System and Method for Aligning and Engaging a Topside to a Floating Substructure

Abstract

Systems and methods for aligning and engaging a topside with a fixed or floating substructure during float-over installation of the topside are disclosed. Some system embodiments include an alignment member coupled to the substructure, an extendable member coupled to the topside, the extendable member having a receptacle configured to receive the alignment member, and a damping system. In some embodiments, the damping system includes a piston-rod assembly having a piston slideably disposed with a housing, wherein a first chamber and a second chamber are formed, and a rod coupled between the piston and the extendable member, a source of pressurized gas coupled to the first chamber, and an accumulator containing fluid coupled to the second chamber.

Description

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims benefit of U.S. provisional application Ser. No. 60/946,647 filed Jun. 27, 2007, and entitled “Big Foot and Docking Probe,” which is hereby incorporated herein by reference in its entirety for all purposes.

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 aligning the topside with the substructure and engaging the two structures prior to load transfer of the topside to 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 rendering 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 docking system and method for aligning a topside with an installed substructure and engaging the two structures prior to load transfer of the topside to the substructure during float-over installation of the topside are disclosed. Some system embodiments include an alignment member coupled to the substructure, an extendable member coupled to the topside, the extendable member having a receptacle configured to receive the alignment member, and a damping system configured to move the extendable member into engagement with the substructure, wherein the alignment member is received within the receptacle.

In some embodiments, the damping system includes a piston-rod assembly having a piston slideably disposed with a housing, wherein a first chamber and a second chamber are formed. The damping system further includes a rod coupled between the piston and the extendable member, a source of pressurized gas coupled to the first chamber, and an accumulator containing fluid coupled to the second chamber.

Some method embodiments for engaging a topside with a substructure during float-over installation of the topside include extending a member having a receptacle from the topside to engage an alignment member coupled to the substructure, applying force to the member to resist downward motion of the topside relative to the substructure, and applying force to the member to maintain engagement of the member with the substructure in response to upward motion of the topside relative to the substructure.

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:

FIG. 1 is a cross-sectional view of a docking system in accordance with embodiments of the invention;

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

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

FIG. 4 is a cross-sectional view of the docking system of FIG. 1 extended to align and engage the topside with the substructure of FIG. 3.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Various embodiments of the invention will flow 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 docking system and method for aligning and engaging a topside with an installed fixed or floating substructure prior to load transfer of the topside to the substructure during float-over installation of the topside. 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.

FIG. 1 depicts a representative cross-section of a topside or deck 100 in proximity to a representative cross-section of a substructure 105 for a semi-submersible offshore platform, such as a multicolumn floating (MCF) platform. As described above, during float-over installation of topside 100 on substructure 105, topside 100 is floated over and substantially aligned with substructure 105 using a barge. Substructure 105 is then deballasted to engage or dock with and lift topside 100 from the barge, thereby assembling the semi-submersible platform. FIG. 1 illustrates the position of topside 100 relative to substructure 105 prior to docking of topside 100 with substructure 105. Embodiments of the invention are directed to a docking system 110 that enables alignment and engagement of topside 100 with substructure 105 during the docking procedure. Topside 100 includes an upper surface 115 and a deck column member 120 extending therefrom. Substructure 105 includes an upper surface 125.

Docking system 110 includes a damping system 130 with a docking pin 135 coupled thereto, an alignment member 140, and a plurality of centralizers 145. Damping system 130 is coupled to and supported by upper surface 115 of topside 100. Docking pin 135 is suspended from damping system 130 into deck column member 120 of topside 100. Further, docking pin 135 includes a receptacle 225 at its lower end 150 configured to receive alignment member 140 therein. To maintain the substantially vertical orientation of docking pin 135 within deck column member 120 and minimize bending loads to docking pin 135, centralizers 145 are disposed along the interior surface deck column member 120 proximate both ends of deck column member 120. Alignment member 140 is coupled to upper surface 125 of substructure 105. Damping system 130 is selectably actuatable to extend docking pin 135 within deck column member 120 toward alignment member 140. While alignment member 140 may assume virtually any shape the envelope of alignment member 140 is selected such that alignment member 140 fits within receptacle 225 of docking pin 135 when docking pin 135 is lowered over alignment member 140 to engage upper surface 125 of substructure 105.

In this exemplary embodiment, damping system 130 includes two piston-rod assemblies 160, each assembly 160 slidingly disposed within a housing 165. Other embodiments of damping system 120 may include only a single piston-rod assembly 160 or more than two such assemblies 160. Housings 165 are supported by a structure 155 coupled to surface 115 of topside 100 and substantially concentric to deck column member 120. In other embodiments, housings 165 may be disposed within deck column member 120. Each assembly 160 includes a piston 170 that sealingly engages the inner surface of housing 165, dividing housing 165 into an upper clamber 175 (best viewed in FIG. 2) and a lower chamber 180. A rod 185 is coupled to each piston 170 and extends downward through lower chamber 180, the base of housing 165, and support structure 155 to a plate 190 coupled to the upper end 200 of docking pin 135. Each piston 170 is slideable within housing 165, depending on the pressure of fluid contained within chambers 175, 180. As pistons 170 translate within housings 165 in reaction to changes in fluid pressure, rods 185 similarly translate, sliding upward or downward relative to housings 165 and support structure 155, within deck column member 120.

Damping system 130 further includes a source of pressurized gas 205, such as but not limited to one or more bottles of pressurized nitrogen 210, and a fluid accumulator 215 containing an incompressible fluid 220, such as but not limited to oil. Pressurized gas source 205 is coupled to upper chambers 175, and accumulator 215 coupled to lower chamber 180. Gas source 205 is selectably actuatable to inject pressurized gas 210 into upper chambers 175, causing the pressure in chambers 175 to increase. As the pressure within chambers 175 increases, the force exerted on pistons 170 by gas 210 exceeds fluid pressure within chambers 180, at which point pistons 170 translate downward within housings 165. When pistons 170 translate downward, docking pin 135 also translates downward or extends within deck column member 120, and fluid 220 contained within lower chambers 180 of housings 165 is forced from housings 165 into accumulator 215. Conversely, when a force is applied to lower end 150 of docking pin 135 in excess of the force exerted against pistons 170 by gas 200, docking pin 135 translates upward within deck column member 120, causing pistons 170 to displace upward within housings 165. As pistons 170 translate upward, gas 210 contained within upper chambers 175 is vented from housings 165, and fluid 220 is drawn from accumulator 215 into lower chambers 180. Gas 210 vented from upper chambers 175 may exhaust from housings 165 through relief valves (not shown) coupled to upper chambers 175 to the surrounding atmosphere or return to gas source 205.

Components of docking system 110 are installed on or within topside 100 or substructure 105, as appropriate, prior to transport of topside 100 and substructure 105 to the desired offshore installation site. Substructure 105, with alignment member 140 coupled thereto, is then towed to the installation site, as shown in FIG. 2. Upon reaching the installation site, substructure 105 ballasted to the desired depth, as shown in FIG. 3. Topside 100, with the remaining components of docking system 110 coupled thereto, is next towed to substructure 105 and floated over substructure 105 using a barge 107, as previously described and shown. After topside 100 is substantially aligned over substructure 105, the docking procedure begins.

Substructure 105 is deballasted such that substructure 105 rises upward to engage topside 100. As will be described, docking system 110 enables alignment of topside 100 with substructure 105 and eliminates the banging of topside 100 against substructure 105 experienced during a conventional docking procedure. Referring again to FIG. 1, substructure 105 is deballasted such that substructure 105 is positioned proximate topside 100, yet not close enough to permit topside 100 to contact or bang against substructure 105 as barge 107 (FIG. 3) supporting topside 100 moves with the motion of the surrounding water 230 (FIG. 3).

Next, damping system 130 is actuated to extend docking pin 135 downward through deck column member 120 toward alignment member 140. Compressed gas 210 is injected into upper chambers 175 of housings 165, causing pistons 170, and thus docking pin 135, to displace downward. Turning now to FIG. 4, docking pin 135 is shown fully extended by damping system 130. Also, as shown, deballasting of substructure 105 has brought docking pin 135 into contact with upper surface 125 of substructure 105, such that alignment member 140 is received within receptacle 225 of docking pin 135. Once docking pin 135 is seated over alignment member 140 in this manner, lateral movement of topside 100 relative to substructure 105 is prevented. Thus, topside 100 is laterally aligned relative to substructure 105. Due to the structural integrity of docking pin 135 and its ability to withstand lateral loads exerted on it by alignment member 140 as topside 100 shifts laterally relative to substructure 105, docking pin 135 remains aligned over alignment member 140 for the remainder of the docking procedure.

However, because the load of topside 100 has not yet been transferred to substructure 105, topside 105 continues to move vertically relative to substructure 105 due to the motion of barge 107. Docking system 110 accommodates the relative vertical movement of topside 100, while at the same time, maintains engagement of docking pin 135 with substructure 105 over alignment member 140 and prevents banging of topside 100 against substructure 105. As barge 107 supporting topside 100 falls with the surrounding water 230, the contact force between docking pin 135 and substructure 105 increases. When this force exceeds the force exerted against pistons 170 by gas 210 in upper chambers 175, docking pin 135 translates upward within deck column member 120. Due to the presence of pressurized gas 210 in upper chambers 175, translation of docking pin 135 in this manner is smooth and limited. As docking pin 135 translates upward, gas source 205 controls the pressure of gas 210 in upper chambers 175 to provide sufficient force on docking pin 135 such that docking pin 135 remains in contact with substructure 105. At the same time, gas 210 is compressed by the upward translation of docking pin 135. The compression of gas 210 enables gas 210 to absorb the energy of relative movement between topside 100 and substructure 105 and to resist any tendency for topside 100 to impact or bang against substructure 105. Thus, damping system 130 maintains engagement of docking pin 135 with substructure 105 and simultaneously prevents banging of topside 100 against substructure 105.

Conversely, as barge 107 rises with the surrounding water 230, the contact load between docking pin 135 and substructure 105 decreases. When the force exerted by pressure of gas 210 in upper chambers 175 on pistons 170 exceeds the force on docking pin 135, docking pin 135 translates downward within deck column member 120. Due to the presence of fluid 220 in lower chambers 180, translation of docking pin 135 in this manner is smooth. As docking pin 135 translates downward, gas source 205 controls the pressure of gas 210 in upper chambers 175 to provide sufficient force on docking pin 135 such that docking pin 135 remains in contact with substructure 105. Thus, as topside 100 rises and falls relative to substructure 105, damping system 130 responds continuously to maintain engagement of docking pin 135 with substructure 105. Further, damping system 130 absorbs and resists the force exerted on docking pin 135 due to vertical displacement of topside 100 relative to substructure 105 so that topside 100 does not bang against substructure 105.

Meanwhile, the docking procedure continues with further deballasting of substructure 105. Substructure 105 continues to rise relative to topside 100. As the two structures 100, 105 approach one another, damping system 130 continues to absorb the energy from relative vertical movement of structures 100, 105 and to resist downward movements of topside 100 relative to substructure 105 due to motions of barge 107, as described above. When the relative movement of topside 100 and substructure 105 is small, damping system 130 responds to allow docking pin 135 to translate smoothly upward within deck column member 120 until substructure 105 contacts topside 100.

After substructure 105 contacts topside 100, continued deballasting of substructure 105 enables load transfer of topside 100 from the barge to substructure 105. In other words, substructure 105 begins to lift topside 100 front the barge. When approximately twenty percent of the topside load has been transferred to substructure 105, the relative motion of topside 100 and substructure 105 is very small, meaning topside 100 and substructure 105 move together as a single body. At this point, topside 100 can be safely set down on substructure 105. Further deballasting of substructure 105 enables complete transfer of the topside load from the barge to substructure 105. When the load of topside 100 is completely supported by substructure 105, the docking procedure is complete. Topside 100 may then be coupled to substructure 105 through welding or other means, and the barge subsequently released from topside 100.

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 engaging a topside with a substructure during float-over installation of the topside, the system comprising:

an alignment member coupled to the substructure;

an extendable member coupled to the topside, the extendable member having a receptacle configured to receive the alignment member; and

a damping system configured to move the extendable member into engagement with the substructure, wherein the alignment member is received within the receptacle.

2. The system of claim 1, wherein the damping system is further configured to:

apply force to the extendable member; and

resist force from the extendable member.

3. The system of claim 2, wherein the damping system is configured to resist force from the extendable member due to downward movement of the topside relative to the substructure.

4. The system of claim 2, wherein the damping system is configured to apply force to the extendable member when the topside moves upward relative to the substructure.

5. The system of claim 2, wherein the damping system is further configured to allow the extendable member to retract with relative vertical movement of the topside and the substructure are less than a predetermined amount.

6. The system of claim 2, wherein the extendable member remains engaged with the substructure under the force applied to the extendable member.

7. A system for engaging a topside with a substructure during float-over installation of the topside, the system comprising:

an alignment member coupled to the substructure;

an extendable member coupled to the topside, the extendable member having a receptacle configured to receive the alignment member; and

a damping system comprising: a piston-rod assembly comprising: a piston slideably disposed with a housing, wherein a first chamber and a second chamber are formed; and a rod coupled between the piston and the extendable member; a source of pressurized gas coupled to the first chamber; and an accumulator containing fluid coupled to the second chamber.

8. The system of claim 7, wherein the damping system is configured to resist force from the extendable member by injecting pressurized gas into the first chamber, wherein the pressurized gas reacts against the force of the extendable member.

9. The system of claim 8, wherein the damping system is further configured to allow the pressurized gas in the first chamber to compress under the force of the extendable member.

10. The system of claim 9, wherein the damping system is further configured to exhaust a portion of the pressurized gas from the first chamber when compressed.

11. The system of claim 9, wherein fluid is drawn into the second chamber as the pressurized gas is compressed.

12. The system of claim 9, wherein the extendable member is retractable as the pressurized gas is compressed.

13. The system of claim 7, wherein the damping system is configured to apply force to the extendable member by injecting pressurized gas into the first chamber, wherein the pressurized gas exerts force against the piston.

14. The system of claim 13, wherein the extendable member is extendable under the force applied by the pressurized gas against the piston.

15. The system of claim 14, wherein the damping system is further configured to exhaust fluid from the second chamber into the accumulator as the extendable member extends.

16. The system of claim 14, wherein the extendable member remains engaged with the substructure under the force applied by the pressurized gas against the piston.

17. The system of claim 14, wherein pressurized gas is drawn into the first chamber as the extendable member extends.

18. A method for engaging a topside with a substructure during float-over installation of the topside, the method comprising:

extending a member having a receptacle from the topside to engage an alignment member coupled to the substructure;

applying force to the member to resist downward motion of the topside relative to the substructure; and

applying force to the member to maintain engagement of the member with the substructure in response to upward motion of the topside relative to the substructure.

19. The method of claim 18, further comprising retracting the member when the relative vertical movement between the topside and the substructure reaches a predetermined amount as the substructure is deballasted.

20. The method of claim 18, wherein the extending comprises injecting a pressurized gas into a first chamber, wherein the pressurized gas exerts force on a piston coupled to the extendable member, wherein the piston translates.

21. The method of claim 20, further comprising exhausting fluid from a second chamber as the piston translates.

22. The method of claim 18, wherein the applying force to the member to resist downward motion comprises injecting a pressurized gas into a chamber, wherein the pressurized gas exerts force against a piston coupled to the extendable member.

23. The method of claim 18, wherein the applying force to the member to maintain engagement comprises injecting a pressurized gas into a chamber, wherein the pressurized gas exerts force on a piston coupled to the extendable member, wherein the piston translates.

24. The method of claim 23, further comprising exhausting fluid from a second chamber as the piston translates.