substructure

Abstract

Systems and methods for coupling a topside to a fixed or floating substructure during float-over installation of the topside are disclosed. Some system embodiments include a first plate coupled to a leg of the substructure and a retaining wall coupled to the first plate and extending substantially normally therefrom, wherein the retaining wall and the first plate form a recess. The system embodiments further include a second plate disposed at an end of a leg of the topside, the second plate received within the recess and engaging the first plate, and a plurality of shims disposed between the second plate and the retaining wall, wherein the plurality of shims are configured to inhibit translational movement of the second plate relative to the first plate.

Description

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not applicable.

BACKGROUND OF THE INVENTION

Embodiments of the invention relate to systems and methods for installing a topside or deck on a substructure to form a fixed or floating offshore platform. More particularly, embodiments of the invention relate to a novel system and method for coupling the topside with the substructure during float-over installation of the topside.

Float-over installations offer opportunities to install heavy topsides beyond the lifting capacity of available crane vessels on offshore substructures located in remote areas. A float-over installation includes four primary procedures. The first procedure involves transporting the topside or deck to the offshore substructure. Typically, the topside is placed on a barge or heavy transport vessel and towed to the substructure.

The second procedure involves docking the transport barge to the installed substructure. The barge is maneuvered into the slot of the substructure, such that the topside is floated over and substantially aligned with the substructure. Once in the slot, mooring lines, sometimes in combination with a fendering system, are utilized to suppress surge and sway motions of the barge. After the mooring lines are set, deballasting of the substructure commences.

The third procedure involves transferring the load of the topside from the barge to the substructure, and is a critical phase of the float-over installation. Deballasting of the substructure continues as the substructure rises toward the topside. Once the topside and the substructure reach close proximity, the two bodies may impact each other repeatedly due to wave action. Such impacts may damage the structures when the relative motion between the two bodies is not controlled. As deballasting of the substructure continues, the weight of the topside is gradually transferred from the barge to the substructure. After a critical fraction of the weight is transferred, the relative motion between the two bodies ceases. At that point, the two structures move as a single unit, and the possibility of damage due to hard impact is eliminated. Therefore, it is desirable to complete the load transfer up to the critical fraction as quickly as possible.

After the topside is fully supported by the substructure, the legs of the two structures are coupled by welding legs extending downward from the topside to legs extending upward from the substructure. To achieve the high quality welds required to withstand the harsh load regimes of offshore environments, proper alignment of the topside with the substructure during the float-over operation is critical.

The final procedure involves separating the barge from the topside, and is also a critical phase of the float-over installation. The substructure is deballasted further until the topside separates from the barge. At and immediately after separation, the relative motions between barge and topside pose a danger of damage due to impact between these bodies. That danger can be minimized by rapid separation of the barge and the topside. To promote such rapid separation, the topside may be supported on the barge by a number of loadout shoes. At the appropriate time, the loadout shoes are actuated to quickly collapse or retract, thereby providing rapid separation between the barge and the topside. These systems, however, have a propensity to malfunction and permit hard contact between the loadout shoes and the topside. In any event, hard contact between the barge and the topside may continue until the substructure is deballasted to provide sufficient separation between the barge and the topside. After which point, the barge is towed from the installation site.

Thus, embodiments of the invention are directed to apparatus and methods that seek to overcome these and other limitations of the prior art.

SUMMARY OF THE PREFERRED EMBODIMENTS

A system and method for coupling a topside to a fixed or floating substructure during float-over installation of the topside are disclosed. Some systems embodiments include a first plate coupled to a leg of the substructure, a retaining wall coupled to the first plate, and a second plate disposed at an end of a leg of the topside. The retaining wall extends substantially normally from the first plate, such that the retaining wall and the first plate form a recess. The second plate is received within the recess and engages the first plate. The system embodiments may further include a plurality of shims disposed between the second plate and the retaining wall, wherein the shims are configured to inhibit translational movement of the second plate relative to the first plate.

The system embodiments may further include a tensioning system. The tensioning system includes a connector coupled to the first plate and disposed within the second plate, wherein the second plate is annular. The tensioning member further includes a support plate coupled to the topside, a rod extending between the connector and the support plate, and a securing device coupled to an end of the rod. The securing device is configured to apply a tension load to the rod.

Some method embodiments for coupling a topside to a fixed or floating substructure during float-over installation of the topside include coupling a receptacle to a leg of the substructure. The receptacle includes a first plate coupled to the leg of the substructure and a retaining wall coupled to the first plate. The retaining wall extends substantially normally from the first plate, wherein the retaining wall and the first plate form a recess. The method embodiments further include disposing a second plate at an end of a leg of the topside, receiving the second plate within the recess, wherein the second plate engages the first plate, and installing a plurality of shims between the second plate and the retaining wall. The plurality of shims are configured to inhibit translational movement of the second plate relative to the first plate.

Thus, the embodiments of the invention comprise a combination of features and advantages that enable substantial enhancement of float-over installation systems and methods. These and various other characteristics and advantages of the invention will be readily apparent to those skilled in the art upon reading the following detailed description of the preferred embodiments of the invention and by referring to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

For a detailed description of the preferred embodiments of the invention, reference will now be made to the accompanying drawings in which:

FIGS. 1A and 1B are cross-sectional and top views of weldless topside coupling system in accordance with embodiments of the invention;

FIG. 2 is a cross-sectional view of an installed substructure including some components of the coupling system of FIG. 1;

FIG. 3 is a cross-sectional view of a topside including the remaining components of the coupling system of FIG. 1 floated over the substructure of FIG. 2;

FIG. 4 is a cross-sectional view of a tensioning member coupled between a topside and a substructure; and

FIG. 5 is a cross-sectional view of a weldless coupling system and tensioning member coupled between the topside and the substructure of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Various embodiments of the invention will now be described with reference to the accompanying drawings, wherein like reference numerals are used for like parts throughout the several views. The drawing figures are not necessarily to scale. Certain features of the invention may be shown exaggerated in scale or in somewhat schematic form, and some details of conventional elements may not be shown in the interest of clarity and conciseness.

Preferred embodiments of the invention relate to a weldless system and method for coupling a topside with an installed substructure to form a fixed or floating platform. The invention is susceptible to embodiments of different forms. There are shown in the drawings, and herein will be described in detail, specific embodiments of the invention with the understanding that the disclosure is to be considered an exemplification of the principles of the invention and is not intended to limit the invention to that illustrated and described herein. It is to be fully recognized that the different teachings of the embodiments discussed below may be employed separately or in any suitable combination to produce desired results.

As described above during a conventional float-over installation of a topside on an installed substructure, the topside is floated over and substantially aligned with the substructure using a barge. The substructure is then deballasted to engage and lift the topside from the barge, thereby assembling the fixed or floating platform. The topside is then coupled to the substructure by welding. Embodiments of the invention are directed to a system and method for coupling the topside to the substructure without the need for precise alignment of the topside relative to the substructure and subsequent welding.

FIGS. 1A and 1B depict representative cross-sectional and top views, respectively, of a topside or deck installed via float-over on a representative cross-section of a substructure 105 for a semi-submersible offshore platform, such as a multicolumn floating (MCF) platform. More specifically, a leg 110 of the topside is shown coupled to a leg 115 of the substructure by a weldless topside coupling system 120. Coupling system 120 includes an annular plate 125 disposed at the lower end 130 of leg 110. In this exemplary embodiment, plate 125 is formed separately from leg 110 and then coupled to leg 110 as shown. In other embodiments, however, plate 125 may be formed integrally with leg 110. After the topside is landed on the substructure, as shown, leg 115 of the substructure supports leg 110 of the topside. By disposing annular plate 125 at end 130 of leg 110, the area or footprint of leg 110 in contact with leg 115 is significantly increased, in comparison to the footprint of leg 110 that would otherwise contact leg 115 in the absence of plate 125. Because annular plate 125 increases the footprint of leg 110, annular plate 125 is also referred to the big foot.

Weldless coupling system 120 further includes a receptacle or bucket 135 disposed at the upper end 140 of leg 115. Bucket 135 includes a base plate 145 having an upper surface 155 and a retaining wall 150 coupled thereto. Retaining wall 150 extends substantially normally upward from upper surface 155. As shown in FIG. 1B, retaining wall 150 is generally circular in shape. Further, the inner envelope of retaining wall 150 is selected such that annular plate 125 may be received therein.

For additional support, one or more small gusset plates 160 are coupled to bucket 135 between upper surface 155 of base plate 145 and the outer surface 165 of retaining wall 150. Plates 160 provide support to retaining wall 150 when lateral force is applied to the inner surface 170 of wall 150, where the lateral direction is substantially parallel to base plate 145. Also for additional support, one or more large gusset plates 175 are coupled to bucket 135 between the lower surface 180 of base plate 145 and the outer surface 185 of leg 115. Plates 175 provide support to base plate 145 when an asymmetric vertical load, defined relative to a longitudinal centerline 190 through leg 115, is applied to upper surface 155 of base plate 145.

In some embodiments, weldless coupling system 120 further includes two or more pairs of tapered or wedge-shaped shims 200 disposed on upper surface 155 of base plate 145 between the outer surface 205 of plate 125 and inner surface 170 of retaining wall 150. When installed, shims 200 prevent translational movement of plate 125 relative to base plate 145, and thus lateral movement of leg 110 relative to leg 115. In at least some embodiments, shims 200 are formed of steel. Each pair of shims 200 comprises an inner shim 210 proximate plate 125 and an adjacent outer shim 215 proximate retaining wall 150. The adjacent surfaces of inner shim 210 and outer shim 215 form a non-slip taper 220 configured to prevent sliding of shims 210, 215 relative to each other.

Weldless coupling system 120 may further include a coating 225 disposed between retaining wall 150 and plate 125 and covering shims 200. Coating 225 is configured to prevent corrosion of shims 200 and potential slippage of inner shims 210 relative to outer shims 215. Coating 225 may include an epoxy resin material, such as chalk-fast, tar, or other equivalent material known in the art.

Alternatively, weldless coupling system 120 may include a hardenable material 455 (FIG. 5) in place of shims 200 and coating layer 225, if present. Hardenable material 455 is disposed within bucket 135 surrounding and covering plate 125. Further, hardenable material 455 is applied in liquid form but subsequently hardens into solid form. Like shims 200, material 455, once hardened, prevents slippage of plate 125 relative to base plate 145, and thus lateral movement of leg 110 relative to leg 115. Hardenable material 455 may include a grout, epoxy resin, or other equivalent material.

With the exception of shims 200, coating layer 225 and hardenable material 455, components of docking system 110 are coupled to leg 110 of the topside or leg 115 of the substructure, as appropriate, prior to transport of the topside and the substructure to the desired offshore installation site. Bucket 135 and plates 160, 175 are coupled to leg 115 of the substructure, for example, by welding. Similarly, annular plate 125, if formed separately from leg 110, is coupled to leg 110, for example, by welding.

The substructure, with leg 115 and components of weldless coupling system 120 coupled thereto, is then towed to the installation site, as shown in FIG. 2. Upon reaching the installation site, the substructure 105 is ballasted to the desired depth. The topside 100, with leg 110 and components of weldless coupling system 120 coupled thereto, is next towed to and floated over substructure 105 by a barge 107, as previously described and shown in FIG. 3.

After topside 100 is aligned over substructure 105, substructure 105 is deballasted to engage topside 100. More particularly, substructure 105 is deballasted to allow bucket 135, coupled to upper end 140 of leg 115, to receive annular plate 125, coupled to lower end 130 of leg 110, such that plate 125 lands on upper surface 155 of base plate 145 within retaining wall 150, as shown in FIG. 1A. Continued deballasting of substructure 105 enables load transfer of topside 100 from barge 107 to substructure 105. In other words, substructure 105 begins to lift topside 100 from barge 107.

When the load of topside 100 is completely supported by substructure 105, shims 200 may then hammered into position between annular plate 120 and retaining wall 150. Once installed, shims 200 prevent subsequent sliding of plate 125, and leg 110 coupled thereto, relative to bucket 135, and leg 115 coupled thereto. Lateral loads exerted by leg 110 in response to the surrounding water are instead transferred through shims 200 to retaining wall 150, which resists these loads with support from gusset plates 160. If desired, coating 225 is then applied between plate 125 and retaining wall 150 to cover shims 200. Alternatively, hardenable material 455 may be applied to fill bucket 135 and cover plate 125 and allowed to harden. Finally, barge 107 is released from topside 100.

Weldless coupling system 120 does not require welding to couple the topside to the substructure. Analysis has shown that welding is unnecessary because the dynamic motions of the substructure, even during expected hurricane conditions, will not cause plate 125 to separate or lift off of bucket 135 due to the weight of installed topside 100. Further, when weldless coupling system 120 is utilized to couple a topside to a substructure, precise alignment of the topside prior to deballasting the substructure to engage and lift the topside is also unnecessary for a number of reasons. For one, the topside will not be welded to the substructure once engaged. Also, bucket 135 provides a significantly increased area upon which leg 110 may land, relative to that available during conventional float-over procedures in the absence of coupling system 120. Thus, the topside may be misaligned to a degree and leg 110 will still land within the inner envelope of bucket 135 as the substructure is deballasted. Further, the structural integrity of base plate 145 in combination with support from gusset plates 175 is capable of supporting leg 110 with annular plate 125 coupled thereto of withstanding asymmetric vertical loading, such as those resulting when leg 110 lands within bucket 135 off-center of centerline 190 of leg 115. Similarly, annular plate 125 is also capable of withstanding asymmetric vertical loading resulting from off-center engagement of plate 125 with bucket 135.

If desired, weldless coupling system 120 may be supplemented with a positive tie-down means coupled between topside 100 and substructure 105 in case of an unforeseen extreme event, such as an atypical hurricane or an earthquake. For example, and referring now to FIG. 4, one or more tensioning members 400 may be coupled between topside 100 and substructure 105, as shown. Tensioning member 400 includes a support plate 405, a connector 410 and a tie rod 415 extending therebetween. Support plate 405 is coupled to an upper surface 420 of topside 100. Support plate 405 includes a throughbore 435 configured to receive the upper end 440 of tie rod 415. Connector 410 is coupled to an upper surface 430 of substructure 105. Tie rod 415 is coupled to connector 410 and extends upward through throughbore 435 of support plate 405. In some embodiments, tie rod 415 extends within a deck column member 425, as shown. Upper end 440 of tie rod 415 is coupled to support plate 405 by a tensioning and securing device 445 seated on plate 405. Device 445 is configured to apply a tension load to tie rod 415.

Like those of coupling system 120, components of tensioning member 400 are coupled to topside 100 or substructure 105, as appropriate, prior to transport of topside 100 and substructure 105 to the desired offshore installation site. After topside 100 is landed on substructure 105 as described above, meaning leg 110 of topside 100 with plate 125 thereto is landed within bucket 135 coupled to leg 115 of substructure 105, tie rod 415 is inserted through throughbore 435 of support plate 405 and lowered to engage connector 410. Securing and tensioning device 445 is then disposed over upper end 440 of tie rod 415 and seated on support plate 405. Device 445 is next operated to apply a tension load to tie rod 415. Once tie rod 415 is tensioned to the desired load, installation of tensioning member 400 is complete.

In some embodiments, tensioning member 400 may be installed between legs 110, 115 of topside 100 and substructure 105, respectively, coupled using weldless topside coupling system 120, shown and described above with reference to FIGS. 1-3. In such embodiments, connector 410 of tensioning member 400 is coupled to upper surface 155 of base plate 145 of weldless coupling system 120, as shown in FIG. 5. Also, support plate 405 of tensioning member 400 is coupled to an upper surface 115 of topside 100 from which leg 110 extends. Otherwise, the remaining components of tensioning member 400 are positioned and installed as described above in reference to FIG. 4.

While preferred embodiments have been shown and described, modifications thereof can be made by one skilled in the art without departing from the scope or teachings herein. The embodiments described herein are exemplary only and are not limiting. Many variations and modifications of the systems are possible and are within the scope of the invention. For example, the relative dimensions of various parts, the materials from which the various parts are made, and other parameters can be varied. Accordingly, the scope of protection is not limited to the embodiments described herein, but is only limited by the claims that follow, the scope of which shall include all equivalents of the subject matter of the claims.

Claims

1. A system for coupling a topside to a substructure during float-over installation of the topside, the system comprising: a first plate coupled to a leg of the substructure;a retaining wall coupled to the first plate and extending substantially normally therefrom, wherein the retaining wall and the first plate form a recess; anda second plate disposed at an end of a leg of the topside, the second plate received within the recess and engaging the first plate.

2. The system of claim 1, wherein the second plate is annular.

3. The system of claim 1, wherein the second plate has a lower surface in contact with the first plate and wherein the topside leg has a cross-section substantially parallel to the second plate, wherein the lower surface in contact with the first plate has an area greater than the area of the cross-section.

4. The system of claim 1, further comprising a plurality of shims disposed between the second plate and the retaining wall, wherein the plurality of shims are configured to inhibit translational movement of the second plate relative to the first plate.

5. The system of claim 4, wherein the plurality of shims comprises: a first plurality of inner shims, each inner shim positioned adjacent the second plate; andan equal number of outer shims, each outer shim positioned between one of the first plurality of inner shims and the retaining wall.

6. The system of claim 5, wherein each inner shim comprises an outer surface in contact with an inner surface of the adjacent outer shim, wherein the outer surface of each inner shim and the inner surface of each outer shim are configured to resist translational movement relative to one another.

7. The system of claim 6, wherein the inner surface of each outer shim and the outer surface of each adjacent inner shim are tapered.

8. The system of claim 4, further comprising a coating layer covering the plurality of shims.

9. The system of claim 8, wherein the coating layer comprises one of the group consisting of epoxy resin and tar.

10. The system of claim 1, further comprising a hardenable material layer disposed between the retaining wall and the second plate.

11. The system of claim 10, wherein the hardenable material layer comprises one of the group consisting of epoxy resin and gout.

12. The system of claim 1, wherein the retaining wall is circular.

13. The system of claim 1, further comprising a plurality of gusset plates disposed circumferentially around the retaining wall and extending substantially normally therefrom, wherein each gusset plate is coupled to the retaining wall and the first plate.

14. The system of claim 1, further comprising a plurality of gusset plates disposed circumferentially around the leg of the substructure and extending substantially normally therefrom, wherein each gusset plate is coupled to the leg of the substructure and the first plate.

15. A system for coupling a topside to a substructure during float-over installation of the topside, the system comprising: a coupling system comprising: a solid plate coupled to a leg of the substructure;a retaining wall coupled to the solid plate and extending substantially normally therefrom, wherein the retaining wall and the solid plate form a recess; andan annular plate disposed at an end of a leg of the topside, the annular plate received within the recess and engaging the solid plate; anda tensioning system comprising: a connector coupled to the solid plate;a support plate coupled to the topside;a rod extending between the connector and the support plate; anda securing device coupled to an end of the rod, the securing device configured to apply a tension load to the rod.

16. The system of claim 15, wherein the connector is coupled to the solid plate and disposed within the annular plate.

17. The system of claim 15, wherein the annular plate has a lower surface in contact with the solid plate and wherein the topside leg has a cross-section substantially parallel to the annular plate, wherein the lower surface in contact with the solid plate has an area greater than the area of the cross-section.

18. The system of claim 15, further comprising a plurality of shims disposed between the second plate and the retaining wall, wherein the plurality of shims are configured to inhibit translational movement of the annular plate relative to the solid plate.

19. The system of claim 18, wherein the plurality of shims comprises: a first plurality of inner shims, each inner shim positioned adjacent the second plate; andan equal number of outer shims, each outer shim positioned between one of the first plurality of inner shims and the retaining wall;wherein each inner shim comprises an outer surface in contact with an inner surface of the adjacent outer shim, wherein the outer surface of each inner shim and the inner surface of each outer shim are configured to resist translational movement relative to one another.

20. The system of claim 15, further comprising a hardenable material layer disposed between the retaining wall and the annular plate.

21. The system of claim 15, further comprising a plurality of gusset plates disposed circumferentially around the retaining wall and extending substantially normally therefrom, wherein each gusset plate is coupled to the retaining wall and the first plate.

22. The system of claim 15, further comprising a plurality of gusset plates disposed circumferentially around the leg of the substructure and extending substantially normally therefrom, wherein each gusset plate is coupled to the leg of the substructure and the first plate.

23. The system of claim 15, further comprising a coating layer covering the plurality of shims.

24. A method for coupling a topside to a substructure during float-over installation of the topside, the method comprising: coupling a receptacle to a leg of the substructure, the receptacle comprising: a first plate coupled to the leg of the substructure; anda retaining wall coupled to the first plate, the retaining wall extending substantially normally therefrom;wherein the retaining wall and the first plate form a recess;disposing a second plate at an end of a leg of the topside; andreceiving the second plate within the recess, wherein the second plate engages the first plate.

25. The method of claim 24, further comprising installing a plurality of shims between the second plate and the retaining wall, wherein the plurality of shims are configured to inhibit translational movement of the second plate relative to the first plate.

26. The method of claim 25, further comprising covering the plurality of shims with a coating layer.

27. The method of claim 24, wherein the receiving comprises deballasting the substructure to position the second plate within the recess and in engagement with the first plate.

28. The method of claim 24, further comprising coupling a first plurality of gusset plate between an outer surface of the retaining wall and the first plate and coupling a second plurality of gusset plates between an outer surface of the leg of the substructure and the first plate.

29. The method of claim 24, further comprising applying a hardenable material layer between the retaining wall and the second plate.