US3289419A - Sea raft - Google Patents

Description

Dec 5 W66 H. E. MGGOWEN, 1m Bgw SEA RAFT Filed Feb. 5, 1964 4 S11eetsS11eet 1 hf. f. //c 60m/fswB (//t INVENTQR.

BY /gC/W Decn 6, E966 H, E, MCGOWEN, JR gww SEA RAFT Filed Feb. s, 1964 4 sheets-sheet 2 Z/ u l! 2/ l Z INVENTOR. 7 BY Q/lw' @'C @a 31%@ H, E. MCGDWEN, JR 3,2%?@9 SEA RAFT Filed Feb. 5, 1964 4 Sheets-Sheet 5 ,M .n WJ @m M WN, m ow .f r 6m MM A M U 00 3 f vl H B \.-,.v\\ WU, j

Z H w y 3 f f p f 3 w ff Q wmf w Dem w66 H. E. MCGOWEN, .im 3,2%,419

SEA RAFT Filed Feb. l5, 1964 4 Sheets-Sheet 41 /74 f, /Wc 60m/ef?) df.

INVENTOR.

BY @JQ/Jam? Unite ttes Patent 3,289,4l9 Patented Dec. 6, 1966 3,289,419 SEA RAFT Harold E. McGowen, Jr., Houston, Tex., assigner to Cameo, incorporated, Houston, Tex., a corporation of Texas Filed Feb. 3, 1964, Ser. No. 341,872. Claims. (Cl. dil- 465) This invention relates to marine craft for anchorage at and travel to Vand from a location where work is to be performed, as, for example, on a well drilled through the earth beneath a body of water. Workover and other operations on offshore oil and gas wells without permanent platform installations have Ibeen taken care of heretofore from floating barges which present serious problems of position maintenance against displacement forces from Water action with tides, currents, waves and other disturbances. Storms endanger barge crew safety, especially if advance warning is received too late for obtaining tow service back to land before a 1bad storm strikes.

It is an object of the present invention to provide a self propelled work raft of greater maneuveralbility and less bulk than the usual ibarge t-o handle certain well reworking operati-ons and of relatively light weight structurally as not to require heavy power equipment for fast travel on the surface to and from well locations and which can `be securely anchored -with its major surface areas substantially free from action thereon of displacement forces incident to surface water movements and which also can be quickly restored to mobility as may be called for to escape sudden storm conditions.

A further object of the invention is to provide a raft comprising a pair of transversely spaced apart long and narrow pontoons capable of floating the entire load of the vessel and from which an open frame of spaced risers project upwardly and support a crew deck at a height elevated above the water surface and the crests of waves rwhose height is safe for continued working operations and from beneath which pontoons there can be projected downwardly a Igroup of rigid posts or spuds terminating in elongated and weighted ancho-r pontoons to ibottom on the sea floor and to hold down the raft pontoons submerged below the sea surface a distance out of surface wave forces.

`Other objects will |become apparent during the course of the following specification having reference to the accompanying drawings wherein FIG. 1 is a side elevation of the improved sea raft anchored at a well location;

FIG. 2 is an end elevation of the sea raft;

FIG. 3 is a large scale transverse section showing one raft pontoon with a set of anchor pontoons retracted in travel position;

FIG. 4 is a detail elevation partly in section of a spud and anchor joint with the section tbeing taken at right angles to the same parts as shown in FIG. 3;

FIG. 5 is a vertical section on a still larger scale of a fragment of a spud assembly havin-g a coupling between spud sections;

FIG. 6 is a longitudinal sectional view of a portion of an anchor pontoon;

FIG. 7 is a detail view of an automatic valve forming a part of the pontoon flooding and deflooding system;

FIG. 8 is a vertical sectional view of another control valve in the flooding and deflooding system; and

FIG. 9 is a side elevation with parts in section of a spud positioning and clutch `and lbrake unit.

In the drawings, the improved sea raft 1 includes an elevated work platform or deck 2 to be positioned at a height above the sea water at all times in normal use and also a pair of transversely spaced apart and longitudinally elongated pontoons or hollow cylinders 3-3 tied together and to the -deck 2 by a group of co-operating narrow Ibeams and posts interconnected and extended horizontally, vertically and diagonally one to the other in the form of an open framework and superstructure support 4. The large clear areas within the open framework minirnize the action of waves and washover on the raft in the space between the elevated deck and the floating pontoons.

By way of example of a raft assembly suitable for offshore work, the pontoons 3 will each have `an outside diameter of four feet five inches and a length of fifty-five feet, with the two pontoons spaced apart transversely on thirty feet centers and the open framework will support the .deck door a distance of fifteen feet two inches above the centers of the pontoons.

A crane assembly 5 illustrated as including Iblock and tackle and an adjustable boom, is mounted. at the forward work area of the deck 2. Additional work platforms or landings 66 at vertically spaced apart levels across the -bow end are joined Iby stairs 7 extending between the elevated deck and the flotation pontoons. Rearwardly of the deck work area is an enclosure 8 for housing crew quarters and machinery. Such machinery, among other things, will consist of one uni-tary engine and driven hydraulic pump assembly indicated generally at 9 in FIG. 2 and one hydraulically driven compressor unit 10, also indicated generally by rbroken lines. Various equipment controls including valvin-g in hydraulic and pneumatic transmission lines, `are to be conveniently l0- cated, as, for example, at a control panel 11 in the pilot house 12 on the bridge deck. From the control panel 11, power transmission lines will extend to control the action of the several work performing units not only on the opper deck but also within the raft and anchor pontoons.

Such work performing units include hydraulic motors not shown but located in motor rooms within stern portions of both raft pontoons 3 for drive connections respectively with a rudder 13 and a propeller 14. Stifening bulkhead walls within each raft pontoon will compartmentize the interior hollow space for fuel and fresh water storage and for both solid ballast and water ballast.

One such compartment wall in each raft pontoon 3, as indicated at l5 in FIG. 1, closes off the forward end of the pontoon as a floodable and defloodable ballast water chamber. An upstanding pressure air conduit 16 communicates the upper interior of the water ballast chamber through a suitable valve at the control panel 11 with the source of pressure air 10 and a bottom opening, as at 17 through the pontoon wall, admits and exhausts sea water to and from the bow chamber as controlled by the pressure air supply. Sea water admitted at the opening 17 fills the forward ballast chamber when the top of the chamber is vented through the conduit 16 and its control valve. On the other hand, sea water is exhausted through the opening 17 to deilood the chamber when pressure air is delivered through the conduit 16. Closure of the control valve for the conduit 16 will maintain the pressure air entrapped within the chamber and preclude entry of sea water into the chamber'. By joining or manifolding the conduits 16 of the two raft pontoons 33, flooding and deooding of both chambers can be effected concurrently and through a single valve common to the interconnected conduits.

Buoyancy and weight distribution of the raft assembly 1 is purposefully arranged so that flooding of the forward water ballast chambers presents the deck in a horizontal plane while deflooding of the valve chambers allows the sea raft to tilt to a downwardly and rearwardly inclined plane. Such rearward tilt and buoyancy in relation to weight when the anchor is suspended off bottom minimizes immersion area of the raft pontoons 3-3 and lowers the stern for proper rudder and propeller action while raising the bow for less water contact surface and travel resistance.

For anchoring the sea raft at a working location, there is here proposed a novel elongated bearing weight and deck connected rigid spud system, whose components are duplicated in two sets, one along each longitudinal side of the raft. Near each of the four corners of the deck 2 there is mounted a spud jack enclosed by a housing 18 and comprised of a hydraulic drive transmission unit whose driving train includes a reversible motor connected through a clutch and brake combination with a gear pinion 19. The pinion 19, as seen in FIG. 9, meshes with the teeth of a rack 20 carried exteriorly by an adjacent spud or post 21 and by control of the drive unit, the spud can be raised or lowered as desired and locked against displacement in any selected position.

Each spud is a string of separate sections detachably coupled in end to end succession, as by a screw threaded coupling member 22 shown in FIG. 5. The length of each spud can be increased or decreased to `suit the depth of the sea bottom or oor by adding or removing spud sections. Secure anchorage can be made at depths to about one hundred feet. Spud sections when not in use can be conveniently stored in suitable racks in an out of the way position, as, for example, a suspended position beneath the deck 2.

The spuds 21 project downwardly below the deck 2 and in co-operating sets of one forward spud and one rearward spud along each side of the raft 1 and the lower ends of the spuds of each set are universally jointed with and near opposite ends of an elongated anchor assembly 23 positioned beneath and in vertical alignment with a raft flotation pontoon 3. In the region between the deck 2 and the pontoon 3, each spud is housed within and is slidably guided by a tubular post 24 of the deck supporting framework 4. Each tubular post 24 has its lower end portion welded to the pontoon 3 and has a downward hollow extension 25 terminating in a circular enlargement 26 rising upwardly from the pontoon wall at the underside thereof. This enlargement 26 will house the anchor and spud joint connection when the spud is fully retracted, as seen in FIG. 3.

As one element of the universal joint connection, the spud 21 has tted to it a terminal coupling head 27 having oppositely and radially disposed bearing recesses for a pair of trunnion pins 28. These pins 28 project outwardly into inwardly counterbored holes in a gimbal or gudgeon ring 29 which has a pair of radial trunnion pins 30 on an axis spaced ninety degrees from the axis of the trunnion pins 28 and projected as seen in FIG, 4 into bearing sockets within centrally disposed risers of a pair of I-beams 31. The I-beams 31 extend transversely across with opposite ends secured to a pair of hollow cylindrical pontoons 32 which extend longitudinally between the forward and rearward spuds. The universal joints afford ilexibility for enabling the anchor pontoons 31 to t themselves to the contour of the seat floor whether it be level or inclined and thus reduce strain and assure a large area of bearing contact on the floor.

The rearward spud of each set is tubular and affords a hollow conductor of pressure air to be directed into both of the anchor pontoons 32 of the beam tied together set, such delivery of pressure air to blow out water for deflooding the hollow pontoons. Concentrically nested within the rear tubular spud is a second and smaller air conductor or pipe 33 by which pressure air is delivered to open normally closed valves through which sea water is permitted to ow into and out of both of the associated anchor pontoons 32. The upper ends of the conductor pipe 33 and the hollow spud 21 are coupled through flexible hoses in a bundle 34 connected to be reeled on or off a suitable winding drum and piped through control valves at the panel 11 with the pressure air source 10.

As in the case of the sectional spud, the conductor pipe 33 is a string of coupled sections. Conveniently, the

upper end of each section, as seen in FIG. 5, terminates in a box or female nipple 35 for slidably and sealingly receiving the pin end 36 at the bottom of the next adjoining section.

The bottom of the lowermost section of the smaller pipe 33 is shown in FIG. 3 as extending into a dead-ended bore of the coupling head 27 and as opening into the enclosed space below an annular partition ring 37. From this space, a pair of side ports project laterally and receive the ends of flow pipe 38-38 which lead to pressure air operated valves within the respective anchor pontoons 32. Inasmuch as the two sets of pipes 38 and valves controlled thereby are alike, the detail of only one set is shown in FIG. 3 and at the right-hand side thereof.

Similarly, the air conductor space within the tubular spud 21 communicates above rthe partition 37 with two side ports and piping connections 39-39, only a portion of one of the pipe sections being shown inasmuch as one is a duplicate of the other. In each instance, the pipe connections 38-38 and 39-39 contain swivel couplings to accommodate relative movements between the spud and the anchor units as permitted by their universal joint connection.

One of the piping connections 38 leads into the upper space inside a housing 40 interiorly of one of the anchor pontoons 32. The other pipe connection 38 similarly leads to a like housing unit in the other anchor pontoon. An externally accessible closure cap 41 is removably tted to one end of the housing 40, whose bottom portion has a tapped opening for screw threaded attachment thereto of a bored tip on a body 42 of a replaceable valve unit. The valve body 42 has a pair of spaced apart ports 43 and 44 opening through the side thereof and into separate internal grooves formed within the housing 40 for communication respectively with the pressure air pipe 38 and a Water flow pipe 45 which opens into the interior of the anchor pontoon 32. The pipe 45 has valved communication through the bored tip of the body 42 with a lateral bore 46 in the housing 4t). This lateral bore 46 has a pipe connection 46a with one or more screened inlet-outlets 47 that extend outside the pontoon wall for the entrance and exhaust of sea water.

As seen in the detail section of FIG. 8, the body 42 of the valve unit encloses a spool-like slidable valve having a piston head 48 at one end within a piston chamber with which the pressure air port 43 communicates above the piston head. A valve stern 49 joins the piston head 48 with a valve head 50 which normally is seated upwardly against an annular valve seat S1 separating the port 44 from the outside water pipe 46a. A coil spring 52, as well as sea water pressure against the underside of the valve head, biases the valve head to normally closed position for a fail safe operation. When the anchor pontoons are to be ooded, pressure air is supplied on top of the piston 48 for unseating the valve 50. This will enable sea water to enter and fill the pontoon chamber providing the pontoon chamber is then vented through the hollow spud and the piping connection 39. When deooding is desired, pressure air is supplied to the interior of the pontoon from the spud and piping 39 and the blowout pressure on the water above the valve lhead 5i) will unseat the valve for exhaust through the pipe 46a, either with or without pressure air delivery to the valve chamber above the piston 48.

Inside the chamber of each anchor pontoon 32, air blowout piping 39 leads to a pair of branch pipes 39a- 39a running longitudinally and opening Iinto the upper portion of both ends of the chamber, and a water llow pipe 45u-45a leads from the water pipe 45 and longitudinally -to opposite ends of the pontoon for termination at the bottom of the ooda'ble chamber. Each anchor pontoon may enclose a single loodable chamber or may have its chamber partitioned into a succession of separate cornpartments somewhat as indicated in FIG. 7. In the latter event, the internal piping is duplicated in each compartment and the air piping 38 and 39 will be manifolded for supplying the several sets of internal pipes. In either case, the longitudinal branch pipes 39a and 45a which terminate at opposite ends of the chamber insure ready and complete deflooding even though the anchor pontoon may be so bottomed as to lie in an inclined plane with gravitation of the confined water toward the lower end of the chamber.

For complete blowout, the open ends of 'both wat-er flow branches 45ti--45a are arranged for self-closing action whenever either is uncovered above water. For such purpose, a perforated cage or guide 53, as best seen in FIG. 7 projects upwardly from each branch terminal and houses a float `ball valve 54 that rises and falls with changes in water level and seats over and closes the open pipe end at the oat bottom limit. lt will be so held in closed position by air pressure within the chamber at the time increasing air pressure is pushing sea water out through a lower opposite open end of a longitudinally tilted flow pipe.

Each anchor pontoon assembly is weighted with sufficient lead ballast to bring Iits over-all and dellooded weight substantially equal to the amount of water displaced thereby. With zero flotation weight, the deflooded anchor pontoons, when not resting on the sea oor, will be spud suspended from the deck. During distance travel to or from well location, the retracted spuds position the anchor pontoons close to the raft pontoons 3 3, as sho-wn by broken lines in FIGS. 1 and 2. Upon yreaching location, the forward compartment of both raft pontoons 3--3 will be flooded for lowering the bow and bringing the deck into a horizontal plane whereupon the spuds 2l can be projected toward bottom.

In protected waters relatively free of currents and wave action, the kraft pontoons may remain floating at the water surface with the anchor pontoons flooded for bearing on bottom so as to hold position. Otherwise, the distance between the floating raft l and the anchor pontoons 32 can be adjusted by controlled spud length for submergence of the raft flotation pontoons 3 3 to a depth somewhat more than half the distance between the raft pontoons 3 and the elevated deck, as illustrated in FIGS. l and 2, where a line SS indicates still water surface. In this relationship, water disturbances exert a minimum of force on the raft assembly since only the small areas of the supporting framework are exposed to surface water movements. This will be substantially true in rough waters ordinarily experienced in offshore well areas other than during the more severe windstorms. Should a bad storm develop, the crew can discontinue operat-ions and quickly dellood the pontoons and return to land without having to call for and await availability and arrival of a tow.

With the sea raft in the operational setting of FIGS. 1 and 2, the flooded anchor pontoon-s 32 will 'be so weighted as to resist buoyancy of the raft assembly and displacement from well location. Anchor `weight will always exceed the effective upward forces on the raft pontoon assemblies including the wave upward forces excepting only those at times kof such severe storms as to render completely unsafe the attempt to operate. Under most conditions, the spuds will be under tension although they will be subjected intermittently to compression load should down wave force on the raft pontoons 3-3 exceed the net upward pull on the spuds. Thus the rigid spud tie connections acting either in compression or in tension afford more positive and steady anchorage against displacement -of the sea raft as distinguished from the common use heretofore of flexible anchor lines which can only act in tension and become alternately taut and slack as a vessel rides up during cresting of successive waves and down in wave troughs and imposes sudden and powerful jerks at both end connections with both the vessel and its anchorage.

The foregoing detailed description is to disclose a preferred embodiment and various modifications and substitutions are contemplated for use without departure from the invention as here claimed.

What is claimed is:

l. In a marine craft for use in positioning work equipment at an offshore well, a raft comprising,

a work deck superstructure,

a buoyant pontoon structure underlying and supporting said work deck superstructure above water level at all times and having a floodable compartment for receipt of ballast water of a volume insufficient for a negative pontoon buoyancy,

weighted anchor means suspended beneath said craft and provided with a water compartment of a size that when empty of water renders the anchor means of substantially zero flotation weight,

a series of vertical rigid posts slidably connected with said raft,

means mounted on the raft for projecting and rctracting the posts towards and from the sea bottom,

said anchor means including an elongated hollow member joined near its opposite ends to a pair of said vertical posts,

a universal joint connecting the lower end of each of said vertical posts to said hollow member,

a pressure air supply conduit extending through a post and swivelly connecting with the interior of the member,

sea water piping containing a valve and controlling entrance and exhaust of sea water to and from said hollow member and including a valve unit having a flow passage and a closure therefor normally biased to passage closing position,

a conduit connecting said passage with the exterior of the hollow member,

a conduit having a'pair of branches connecting said passage with the interior of such hollow member and terminating near opposite ends of the member,

a float valve and a vertical guide cage therefor at each of the ends of the branches and seated downwardly -to close the same,

means responsive to pressure air to open the rst mentioned valve and connected to said pressure air supply conduit, and

means on the raft controlling the delivery of pressure air to the air supply conduit.

2. In a marine craft to be anchored for work on an offshore well, a raft comprising,

an elevated work deck,

a pontoon assembly supporting the deck at a fixed distance above the pontoon assembly and having a floodable and deloodable hollow chamber, said chamber being of a size which when deflooded causes the pontoon assembly to float partly immersed on the surface of the body of Water and when flooded causes the pontoon assembly to be wholly submerged,

an anchor pontoon assembly having a floodable and defloodable hollow chamber and being of a weight substantially equal to the weight of water displaced thereby when its chamber is dellooded and whose weight when its chamber is flooded greatly exceeds the upward force that floats the raft pontoon assembly,

a group of spaced apart rigid studs extending vertically between and connecting the raft and the anchor pontoon assembly and being active in tension under still water conditions and being capable, with the anchor pontoon assembly on bottom, of action in compression to resist wave downward force on the raft pontoon assembly in excess of said upward force on the raft pontoon assembly,

a universial joint connecting the lower end of each spud to said anchor pontoon,

means communicating the interior of the hollow chamber of the anchor pontoon assembly with the exterior thereof for entry and exhaust of sea water including a body enclosing a piston chamber and a valve chamber having a port communicating with the interior of said hollow member and a port communicating with the exterior thereof,

a valve seat in the valve chamber between said ports,

a valve stem having a valve head engageable with the valve seat on the side thereof toward the exterior communicating port,

a piston carried by the stern within the piston chamber,

spring means active on the spring to bias the same in the direction for engaging the Valve head with the valve seat,

a pressure uid conduit communicating with the piston chamber above the piston for supplying force in opposition to said spring bias and movably connected through a universial joint to the raft, and

means on the raft controlling the supply of pressure fluid to said conduit,

3. The apparatus of claim 2 including,

a conduit extending longitudinally within an opening into opposite ends of the hollow chamber of the anchor pontoon assembly and being connected intermediate its open ends with the rst mentioned port of the valve chamber,

a oat valve and a vertical cage therefor at each open end of said conduit for float valve movement toward and from said closing relation with the open and,

a pneumatic blowout conductor leading from the raft to the interior of the hollow chamber of the anchor pontoon assembly swivelly 'through a universal joint for delivery of pneumatic pressure to the chamber of the anchor pontoon.

4. In a marine craft to be anchored for work on an offshore well, a raft comprising,

8 stantially equal to the weight of water Adisplaced thereby when its chamber is deflooded and whose weight when its chamber is ooded greatly exceeds the upward force that lloats the raft pontoon assembly,

a group of spaced apart rigid spuds extending vertically between and connecting the raft and the anchor pontoon assembly and being active in tension under still water conditions and being capable, with the anchor pontoon assembly on bottom, of acting in compression to resist wave downward force on the raft pontoon assembly in excess of said upward force on the raft pontoon assembly,

a universal joint connecting the lower end of each Spud to said anchor pontoon assembly,

one of the pontoon connected spuds comprising a pair of pressure air conductors connected through the universal joint,

means swivelly coupling the lower ends of said air conductors with the interior of said hollow pontoon to control ooding and delooding thereof and accommodating relative movement permitted by the universal joint, and

valved pressure air connections mounted on the raft and coupled with the upper ends of said air conductors for the control delivery of pressure air thereto.

5. The apparatus of claim 4, wherein, each of said studs comprising,

sections detachably coupled in end to end succession to make up a desired assembled spud length,

the spud which comprises a pair of pressure air conductors also comprising sectional inner and outer tubular members nested one within the other and each such member being swivelly connected at its lower end with the interior of the hollow pontoon.

References Cited by the Examiner UNITED STATES PATENTS 2,248,051 7/1941 Armstrong 61-46.5 2,308,743 l/1943 Bulkley et al. 6l-46.5 2,600,761 6/1952 Halliburton 6l-46.5 2,927,436 3/1960 Besse 6l-46.5 2,953,904 9/1960 Christenson 6l-46.5

CHARLES E. OCONNELL, Primary Examiner.

l. SHAPIRO, Assistant Examiner.

Claims (1)

1. IN A MARINE CRAFT FOR USE IN POSITIONING WORK EQUIPMENT AT AN OFFSHORE WELL, A RAFT COMPRISING, A WORK DECK SUPERSTRUCTURE, A BUOYANT PONTOON STRUCTURE UNDERLYING AND SUPPORTING SAID WORK DECK SUPERSTRUCTURE ABOVE WATER LEVEL AT ALL TIMES AND HAVING A FLOODABLE COMPARTMENT FOR RECEIPT OF BALLAST WATER OF A VOLUME INSUFFICIENT FOR A NEGATIVE PONTOON BUOYANCY, WEIGHTED ANCHOR MEANS SUSPENDED BENEATH SAID CRAFT AND PROVIDED WITH A WATER COMPARTMENT OF A SIDE THAT WHEN EMPTY OF WATER RENDERS THE ANCHOR MEANS OF SUBSTANTIALLY ZERO FLOTATION WEIGHT, A SERIES OF VERTICAL RIGID POSTS SLIDABLY CONNECTED WITH SAID RAFT, MEANS MOUNTED ON THE RAFT FOR PROJECTING AND RETRACTING THE POSTS TOWARDS AND FROM THE SEA BOTTOM, SAID ANCHOR MEANS INCLUDING AN ELONGATED HOLLOW MEMBER JOINED NEAR ITS OPPOSITE ENDS TO A PAIR OF SAID VERTICAL POSTS, A UNIVERSAL JOINT CONNECTING THE LOWER END OF EACH OF SAID VERTICAL POSTS AND SAID HOLLOW MEMBER, A PRESSURE AIR SUPPLY CONDUIT EXTENDING THROUGH A POST AND SWIVELLY CONNECTING WITH THE INTERIOR OF THE MEMBER, SEA WATER PIPING CONTAINING A VALVE AND CONTROLLING ENTRANCE AND EXHAUST OF SEA WATER TO AND FROM SAID HOLLOW MEMBER AND INCLUDING A VALVE UNIT HAVING A FLOW PASSAGE AND A CLOSURE THEREFOR NORMALLY BIASED TO PASSAGE CLOSING POSITION.

Images