SUPPORT SPACER FOR SEMI-SUBMERSIBLE

Abstract

A semi-submersible offshore structure, including a deck supported by a plurality of support columns, a submersible pontoon structure having the plurality of support columns extending to the deck therefrom, and a support spacer disposed between a sea bed and the pontoon structure.

Description

FIELD OF THE DISCLOSURE

Embodiments disclosed herein generally relate to a support spacer. More specifically, embodiments disclosed herein relate to a support spacer for use in offshore environments with a semi-submersible platform.

BACKGROUND OF INVENTION

In oilfield exploration and production operations, floating vessels, such as semi-submersibles (“semis”), are commonly used for various offshore tasks, including, but not limited to, drilling rigs, production platforms, safety platforms, and heavy lift cranes. For example, in an offshore environment with water depth greater than 120 meters, semis are used where a fixed structure is not practical to build, maintain, or support at such great water depths. Furthermore, semis may be advantageous over other floating vessels, such as drillships, as drillships can be unstable in rough offshore conditions having large waves and strong tidal forces. As would be understood by one having ordinary skill, offshore semis are not limited to the aforementioned water depths described in the above example

SUMMARY OF INVENTION

In general, in one aspect, the present disclosure relates to a semi-submersible offshore structure including a deck supported by a plurality of support columns, a submersible pontoon structure having the plurality of support columns extending to the deck therefrom, and a support spacer disposed between a sea bed and the pontoon structure.

In general, in another aspect, the present disclosure relates to an apparatus to support a semi-submersible having a pontoon structure, the apparatus including a support spacer configured to be disposed on a sea bed, in which the support spacer is configured to have the pontoon structure disposed thereon, and in which the support spacer is separable from the pontoon structure.

In general, in yet another aspect, the present disclosure relates to a method to submerge a semi-submersible offshore structure, the method including submerging a semi-submersible comprising a pontoon structure having a plurality of support columns connected thereto, and supporting the semi-submersible with a support spacer, in which the support spacer is disposed on a sea bed, in which the pontoon structure is disposed on the support spacer, and in which the support spacer is separable from the pontoon structure.

Other aspects and advantages of the disclosure will be apparent from the following description and the appended claims.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A-1D show side views of a semi-submersible in several different offshore environments in accordance with one or more embodiments of the present disclosure.

FIG. 2 shows a side view of a semi-submersible and support spacers in accordance with one or more embodiments of the present disclosure.

FIG. 3 shows a cross-section of a semi-submersible pontoon and a support spacer in accordance with one or more embodiments of the present disclosure.

FIG. 4 shows a top view of a portion of semi-submersible pontoon and a support spacer in accordance with one or more embodiments of the present disclosure.

DETAILED DESCRIPTION

Specific embodiments of the present disclosure will now be described in detail with reference to the accompanying figures. Like elements in the various figures may be denoted by like reference numerals for consistency. Further, in the following detailed description of embodiments of the present disclosure, numerous specific details are set forth in order to provide a more thorough understanding of the invention. However, it will be apparent to one of ordinary skill in the art that the embodiments disclosed herein may be practiced without these specific details. In other instances, well-known features have not been described in detail to avoid unnecessarily complicating the description.

Furthermore, those having ordinary skill in the art will appreciate that when describing a first element and a second element disposed thereon, it is understood that disposing may be either directly disposing the first element on the second element, or indirectly disposing the first element on the second element. For example, a first element may be directly disposed on a second element, such as by having the first element and the second element in direct contact with each other, or a first element may be indirectly disposed on a second element, such as by having a third element, and/or additional elements, disposed between the first and second elements.

Additionally, those having ordinary skill in the art will appreciate that when describing a first element having a second element connected thereto, it is understood that connecting may be either directly connecting the first element to the second, or indirectly connecting the first element to the second element. For example, a first element may be directly connected to a second element, such as by having the first element and the second element in direct contact with each other, or a first element may be indirectly connected to a second element, such as by having a third element, and/or additional elements, connected between the first and second elements.

In one aspect, embodiments disclosed herein generally relate to a support spacer for use in offshore environments with a semi-submersible. In addition, the support spacer may be designed for use with offshore vessels, in particular, offshore floating vessels, such as submersibles or other surface floating vessels. Additionally, the offshore vessels may be in any marine environment without departing from the scope of the present disclosure.

FIGS. 1A-1D illustrate side views of a semi-submersible 113 in different offshore marine environments. Referring to FIGS. 1A-1D, a deck 101 sits above a surface of water 111. The deck 101 is typically used for drilling, production, or other operations and therefore operating equipment, personnel, and operation gear may be disposed thereon. The deck 101 may be supported by one or more support columns 103A and 103B. In one or more embodiments, the support columns 103A and 103B may have multiple sides (i.e., may have polygonal cross-sections). In particular, the support columns 103A and 103B may have four, five or six sides (not shown). In alternative embodiments, support columns 103A and 103B may have circular or oval cross-sections.

As shown in FIGS. 1A-1D, the deck 101 is disposed on support columns 103A and 103B and is therefore kept away from any large waves at the surface of the water 111. Support columns 103A and 103B are used to support the deck 101, but may also serve as storage. In addition, support columns 103A and 103B may be subdivided into chambers which can be ballasted to help stabilize the semi-submersible 113 while offshore. As shown, a pontoon base 105 may have support columns 103A and 103B disposed thereon and/or connected thereto. The pontoon base 105 may be substantially rectangular in shape from a side view perspective, a plan view perspective, or both. One having ordinary skill would know that the shape of the pontoon base, deck, and support column(s) are not limited to those shapes, sizes, arrangements, and configurations shown in the figures and described above.

In addition, referring to FIGS. 1A-D, the semi-submersible 113 may obtain buoyancy from additional ballastable pontoons or ballastable columns. As such, the ballasted structure(s) (ballasted pontoons or ballasted columns or both) may be filled with water or any other ballasting material or combination of materials (during a process known as ballasting) or may release water or any other ballasting material or combination of materials (during a process known as deballasting) to stabilize the semi-submersible 113.

Referring to FIG. 1A, a semi-submersible 113 is shown in an ultra shallow marine environment. In an ultra shallow marine environment, the depth of the water 111 may be anywhere between about 20 feet (6 meters) and about 70 feet (21 meters). Further, in this environment, the semi-submersible 113 may be adapted to be disposed on a seabed 109, as shown. In this example, pontoon base 105 may be disposed on the seabed 109 and may be affixed to the seabed 109 using an affixing means (not shown) in order to affix the pontoon base 105 and ultimately, the semi-submersible 113, to the seabed 109.

Referring to FIG. 1B, a side view of a semi-submersible 113 in a shallow marine environment is shown. In this environment, water depths may be anywhere between about 120 feet (36.5 meters) and about 1,000 feet (304 meters). As shown in FIG. 1B, the semi-submersible 113 may be anchored to the seabed 109 by anchor lines 107A and 107B. Anchor lines 107A and 107B may be wires, chains, or any other anchoring device known in the art capable of keeping the semi-submersible in a proper position with respect to the seabed 109. One of ordinary skill in the art would know and appreciate that anchor lines 107A and 107B may not be limited to only two lines as shown in this example. Particularly, the semi-submersible 113 may be anchored by any number of anchor lines.

Referring to FIG. 1C, a side view of a semi-submersible 113 in a deep marine environment is shown. In this environment, water depths may be anywhere between about 1,000 feet (304 meters) and about 10,000 ft (3048 meters), although, a deep marine environment may include water depths over 10,000 feet. Similar to FIG. 1B, as shown in FIG. 1C, the semi-submersible 113 may be anchored to the seabed 109 by anchor lines 107A and 107B. Anchor lines 107A and 107B may be wires, chains, or any other anchoring device known in the art capable of keeping the semi-submersible in a proper position with respect to the seabed 109. One of ordinary skill in the art would know and appreciate that anchor lines 107A and 107B may not be limited to only two lines as shown in this example. Particularly, the semi-submersible 113 may be anchored by any number of anchor lines.

Referring to FIG. 1D, a side view of a semi-submersible 113 in a very shallow marine environment is shown. Here, water depths may be anywhere between about 70 ft. and about 120 ft. In this type of environment, if the semi-submersible were to be disposed on the seabed, the deck 101 would be too close to the surface of the water 111 for proper operation.

Furthermore, referring to a very shallow marine environment as shown in FIG. 1D, during high tide and low tide, it may not be practical or feasible to anchor the semi-submersible 113 to the seabed 109. Similarly, it may not be practical or feasible to dispose the semi-submersible 113 on the seabed 109. Moreover, in this environment and because of the impracticality of anchoring or disposing the semi-submersible 113, the semi-submersible 113 may come in contact with the seabed 109. In addition, during rough sea conditions in a very shallow marine environment, the semi-submersible 113 may also come in contact with the seabed 109. In these instances, the contact may result in damage to the semi-submersible 113, damage to the pontoon base 105, damage to the support columns 103A and 103B, and/or instability of the semi-submersible 113. Thus, operating a semi-submersible 113 in this environment may not be ideal due to the many risks associated with the conditions of a very shallow marine environment. In addition, depending on the varying sea conditions and water depth in some environments, it may not even be possible to operate a semi-submersible 113.

As understood by one having ordinary skill in the art, semi-submersibles, similar to semi-submersible 113 above, may be built to accommodate many different water depths. As such, the water depths described herein are for illustrative purposes only and are provided as a means to exemplify different marine environments and operating conditions. Furthermore, damages to the semi-submersible 113 may result from one or any combination of the different sea environments and conditions described above. One of ordinary skill in the art would know and appreciate that the environments and conditions are not limited to those described above.

Referring now to FIG. 2, a semi-submersible 213 is shown in very shallow water in accordance with embodiments disclosed herein. As shown, a deck 201 of a semi-submersible 213 sits above a surface of water 211. Similar to FIGS. 1A-1D, the deck 201 may be used for drilling, production, or other operations and therefore operating equipment, personnel, and operation gear may be disposed thereon. The deck 201 may be supported by one or more support columns 203A and 203B.

In FIG. 2, support columns 203A and 203B are used to support the deck 201, but may also serve as storage. In addition, support columns 203A and 203B may be ballasted to help stabilize the semi-submersible 213 while offshore. As shown in FIG. 2, a pontoon base 205 has support columns 203A and 203B disposed thereon. The pontoon base 205 may be substantially rectangular in shape from a side view perspective, a plan view perspective, or both. One having ordinary skill would know that the shape, size, arrangement, and configuration of the pontoon base, deck, and support column(s) are not limited to those shown in the figures and described above.

In addition, referring to FIG. 2, the semi-submersible 213 may obtain buoyancy from additional ballastable pontoons or ballastable columns. As such, the ballasted structure(s) (ballasted pontoons or ballasted columns or both) may be filled with water or any other ballasting material or combination of materials (during a process known as ballasting) or may release water or any other ballasting material or combination of materials (during a process known as deballasting) to stabilize the semi-submersible 213.

In accordance with one or more embodiments of the present disclosure, any number of support spacers 215A and 215B may be used to support a semi-submersible 213 in a very shallow environment, as shown in FIG. 2. Here, water depths may be anywhere between about 70 ft. and about 120 ft. In particular, support spacers 215A and 215B may be disposed between the pontoon base 205 and the seabed 209. Support spacers 215A and 215B may comprise metal, steel, concrete, or any other material or combination of materials known in the art. At least one of support spacers 215A and 215B may be configured for and/or used for storage. One having ordinary skill would know that the shape, size, arrangement, and configuration of the pontoon base and support spacer(s) are not limited to those shown in the figures and described above.

In addition, the support spacers 215A and 215B may be removably attached to the semi-submersible 213 using one or more attachment devices (not shown). In particular, the support spacers 215A and 215B may be removably attached to the pontoon base 205, at least one of the support columns 203A or 203B, and or at least one of plurality of pontoon sections of the pontoon base 205 using one or more attachment devices (not shown). In addition, the support spacers 215A and 215B may be detached from the pontoon base 205, at least one of support columns 203A and 203B, and/or at least one of a plurality of pontoon sections of the pontoon base 205. Furthermore, the one or more attachment devices (not shown) may be attached to or detached from the support spacers 215A and 215B, the pontoon base 205, at least one of support columns 203A and 203B, and/or at least one of a plurality of pontoon sections of the pontoon base 205. For example, the one or more attachment devices may include hook elements, wires, lines, cables, and/or any other attachment device known in the art. Further, the support spacers 215A and 215B may be attached to the semi-submersible 213 and affixed to the seabed 209.

The support spacers 215A and 215B may be affixed to the seabed 209 using an affixing device (not shown). For example, the one or more affixing devices may include piles, sea bed penetrating skirts, hook elements, wires, lines, cables, and/or any other affixing device known in the art. In particular, support spacers 215A and 215B may be removably affixed to the seabed 209 using one or more affixing devices (not shown). As shown in FIG. 2, the support spacers 215A and 215B may include affixing members 217A and 217B.

Affixing members 217A and 217B may comprise metal, steel, concrete, or any other material or combination of materials known in the art. The affixing members 217A and 217B may penetrate the seabed 209, as shown. In addition, the affixing members 217A and 217B may be arranged spanning the entire height of the support spacers 215A and 215B. Further, the affixing members 217A and 217B may be arranged spanning a portion of the height of the support spacers 215A and 215B. The affixing members 217A and 217B may be included in the one or more affixing devices (not shown). One of ordinary skill in the art would know and appreciate that the affixing members 217A and 217B and support spacers 215A and 215B may not be limited to the above arrangement and configuration.

Referring to FIG. 2, the support spacers 215A and 215B may include one or more guide members 219. The one or more guide members 219 may comprise metal, steel, concrete, or any other material or combination of materials known in the art. In addition, the one or more guide members may include support beam(s), pole(s), and/or any other structural member(s) known in the art. The one or more guide members 219 may be disposed on the support spacers 215A and 215B, as shown. Alternatively, the one or more guide members 219 may be disposed along a portion or the entire height of the support spacers 215A and 215B. Further, the one or more guide members 219 may extend through or along the pontoon base 205, as shown. Alternatively, the one or more guide members 219 may extend through or along a support column 203A or 203B (not shown). In addition, the one or more guide members 219 may extend through or along the pontoon base and a support column 203A or 203B (not shown).

Additionally, in one or more embodiments, the semi-submersible 213 may be guided by one or more guide members 219 when disposing the semi-submersible 213 on the support spacers 215A and 215B. In addition, the support spacers 215A and 215B may be disposed on or affixed to the seabed 209 prior to guiding the semi-submersible 213. Alternatively, the support spacers 215A and 215B may be attached to the semi-submersible 213 and the support spacers 215A and 215B and the semi-submersible 213 disposed on the seabed 209. In addition, the support spacers 215A and 215B and the semi-submersible 213 may be guided onto the seabed 209 by seabed guide members (not shown). Further, the support spacers 215A and 215B may not include one or more guide members 219. In addition, the support spacers 215A and 215B may not include affixing members 217A and 217B.

Referring to FIG. 2, the support spacers 215A and 215B may be about 30 ft. in height. However, the height of the support spacers 215A and 215B may be anywhere between about 10 ft. and about 50 ft. In addition, the support spacers 215A and 215B may have different heights or may be placed at different positions along the pontoon base 205. In addition, a portion of either or both of support spacers 215A and 215B may additionally penetrate the seabed 209 in order to level and stabilize the semi-submersible 213, and to prevent sea bed scour in way of the support spacers due to water movement.

One of ordinary skill in the art would know that the illustration in FIG. 2 may not be limited to the arrangement described above. Furthermore, the number of affixing members, guide members, and support spacers may not be limited to the illustrations and descriptions above.

FIG. 3 shows a cross section view of a pontoon section 301 of a pontoon base disposed on a spacer section 303 of a support spacer in accordance with one or more embodiments of the present disclosure. The pontoon section 301 may be substantially rectangular with rounded corners from a cross-sectional perspective, as shown. However, one of ordinary skill in the art would appreciate that the pontoon section 301 may be any other shape and may include rounded, squared, or chamfered corners (not shown).

In addition, spacer section 303 may include one or a plurality of support members 305, as shown in FIG. 3. The support members 305 are used to support the spacer section 303 and ultimately, the pontoon section 301. The support members 305 may comprise metal, steel, concrete, or any other material or combination of materials known in the art. Further, spacer section 303 may include a lower portion 307 that may be disposed on a seabed (not shown). The lower portion 307 may also be affixed to a seabed by one or more affixing members and/or one or more an affixing devices (not shown). In addition, one or more affixing members and/or one or more affixing devices may extend through or along a portion or an entire height of the spacer section 303 (not shown). Alternatively, affixing members and/or affixing devices may extend from pontoon section 301 to seabed, retaining spacer section 303 therebetween.

Referring to FIG. 3, spacer section 303 may include an upper portion 309. The upper portion 309 may be configured to have the pontoon section 301 disposed thereon, as shown. In addition, or in the alternative, the spacer section 303 may be attached to the pontoon section 301 using one or more attachment devices (not shown). Further, the spacer section 303 may include guide members in order to properly guide or position the pontoon section 301 onto the spacer section 303 (not shown).

As shown in FIG. 3, the spacer section 303 may have an outer portion 311 disposed adjacent to the upper portion 309. The outer portion 311 may be at a greater height than the upper portion 309, as shown. As shown in this example, the outer portion 311 may be configured to coincide with the shape of the pontoon section 301. Further, the outer portion 311 may be used to guide the pontoon section 301 into a proper position with respect to the spacer section 303. In addition, the outer portion 311 may be configured to support the pontoon section 301 in order to prevent or limit movement of the pontoon section 301 with respect to the spacer section 303. Furthermore, the outer portion 311 may extend along a portion or an entire length of the pontoon section 301.

In one or more embodiments, the outer portion 311 may extend outwardly away from the pontoon section 301 in order to provide additional support and/or stability, as shown. Additionally, a support beam, an affixing member, and/or an affixing device may extend through or along the outer portion 311 (not shown). Further, a support beam, an affixing member, and/or an affixing device may extend through or along the outer portion 311 and the lower portion 307 (not shown).

Additionally, in one or more embodiments, the pontoon section 301 may have additional reinforcement structure(s) therein, disposed thereon, or connected thereto (not shown). Such additional reinforcement structure may be necessary to ensure that pontoon section 301 is mechanically strong enough to transfer loads from the sea floor through spacers 303. The additional reinforcement structure(s) may be used for supporting the pontoon section 301 when the semi-submersible is used in conjunction with the support spacer 303, as shown, for example, in FIG. 3. Alternatively, or in addition, the support spacer may have additional reinforcement structure(s) therein, connected thereto, or disposed thereon in order to support the pontoon section 301. Therefore, one or ordinary skill in the art would know and appreciate that either or both the pontoon section 301 and the support spacer 303 may include additional reinforcement structure(s) in order to properly and adequately support a semi-submersible of one or more embodiments of the present disclosure.

Referring to FIG. 4, a top view of a corner of a ring-shaped pontoon base 401 disposed on a support spacer 403 is shown in accordance with one or more embodiments of the present disclosure. The support spacer 403 may include spacer sections 403A and 403B. As understood by one having ordinary skill, the support spacer 403 may not be limited to only two spacer sections 403A and 403B as shown. The support spacer 403 may include any number of spacer sections.

Additionally, support spacer 403 may include one or more support beams 405. The plurality of support beams 405 are used to support the pontoon base 401. In addition, one or more support beams 405 may connect to each other along a portion of or the entirety of the one or more support beams 405. The one ore more support beams 405 may be disposed against or along one another. Furthermore, the one or more support beams 405 may or may not be disposed or connected to one another. Referring to FIG. 4, the support beams 405 may be part of either spacer section 403A or 403B. The support beams 405 may also be part of both or neither of the spacer sections 403A and 403B. Moreover, the one or more support beams 405 may include beams, poles, and/or any other structural members known in the art.

Further, as shown in FIG. 4, the pontoon base 401 may be properly positioned with respect to the support spacer 403 using guide members 407A, 407B, and 407C. The guide members 407A, 407B, and 407C may be disposed along or against the outside of the pontoon base 401. In addition, the guide members 407A, 407B, and 407C may be disposed through a portion of the pontoon base 401 (not shown). The guide members 407A, 407B, and 407C may include beams, poles, and/or any other structural members known in the art. The guide members 407A, 407B, and 407C may be generally rectangular in cross-section as shown by guide members 407A. Further, the guide members 407A, 407B, and 407C may be generally circular in cross-section as shown by guide members 407B. In addition, the guide members 407A, 407B, and 407C may include a cross-section designed to coincide with the shape of the pontoon base 401 as shown by guide members 407C. The arrangement, size, and shape of the guide members 407A, 407B, and 407C may correspond to the arrangement, size, and shape of the pontoon base 401 and/or the support spacer 403. Accordingly, one having ordinary skill would know that the shape, size, arrangement, and configuration of the guide members and support spacer(s) are not limited to those shown in the figures and described above.

The pontoon section 401 may be substantially rectangular with rounded corners from a cross-sectional perspective, as shown. In one or more embodiments, the support spacer 403 may be disposed beneath a corner of the pontoon base 401, as shown. In addition, the support spacer 403 may be disposed beneath one or a plurality of support columns (not shown). Alternatively, the support spacer 403 may be disposed along a portion or the entire length of the pontoon base 401. As such, one having ordinary skill would know that the support spacer 403 may not be limited to the above arrangement.

For example, in one or more embodiments, a semi-submersible may include a pontoon base with four support columns disposed thereon. In particular, the pontoon base may be generally rectangular in shape and a support column may be disposed at each corner of the pontoon base. Additionally, a support spacer may be disposed beneath each of the four support columns and beneath the pontoon base. Further, in one or more embodiments, the support space may be disposed between a seabed and the semi-submersible. The number of support spacers used to support the semi-submersible may correspond to the number and size of the support columns, a number and size of pontoon sections of the pontoon base, and/or the environment.

In particular, in one or more embodiments, the seabed may be uneven and/or unlevel. In this case, the number of spacers and the height of each spacer used to support the semi-submersible may vary. For example, in the case of a pontoon base with four support columns disposed thereon, the semi-submersible may only be support by one, two, or three support spacers if part of the pontoon rests directly on the seabed. Each spacer may vary in height from about 10 ft. to about 50 ft in order to stabilize and/or level the semi-submersible. One of ordinary skill would know and appreciate that the number of columns and spacers and the height of the spacers are for illustrative purposed only and any number of support spacers with any combination of respective heights may be included in the embodiments discussed herein. Additionally, one having ordinary skill will appreciate that the height of each spacer may be adjustable to accommodate a variety of water depth installations.

A support spacer or semi-submersible structure in accordance with one or more embodiments of the present disclosure may be beneficial in multiple areas, such as within the oil and gas industry. In one or more embodiments, the support spacer may be used to prevent damage the semi-submersible, damage to the support columns and, damage to the pontoon structure, and/or to stabilize the semi-submersible while offshore.

Further, in rough sea conditions, during high tide or low tide conditions, or in a very shallow marine environment, the support spacer may be used in order to allow the semi-submersible to be operated. Therefore, the support spacer may be advantageously used in offshore operations in a very shallow marine environment. In addition, as the support spacer may be attached to or detached from the semi-submersible, the semi-submersible may continue to operate in ultra shallow, shallow, and deep marine environments while having the capability of working in a shallow marine environment using the support spacer. Accordingly, a semi-submersible adapted to use the support spacer may be capable of operating in almost any marine environment.

Advantageously, embodiments disclosed herein may allow a rig operator to use a single semi-submersible platform in a variety of water depths that would otherwise require the use of an alternative type (e.g., a “jack-up” rig) of offshore platform. By adapting a single style of offshore platform (i.e., the semi-submersible) to function properly in a full variety of water depths and sea floor conditions, such operators may save costs and rig-up and rig-down times that would otherwise be associated with maintaining a fleet of several different designs. Thus, a single semi-submersible vessel could advantageously operate in a variety of locations that would otherwise dictate the use of a submersible, jack-up, drillship, and/or SPAR-type offshore vessel.

While the present disclosure has been described with respect to a limited number of embodiments, those skilled in the art, having benefit of this disclosure, will appreciate that other embodiments may be devised which do not depart from the scope of the disclosure as described herein. Accordingly, the scope of the disclosure should be limited only by the attached claims.

Claims

1. A semi-submersible offshore structure, comprising:

a deck supported by a plurality of support columns;

a submersible pontoon structure having the plurality of support columns extending to the deck therefrom; and

a support spacer disposed between a sea bed and the pontoon structure.

2. The structure of claim 1, wherein the pontoon structure comprises a plurality of pontoon sections connecting the plurality of support columns.

3. The structure of claim 2, wherein the support spacer supports at least one of the plurality of pontoon sections.

4. The structure of claim 1, wherein at least one of the plurality of support columns comprises a polygonal cross-section.

5. The structure of claim 1, wherein at least one of the plurality of support columns comprises a circular cross-section.

6. The structure of claim 1, wherein the support spacer comprises a plurality of spacer sections.

7. The structure of claim 6, wherein at least one of the plurality of spacer sections is disposed underneath at least one of the plurality of support columns.

8. The structure of claim 1, wherein the support spacer is detachable from the pontoon structure.

9. The structure of claim 1, wherein the support spacer is configured to have the pontoon structure disposed thereon prior to placing the semi-submersible in a position for use.

10. The structure of claim 1, wherein the support spacer is configured to be disposed on the sea bed prior to placing the semi-submersible in a position for use.

11. The structure of claim 1, wherein at least one of the semi-submersible and the support spacer comprises an attachment device to attach the pontoon structure to the support spacer.

12. The structure of claim 1, wherein the support spacer is configured to be affixed to the sea bed.

13. The structure of claim 1, wherein the pontoon structure is configured to be affixed to the sea bed, retaining the support spacer therebetween.

14. The structure of claim 1, wherein at least one of the semi-submersible and the support spacer comprises at least one guiding member to guide the semi-submersible when disposing the pontoon structure on the support spacer.

15. An apparatus to support a semi-submersible having a pontoon structure, the apparatus comprising:

a support spacer configured to be disposed on a sea bed,

wherein the support spacer is configured to have the pontoon structure disposed thereon, and

wherein the support spacer is separable from the pontoon structure.

16. The apparatus of claim 15, wherein the pontoon structure comprises a plurality of pontoon sections connecting a plurality of support columns.

17. The apparatus of claim 15, wherein the support spacer comprises a plurality of spacer sections with at least one of the plurality of spacer sections is positioned underneath at least one of the plurality of support columns.

18. The apparatus of claim 15, wherein the support spacer is configured to have the pontoon structure disposed thereon prior to placing the semi-submersible in a position for use.

19. The apparatus of claim 15, wherein the support spacer is configured to be disposed on the sea bed prior to placing the semi-submersible in a position for use.

20. The apparatus of claim 15, wherein at least one of the semi-submersible and the support spacer comprises an attachment device to attach the pontoon structure to the support spacer.

21. The apparatus of claim 15, wherein the support spacer is configured to be affixed to the sea bed and wherein at least one of the sea bed.

22. The apparatus of claim 15, wherein at least one of the semi-submersible and the support spacer comprises at least one guiding member to guide the semi-submersible when disposing the pontoon structure on the support spacer.

23. A method to submerge a semi-submersible offshore structure, the method comprising:

submerging a semi-submersible comprising a pontoon structure having a plurality of support columns connected thereto; and

supporting the semi-submersible with a support spacer,

wherein the support spacer is disposed on a sea bed,

wherein the pontoon structure is disposed on the support spacer, and

wherein the support spacer is separable from the pontoon structure.

24. The method of claim 23, further comprising attaching the support spacer to the pontoon structure prior to submerging the semi-submersible.

25. The method of claim 23, further comprising disposing the support spacer on the sea bed prior to submerging the semi-submersible.

26. The method of claim 23, wherein at least a portion of the support spacer penetrates the sea bed.