US3474630A - Frangible port closure - Google Patents

Description

0a. 2a, 1969 |.c.PosoNowsKl 3,414,630

FRANGIBLE PORT CLOSURE Filed June 4. 1968 ..L. Y E

United States Patent 3,474,630 FRANGIBLE PORT CLOSURE Ivo C. Pogonowski, Houston, Tex., assignor to Texaco Inc., New York, N.Y., a corporation of Delaware Filed June 4, 1968, Ser. No. 734,342 Int. Cl. E021) 17/00, 21/00; F16 15/06 U.S. Cl. 6146.5 15 Claims ABSTRACT OF THE DISCLOSURE The invention relates to a frangible closure for an aperture formed in a fluid tight bulkhead for use within an underwater structure. It relates particularly to a water tight closure adapted to form a temporary seal across a bulkhead. The closure is adequate to maintain a water tight condition, under pressure, and yet fragile enough to fracture when forcibly contacted by a conductor pipe or similar member being passed through the aperture, whereby the pipe will be sealably engaged with said bulkhead.

BACKGROUND OF THE INVENTION In many structures adapted for underwater usage such as offshore marine drilling platforms, platform supports, and the like, the latter are frequently adapted to be at least partially buoyant. The feature of buoyancy entails several distinct advantages. First, the support structure might be floated to a desired position and thereafter lowered as required by controlled flooding of scalable compartments. Secondly, the scalable compartments within the structure constituted a convenient storage facility for crude oil removed from the ground.

An example of this type of structure is often found in marine platforms supported on a single column. -In such structures, the column extends from the ocean floor to a position above the water surface. The column thereby forms not only a support for the equipment deck, but also a protective jacket about internally positioned conductors which extend longitudinally of the column and are adapted to receive the normal complement of producing and drilling pipes.

The number of such conductors actually used is variable depending on the productivity of the particular location. In the instance of a relatively large support casing, the conductors might number as many as 25 or 30, discretely positionel through the casing.

To facilitate the placing of a marine platform, whether of the single, or multiple support leg type, in a body of Water, it is expedient to insert the pipe conductors subsequent to the casing being set in an upright, supporting position. However, to maintain the controlled buoyancy necessary to effect the positioning of such a casing or platform support, the column must of necessity embody a number of controlled buoyancy tanks. In the instance of a relatively simple structure comprising basically a single elongated support column, the latter is normally provided with transversely placed and longitudinally spaced bulkheads, adjacent of which bulkheads define evacuable or buoyancy controllable chambers.

To maintain the variable buoyant capacity of these respective chambers, the transverse bulkheads are initially made fluid tight and yet adapted to subsequently receive the one or more conductors passing longitudinally of the casing. However in order that the oil storing feature of the column might be retained, the respective chambers, which are transversed by the conductors, must similarly be sealed off between bulkheads.

-For relatively shallow water operation it is a simple matter to provide each casing bulkhead with a number of openings which will subsequently receive a conductor pipe. These openings are initially closed to seal the casing,

'ice

which closure means normally comprises a welded or bolted into place cover disposed across each individual opening. To receive the conductors, the respective closures are usually removed by a diver. After the conductors are lowered through the aligned bulkhead apertures the conductors are Welded into place.

While this procedure is feasible for relatively shallow water adapted to diver operations, in the instance of deep water installations the problem is somewhat compounded. Not only is the initially installation cost greatly increased by the use of divers for waters in depths of approximately 300 to 1,000 feet, but such an operation is time consuming and uneconomical.

For example to install a plurality of conductors in a relatively deep water location, it is necessary for the diver to not only remove the temporary closure at each bulkhead, but also to subsequently weld the conductor pipe to the bulkhead thereby forming a peripheral water tight seal.

It is therefore an object of the present invention to provide a novel marine platform support adapted to receive at least one, and preferably a plurality of longitudinally positioned conductors or similar pipes. Another object is to provide a support column of the type described particularly adapted to receive one or more conductor pipes longitudinally therethrough subsequent to the column being positioned uprightly in an offshore location. A further object is to provide a frangible closure adapted to sealably close an under water aperture subsequent to insertion of conductor members therethrough such that said members will be sealably positioned. A still further object is to provide an arrangement whereby one or more pipe conductors may be set and positioned in a marine platform support column subsequent to the latter being set into working position.

DESCRIPTION OF THE DRAWINGS In the drawings, FIGURE 1 comprises a side elevation illustrating an offshore marine platform set in position on an ocean floor. FIGURE 2 is an enlarged segmentary veiw in cross section showing a portion of the upright casing of FIGURE 1. FIGURE 3 is a view taken along line 33 in FIGURE 2. FIGURE 4 is an enlarged segmentary view in cross section of one embodiment of the closure assembly. FIGURES 5 to 8 are views similar to FIGURE 4 showing alternate embodiments of the closure assembly.

In brief, the basic objectives of the invention are achieved by the provision of an elongated, upright marine platform support which is adapted to receive a plurality of conductor casings. The support, or column member is provided with a plurality of longitudinally spaced water tight bulkheads, each of which includes apertures formed therein and disposed in substantial longitudinal alignment with similar apertures in the other bulkheads. The number of apertures so formed is usually indefinite since the ultimate productivity of the well will determine the number of conductors to be subsequently set in a column, which productivity normally is unknown at the time the platform is lowered into position. Initially, each bulkhead aperture is provided with a frangible closure to fluid tightly seal the opening, which closure however may be readily shattered by a conductor pipe forcefully passed therethrough. The closure assembly serves the further purpose of guiding the downwardly moving conductor pipe as the latter approaches each bulkhead so that the conductor will most effectively strike the frangible portion of the closure, and be sealed to the bulkhead.

Referring to FIGURE 1, a marine platform support member of the type contemplated is shown and includes elongated casing 10 formed of a cylindrical water tight column or casing of relatively large diameter. The upper end of the column supports a drill platform or deck 11 above the water surface. The deck accommodates a drill table, derrick, and accessory equipment normally associated with the drilling and producing facilities of an offshore well site. While the present description and drawings are directed specifically to a structure utilizing but a single column for supporting a platform, it is understood that a plurality of such supports could as readily be utilized depending on the particular circumstance and design of the unit. Further, although the present description relates to a support column 10 adapted to accommodate but four conductors, the actual number which might be practically received is a function of the design of the column which in turn relates to the depth of the Water and the weight of the supported structure.

The lower end of upstanding casing 10 is provided with a supporting base as representatively shown in FIGURE 1, comprising a plurality of footing members 16 and 17. A cross member 20, together with legs 18 and 19 extend from the respective base members upwardly connecting to the column to provide lateral support to the casing 10.

As shown in FIGURE 2, casing 10 includes an elongated cylindrical member fabricated of individual sections of steel pipe or casing. A plurality of bulkheads 12 and 13 are peripherally welded to the casing inner wall, thereby forming between adjacent of said bulkheads, a buoyant chamber. The respective chambers are controlled by a suitable pipe and valving system not presently shown, but which is communicated with sources of oil and water and air. Such piping serves the purpose of regulating the content of the respective chambers whether for controlling the buoyancy of the column or merely for storing oil.

Referring again to FIGURE 2, conductor pipes 21 and 22 depend downwardly from deck 11 and are normally imbedded for a short distance into the ocean floor by jetting, driving, or other appropriate method. Each conductor bulkhead, 12 for example, is provided with a plurality of apertures 15 and 15' disposed in axial alignment, which apertures in adjacent bulkheads being of a size compatible with the downwardly passing conductor pipe.

A closure assembly 23 is positioned at each bulkhead aperture and is adapted to slideably receive, and engage a conductor outer wall to form an annular fluid tight seal with the conductor after the latter has been lowered into place.

Referring to FIGURE 4, closure assembly 23, in its simplest form is shown, and comprises basically a frangible plate or disc 26 disposed across opening 27, having the disc edges overlying at least a portion of the openings rim. A ring seal or gasket 29 is compressibly deformed between bulkhead 28 and frangible plate 26 to form an annular liquid tight seal prior to insertion of a conductor pipe. A conductor guide 32 comprises an inwardly tapered conical section which is larger at one end than the diameter of the conductor and tapers to a constricted opening terminating adjacent the frangible plate. In such position, a conductor will be received in conductor guide 32 and while being lowered is directed to its proper position for fracturing frangible plate 26.

As seen in FIGURE 8, seal ring 29 is deformed against the wall of conductor 21 and maintains the water tight integrity of bulkhead 12 both prior to, and subsequent to insertion of a conductor. Said seal ring 29 includes a center opening of a size slightly smaller in diameter than the conductor 21 outside diameter such that as the latter fractures frangible plate 26, it will engage the seal ring center opening in a sliding, although liquid tight annular seal. Thus as a conductor 21 is progressively passed through each of the bulkhead apertures, the frangible closures in each location will be shattered. Further, the individual fluid tight integrity of each buoyant compartment will be assured by immediate engagement of the conductor outer wall with a seal ring center opening.

FIGURE illustrates an alternate embodiment of the above described closure assembly wherein frangible plate 34 is sealably fixed to the underside of bulkhead 36 with a compressible seal ring 37 deformed between said respective plate and bulkhead to form the desired annular seal both with the bulkhead and with the conductor. The upper side of plate 36 is provided with conductor guide 37 which includes a flange 38 peripherally welded at a Water tight seam 40 to the bulkhead. Guide passage 39 is formed of inwardly tapered Walls as herein noted, which receive a downwardly passing conductor and directs the same toward the bulkhead aperture 41.

FIGURE 6 illustrates a further embodiment of the novel, frangible closure assembly wherein bulkhead 42 is provided with an aperture 43. Frangible plate 44 is positioned across opening 43 overlying the rim of the latter. The plate 44 under surface is provided with a circular fracture groove or notch 46 which in effect weakens the structure of the plate such that upon contact with the downwardly moving conductor 47, said plate will fracture at the weakened portion defined by the fracture notch.

Seal ring 48 is compressibly deformed against the upper surface of the frangible plate 44 to form an annular water tight seal both with the bulkhead, and with the subsequently positioned conductor 47. Plate 44 and gasket 48 are maintained in position by a retainer 49 comprising a flange 51 from which depends a shoulder 52, the inner edge of which defines a central opening adapted to slideably receive conductor 47. Shoulder 52 is spaced from the surface of bulkhead 42 to define a circular channel in which the respective frangible plate and seal ring are retained. A conductor guide portion 53 depends outwardly from shoulder 52 and is incorporated therewith. As in the instance of the embodiment shown in FIGURE 4, the conductor guide 53 includes primarily a conical passage having an opening to receive the conductor 47, and being tapered to a constricted passage slightly larger than the diameter of said conductor.

In the instance of an elongated column 10 disposed in relatively deep water, it is usually necessary to utilize a series of bulkheads both for laterally bracing the column, and for directing the respective conductors. The fracturing of a number of frangible closures could constitute a problem of accumulation particularly in the in stance where a relatively large number of conductors are to pass through a single casing. As shown in FIGURE 6, therefore frangible plate 44 may be provided with a retainer such as a rivet or bracket 54 adapted to receive a restraining chain or similar line 57. The remote end of chain 57 is connected to a similar bracket welded to the underside of bulkhead 42.

' As frangible plate 44 is fractured by the downwardly passing conductor 47, the center of the plate is sheared at the notch 46. The separated center portion then swings to one side, suspended by chain 57 at a position adjacent to conductor 47. The retention of the center portions of the various fractured plates avoids accumulation of said plates at the next lower bulkhead which accumulation might tend to deflect a conductor or provoke a faulty positioning of the conductor on said next lower bulkhead.

FIGURE 7 illustrates still another embodiment of the novel closure comprising essentially a frangible plate assembly 61 which is maintained across aperture 62 by retainer 63. The plate assembly includes frangile plate 64 having a relatively Wide flange 66 with inwardly spaced, upstanding hub or rim 67. The latter forms a confining wall adapted to restrain inward contraction of the seal ring 68 which is deformed outwardly by the hub prior to engaging the wall of conductor pipe 76. As in the previously described embodiments of the closure member, a conductor guide 71 is carried on the casing bulkhead and so shaped to lead a downwardly passing conductor pipe into engagement with the frangible plate 64.

In this arrangement, plate 64 is fabricated in such manner to facilitate its being positioned against bulkhead 72 by locating the plate assembly between the retainer lip 73 and the bulkhead surface. Thus, circular hub 67 is topped by a curved crown 74 at the upper side for engaging the downwardly moving conductor edge.

The function of hub 67 is two-fold. First, it maintains seal ring 68 in a retracted, prestressed position with the center opening stressed apart or deformed radially outwardly. The hub is thus provided with an outer diameter approximately the diameter of downwardly passing conductor 76. As conductor 76 is directed by guide piece 71 into engagement with crown 74, the hub will tend to shear through the thickness of flange 66 thereby in effect shearing out the entire center section of the frangible plate. To facilitate this severing action, a circular fracture not 78 may be formed in the surface of the flange 66 immediately adjacent to the periphery of hub 67.

As the hub is dislodged and urged through the aperture 62 after being severed from the flange, seal ring 68 will release from its deformed position and move outwardly to contact the downwardly passing conductor wall in a peripheral seal. The central opening in seal ring 68 is so formed to provide a suitable water tight, although sliding fit between the seal edge and the conductor thereby assuring that as the latter becomes fully positioned and stationary, the light peripheral seal is maintained to sustain the condition of the respective buoyancy chambers are in condition then to function as buoyancy elements or as oil storage means. Plate 64 may be provided with a chain as mentioned with respect to the assembly shown in FIGURE 6 for retaining the center segment of plate 64 when the latter has been dislodged from its position.

Plate assembly 61 is located across aperture 62 by retainer 63, the lip 73 of which defines, with the bulkhead surface, a confining channel into which the entire plate assembly might readily be inserted prior to retainer 63 being welded to the surface of bulkhead 72. Retainer 63 is preferably so welded to form a water tight peripheral joint about the retainer to again maintain the leak proof condition by the adjacent buoyant chambers formed by the respective bulkheads.

The frangible plate which forms at least a part of the sealing member in the presently described invention may be fabricated of a material best adapted to the dual functions of both withsanding a fluid pressure in deep water, and shattering on impact. For example it has been found that to withstand the water pressure at greatly sumerged depths to the point of being fractured by a force of a downwardly moving conductor, certain glass or glass derivatives constitute a satisfactory plate material. The thickness of the glass is of course dependent on the particular depth of water in which the column will be positioned. Another material suitable to the present application and similar to glass is a thermosetting plastic material such as Lucite. A desirable characteristic of the frangible material of course is that it will sever readily from the main body of the plate and not tear as would be the case in the instance of most metallic closure members although certain thicknesses of such metallic members could produce the desired result.

In that the normal severance portion constitutes a circular area defined by the thickness of the casing wall, the frangible portion of the closure may be limited. To withstand elevated water pressures then, the closure may be reinforced across the center to avoid bending and deflection stresses inherent in circular members subjected to static pressure. Further, while a relatively simple circular gasket is adapted to provide a fluid tight seal about the casing, said seal element may assume a number of configurations to achieve the desired purpose.

With respect to the insertion of one or more elongated conductors into a casing as herein described, the casing is normally floated or barged to its deep water position without the conductors. The unit is then caused to adjust to a substantially upright attitude in the water by controlled flooding of buoyant chambers at the casing lower end. In said upright position, the casing is lowered to its its desired location with the lower end in contact with, or sunk at least partially into the ocean bottom. Following usual practice, it is understood that the casing would have a suitable support base such as shown in FIGURE 1, or an equivalent arrangement for maintaining an upright posture. In such an anchored condition the conductor pipes are individually lowered into the casing from a derrick barge or from the supported deck 11, to engage and be sealed to successive bulkheads.

The conductor, following standard practice, comprises end welded, suitably sized pipe lengths joined to form a continuous conductor having a diameter appropriate to the diameter of the aperture in the respective bulkheads. The weight of the conductor string is normally sufliciently great when lowered and guided onto a closure plate to break or shear the frangible portion thereby permitting the conductor to slide through the bulkhead aperture and sealably engage the surrounding seal ring. The conductor is then successively lowered for a similar engagement with the remaining bulkheads. In each instance, the frangible member is fractured and the peripheral seal made with the conductor outer surface.

While we have described but one form of guide conductor which will suitably bring the lower end of the conductor into engagement with the closure plate, it is understood that other guide means might as well be employed to achieve a similar function. Particularly at extreme water depths, the possibility exists of the column or the casing 10, in assuming a vertical attitude, might incorporate a degree of deflection of the casing due to water pressure. In order therefore to properly guide the conductor into engagement with the next lower frangible plate, additional intermediate guide members might be employed to properly lead the conductor on its downward path.

Obviously many modifications and variations of the invention, as hereinafter set forth, may be made without departing from the spirit and scope thereof, and therefore, only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. In a marine platform for an offshore oil producing installation including a casing normally at least partially submerged in an upright position and extending from the ocean bottom to the surface thereof, a plurality of bulkheads carried in said casing and spaced longitudinally thereof to define fluid tight buoyancy chambers therebetween, said bulkheads including apertures disposed in substantial axial alignment and adapted to sealably register at least one elongated conductor pipe when the latter is passed longitudinally of said casing subsequent to said casing being disposed in an upright, partially submerged position at a drilling site; and

sealing means carried on said plurality of bulkheads to maintain the fluid tight integrity thereof prior to, and subsequent to registration of said at least one conductor pipe therethrough and including;

a closure member disposed in sealing relationship with each of said apertures,

said closure member being formed at least in part of a frangible material to permit fracture of said frangible portion when said closure member is abuttingly engaged by the end of a conductor pipe being passed through said respective aligned apertures, and

seal means defining a peripheral fluid tight joint between said conductor pipe and said bulkhead when said pipe is registered in said apertures.

2. In a marine platform as defined in claim 1 wherein said closure member includes a frangible portion adapted to being fractured and a reinforcing portion cooperative with said frangible portion.

3. In a marine platform as defined in claim 1 wherein the frangible portion of said closure member is formed of a material chosen from the group consisting of glass, ceramic, thermosetting plastic, and Wood.

4. In a marine platform as defined in claim 1 wherein said sealing means includes a gasket disposed intermediate said closure member and said bulkhead, said gasket having a center opening slightly smaller than the diameter of the conductor pipe passed therethrough and being adapted to form an annular seal about the periphery of said pipe.

5. In a marine platform as defined in claim 1 including a guide means carried at the upper side of said closure member and having an opening to guidably receive the end of said conductor pipe for directing the latter into engagement with said closure member.

6. In a marine platform as defined in claim 4 wherein said guide member includes a conical section having an enlarged open end greater than the diameter of said pipe, and tapering to a constricted portion disposed adjacent to said closure member the latter being characterized by a diameter slightly greater than the diameter of said conductor pipe.

7. In a marine platform as defined in claim 5 wherein said guide member is positioned at the upper side of said bulkhead wherein said casing is in said upright position to receive said conductor pipe, and said closure member is sealably positioned at the lower side of the closure member.

8. In a marine platform as defined in claim 5 wherein said guide member includes a flange having a shoulder spaced from said bulkhead and defining an annular channel therebetween, said closure member being disposed within said annular channel and sealably engaging said bulkhead, and a conical portion depending from said shoulder in a direction away from said bulkhead to receive said conductor pipe for guiding the latter into engagement with said closure member.

9. In a marine platform as defined in claim 8 including seal means compressibly retained intermediate said shoulder and said closure member to define an annular liquid tight seal.

10. In a marine platform as defined in claim 1 wherein the frangible portion of said closure member includes a groove formed into the surface thereof adjacent to the rim of said aperture, and having a diameter slightly greater than the diameter of said conductor pipe to permit fracturing of said frangible closure.

11. In a marine platform as defined in claim 10 wherein said groove is formed in the underside of said frangible portion.

12. In a marine platform as defined in claim 10 wherein said groove is formed in the top side of said frangible portion.

13. In a marine platform as defined in claim 1 including connecting means having one end connected to said closure plate and the other end connected to said bulkhead for supporting the fractured portion of said closure member after said conductor pipe has been passed therethrough.

14. In a marine platform as defined in claim 1, wherein said closure member includes an upstanding circular rim formed on the surface thereof and having a diameter approximating the diameter of said conductor pipe, said seal means being disposed externally of said rim and being normally outwardly deformed into an open position by the latter, whereby engagement of said conductor pipe end with said rim will cause the frangible portion of said closure member to fracture, thereby releasing said deformed seal means for engaging the downwardly passing Wall of said conductor pipe.

15. In a marine platform as defined in claim 14 including a circular groove formed into the side of said closure member frangible portion opposite to said rim.

References Cited UNITED STATES PATENTS 2,771,747 11/1956 Rechtin 6l46.5 2,979,910 4/1961 Crake 6l46 JACOB SHAPIRO, Primary Examiner US. Cl. X.R.

Images