US2772539A

US2772539A - Foundation for off-shore drilling rig

Info

Publication number: US2772539A
Application number: US206583A
Authority: US
Inventors: Sandberg William Andrew
Original assignee: Individual
Current assignee: Individual
Priority date: 1951-01-18
Filing date: 1951-01-18
Publication date: 1956-12-04
Anticipated expiration: 1973-12-04

Description

1956 w. A. SANDBERG FOUNDATION FOR OFF-SHORE DRILLING RIG 2 Sheets-Sheet 1 Filed Jan. 18, 1951 s bwuw Til, w

FIG.7

} WM. A. SANDBE'RG INVENTOR FMS.

TORNE'Y Dec, 4, 1956 w. A. SANDBERG 2,772,539

FOUNDATION FOR OFF-SHORE DRILLING RIG Filed. Jan. 18, 1951 2 Sheets-Sheet 2 WM. A ANDBERG INVENTOR TORNEY Unite States Patent FOUNDATION FOR OFF-SHORE DRILLING RIG William Andrew Sandherg, South Pasadena, Calif.

Application January 18, 1951, Serial No. 206,583

6 (Ilaims. (Cl. 61-465) This invention relates to apparatus for drilling submarine wells and useful particularly for the drilling of exploratory wells in the open ocean and in deep water.

A purpose of the invention is to provide a foundation for a drilling rig which may easily be erected and as easily dirnantled after it has servved its purpose.-

A purpose of the invention is to provide a foundation of this type which may be constructed in detachable, relatively portable units, floated to the position in which the foundation is to be placed, assembled at the surface of the ocean and, finally, caused to sink to the ocean bottom in an upright position.

A purpose of the invention is to provide a foundation of the described type which may be plumbed after it is placed in position, regardless of the nature of the bottom on which it rests, be this bottom rough or smooth, level or inclined.

The invention may best be understood with reference to the attached drawings and the following description thereof, in which Fig. l is an elevation of the assembled structure, on a small scale and omitting much of the detail, in its posi tion on the ocean floor;

Pig. 2 is a plan View taken above the upper working platform, as on the line 2-2 of Fig. 1;

Fig. 3 is an elevation of the structure on a larger scale and showing more though not all of the detail, portions being broken away as on the line 3-3 of Fig. 4 to show internal structure;

Fig. 4 is a section through the hub and column and a plan view of one of the legs, taken on the broken line 4 s of Fig. 3;

Fig. 5 is a horizontal section through' the upper part of the column, as on the line 5-5 of Fig. 3;

Fig. 6 is a detail, in side elevation, of one of the pinned joints by which the legs are attached to the hub;

Pig. 7 is a side elevation of one of the hinge elements by which sections of the permanent guys are connected;

Fig. 8 is a vertical section through the same elements at a 90 angle to Fig. '7;

Fig. 9 is a vertical section through one of the piles, the pile guide and the sealing ring;

Fig. 10 is a horizontal section on the line 10-10 of Fig. 9, and

'Fig. ll is a fragment, partly in section, of the lower left side of column 13, illustrating a preferred means for locking the rig-supporting assembly to the ocean floor.

Referring first to Figs. 1, 2 and 3, the structure consists of the following principal elements: a central hub 10 comprising a pivot bearing; three legs 11-11-11 attaci ed to the hub, preferably in such manner as to be removable, and forming with the hub a tripod 12 adapted to rest on the ocean floor; a central column or tower 13 having its lower end closed by curved plating 14 generally spherical in form and in engagement with a cone shaped socket 15 formed in the hub; guys 16-16 extending from the ends of the legs to the upper end of the column, these guys being adjustable to permit the column "ice to be plumbed, and a plurality of tubular piles 17-17 passing through the column and the hub. A lower working floor 18, an upper working floor 19 and a drilling derrick 20 are shown as supported by the column but are no part of the invention.

Referring next to Figs. 3 and 4, hub 10 is constructed as an annular, hollow, water-tight chamber 21, consisting of

concentric cylinders

22 and 23,

cone plates

24 and 15 and

cover plates

25 and 26. The chamber contains a cylindrical bulkhead 27, welded or otherwise secured to plate 26 and the lower end of cone 24. A plurality of downwardly flaring, sheet metal tubes 28, open at both ends, are also extended between cover plate 26 and cone plate 15 to permit the passage of piling 17 therethrough with adequate clearance to provide for the maximum inclination of hub 10 with relation to column 13.

The annular space between bulkhead 27 and cylinder 23 may be filled with concrete to surround tubes 28 and to form a backing for cone plate 15, which serves as a bearing surface to support the spherical lower end of column 13, which thus always contacts cone 15 in a circular path, regardless of the inclination of the column to the hub. Chamber 21 is reinforced and stiffened by radial plates 29-29, and tubes 30 and 31 are provided respectively to admit air to and discharge water from the chamber, to thus control the degree of buoyancy of the hub.

Column 13 may best be constructed as a cylinder of heavy plate and of large diameter, preferably of the order of one-tenth to one-twelfth its total length. For example, if the foundation is to be used in two hundred feet of water, the diameter may be of the order of twentyfeet, as the total height to the upper working platform is then about two hundred and forty feet.

A conductor pipe or tube 32, through which the well is drilled and cased, is centrally disposed in column 13 and extends for its entire length. A plurality of tubular pipe guides 33 are securely attached to the column, being disposed close to its inner face and extending through its curved bottom. The lower ends of these guides are cut off close to the outer face of spherical end plate 14 after welding thereto. The pile guides and conductor pipe may desirably be fixed in position throughout the length of the column by spaced perforated plates 34 which are normally required to brace the column shell radially against collapse.

A suitably reinforced closure plate 35 is located within column 13, adjacent its upper end, and is nonleakably sealed thereto. A manhole 36, with a detachable cover, is cut in this plate, and openings are provided therein for the passage of conductor pipe 32, pile guides 33 and airsupply and water-venting pipes 37 and 38 extending into the column as shown in Fig. 3. All of these openings are effectually sealed around the tubes passing through them and, otherwise, the plate is imperforate.

In order to provide the requisite degree of buoyancy, the principal units comprised in the fabrication of the legs of tripod 12 should be of hollow, air tight construc tion. Accordingly, in the preferred form illustrated in Figs. 3 and 4, the lower members 39-39 of the legs are made in the shape of hollow box girders of rectangular cross section and the upper members 40-40 are made of tubing. At their inner ends, adjacent the hub, these members are tightly sealed, while at their outer ends they are left open, each pair communicating through suitable apertures with the interior of a vertical drum 41 to which they are nonleakably secured, as by welding.

Each of the drums is provided with an inverted V- shaped upper head 42 having one or more vertical flanges 43 drilled for connection of the stay or guy 16. The drum has also a conical lower head 4d, adapted to pene- 3 trate the ocean or other bottom on which the tripod rests while serving as a vertical support or pedestal.

It will be seen that the tripod leg above described is a unit consisting of a drum 41 and four horizontal members 39394d--40, all in continuous intercommunication, and suitable bracing members '45 and 46 for maintaining the horizontal members in position prior to attachment to the hub. The advantage of the conical form of lower drum head is that it provides a firm foundation for the tripod while eifectively preventing transverse shifting on the supporting bottom.

For the purpose of varying the buoyancy of the tripod leg unit, a tube 47 passes only through the upper head of drum 41 and a tube 48 extends to a point close to the drum bottom, providing respectively for supplying pressure air to and venting water from the drum and the communicating horizontal members. These tubes are intended to have hose connections of such length as to extend to the ocean surface when the drum is on the bottom.

The

horizontal leg members

39 and 40 are provided at their inner ends with lugs 49 mating with lugs 50, the

. latter extending outwardly through outer hub wall 22 and being welded to the two sides of plates 29. These lugs are perforated as at 51 to receive a heavy permanent pin. To assist in positioning these pins it is desirable to provide smaller mating lugs 52 and 53, perforated as at 54 for the insertion of a temporary tapered drift pin.

The guys 16 are composed of a plurality of tubular units 55, closed at each end and hinged together by the equivalent of a universal joint. A suggested fonn for this hinge connection is illustrated in Figs. 7 and 8. As shown in these figures, a pair of spaced plates 56 are inserted in slots formed in the wall of the tube and welded in place, and the end of the tube is closed by a cover plate 57. The ends of plates 56 form projecting lugs 58 spanning a thicker plate 59 which swivels on a pin 60 in the plane of Fig. 7.

The lower edge of plate 59 is notched as at 61 and mates with the notched upper edge of a similar plate 62 which is pivoted on the adjacent end of the next lower tubular element in the manner just described. A pin 63 is passed through all of the mating projections,

plates

59 and 62 swivelling around this pin in the plane of Fig. 8.

The lower end of the lowermost section of the guy is swingingly pinned, as at 64 in Figs. '3 and 4, to the flange 43 which projects from the upper end of drum 41, permitting the guy to be collapsed to a position of rest on top of the upper leg members. The upper end of the guy terminates in a threaded rod 65 which, when the guy is extended into functional position, passes through a plate 66 projected angularly from the wall of cylinder 13. A nut 67 rotated by a worm gear and pinion 68 (Fig. is provided for adjusting the tension of the guy. A cable 69 running over a winding drum 70 and attached to drum 41 as: at 71, is used as a temporary guy in assembling.

The method of assembling the above structure is based primarily on such proportioning of weight to displacement that the hub, central column and detached 'legs will float partially submerged in water and thus may be'towed separately to the approximate point of assembly and erection.

The first step is to draw the legs, one at a time, toward the hub until the openings through lugs 52 and 53 are close enough to register to permit a drift pin to be driven through mating holes 54. This will bring the larger openings through

lugs

49 and 50 into register and permit the heavy pins 51 to be inserted. Cables 72 running over winding drums 73, temporarily mounted on the upper face of the hub, are useful for bringing these parts together. The operation will also be facilitated by the use of the removable hydraulic jacks 74. These have a plunger 75 entering a conical element 76 mounted .in a previously exactly located position on the side of the hub (Figs. 3 and 4). The contact of the plunger with the interior of the cone guides the leg into the exact vertical and horizontal positions required for the insertion of the pins and also cushions the separately floating elements against excessive shocks due to wave action.

When these elements are assembled they form a rigid tripod, by reason of the wide vertical spacing of the inner ends of

leg members

39 and 49. This unit is lighter than water and remains at the surface so long as filled with air. When assembled, the unit is guided to the exact spot at which it is to be used and water is admitted to chamber 21, drums 41 and

leg members

39 and 40 until the unit sinks and comes to rest on the ocean floor, in the position shown in Fig. 1. At this time the guys 16 will float in a generally vertical position, and may later be drawn into position for connection with plates 66 by the use of a line passed around rod 65 and over a winch mounted temporarily on the upper end of the central column.

The central column 13 is then maneuvered until its rounded or lower end, which has previously been provided with a block of concrete 77 to cause it to float at a gentle inclination, is directly over the socket in hub 10. Water is then slowly admitted to the column through supply tube 37, causing the column to become more steeply inclined and more deeply submerged, until finally it assumes an upright position. The lower end of the column being maintained, during this subsidence, over the enlarged upper end opening in the hub, this rounded end is guided into its seat by the sloping inner wall 24. Before the column rests too heavily on its seat to permit it to be rotated, solid mandrels not shown are lowered through the pile guides 33 until they rest on the seat and will enter openings 28 in the seat when the column is slowly rotated. These mandrels are withdrawn after the column is locked down.

At any convenient time during the operation just described, the temporary guy cables 69, which have been attached to drums 41 prior to the submersion of the tripod, are carried over winding drums 70 and so adjusted as to maintain the column erect without other assistance.

When the bottom of the column is firmly seated in its socket, the permanent guys 16 are connected to the column as above described and the slack taken up, after which the temporary guys 69 are disconnected. The column and the tripod unit are then completely filled with water to help bring the assembly into firm engagement with the ocean floor. The column is then plumbed by adjustment of nuts 67 on rods 65.

The tubular piles 17 are now inserted through pile guides 33 and driven firmly into the ocean floor or, if preferred, cemented into previously prepared holes in the floor. When all have been firmly seated the piles are cut off at a level 83 above the upper ends of the pile guides and turnbuckles 84 are welded to the upper ends of the piles and to brackets 85 projected inwardly from the wall of the column. The turnbuckles are tightened until the column is brought into the firmest possible engagement with its seat and the conical lower ends of drums 41 are firmly embedded in the ocean floor. The piles are then filled with concrete up to at least the ocean floor level.

Air under pressure is then admitted to column 13 through pipe 37 and the water blown out of the column through vent pipe 38 (Fig. 3).

The pile guides '33 have been provided, prior to insertion in the column, with the sealing rings 78 detailed in Figs. 9 and 10, these rings being located at any convenient distance above concrete block 77, for example as illustrated in Fig. 3. Each of these units consists of a heavy, internally grooved steel ring 79, to which the ends of the adjacent guide sections are welded, a plurality of set screws 80 bearing on a steel split ring 81 located in the bottom of the groove, and a resilient ring 82, of

amass rubber or neoprene, Within the split ring and partially within the groove. The internal diameter of the resilient ring should be slightly greater than the outside diameter of the pile.

After the piles have been driven, the tightening of the set screws crowds the resilient ring against the face of the pile and the corners of the groove, forming a tight seal to prevent incursion of outside water after the column has been emptied.

The final step is to cut out a short length of pile guide, preferably immediately above grooved ring 79, remove the cut-out section of the guide and firmly weld the pile to the upper inner edge of ring 79. That portion of the pile above the weld may then be cut off and removed, and the cut-out section of the pile guide replaced and welded into position.

By these operations the assembly of column and tripod is firmly locked to the ocean floor, the column being maintained in a vertical position, even against heavy wave action, by the wide spread of the tripod legs, which may well be about one-half as long (each) as the column is high. The assembly is now ready for the attachment of the working platforms and for the placing of derrick and rig, after which drilling and casing operations may be carried on through conductor pipe 32.

When the drilling and testing of an exploratory well have been completed it will usually be desirable to salvage the rather costly foundation above described for use at a new location.

Salvaging requires substantially the reversal of the assembling steps above described, or a portion of them depending on the distance to the new location. The first step is to remove all equipment and portable sections of platforms. The piles are then cut off below the sealing rings, the guys disconnected after closing the upper end of the co umn, and the water level within the column reduced to the point at which it may be floated off its seat. The tripod is then brought to the surface by emptying it of water and the legs may be disconnected from the hub for towing to a distant point or the tripod may be towed as a unit to a nearby location.

If it is the intent to drill several wells at points reasonably adjacent, it is feasible and within the scope of the invention to construct tripod 12 as a unit, the legs being permanently attached to the hub. This will materially simplify and lessen the cost of the assembly and will not alter any other of the steps above described, the only difhculty introduced by this change being that of towing so large and unwieldy a structure for any great distance, particularly over rough water.

i claim as my invention:

1. A foundation for one off-shore well-drilling rig comprising a metallic cylinder of length exceeding the depth of water at the location of use and of substantially uniform diameter throughout its length, one end of said cylinder being closed and formed to spherical arcuate curvature and being weighted to cause the cylinder to float in an inclined position, the other end of said cylinder being provided with a removable closure and with means for controllably introducing and expelling water, a base member consisting of a hub element having an annular seat with a concave surface mating the curved end of said cylinder and a plurality of rigid legs projected radially from said hub element and formed to engage the ocean floor at their extremities only and to support said hub element free from said floor, a conductor pipe axially disposed within said cylinder, and a plurality of tubular piling guides within said cylinder and spaced around its inner wall, said guides and conductor pipe extending through the curved end of said cylinder and sealed therein and registering with openings formed in said hub element.

2. A foundation for an off-shore well-drilling rig comprising a hollow cylinder of length exceeding the depth of water at the location of use, one end of said cylinder being closed and having a convex curvature, a base member separable from the cylinder consisting of a hub element having an annular seat with a concave surface mating the curved end of said cylinder, said hub element having a closed flotation chamber and being weighted to cause the concave surface of said seat to be upwardly directed while said hub element: is floating, a plurality of rigid legs projected radially from said hub element and having projections at their extremities which extend transversely with respect to the length of the legs for engaging the ocean floor and supporting said hub element free from said floor, a conductor pipe axially disposed within said cylinder, a plurality of tubular piling guides within and spaced around said cylinder, said guides and conductor pipe extending through the curved end of said cylinder and sealed therein and reg isterin with openings formed in said hub element, a plurality of piles extending through the tubular piling guides in said cylinder and the corresponding openings in the hub element for engaging the ocean floor, stays extending from the upper end of said cylinder to the extremities of said legs, and means for adjusting the relative length of said stays to maintain said cylinder in vertical position.

3. A foundation for an off-shore well-drilling rig cornprising a metallic cylinder of length exceeding the depth of water at the location of use and of substantially uniform diameter throughout its length, one end of said cylinder being closed and formed to convex spherical arcuate curvature, a base member separable from the cylinder and consisting of a hub element having an annular seat with a concave surface mating the curved end of said cylinder and a plurality of rigid legs projecting radially from said hub element and having protrusions at their extremities which extend approximately at right angles with respect to the length of the legs for engaging the ocean floor and supporting said hub element free from said floor, said hub element including a closed, annular flotation chamber surrounding said annular seat and being weighted to cause the concave surface of said seat to be upwardly directed while said hub element is floating, a conductor pipe axially disposed within said cylinder, a plurality of tubular piling guides within and spaced around said cylinder, said guides and conductor pipe extending through the curved end of said cylinder and sealed therein and registering with openings formed in said hub element, a plurality of piles extending through said tubular piling guides and the corresponding openings in said hub element for engaging the ocean floor, a plurality of stays extending from the upper portion of said cylinder to the outer ends of said legs, and means for adjusting the relative lengths of the stays to maintain the cylinder in vertical position.

4. A foundation for an off-shore well-drilling rig comprising a metallic cylinder of a length. exceeding the depth of water at the location of use and of substantially uniform diameter throughout its length, one end of said cylinder being closed and having convex spherical arcuate curvature and being weighted to cause the cylinder to float in an inclined position, the other end of said cylinder being provided with a removable closure and with means for controllably introducing and expelling water, a base member separable from the cylinder and consisting of a hub element having an annular seat with a concave surface mating the curved end of said cylinder and a pluraiity of rigid legs extending radially from said hub element and having protrusions at their extremities which extend transversely with respect to the length of the legs for engaging the ocean floor and supporting said hub element free from said floor, a conductor pipe axially disposed within said cylinder, a plurality of piling guides located within and spaced around said cylinder, said guides and conductor pipe extending,

through the curved end of said cylinder and being sealed therein and registering with corresponding openings in said hub element, a plurality of piles extending through said piling guides and the corresponding openings in the hub element for engaging the ocean floor, and a plurality of stays extending from the upper portion of said cylinder to the outer ends of the legs for maintaining the cylinder in a vertical position.

5. A foundation for an off-shore Well-drilling rig comprising a metallic cylinder of length exceeding the depth of Water at the location of use and of substantially uniform diameter throughout its length, one end of said cylinder being closed and having convex sphe 'cal arcuate curvature, a base member separable from the cylinder and consisting of a hub element having an annular seat with a concave surface mating the curved end of said cylinder, said hub element having a closed annular flotation chamber surrounding said annular s at and being weighted to cause the concave surface of said seat to be upwardly directed while said hub element is float ing, the flotation chamber which surrounds said annular seat being defined in part by an annular inner wall which is downwardly convergent to provide a guide for the curved end of said cylinder as it approaches said seat, a plurality of rigid legs extending radially from said hub element and having protrusions at their extremities which extend approximately at right angles With respect to the length of the legs for engaging the ocean door and supporting said hub element free from said floor, a conductor pipe axially disposed Within said cylinder, a plurality of tubular piling guides located Within and spaced around said cylinder, said guides and conductor pipe extending through the curved end of said cylinder and being sealed therein and registering with corresponding openings in said hub element, a plurality of piles extending through the piling guides and the corresponding openings in the hub element and into the ocean floor, and a plurality of stays extending from the upper portion of said cylinder to the outer ends of said legs for maintaining the cylinder in a vertical position.

6. A foundation for an oil-shore Well-drilling rig comprising a metallic cylinder of length exceeding the depth of Water at the location of use and of substantially uniform diameter throughout its length, one end of said cylinder being closed and having convex spherical arcuate curvature, a base member separable from the cylinder consisting of a hub element having an annular seat with a concave surface mating the curved end of said cylinder and a plurality of rigid legs extending radially from said hub element having protrusions at their extremities which extend transversely With respect to the length of the legs to: engaging the ocean floor and supporting said hub element free from said floor, a conductor pipe disposed axially within said cylinder, a plurality of tubular piling guides located within and spaced around said cylinder, said guides and conductor pipe extending through the curved end of said cylinder and being sealed therein and registering with corresponding openings in said hub ele ment, an adjustable annular compression seal located coaxia-lly inside and at a medial point in the length of each of the piling guides, so that the seals can be adjusted to prevent the passage of Water between said guide and a pile driven therethrough when said guide is cut off below ocean level, a plurality of piles extending through the piling guides and the corresponding openings in the hub element for engaging the ocean floor, and a plurality of stays extending from the upper portion of said cylinder to the outer ends of said legs for maintaining the cylinder in a vertical position.

References Cited in the file of this patent UNITED STATES PATENTS 1,048,194 Mitchell Dec. 24, 1912 1,867,030 Roberts July 12, 1932 2,187,871 Voorhees Ian. 23, 1940 2,398,351 Baker Apr. 16, 1946 2,430,014 Hansen Nov. 4, 1947 2,503,516 Shrewsbury Apr. 11, 1950 2,534,480 Shannon Dec. 19, 1950 2,586,966 Kass et al. Feb. 26, 1952 2,612,025 Hunsucker Sept, 30, 1952 2,637,978 Evans et a1. May 12, 1953 2,661,600 Hopkins Dec. 8, 1953 2,691,272 Townsend Oct. 12, 1954 2,699,321 Nelson Jan. 11, 1955 FOREIGN PATENTS 924,645 France 1947 OTHER REFERENCES Construction Methods and Equipment, August 1950, pages 94-95.