In the search for oil and gas, offshore areas offer significant hydrocarbon reservoir potential. In order to search and produce hydrocarbons from offshore areas, various types of structures have been developed. For instance, the four-pile jacket structure is a platform having four legs. Generally, the four legs are attached together by various horizontal deck members along with horizontal, vertical and diagonal bracing.

The legs are tapered so that the base is larger than the production deck portion. The water depth may vary from just a few feet to several hundred feet of water.

Piles are driven into the ocean floor in order anchor the jacket to the ocean floor. Various pile driving mechanisms have been developed through the years. Design criteria for these jackets include load considerations and ocean currents. For a complete discussion of these types of offshore structures, see Petroleum Engineering Handbook, Chap. 18"Offshore Operations", Society Of Petroleum Engineers, Second Printing which is incorporated herein by reference.

A typical construction sequence includes yard construction, then moving the assembled structure to a barge. Once the barge is floated to the proper location, usually floating horizontally, it is upended by ballasting members at the lower end. Once upright, it is moved onto the final site and lowered to the seabed by continued ballasting.

This construction process is costly and lengthy. As the search for hydrocarbon reserves continues, operators are very

concern with the cost-effective depletion of the reservoirs.

This is particularly true of older fields that are considered marginal. In these mature and/or marginal fields, many times all that is required is a platform that will support one to five total wells. Thus, there is a need for an offshore structure that can be built for a minimal of cost. There is also a need for a platform structure that is easily installed and can withstand the harsh offshore environment.

SUMMARY OF THE INVENTION A novel offshore platform is disclosed. The platform may be used for supporting an offshore caisson. In the preferred embodiment, the structure comprises an ocean floor mat having a first section and a second section. The first section includes a first member, a second member and a third member arranged in a triangular base. A first caisson means, operatively adapted to the triangular base, is provided for fastening about the caisson.

The second section includes a fourth member, a fifth member and a sixth member arranged in a triangular base. It should be noted that the triangular base of the first and second section are essentially identical to each other. The second section will have a second caisson means, operatively adapted to the triangular base, for cooperating with the first caisson means so that the ocean floor mat is secured about the caisson. When the triangular bases are formed, an essentially square ocean floor mat is formed.

The structure may further comprise a first modular deck having a first segment and a second segment. The first segment comprises a first member, a second member and a third member arranged in a first triangular base. Associated with this segment will be a first caisson means, adapted at the convergence

of the first and second member, for fastening about the caisson.

The second segment comprises a fourth member, a fifth member and a sixth member arranged in a second triangular base. A second caisson means, adapted at the convergence of the fourth and fifth member, is provided for cooperating with the first caisson means so that the modular deck is fastened about the caisson. When the triangular bases are formed, an essentially square ocean floor mat is formed.

The structure will then contain a second modular deck having a first segment and a second segment. Thus, the first segment will include a first member, a second member and a third member arranged in a third triangular base. A first caisson means, adapted at the convergence of the first and second member, is provided for fastening about the caisson. The second segment comprises a fourth member, a fifth member and a sixth member arranged in a fourth triangular base as well as a second caisson means, adapted at the intersection of the fourth and fifth member, for cooperating with the first caisson means so that the modular deck is fastened about the caisson.

The first and second modular decks may have associated therewith a first lateral support extending from the first segment, and a second lateral support extending from the second segment. Also, the first, second, third, and fourth triangular bases may contain openings at its corners so that the structure further comprises a casing driven through the openings contained within the first, second, third and fourth triangular bases.

Also included may be a horizontal pin means for connecting the triangular base segments together.

Also disclosed is a method of constructing an offshore platform about a caisson. Basically, the method comprises the steps of joining a first triangular base section of an ocean floor mat, the first triangular base section having first caisson means for fastening about the caisson with a second triangular base section of the ocean floor mat, the second triangular base

section having second caisson means for fastening about the caisson. Then, the joined first triangular base section and the second triangular base section are lowered to the ocean floor, and thereafter, connecting the joined first triangular base section and the second triangular base section about the caisson.

The method would further comprise the steps of joining a third triangular base section of a first modular deck, the third triangular base section having third caisson means for fastening about the caisson with a fourth triangular base section of the modular deck, the second triangular base section having second caisson means for fastening about the caisson. Next, the operator would lower onto the ocean floor mat the joined first triangular base section and the second triangular base section to the ocean floor mat. Then, the operator connects the joined third triangular base section and the fourth triangular base section about the caisson.

In one embodiment, the third and fourth triangular base further contains a diagonal support means for connecting to the first and second triangular base of the ocean floor mat, and the method further comprises connecting the diagonal support means to the first and second triangular base. The method would further include the steps of joining a fifth triangular base section of a second modular deck (the fifth triangular base section having fifth caisson means for fastening about the caisson) with a sixth triangular base section of the modular deck (the sixth triangular base section having sixth caisson means for fastening about the caisson). Next, the operator would lower onto the first modular deck the joined fifth triangular base section and the second triangular base section. The operator would then connect the joined fifth triangular base section and said sixth triangular base section about the caisson.

In the preferred embodiments, the first, second, third, fourth, fifth and sixth triangular base has openings at their corners. Thus, the method would further comprise driving a

casing string through at least one of the openings in the triangular bases, with the casing string extending into the ocean floor. Thereafter, a well may be drilled to a subterranean reservoir utilizing the casing string.

In another embodiment, a method of constructing an offshore platform about a caisson is disclosed that effectively makes the structure a tri-pod. In this embodiment, method comprises the steps of providing a first triangular base section of an ocean floor mat, the first triangular base section having first caisson means for fastening about the caisson. Then, the operator lowers onto an ocean floor the first triangular base section to the ocean floor, and thereafter connects the first triangular base section about the caisson so that the ocean mat is formed. Next, the operator provides a second triangular base section of a first deck, the second triangular base section having second caisson means for fastening about the caisson. Then, the operator would lower onto the ocean floor the second triangular base section to a first predetermined location, and thereafter, connects the second triangular base section about said caisson so that the first deck is formed. The operator may then provide a third triangular base section of a second deck, with the third triangular base section having third caisson means for fastening about the caisson. Once again the operator would lower to a second predetermined location the third triangular base section, and thereafter, would connect the third triangular base section about the caisson so that the second deck is formed.

In the preferred embodiment, the structure is basically a 4-pile, braced, vertical truss. The vertical loads are resisted by tension/compression in main piles, base piles and base pile braces. The horizontal loads induce transverse shear and overturning moment. The transverse shear is resisted by main piles, caisson, and base piles. Overturning moment is resisted by tension/compression in main piles and base piles, which is transferee through wall friction to mud.

An advantage of the present invention is that the platform is constructed in sub-assembly modules. Another advantage of the present invention is that the modules may be fabricated at inland locations. Another advantage is that the modules may be transported to an offshore loading dock via truck means.

Yet another advantage is that transportation of the modules to the offshore location includes the ability of using a barge, a jack-up rig, or other equivalent transportation means. Still yet another advantage includes the ability to lower individual modules via crane from the working platform. Another advantage includes assembling and integrating the individual modules with the aid of a diver.

A feature of the present invention includes the platform will adequately support an offshore caisson. Another feature is the invention can be adapted as support for an existing well.

Yet another feature is that the novel structure may be used for supporting new wells.

Another feature is that the corners of each triangle may be used as a caisson for additional oil and gas wells. Another feature is that the novel design may be used in varying water depth. Yet another feature is the cost effective nature of the construction. Still yet another feature is that the platform may be constructed faster than conventional four-pile jackets.

Yet another feature is the structure is composed of sub- assemblies and sub-components. All sub-assemblies and sub- components are small enough that they can be trucked to the dock.

Yet another feature is that diagonal and/or horizontal bracing may be increased or decreased depending on the structural requirements of the particular environment.

Yet another feature is the operator has the option of utilizing only one of the triangular bases to form a series of stacked decks. In this embodiment, the offshore structure

effectively becomes a tri-pod since only a single triangular base is used for a deck. In other words, the triangular bases are not joined together to form a rectangular shape. Instead, the operator will stack the triangular decks in series, with the number of triangular decks being dependent on the water depth.

A feature of this embodiment is that once the invention is installed at an offshore location, the structure becomes a tri- pod with the caisson being in one corner, a pile member in the second corner and another pile member in the third corner.

BRIEF DESCRIPTION OF THE FIGURES FIGURE 1A is a top-view schematic of the cooperating caisson means of the present invention.

FIGURE 1B is a side-view schematic of the caisson means of the Fig. 1A.

FIGURE 1C is a side-view of one of the caisson means.

FIGURE 2 is the top-view schematic of the bell guide means of the present invention.

FIGURE 3 is the side-view schematic of the guide clamp means of the present invention.

FIGURE 4A is a top-view schematic of a triangular base of the ocean floor mat.

FIGURE 4B is a top-view schematic of a triangular base of the ocean floor mat.

FIGURE 5 is a top-view schematic of the triangular bases of Fig. 4A and 4B assembled.

FIGURE 6A is a top-view schematic of a triangular base of the deck member.

FIGURE 6B is a top-view schematic of a triangular base of the deck member.

FIGURE 7 is a top-view schematic of the triangular bases of Fig. 6A and 6B assembled to form a deck.

FIGURE 8 is a side-view schematic the assembled bottom mat on the ocean floor.

FIGURE 9 is a side-view schematic of one deck member assembled with the bottom mat of Fig. 8.

FIGURE 10 is a side-view schematic of a second deck member assembled with platform of Fig. 9.

FIGURES 11A-11E is another embodiment of the invention depicting a sequence of installation.

FIGURE 12 is illustrated view of one embodiment of the platform constructed in accordance with the teachings of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to Fig. lA, a top-view schematic of the cooperating caisson means 2 and 4 of the present invention is shown. As illustrated, the caisson means 2,4 are used for fastening about a caisson that extends into the ocean floor.

Generally, the caisson means 2,4 will have a leg member 6, 8 that extends to the half-tubular member 10, 12 that in turn terminates at the leg members 14, 16.

In Fig. 1B, a side-view schematic of the caisson means 2,4 of the Fig. 1A is depicted. In Fig. 1C, the side-view of the caisson means 2 depicts the leg member 6 that will contain the openings 18 for bolts (not shown) that can be used for fastening.

The leg member 14 will contain the openings 20 for placement of the bolts (not shown). Thus, the caisson means 2 and caisson means 4 can be bolted together via bolts through the openings 18, 20.

Referring now to Fig. 2, the top-view schematic of the bell guide means 22 of the present invention is shown. Generally, the bell guide means 22 has a tubular configuration 24 that extends from a first face 26 to a second face 28 with the bolt plate 30 being attached to the face 26 and the bolt plate 32 being attached to the face 28. The plates 30 and 32 are operatively adapted to each other by the bolt 34. Thus, the size of the internal diameter 36 of the may be varied via the bolt tightening as is well understood by those of ordinary skill in the art.

The bell guide means 22 will have extending therefrom a first member 38 and a second member 40, with the member 38 extending to another bell guide means (not shown) and the member 40 extending to a caisson means (not shown). The bell guide means 22 has operatively associated therewith a horizontal brace 42 that will be connected to the bell guide means 22 in a conventional manner such as the bolt plates 44,46 which have inserted therethrough the pin 48 fastened thereby with the bolt 50. In the preferred embodiment, the horizontal brace 42 is included and will be attached to another bell guide means.

In Fig. 3, the side-view schematic of the guide clamp means 54 of the present invention will now be described. The guide clamp 54, which is similar to the bell guide clamp means 22, has

an essentially tubular member 56 that has a first funnel end 58 and a second end 60. The guide clamp is a tubular bond style clamp. It is formed from rolled plate, generally 3/4"-2" thick, with a length of 3 to 4 feet with bolt plates associated therewith. The bolt plates may be reinforced with gussets (not shown). Attached on one side of the tubular member 56 is the bolt plate member 62 (similar to the plates 30,32 shown in Fig. 2) that has openings 64. The guide clamp means 54 also has the bolt plate member U for bolting a horizontal member 68 and/or a diagonal member 70. The bolt plate 66 will have openings 72 that will cooperate with the attaching plates 74 and 76. During installation, the clamps will be made rigid by clamping the bolt plates on spacers (not shown). Thus, to tighten the clamp, wedges are first inserted. The bolts are then loosened and spacers are removed, and the bolts then tightened.

Fig. 4A is a top-view schematic of a triangular base 80 of the ocean floor mat while Fig. 4B is also a top-view schematic of the cooperating triangular base 82. In Fig. 4A, the base 80 includes a first bell guide means 84 and a second bell guide means 86. The bell guide means 84,86 have adapted thereto the horizontal member 88. The first bell guide means 84 has extending therefrom the support member 90 while the second bell guide means 86 has extending therefrom the support member 92.

As shown, the members 88,90 and 92 form a triangular base. The members are welded to the bell guide means. A jig is used during fabrication to ensure identical location of components. The caisson means 2A is adapted at the intersection of the support members 90,92 for cooperating with the caisson means 4A so that the ocean floor mate is fastened about the caisson.

In Fig. 4B, the base 82 includes a first bell guide means 94 and a second bell guide means 96. The bell guide means 94,

96 have adapted thereto the horizontal member 98. The first bell guide means 94 has extending therefrom the support member 100 while the second bell guide means 86 has extending therefrom the support member 102. As shown, the members 98,100,102 form a triangular base 82. The caisson means 4A is adapted at the intersection of the support members 100,102 for cooperating with the caisson means 2A so that the ocean floor mate is fastened about the caisson as previously described.

The additional foundation supports 104, 106 that extend from the bell guide members 84,86, as well as the additional foundation supports 108,110 that extend from the bell guide members 94,96 may be provided. These additional foundation supports 104,106,108,110 have the effect of enlarging the base which enhances the foundation of the overall platform. The foundation supports 104,106,108 and 110 are connected via the bolt plates 30,32 as is well understood by those of ordinary skill in the art. The foundation supports 104,106,108,110 will have associated therewith the base clamps 112,114,116, 118, respectively so that piles may be driven therethrough for purposes of anchoring the ocean floor mat in place.

Referring now to Fig. 5, a top-view schematic of the triangular bases 80,82 of Fig. 4A and 4B are assembled.

Generally, the two triangular bases are individually fabricated.

The bases may be integrated at the construction site or may be integrated together on the working barge offshore. Once the triangular bases are joined together as seen in Fig. 7, the horizontal members 148, 150A are added that connects and further adds structural support to the deck. Hence, once the triangular bases are joined together as seen in Fig. 5, the ocean floor mat may be stripped over the caisson i. e. the caisson means is placed over the caisson. Thereafter, the entire ocean floor mat 123

(which is essentially in a square pattern) is lowered to the sea floor about the caisson. Bolts will join the 2 halves of the caisson clamp, making it a self sufficient load carrying member.

The two pinned horizontal members 148A, 150B will be used to connect the open sides of the mat. Wedges and set screws will be used to center the assembly about the caisson. Once the piles are driven through the base clamps, the clamp spacers will be removed and wedges inserted, then the base clamps can be tightened.

The modular deck designed and constructed in accordance with the teachings of the present invention will now be described.

In Fig. 6A, a top-view schematic of a triangular base 124 of the deck member is illustrated. In Fig. 6A, the base 124 includes a first bell guide means 126 and a second bell guide means 128.

The bell guide means 126,128 have adapted thereto the horizontal member 130. The first bell guide means 126 has extending therefrom the support member 132 while the second bell guide means 128 has extending therefrom the support member 134. As shown, the members 130,132,134 form a triangular base. The support members are welded to the bell guide means and caisson means. The caisson means 2A is adapted at the intersection of the support members 132,134 for cooperating with the caisson means 4A so that the modular deck is fastened about the caisson.

A jig during fabrication is used to ensure identical location of components. It should also be noted that downward diagonal supports may also be included with the triangular base, with the downward diagonal supports being illustrated in the Figs. 9,10, 11 and 12.

In Fig. 6B, the base 136 includes a first bell guide means 138 and a second bell guide means 140. The bell guide means 138, 140 have adapted thereto the horizontal member 142. The first bell guide means 94 has extending therefrom the support member

144 while the second bell guide means 149 has extending therefrom the support member 146. As shown, the members 140,142,144 form the triangular base 136. The caisson means 4A is adapted at the intersection of the support members 144,146 for cooperating with the caisson means 2A so that the modular deck is fastened about the caisson as previously described. It should also be noted that downward diagonal supports may also be included with the triangular base, with the downward diagonal supports being illustrated in the Figs. 9,10,11 and 12.

Referring now to Fig. 7, a top-view schematic of the triangular bases 124,136 of Fig. 6A and 6B are assembled in essentially a square pattern. Generally, the two triangular bases are individually fabricated. The bases may be joined at the construction site or may be joined together on the working barge offshore. Once the triangular bases are joined together as seen in Fig. 7, the horizontal members 148B, 150B are added that connects the individual triangular bases and further adds structural support to the deck.

It should be noted that in another embodiment, the operator has the option of utilizing only one of the triangular bases (80 or 82) to form a series of stacked decks. In this embodiment, the offshore structure effectively becomes a tri-pod since only a single triangular base is used for a deck. In other words, the triangular bases are not joined together. Instead, the operator will stack the triangular decks in series, with the number of triangular decks being dependent on the water depth. In this embodiment, the caisson means (2A or 4A) will be a full caisson clamp (versus the half-caisson clamp previously described) since the full caisson clamp will have to be used to attach to the caisson. Once assembled, this embodiment becomes a tri-pod with the caisson being in one corner, a pile member in the second corner and another pile member in the third corner.

Referring back to Fig. 7, the assembly of the individual triangular bases, in the preferred embodiment, will take place on the working barge. Bolts will be used to join the 2 half caisson clamps. The two pinned horizontal braces will then be used to connect the two open halves of the structure. The structure will then be raised and the 8 pin diagonals will be suspended, two from each corner. The deck may thereafter be stripped over the caisson i. e. the caisson means is placed over the caisson. Next, the entire modular deck 151 is lowered to the ocean floor mat 123. As stated above, the downward diagonal supports may also be included with the assembled modular deck, with the downward diagonal supports being illustrated in the Figs. 9,10,11 and 12.

When it reaches the bottom, the internal diagonals will be pinned to the caisson clamp and the external diagonals will pin to the guide clamp. Wedges and set screws will be used to center the caisson in the structure. Decks will be lowered and pinned in this manner until all the decks have been installed. As will be more fully explained later, pilings can then be driven through the corners (guide clamps). Wedges will be inserted in the guide clamps. The clamp spacers will be removed and the clamps tightened.

Referring now to Fig. 8, a side-view schematic of the assembled bottom mat 80,82 on the ocean floor is shown. Thus, the caisson means 2A and 2B are shown arranged about the caisson 154, with the caisson being driven through the ocean floor 156.

Generally, the caisson 154 is the central structure element which is driven first and serves as an alignment/locating member. The typical material is 48"O. D. tube with a 1"wall. In this position, the bell guides 86,96 have attached thereto the support members 92,102 as previously described. Also, the base clamps 114,118 are associated therewith via the foundation supports 106,110.

The base clamps 114,118 may have surface piles 212 and 214 driven therethrough. Also, the bell guides 86,96 have funnel ends 158, 160 respectfully. The funnel ends 158,160 aid in the placement of the casing and/or piles 216 and 218 that will be driven therethrough upon completion of the positioning of the modular decks as will be more fully discussed hereinafter. It should be noted that the preferred method of installation is described with reference to Figs. 11A through 11E.

Returning to Fig. 8, the bottom mat 80,82 will be lowered via a crane. The caisson means 2A and 4A will be joined together; they will also have a spacer member that allows the internal diameter to be larger enough in order to slip-over the caisson 154. Once at the proper depth, the spacer may be removed and the leg members (numbers 6,8,14, and 16 of Fig. 1A) may be properly tightened about the caisson 154 by underwater divers.

With reference to Fig. 9, the first modular deck member being associated with the ocean floor mat will now be described.

The bell guides 128 and 140 have attached thereto the support members 134,146 which in turn attach to the caisson means 2A and 4A. Extending from the bell guide 128 is the diagonal cross- support 162 that attaches to the caisson means 2A while extending from the bell guide 140 is the diagonal cross-support 164 that attaches to the caisson means 4A. Extending from the caisson means 2A is the diagonal cross-support 166 that attaches to the bell guide means 86. Extending from the bell guide caisson means 4A is the diagonal cross-support 168 that attaches to the bell guide means 96. It should be noted that in the preferred embodiment, only the diagonal cross-supports 162 and 164 are provided.

The modular deck 124,136 will be lowered via a crane. The

caisson means 2A and 4A will be joined together; they will also have a spacer member that allows the internal diameter to be large enough in order to slip-over the caisson 154. Once at the proper depth, the spacer may be removed and the leg members (numbers 6,8,14, and 16 of Fig. 1A) may be properly tightened about the caisson 154 by underwater divers.

In reference to Fig. 10, a side-view schematic of a second deck member assembled together with the structure of Fig. 9 will now be described. The components used for this deck are essential identical to those of Fig. 9; therefore, the letter"B" has been added to those components in order to distinguish those components of Fig. 9.

Thus, the bell guides 128B and 140B have attached thereto the support members 134B, 146B which in turn attach to the caisson means 2A and 4A. Extending from the bell guide 128B is the diagonal cross-support 162B that attaches to the caisson means 2A while extending from the bell guide 140B is the diagonal cross-support 164B that attaches to the caisson means 4A.

Extending from the caisson means 2A is the diagonal cross-support 166B that attaches to the bell guide means 86B. Extending from the bell guide caisson means 4A is the diagonal cross-support 168B that attaches to the bell guide means 96. It should be noted that the bell guides 84,94 and caisson means 2A, 4A may also have diagonal cross-supports.

The modular deck 124B, 136B will be lowered via a crane.

The caisson means 2A and 4A will be joined together; they will also have a spacer member that allows the internal diameter to be larger enough in order to slip-over the caisson 154. Once at the proper depth, the spacer may be removed and the leg members (numbers 6,8,14, and 16 of Fig. 1A) may be properly tightened

about the caisson 154 by underwater divers as previously set out.

The number of modular decks will be based on the depth of the water. Several more modular decks may be added to the structure of Fig. 10 if necessary. One of the advantages of the present invention is that the modular deck components are essentially identical. Multiple decks may be fabricated and placed onto the working barge which aids in the speed of completion as well as the economic efficiency.

Once the number of modular decks are positioned and attached to the caisson, the operator may then drive piles 216,218 into the corner bell guide means 128,140. After the piles 216,218 are driven into the corner bell guide means 128,140, the operator may complete installation of a surface deck, and may thereafter, drill a well utilizing the caisson means 154.

Further, the operator may actually use the piles 216,218 thus driven for well bores in order to drill additional wells. Still yet another operation is to install additional well bores in the inner triangular areas of the various connected decks, that area being represented by the numeral 200 of Figs. 5 and 7. In other words, with appropriate bracing, additional well bores may be added in the area 200.

Referring now to Figs. 11A-11E, another embodiment of the invention depicting a sequence of installation will now be described. Thus, Fig. 11A shows the caisson 154 already in place on the sea floor 156, with the numeral 210 representing the ocean. The Fig. 11B depicts the sequence wherein the ocean floor mat 123 has been assembled and lowered onto the ocean floor 156.

Afterwards, the operator will have the surface pilings 212,214 driven into place as shown in Fig. 11C.

Next, Fig. 11D shows the sequence wherein the operator has lowered and fastened the modular decks 151A, 151B, 151C, 151D,

151E, and 151F about the caisson 154. The modular decks 151A- 151F characterize the situation wherein the modular decks 151A- 151F are stacked high enough so that the top deck 151F is placed above the ocean 210. It should be noted that with the embodiments described, the ocean mat 123, the first modular deck 151A, the second modular deck 151B, etc will contain the bell guides which form a first corner, a second corner, a third corner and a fourth corner, with the first corner of the deck 151A matching up with the first corner of the deck 151B and so on.

Therefore, as seen in Fig. 11E, the operator has driven pile members 216 and 218 through the bell guides (actually four pile members have been placed therein, but only two are shown since the Fig. 11E is two-dimensional). A platform 220 has been added above the top deck above the water line.

Fig. 12 is an illustrated view of the embodiment from Fig.

11 constructed in accordance with the teachings of the present invention. Thus, the ocean floor mat 123 coupled with five modular decks 151A, 151B, 151C, 151D, and 151E have been positioned on the caisson 154, with the surface piles 212 and 214 as well as the piles 216 and 218 driven into place in accordance with the teachings of the invention.

Changes and modifications in the specifically described embodiments can be carried out without departing from the scope of the invention which is intended to be limited only by the scope of the appended claims.