Undersea Riser Structure

Abstract

A means, which allows a multipipe riser to be remotely connected to a base located on the ocean floor from a floating vessel, has, formed on the base, a fixed rigid vertical post and, formed on the riser, a column at the lower end thereof which column mates with the post. A pulldown line is threaded through a suitable structure on the base from a surface vessel and attached to the column on the riser so that the column can be pulled down over the post by pulling on the line. Since various pipes in the riser need to communicate with specific pipes in the base, the riser and base have means for rotating the riser on a vertical axis as the column engages the post to orient azimuthally the riser to the base.

Description

FIELD OF THE INVENTION

This invention relates to the art of connecting a riser to an underwater structure and more particularly to the art of connecting the two remotely from the surface of the water.

BACKGROUND

One method of producing oil and gas from deep sea wells is described in the U.S. Pat. No. 3,366,173. The oil and gas, from a plurality of wells, are fed to the centrally located satellite located on the ocean floor. A riser delivers the oil and gas to the surface and feeds electrical power and water to the satellite as required. Normally, subassemblies of the system are made on land and dropped to the ocean floor where they are assembled by divers if the water is not too deep. In deep water, submarines with suitable manipulators are used. The capabilities of these manipulators are limited besides being expensive to operate.

Therefore an object of this invention is to provide a riser and an ocean base wherein the riser can be connected to the base from a surface vessel with the minimal use of or, preferably, without the use of submarines or divers.

Another object of this invention is to provide a means for aligning remotely the various pipes of a multiple riser with respective pipes in the base.

These and other objects and features of advantage will become apparent from the following description when taken in conjunction with the accompanying drawings wherein:

FIG. 1 is a schematic illustration of the overall operation of connecting the riser to an ocean base from the surface of the ocean;

FIG. 2 is an enlarged partial sectional elevation of a portion of the base and riser shown in FIG. 1;

FIG. 3 is a view taken on line 3--3 of FIG. 2 showing a plan of a portion of the base and riser;

FIG. 4 is a view taken on line 4--4 of FIG. 2 showing a side elevation of a portion of the base and riser; and

FIG. 5 is a further enlarged section of the base and riser in elevation.

DESCRIPTION OF THE DRAWINGS

Referring to the drawings and to FIG. 1 in particular, there is shown the preferred method of connecting a riser 10 to a base or foundation 12. Two floating barges 14 and 15 are utilized to make the connection with the aid of pull down and guidelines made of wire rope 16 and 17, that are connected between the respective barges and the riser 10 as shown in FIG. 2 and will be described hereinafter.

Referring to FIGS. 2 and 3, the base 12 has radially extending pipes 21 and 22 disposed one over the other as shown in FIG. 2. The pipes 21 and 22 extend radially from a center post 23. The pipes 21 and 22 and post 23 form an integral unit. For example, each pipe 21 is braced to a respective pipe 22 disposed below by gusset plates 24. An annular platform plate 26 is welded over the pipes 21 and to the center post 23 while another annular plate 27 is welded to pipes 22 and also to post 23 to provide further stiffness and strength. The base 12 is fixed to the ocean floor by tying down the free ends of pipes 21 and 22 by suitable means such as piling, (not shown). Axially disposed within post 23 is a main pipe 31 which has a 90.degree. bend and protrudes through an opening 32a in the post 23 to a place of use. The main pipe 31 is supported by, for example, an aperture disk 32 at the lower end and its upper end is fixed to a suitably male coupling 33 which is mounted on an inwardly extending flange 34 on the post 23. On platform plate 26 is disposed a fixture 36 which supports the ends of, for example, three pipes 37, 38 and 39. The ends terminate in a suitable male coupling 41 of the type described in a copending U.S. Pat. Application Ser. No. 837,083, filed June 25, 1969, and assigned to the same assignee as this application. Another fixture 42 is also disposed on plate 26 which fixture 42 supports an asmuth alignment means 42a to be described hereinafter. The base 12 also includes a J-shaped cable guide tube 44 which has one end located within the post 23 and the other end located outside the post 23. Tube 44 is suitably fixed to the base 12, for example, by welds. A suitable aperture 35 is formed in flange 34 on post 23 through which passes the rope 16 that is also threaded through tube 44.

The riser 10 has a rigid tubular column 51 which slides over the center post 23 onto the base. Column 51 encloses, for example, pipes 31a, 37a, 38a and 39a. Pipe 31a is preferably centrally located and has its lower end supported within an apertured disk 52 so that some lateral movement is provided between the pipe 31a and column 51, as will be explained hereinafter. On the end of pipe 31a is disposed a suitable female coupling 33a that engages in a standard manner to male coupling 33. Pipes 37a, 38a and 39a extend down the column 51, bend and preferably pass through the wall of the column 51. The pipes bend downward and terminate within a female coupling 41a that engages the male coupling 41. Coupling 41a is attached to column 51 by a suitable structure 53. On the internal wall surface of column 51 is disposed a lug 54 having an eyelet through which a rope socket 55 is attached. Rope socket 55 is fixed to the end of the wire rope 16. Rope 17 is attached to the outer surface of column 51 through an eyelet 67. In addition, guide sleeves 61 and 62 (FIG. 3) for wire ropes 16 and 17, respectively, are attached to column 51 by, for example, angle steel beams 63, 64 and 65 and a tee steel beam 66.

METHOD OF ASSEMBLY

The base 12 has been installed on the ocean floor by some suitable means which is not part of this invention, with the center post 23 extending substantially vertically. Wire rope 16 has been threaded through J-shaped pipe 44 by means which form no part of this invention. The riser 10 was in an initial floating position on the surface of the ocean with the rope socket 55 attached to lug 54. In addition, wire rope 16 has been also threaded through guide sleeve 61 and wire rope 17 has been threaded through guide sleeve 62 and fixed to eyelet 67. Through suitable winches on barge 14, wire rope 16 is hauled into the barge causing the column 51 to be pulled to the ocean floor. Meantime wire rope 17 is payed out from floating barge 15 at a rate to stabilize the descent of the riser. When the column 51 is over the center post 23 a tapered conical portion 71 on the lower end of the column 51 and a tapered conical portion 72 on the upper end of the post function to aid the alignment of the column 51 over the posts 23. To align the two in the azimuthal position in order that pipes 37, 38 and 39 can be connected to pipes 37a, 38a and 39, respectively, column 51 has fixed to its outside surface a radially extended lug 75 which engages the alignment plate 43 fixed to fixture 42. Referring to FIG. 4 the radially extended lug 75 on the column engages the sloping edges 43a on plates 43 causing the lug to be guided into a slot formed in the plate 43 and in turn rotates the column 51. When the lug 75 is located just above a slot, coupling 41a is located above coupling 41 and coupling 33a is located above coupling 33. Now the male portions of the coupling can slip into the female portions of the couplings as column 51 is further lowered over the center posts 23 by pulling on wire rope 16. To further insure that each female portion of the couplings is aligned with each male portion of the couplings each female portion is made to move laterally slightly with respect to the column 51. This lateral motion is provided as shown in FIG. 5 by providing play between the parts. For example, pipe 31a has mounted thereto a spherical shaped flange 81 as shown. The radius of curvature of this flange is such that its center is at a point A, located axially on pipe 31a at the end thereof. This flange is disposed within a spherically shaped recess 82 formed by an annular washer 83 bolted to the apertured disk 52. The washer and disk are so shaped as to form the recess 82 when the two are bolted together. This same structure can be adapted to fixture 53 to provide spherical motion relative to the female coupling 41a. The couplings are secured remotely in the same manner as described in the abovementioned copending patent application.

With the present disclosure in view modification of the invention will appear to those skilled in the art. Accordingly the invention is not limited to the exact details of the illustrated preferred embodiment but includes all such modifications and variations coming within the scope of the invention as defined in the claims.

Claims

What is claimed is:

1. An undersea riser structure in an ocean comprising:

a base fixed to the ocean floor;

a vertically disposed hollow rigid post fixed to said base;

a plurality of fluid conducting pipes fixed to said base;

a riser that is attached to said base and rises towards the surface of the ocean;

a rigid tubular column fixed to the lower end of said riser for sliding over said post;

a plurality of fluid conducting pipes carried by said risers;

a J-shaped tube fixed to said base with one end disposed within said post and the other end disposed outside of said post;

a wire rope threaded through said J-shaped tube and having one end extending to the ocean surface and the other end connected to the interior of said tubular columns to allow the column to slip over said post as said rope is pulled at the surface; and

first and second means for rotating the riser on a vertical axis as said riser is being lowered to said base so that said pipes in said riser are aligned with preselected pipes in said base before the respective pipes come in contact, said first means is disposed on said risers, while said second means is disposed on said base.

2. The structure of claim 1 wherein:

said fourth means includes a lug protruding radially from said column;

said fifth means includes an alignment plate disposed on said base spaced from said post and oriented substantially normal to a radius extending from the axis of said post; and

said alignment plate having a V-slot for engaging said lug as said riser is being lowered.

3. The structure of claim 2 wherein:

a guide sleeve is disposed on said riser, radially spaced from said column for each of said wire ropes.

4. The structure of claim 1 wherein:

said first means includes a lug protruding radially from said column;

said second means includes an alignment plate disposed on said base spaced from said post and oriented substantially normal to a radius extending from the axis of said post; and

said alignment plate having a V-slot for engaging said lug as said riser is being lowered.

5. The structure of claim 4 wherein:

a guide sleeve is disposed on said riser, radially spaced from said column for each of said wire ropes.

6. An undersea base structure which is capable of being attached to a riser, said base structure comprising:

a foundation fixed to the sea floor;

a plurality of fluid conducting pipes fixed to said foundation;

a vertically disposed hollow post fixed to said foundation;

a vertically disposed hollow post fixed to said foundation and disposed to engage said riser;

second means on said foundation disposed to engage said riser to rotate said riser on a vertical axis to a preselected aximuthal position; and

a J-shaped tube disposed on said foundation and having one end disposed within said post and having the other end disposed outside of said post, said shaped tube being adapted to engage a wire rope in sliding relationship.