Application No. 62/329,899, filed on April 29, 2016, which is incorporated by reference herein in its entirety.

BACKGROUND OF THE DISCLOSURE

[0002] This disclosure relates to a flotation module, system, and method for reducing the load force applied to an offshore platform by a tubular string.

SUMMARY OF THE DISCLOSURE

10003] Described herein is an apparatus for reducing a load force applied to an offshore platform by a tubular string. The apparatus includes a flotation module. The flotation module has an internal core made of a buoyant material. The internal core forms an inner bore wall for accommodating the tubular string. The flotation module includes a first section, second section, and an interlocking means. The first section has a C-shaped interior profile. The first section includes a base portion, a first kg portion, and a second leg portion, 1 ^" he base portion interconnects the first leg portion and the second leg portion of the first section. The first leg portion nd second leg portion of the first section each have an end face. The second section has a C-shaped interior profile. The second section includes a base portion, a first leg portion, and a second leg portion. The base portion interconnects the first leg portion and the second leg portion of the second section. The first leg portion and the second leg portion of the second section each have an end face. The interlocking means is configured to slidably engage the first and second sections into an operative arrangement about the tubular string by detachably interlocking the end faces of the first and second leg portions of the first section to the end faces of the first and second leg portions of the second section.

[0004] in one embodiment, the interlocking means includes a first projection and a first recess. The first projection extends from the end face of the first leg portion of the first section. The first projection has a contoured profile with a smaller diameter proximal section and a larger diameter distal section. The first recess is positioned within the end face of the first leg portion of the second section. The first recess is shaped to siidabiy receive the contoured profile of the first projection and provide an interlocking dovetail joint between the first and second sections.

[ 5) I.n a further embodiment, the interlocking means also includes a second projection and a second recess. The second projection extends from the end face of the second leg portion of the second section. The second projection has a contoured profile with a smaller diameter proximal section and a larger diameter distal section. The second recess is positioned within the end lace of the second leg portion of the first section. The second recess is shaped to siidabiy receive the contoured profile of the second projection and provide an interlocking dovetail joint between the first and second sections. C 9 i?| In another embodiment the interlocking means also includes a second projection and a second recess, in this embodiment, the second projection extends from the end face of the second leg portion of the first section. The second projection has a contoured profile with a smaller diameter proximal section and a larger diameter distal section, in this embodiment, the second recess is positioned within the end face of the second leg portion of the second section. The second recess is shaped to siidabiy receive the contoured profile of the second projection and provide an interlocking dovetail joint between the first and second sections.

[0007] in one embodiment, each end face of the first and second leg portions of the first section includes an upper section with a planar surface and a lower section with a planar surface; the planar surface of the upper section extends outwardly beyond the planar surface of the lower section, in this embodiment, each end face of the first and second ieg portions of the second section includes an upper section with a planar surface and a lower section with a planar surface; the planar surface of the lower seciion extends outwardly beyond the planar surface of the upper section. Also, in this embodiment, the interlocking means includes a first projection, a second projection, a third projection, a fourth projection, a first recess, a second recess, a third recess, and a fourth recess. The first projection extends from the planar surface of the upper section of the end fa.ee of the first ieg portion of the first section. The first projection has a contoured profile with a smaller diameter proximal section and a larger diameter distal section. The second projection extends from the planar surface of the upper section of the end face of the second leg portion of the first section. The second projection has a contoured profile with a smaller diameter proximal section and a larger diameter distal section. The third projection extends from the planar surface of the upper section of the end face of the first leg portion of the second section. The third projection has a contoured profile with a smaller diameter proximal section and a larger diameter distal section. The fourth projection extends from the planar surface of the upper section of the end face of the second leg portion of the second section. The fourth projection has a contoured profile with a smaller diameter proximal section and a larger diameter distal section. The first recess is positioned within the planar suriace of the lower section of die end face of the first leg portion of the first section. The first recess is shaped to siidably receive the contoured profile of the fourth projection and provide an interlocking dovetail joint between the first and second sections. The second recess is positioned within the planar surface of the lower section of the end face of the second leg portioa of the first section. The second recess is shaped to siidably receive the contoured profile of the third projection and provide an interlocking dovetail joint between d e first and second sections. The third recess is positioned within the planar surface of the lower section of the end face of the first leg portion of the second section. The third recess is shaped to siidably receive the contoured profile of the second projection and provide an interlocking dovetail joint between the first and second sections. The fourth recess is positioned within the planar surface of the lower section of the end face of ^* the second leg portion of the second section. The fourth recess is shaped to siidably receive the contoured profile of the first projection and provide an interlocking dovetail joint between the first and second sections.

{ 0 8J in another embodiment the flotation module has a cylindrical outer surface,

[00 9] In further embodiment, the cylindrical outer surface of the flotation module includes a protective outer layer, jiuJ.Oj in a still further embodiment, the protective outer layer is ^" bonded to the internal core and the protective outer layer has a thickness in the range of 7 to 10 asm, jSSf ! j in yet a further embodiment, the protective outer layer is formed of polyuret! ane. [0012] In one embodiment, the buoyant material in the internal core of the flotation module- is a syntactic foam.

(0013| In another embodiment, the flotation module has a length in the range of 1 to 10 feet,

[0014] in yet another embodiment, the flotation module has an outer diameter in the range of 14 to 22 inches, f ^' 0015) In one embodiment, the inner bore wail of the internal core has an inner diameter in the range of 2 to 8 inches.

[00J 6] in another embodiment the flotation module includes an RF1 D chip. {0017] In still another embodiment the flotation module further includes a locking device securing the first section to the second section. 0018] in one embodiment where the interlocking means includes a first projection extending from die end face of the first leg portion of the first section and a first recess positioned within the end face of the first leg portion of the second section, the contoured profile of the first projection is tapered.

[0019] In one embodiment whe e the interlocking means includes a first projection extending from the end face of the first leg portion of the first section, a second projection extending from the end face of die second leg portion of the second section, a first recess positioned within the end face of the first leg portion of the second section, and a second recess positioned within the end face of the second leg portion of the first section, the contoured profile of the first and second projections are each tapered. [0020] In one embodiment where the interlocking means includes a first projection extending from the end face of the first leg portion of the first section, a second projection extending from the end face of the second leg portion of die first section, a first recess positioned within the first leg portion of the second section, and a. second recess positioned within the end face of the second leg portion of the second section, the contoured profile of the first and second projections are each tapered.

[002 1 in one embodiment where the interlocking means includes a first projection, a second projection, a third projection, and a fourth projection, the first, second, third, and fourth projections are each tapered.

[0022] In another embodiment, the flotation module further includes a stepped section positioned between the upper and lower sections of each end face of the first and second leg portions of the first and second sections. Each stepped section includes a central-planar surface portion, a lower shoulder, and an upper shoulder, ^' The central-planar surface portion has a top edge and a bottom edge. The lower shoulder Is positioned at the bottom edge of the central-planar surface portion and extends to the planar surface of the lower section. The upper shoulder is positioned at the top edge of the central -planar surface portion and extends to the planar surface of the upper section. In this embodiment, when the first and second sections are sSidabiy engaged in the operative arrangement: the lower shoulder of the stepped section of the end face of the second leg portion, of the second section abuts the upper shoulder of the stepped section of the end face of the first leg portion of the first section, the upper shoulder of the stepped section of the end face of the second leg portion of the second section abuts the lower shoulder of the stepped section of the end face of the first leg portion of the first section, the lower shoulder of the stepped section of the end face of the first leg portion of the second section abuts the upper shoulder of the stepped section of the end face of the second leg portion of the first section, and the upper shoulder of the stepped section of the end face of the first leg portion of the second section abuts the lower shoulder of the stepped section of the end face of the second leg portion of the first section.

(0023 ^' j Also described herein a system for reducing a load force applied to an offshore platform by a tubular string. The system includes a plurality of flotation modules positioned about the tubular string in a stacked arrangement to form a first series of stacked flotation modules. The first series of stacked flotation modules has art uppermost flotation module and a lowermost flotation module. Each flotation module has a top end, a bottom end. an outer surface, and an interna! core. The internal core is made of a buoyant material, The internal core forms an inner bore wall for accommodating the tubular string, Each flotation module includes a first section, a second section, an interlocking means, an upper stop collar. and a lower stop collar. The first section of the flotation module has a C-shaped interior profile. The first section of die flotation module includes a base portion, a first leg portion and a second leg portion. The base portion of the first section of the flotation module interconnects the first leg portion to the second leg portion. The first leg portion and second leg portion of the first section of the flotation module each have an end face. The second section of the flotation module has a C-shaped interior profile. The second section of the flotation module includes a base portion, a first leg portion, and a second leg portion; the base portion interconnects the first leg portion and the second leg portion. The first leg portion and the second leg portion of the second section of the flotation module each has an end face. The interlocking means is configured to siidabfy engage the first and second sections of the flotation module into an operative arrangement about the tubular siring by detachably interlocking the end faces of the first and second leg portions of the first section to the end faces of the first and second leg portions of the second section. Each of the upper and lower stop collars has a top end, a bottom end, an outer surface, and an internal portion. The internal portion of the upper and lower stop collars forms an inner bore wall for accommodating the tubular string. Each of the upper and lower stop collars includes a first section, a second section, and a securing means. The first section of the upper and lower stop collars has a C-shaped interior profile. The first section of the upper and lower stop collars includes a base portion, a first leg portion, and a second leg portion; the base portion interconnects the first leg portion and the second leg portion. The first and second leg portions of the first section of the upper and lower stop col lars each has an end face. The second section of the upper and lower stop collars has a C-shaped Inferior profile. The second section of the upper and lower stop collars includes a base portion, a first leg portion, and a second leg portion; the base portion interconnects the first leg portion and the second leg portion . The first and second leg portions of the second section of the upper and lower stop collars each has an end face. The securing means of the upper and lower stop collars is configured to detachably secure the first and second sections of each of the upper and lower stop collars together in an operative arrangement about the tubular string. The upper stop coilar is secured about the tubular string at an upper end of the first series of stacked flotation modules such that the bottom end of the upper stop collar abuts the top end of the uppermost flotation module in the first series of stacked flotation modules. The lower stop collar is secured about the tubular string at a lower end of the first series of stacked flotation modules such that the bottom end of the lower stop collar abuts the bottom end of the lowermost flotation module in the first series of stacked flotation modules. [0024] In a further embodiment, the internal portion of each of the upper and lower stop collars includes a polymer composite frame structure.

[0025] In a further embodiment, the outer surface of each of the upper and lower stop collars is conical iy shaped.

[0026] In a stil l further embodiment, the outer surface of each of the upper and lower stop collars includes a protective outer layer. [0027{ In a further embodiment, the protective outer layer of the outer surface of the upper and lower stop collars is bonded to the composite f ame structure and has a thickness in the range of 7 to 10 mm,

[00:28] in a still further embodiment, the protective outer layer i» formed of polyurethane.

[0029] In one embodiment, the system includes a second series of stacked flotation modules spaced apart from the first series of stacked flotation modules. [0030] In another embodiment of the system, each end face of the first and second leg- portions of the first section of the flotation module includes an upper section with a planar surface and a lower section with a planar surface; the planar surface of the upper section extends beyond the planar surface of the lower section. In this embod.iro.ent, each end face of the first and second leg portions of the second section includes an upper section wit a planar surface and a lower section with a planar surface: the planar surface of the lower section extends outwardly beyond the planar surface of the upper section. Also, in this embodiment, the interlocking means includes a first projection, a second projection, a third projection, a fourth projection, a first recess, a second recess, a third recess, and a fourth recess. The first projection extends from the planar surface of the upper section of the end face of the first leg portion of the first section; the first projection has a contoured profile with a smaller diameter proximal section and a larger diameter distal section. The second projection extends from the planar surface of the upper section of the end face of the second leg portion of the first section; the second projection has a contoured profile with a smaller diameter proximal section and a larger diameter distal section. The third projection extends from the Dianar surface of the upper section of the end face of the first leg portion of the second section; the third projection has a contoured profile with a smaller diameter proximal section and a larger diameter distal section. The fourth projection extends from the planar surface of the upper section of the end face of the second leg portion of the second section; the fourth projection has a contoured profile with a smaller diameter proximal section and a larger diameter distal section. The first recess Is positioned within the planar surface of the lower section of the end face of the first leg portion of the first section. The first recess is shaped to siidably receive the contoured profile of the fourth projection and provide an interlocking dovetail joint between the first and second sections. The second recess is positioned within the planar surface of the lower section of the end face of the second ieg portion of the first section. The second recess is shaped to siidably receive the contoured profile of the third projection and provide an interlocking dovetail joint between the first and second sections. The third recess is positioned within the planar surface of the lower section of the end face of the first leg portion of the second section. The third recess is shaped to siidably receive the contoured profile of the second projection and provide an interlocking dovetail joint between the first and second sections. The fourth recess is positioned within the planar surface of the lower section of the end face of the second leg portion of the second section. The fourth recess is shaped to siidably receive the contoured profile of the first projection and provide an Interlocking dovetail joint between the first and second sections.

[1831 ] In a further embodiment, the first, second, third, and fourth projections are each tapered.

[0032] In a still further embodiment, the flotation module also includes a stepped section positioned between the upper and lower sections of each end face of the first and second leg portions of the first and second sections. Each stepped section includes a central- planar surface portion, a lower shoulder, and an upper shoulder. The central-planar surface portion has a top edge and a bottom edge. The lower shoulder is disposed at the bottom edge of the central-planar surface portion and extends to the planar surface of the lower section. The upper shoulder is disposed at the top edge of the central-planar surface portion and extends to the planar surface of the upper section, in this embodiment, when the first and second sections are siidably engaged in the operative arrangement: the lower shoulder of the stepped section of the end face of the second leg portion of the second section abuts the upper shoulder of the stepped section of the end face of the first leg portion of the first section, the upper shoulder of the stepped section of the end face of die second leg portion of the second section abuts the lower shoulder of the stepped section of the end face of the first leg portion of the first section, the lower shoulder of the stepped section of the end face of the first teg portion of the second section abuts the upper shoulder of the stepped section of the end face of the second leg portion of the first section, and the upper shoulder of the stepped section of the end face of the first leg portion of the second section abuts the lower shoulder of the stepped section of the end face of the second leg portion of the first section.

( 033] Also described herein is a method for reducing a load force applied to an offshore platform by a tubular string. The method includes the steps of (a) providing a flotation system that may include a plurality of flotation modules positioned about the tubular string in a stacked arrangement to form a first series of stacked flotation modules and (b) lowering the tubular string through a subsurface conduit and having the load force applied to the offshore platform reduced by the tubular string due to a buoyancy effect of the first series of stacked flotation modules. The first series of stacked flotation modules has an uppermost flotation module and a lowermost flotation module. Each flotation module has a top end, a bottom end, an outer surface, and an internal core. The internal core is made of a buoyant material. The internal core forms an inner bore wall for accommodating the tubular string. Each of the flotation modules includes a first section, a second section, an interlocking means, an upper stop collar and a lower stop collar. The first section of the flotation module has a C-shaped interior profile. The first section of the flotation module includes a base portion,, a first leg portion, and a second leg portion; the base portion interconnects the first leg portion and the second leg portion. The first and second leg portions of the first section of the flotation module each has an end face. 1 be second section of the flotation module has a C-shaped interior profi le. The second section of the flotation module includes a base portion, a first leg portion, and a second leg portion: the base portion interconnects the first leg portion and the second leg portion. The first and second leg portion of the second section of the flotation module each has an end face. The interlocking means is configured to siidabiy engage the first and second sections into an operative arrangement about the tubular string by detaehably interlocking the end faces of the first and second leg portions of the first section of the flotation module to the end faces of the first and second leg portions of the second section of the flotation module. Each of the upper and lower stop collars has a top end, a bottom end, an outer surface, and an internal portion forming an inner bore wall for accommodating the tubular string. Each of the upper and lower stop collars includes a first section, a second section, and a securing means. The first section of the upper and lower stop collars has a C- shaped interior profile, The first section of the upper and lower stop collars includes a base portion, a first leg portion, and a second leg portion; the base portion interconnects the first leg portion to the second leg portion. The first and second leg portions of the first section of the upper and lower stop collars each has an end face, The second section of the upper and lower stop collars has a C-shaped interior profile, a base portion, a first leg portion, and a second leg portion; the base portion interconnects the first leg portion and the second leg portion. The first and second leg portion of the second section of the upper and lower stop collars each has an end See, The securing means is configured to detachably secure the first and second sections of each of the upper and lower stop collars together in operative arrangement about the tubular string. The upper end of the stop collar is secured about the tubular string at an upper end of the first series of stacked flotation modules such that the bottom end of the upper stop collar abuts the top end of the uppermost flotation module in the first series of stacked flotation modules. The lower stop collar is secured about the tubular string at a lower end of the first serie of stacked flotation modules such that the bottom end of the lower stop collar abuts the bottom end of the lowermost flotation module in the first series of stacked flotation modules.

[0034] In a further embodiment of the method, the subsurface conduit is a marine riser.

10035] In a still further embodiment, the method also includes the step of providing a second series of stacked flotation modules on the tubular string spaced apart from the first series of stacked flotation modules.

{0036] In a further embodiment, the method includes the step of lifting the tubular string through the marine riser, in this embodiment, the load force applied to the offshore platform by the tubular string is reduced due to a buoyancy effect of the first and second series of stacked flotation modules,

BRIEF DESCRIPTION OF THE DRAWINGS

|003?] Figure 1 is a perspective view of an embodiment of a flotation module [ΘΘ38] Figure 2 is an end view of the flotation module shown in Figure 1.

[0039} Figure 3 is a perspective view of the first and second sections of the flotation module shown in Figure 1.

[0040] figure 4 A is an: end view of another embodiment of the flotation module.

Figure 4B is a perspective view of the first and second sections of the flotation module shown in Figure 4A,

}0 42| Figure 5 A is an end view of another embodiment of the flotation module.

[1)043] Figure SB is a perspective view of the first and second sections of the flotation module sh wn in Figure 5.A.

[0044] Figure 6 is a cross-sectional view of the flotation module shown in Figure I,

[9045] Figure 7 is a side view of an embodiment of die flotation system positioned on a tubular string,

[0046] Figure 8 is a perspective view of an embodiment of stop coliar and flotation module of the flotation system positioned on a tubular string.

[00471 Figure 9 is a partially exploded view of an embodiment of the stop coliar of the flotation system.

[0048] Figure 10 is a cross-sectional view of the stop collar shown in Figure 9.

[0049] Figure 1 1 is a schematic view of an offshore p!attbrm handling an embodiment of the flotation system positioned on a tubuiar string extending subsurface. DET AILED DESCRIPTION OF THE DISCLOSURE

[0050] As shown in Figures 1 -3 , flotation module j O contains a first section .1 2 and a second section 14. A flotation module with a bore .15 is formed when the first section 12 and second section 1 4 are joined together. First section 12 and second section 14 may each have internal eore 16. Internal core 1 6 may be made of a buoyant material. In one embodiment the buoyant material is formed of a syntactic foam, as tor example, syntactic foam commercially available from CRP Corporation under the name syntactic foam. The flotation module may have an outer surface. ID one embodiment, the outer surface includes a protective outer layer. In a further embodiment, the protective outer layer may be bonded onto the exterior surface of the buoyant material. In one embodiment die protective outer layer is formed of polyurcthane. in one embodiment, the protective outer layer is approximately 7 - 1 0 millimeters thick, 100511 In one embodiment, first section .12 and second section 14 are h if-cyiinders.

In a further embodiment, as shown in figure 1, when the first section 12 and second section 14 are joined, the flotation module 10 has an outer surface thai is cylindrical,

[0052] As shown, in Figures 1 - 3, first section 12 and second section 14 may each have a c-shaped interior profile when viewed from the end. First section 12 and second section 14 may be joined together to form a bore I S, Bore 15 includes an inner bore wall for accommodating the tubular siring. First and second sections 12, 14 may include an interlocking means that is configured to siidabiy engage the first and second sections into an operative arrangement. The interlocking means detaehabiy interlocking the end faces of the first and second sections. In one embodiment, the interlocking means includes proiections and reciprocal recesses on the adjoining end faces of the c-shaped members. For example, first section 1 2 may include one or more projections that engage reciprocal recesses of second section 1 4 to secure first and second sections 12, 14 together. Alternatively, second section 14 may include one or more projections that engage reciprocal recesses of first section 12 to secure first and second sections 1 2, 14 together. In another embodiment first and second sections 12, 14 may each include a projection that engages a reciprocal recess on the other section. [ 0S3] The projections and recesses may be elongated along the longitudinal axis of f rst and/or second sections 12, 14. in one embodiment the projections and reciprocal recesses may extend along the entire length of first and second sections 12, 14. in other embodiments, the projections and recesses may extend along only a portion of the length of first and second sections 12, 14, The recesses are shaped reciprocally relative to the projections- T he projections may have a contoured profile with a smaller diameter proximal section and a larger diameter distal section, For example, a width of the projection's profile ai a first point thai is adjacent to the end face of the first or second section 12. 14 is less than a width of the projection at a second point that is spaced apart from the end face of first or second section 12, 14, with the second point being any point on the projection beyond the first point (e.g., the second point may be at a distal end of the projection's profile or any point between the distal end and the end face, such as ¼ distance, 1 /3 distance, ½ distance, or ¾ distance), in one embodiment, as shown in Figures 1 -3 and SA-5B, the projections have a tapered shape such that the projections and reciprocal recesses form a dovetail joint between the first and second sections 12, 14. in another embodiment, as shown in Figures 4A and 4B, the projections may be shaped such that the projection has a rounded profile.

[1054] In the embodiment shown In Figures 1 -3, first section 12 has a first end 22, a second end 24., a base portion, a first leg portion 17, and a second leg portion 19. The base portion interconnects the first leg portion 1 7 and the second leg portion 19. Both first leg portion 17 and second leg portion 19 each includes an end face. Second section 14 has a first end 23, a second end 25, a base portion, a first leg portion 2.1 , and a second leg portion 27, The base portion Interconnects the first leg portion 21 and the second leg portion 27. Both first leg portion 21 and second leg portion 27 each Includes an end face, hirst section 12 and second section 14 may each include projections 18 located on and reciprocal recesses 20 located within the end faces of the first and second leg portions. Tapered projections 18 are located on the end faces on first end 22 of first section 12, with one tapered projection located on each end face. Tapered projections 18 are located on the end faces on second end 25 of second section 14, with one tapered projection being located on each end face. Reciprocal recesses 20 are located within the end faces on second end 24 of first section 12, with one reciprocal recess being located within each end face. Reciprocal recesses 20 are located within the end faces on first end 23 of second section 14, with one reciprocal recess being located within each end face. Tapered projections 1 8 and reciprocal recesses 20 are configured such that tapered projections 18 are configured to be slidably received into reciprocal recesses 20 of another section in a retaining engagement. To join first section 12 to second section 1 , the tapered projections 1 8 located on the first end 22 of first section 12 are inserted into the reciprocal recesses 20 located on the first end 23 of second section 14. Tapered projections 18 located on the second end 25 of second section 14 are also inserted into the reciprocal recesses 20 located on the second end 24 of first section 12 , in this way. the first section 12 and second section 14 in Figures 1 -3 are joined in an interlocking dovetail arrangement.

(0055| In one embodiment, as shown in Figures 1 -3, each end face of the first and second leg portions 17, 19 of the first section 12 may include an upper section and a tower section. Soth the upper section and the lower section have a planar surface. The planar surface of the upper section extends outwardly beyond the planar surface of the lower section. Each end face of the first and second leg portions 21 , 2? of the second section 14 may also include an upper section and a lower section. Both the upper and tower section have planar surfaces. The planar surface of the lower section extends outwardly beyond the planar surface of the upper section . In this embodiment; a projection 18 extends from the planar surface of the upper section of the end face of the first leg portion 1 7 of the first section 12, a projection 1 8 extends from the planar surface of the upper section of the end face of the second leg portion 19 of the first section 12, a projection 18 extends from the planar surface of the upper section of the end face of the first leg portion 21 of the second section 14, and a projection 18 extends from the planar surface of the upper section of the end face of the second kg portion 27 of the second section 14. Also in tins embodiment: a recess 20 shaped to slldabiy receive the projection 18 located on second leg portion 27 of the second section 14 is positioned within the planar surface of the lower section of the end face of the first leg portion 17 of the first section 12, a recess 20 shaped to slidahly receive the projection 18 located on the first leg portion 21 of the second section 14 is positioned within the planar surface of the lower section of the end face of the second leg portion 19 of the first section 12, a recess 20 shaped to slldabiy receive projection 18 located on the second leg portion 1 of first section 12 is positioned within the planar surface of the lower section of the end face of the first leg portion 2.1 of the second section 14, and a recess 20 shaped to slidabiy receive projection I S located on the first leg portion 17 of the first section 12 is positioned within the planar surface of the lower section of the end face of the second leg portion 27 of the second section 14 , in a further embodiment, the projections 18 have a contoured profile with a smaller diameter proximal section and a larger diameter distal section. (00S6] As shown in Figure 3, in a further embodiment, a stepped section may be positioned between the upper and lower sections of each end face of the first and second leg portions 17, 21 and 19, 27 of the first and second sections 12, 14, Each stepped seetion includes a central-planar surface portion, a lower shoulder, and an upper shoulder. The central-planar surface portion has a top edge and a bottom, edge. The lower shoulder is positioned at the bottom edge of the central-planar surface portion and extends to the planar surface of the lower section. The upper shoulder is positioned at the top edge of the central- planar surface portion and extends to the planar surface of the upper section, in this embodiment, when the first and second sections 12,. 14 are slidably engaged in the operative arrangement: the lower shoulder of the stepped section of the end face of the second leg portion 2? of the second seetion 14 abuts the upper shoulder of the stepped section of the end face of the first leg portion 17 of the first section 12; the upper shoulder of the stepped section of the end face of the second leg portion 27 of the second seetion 14 abuts the lower shoulder of the stepped section of the end face of the first leg portion 17 of the first section 12; the lower shoulder of the stepped section of the end face of the first leg portion 21 of the second section 14 abuts the upper shoulder of the stepped section of the end face of the second leg portion 19 of the first seetion 12; and the upper shoulder of the stepped seetion of the end face of the first leg portion 21 of the second section 14 abuts d e lower shoulder of the stepped section of the end face of the second leg portion 19 of the first section 12.

[0057] in one embodiment, first section 12 and second section 14 each may have a length in the range of 1 to 10 feet, in another embodiment, first and second sections 12, 14 may each have a length of about 2 feet. In one embodiment, when first section 12 and second section 14 are joined together, the outer diameter of flotation module 10 may be in the range of 14 to 22 Inches, fa n embodiment, the outer diameter of flotation module 10 may be between 1 5 ana 17 inches, in one embodiment, when first section 12 and second section l a are joined together, the diameter of the inner bore wall may be in the range of 2 to 8 inches. However, the external and internal diameter of flotation module 10 can be sized to accommodate tubular strings of different diameters. Additionally, the length of the f rst section 12 and second seetion 14 can be any length as long as it does not buckle if the tubular string about which the first and second sections are arranged flexes.

{00S8J Flotation module 10 is self-locking due to the interlocking feature of the projections and recesses that when slidably engaged provide a dovetai l joint between the first and sections 12, 14 of flotation ^' module 10. While not necessary, flotation module 10 m y be equipped with a back-up locking means. For example, flotation module 10 may include a locking device. The locking device may be any mechanism ihat detachafaly secures first and second sections 12. 14 together. For instance, the locking device ma be a locking pin, bolt, screw, plug, or like device.

1 59] As seen in Figs, 1 -3, tire locking device may be locking i n 28 configured to be received in a bore formed by half bores 26 located on first section 12 and the second section 14. In this embodiment fi st section 12 and second section 14 each have at least one half bore 26. Half bores 26 may be located between projections 1 8 and recesses 20 on the end faces of first and second sections 12, 14, Alternatively, half bores 26 may be positioned in a central region along the length of each of first leg portions 17, 21 and second leg portions 19,

27 of first and second sections 12, 14. When first section 12 and second section 14 are joined together, the half bores 26 on each section substantially align with the half bores 26 on the other section to form bores, The bores are configured to receive a locking pin 28. Locking pin

28 is inserted into the bore to lock first section 12 and second section 14 together. In one embodiment, locking pin 28 is made from a polymer composite, as for example, PA66 + ^■ 50% GF. [6CMI] As shown in Figure 7, a flotation system may include a plurality of flotation modules 10 configured to be secured in at least one series about a tubular string 29, As used herein, "plurality" means two or more. In one embodiment, the tubular string may be a landing string. It should be noted, that whi le fourteen flotation modules 10 are shown in Figure 7, the actual number of flotation modules 10 placed on a tubular string can vary. In fact, with some tubular strings, it is possible to alternate the placement of d e flotation modules 10 amongst various joints. The actual number of flotation modules 10, length of the flotation modules 1 , number of series of flotation modules 10, and thickness of the buoyancy material will depend on specific design criteria. Many design criteria can be considered, such as the amount of weight reduction required, and rig or platform space. The flotation modules 1 0 provide buoyancy to the tubular string 29, which can be run into the marine riser using conventional means known to those of ordinary skill in the art,

[0061] The flotation system may further include stop collars 30 configured to be secured at opposing ends of the series of flotation modules 10, as shown in Figure 10, If only one flotation module 10 is used, then stop collars 30 would be placed on either side of the single flotation module 10, As shown in Figures 5 and 6, stop collars 30 include first section 32 and second section 34. A conical-shaped member with a bore 35 is formed when the first section 32 and second section 34 are joined together. When the stop collars 30 are positioned at opposing ends of a series of flotation modules 10, the upper sto collar is secured about the tubular siring at an upper end of the first series of stacked flotation modules 10 so that the bottom end of the upper stop collar abuts the top end of the uppermost flotation module in the series. Further, the lower stop collar is secured about die tubular string at the lower end of the series of stacked floatation modules so thai the bottom end of the lower stop col lar abuts the bottom end of the lowermost flotation module 10 in d e series of stacked flotation modules, In a further embodiment, when there are multiple series of flotation modules 10 positioned about a tubular string, there may be an upper and lower stop collar positioned at the upper end and lower end, respectively, of each series of flotation modules 10, [0062} As shown in Figures 8 and 9, first section 32 includes a frame structure 3J .

Structural body 31 also includes a securing means configured to detachably secure the first and second sections 32, 34 of each stop collar 30 together in an operative arrangement, In one embodiment the securing means Includes bores 48, with two bores 48 being located on each side of structural body 31 , as shown in Figures 8 and 9. In one embodiment, the structural body 1 Is composed of a polymer composite. In a further embodiment, the polymer composite is PA66 50% GF. In one embodiment, die outer surface of frame structure 31 includes a protective outer layer 33, In one embodiment, protective outer layer 33 is formed of poiyureihane and is bonded to the frame structure' 31 . Second section 34 section 32. | 063| First section 32 and second section 34 are fastened together with a securing mechanism placed through bores 48 of first section 32 and second section 34. The securing mechanism may be any device, tool, component, or assembly capable of fitting into bores 48 and fastening first section 32 and second section 34 together. For example, the securing mechanism may comprise a bolt, screw, or any other similar device, in the embodiment shown in Figures 8 and 9, first section 32 and second section 34 are joined with hex cap bolts 38 and locking nuts 40, I lex cap bolts 38 are placed through bores 48 of both the first section 32 and second section 34 and threaded through locking nut 40, which is located on the opposite side of stop collar 30. Hex cap bolts 38 and locking nuts 40 may be made of a thermoplastic resin, as for example, lsopiast¾ poiyurethane. [0064] In one embodiment, flotation module 10 includes an RF!D chip 50, as shown in Figure I . FiD chip 50 may be located on the exterior of first section 12 and second section 14. RFID chip 50 may be used to track the length of use and location of each flotation module 10 and each half cylindrical sleeve 12 and 14 as readily understood by one of skill in the art.

( 065 ^' j Figures 4A and 4B show an alternate embodiment of a flotation module 110. in this embodiment, the first section 112 and second section 114 are C-shaped when viewed from the end. When first section 1 12 and second section 1 14 are joined together, a bore 115, having an inner bore all for accommodating a tubular string, is formed. First section 1 12 has a projection 118 located on the first leg portion 117 and a recess 120 located on the second leg portion 119. . Second section i 14 has a projection 1 18 located on the second leg portion 127 and a recess 120 located on the first leg portion 121, Projections 1 18 and reciprocal recesses 1 20 are configured such that each projection 1 18 is capable of being received into the reciprocal recess 120 of another section in a retaining engagement. To join first section 1 12 to second section 114, the projection 1 1 8 of first section 1 12 is inserted into the reciprocal recess 120 of second section 14 and the projection 1 18 of second section 1 14 is inserted into the reciprocal recess 120 of first section 1 12. In this way, the first section 1 12 and second section 14 are joined in a dove-tail arrangemen

[Θ 66] Figures 5A and 5B show an alternate embodiment of a flotation module 210.

In this embodiment, the first seciion 212 and second section 214 are C-shaped when viewed from the end. When first section 212 and second section 214 are joined together, a bore 215 is formed , Bore 21 5 has an inner bore wail for accommodating the tubular string. First section 21 2 has tapered projections 218 located on both first leg portion 217 and second leg portion 219 of the fi st section 212, Second section 214 has reciprocal recesses 22Θ located on both first ieg portion 214 and second ieg portion 227 of the second section 214. Tapered projections 218 and reciprocal recesses 220 are configured such that tapered projections 218 are capable of being received into reciprocal recesses 220 of another section in a retaining engagement To join first section 212 to second section 214, the tapered projections 218 of the first section 212 are inserted into the reciprocal recesses 220 of second seciion 214. In this way, the first section 212 and second section 214 are joined in a dove-tail arrangement. [0067] The flotation system may be affixed to a tubular string, in the embodiment shown in F igs, 1 -3 and 7-9, first nd second sections 12, 14 of each flotation module 10 may be connected to one another around the outer surface of tubular string 29 such that tubular string 29 is disposed through bore .15 of each flotation module 10. Specifically, projections 18 of each section 12, 14 may be inserted into reciprocal recesses 20 on the other section 12. 14. A Socking pin 28 may then be inserted through the bore formed by half bore 26 on first and second sections 12, 14, A stop collar 30 may be connected to tubular string 29 ai each end of the series of flotation modules 10 such that tubular string 29 is disposed through bore 35 of each stop collar 30. Specifically, first section 32 and second section 34 may be positioned around tubular string 29, and a securing mechanism (e.g., hex cap bolts 38 and locking nuts 40) may be secured through bores 48 in each structural body 31 and bores 36 in each skin 33.

[0068] in the same way, alternate flotation modules 1 10 or 210 shown in Figures 4A- 5B may be affixed to a tubular string. First and second sections 1 12, 1 14 or 212, 214 of each flotation module 1 10 or 210 may be connected to one another around the outer surface of a tubular string such that the tubular string is disposed through bore 1 15 or 215 of each flotation module 1 10 or 210, respectively. Specifically in flotation module 1 10, projections 1 1 8 of each section 1 12, 1 14 may be inserted into reciprocal recesses 120 of the other section ] 12. 1 14, In flotation module 210, projections 21 8 of first section 212 may be inserted into reciprocal recesses 220 of second section 214. 006 ] With reference now to Figure 1 1 , the flotation system may be attached to tubular string 310. in one embodiment, a series of flotation modules 10 and stop collars 30 are attached to tubular string 310 on floating platform 312, Platform 312 may be an offshore drilling rig, drilling ship, or other deck or platform where s bsea or subsurface (below the surface of the body of water) oil and gas operations take place. Floating platform 312 may be positioned above wellbore 314, Marine riser 316 may extend from floating platform 312 to sub-sea well head 318 positioned on the ocean floor above wellbore 314. Tubular string 10 may be a landing string, a work siring, or any other tubular member lowered into a sub-sea well bore through a subsurface conduit. For example, the tubular string may be used to properly position a down hole component (e.g., a casing string, bottom hole assembly containing a drilling tool with bit and mud motor, production and testing assembly) within wellbore 3 14. Tubular string 310 with attached flotation modules 10 may be lowered through a subsurface conduit (such as a marine riser 316), sub-sea well head 318, and into vveilbore 314. Since marine riser 3 16 wiil have a fluid therein, the weight of tubular string 310 being lowered into the marine riser 316 will be reduced, according to the teachings of this invention, in this way, tubular string 310 may be lowered to a desired depth safely by reducing the fig or platform hoisting requirements. The flotation system may also be attached to tubular strings used in a production assembly for producing hydrocarbons or a testing assembly for testing a well. Furthermore, the flotation system including flotation module 1 10 or 210 may be attached to tubular string 310 to reduce rig or platform hoisting requirements.

[0070] Flotation module 10 and system provide superior buoyancy by reducing or eliminating component parts that are not composed of buoyant material and/or which have increased weight. This feature is achieved In part due to the novel dovetail interlocking design of the projections and recesses of the first and second sections of the flotation modules that serve to interlock the two sections of flotation modules about the tubular string by using parts composed of buoyant material. The superior buoyancy of the flotation modules achieves considerable costs savings to the rig or platform operator, which In light of the igh costs of offshore drilling and other operations can result In operational savings in the tens of millions of dollars. 007J Although the present invention has been described In terms of specific embodiments, it is anticipated that aiterations and modifications thereof will no doubt become apparent to those skilled in the art. It is therefore intended that the following claims be interpreted as coverin all such alterations and modifications as tall within the true spirit and scope of the invention.