CA1075999A - Materials delivery system for offshore terminal and the like - Google Patents

Abstract

MATERIALS DELIVERY SYSTEM FOR OFFSHORE
TERMINAL AND THE LIKE

ABSTRACT OF THE DISCLOSURE

A spar having fluid flow lines or material con-veyors extending along the same is anchored by a ball joint, U-joint, elastic joint or the like to a base on the bottom of a body of water, such as a sea bottom. The spar has a buoyancy chamber near its upper end for applying an upward tension thereto at all times. When a vessel is adjacent to the upper end of the spar, tension means extends between the spar and structures on the vessel bow to couple the two together. The tension means provides a lateral force exerted on the spar to bias the spar toward the vessel even as the latter changes position relative to the spar due to current, wave and wind action. Several embodiments of the tension means are disclosed. The fluid flow lines carried by the spar connect a base manifold on the bottom of a body of water with delivery hose4s or other conductors which can provide flexibility and are connected to the vessel for the transfer of crude oil and other fluids thereto. In lieu of fluid flow lines, material conveyors carried by the spar, such as bucket or pneumatic conveyors, can be used to raise paricle material, such as manganese nodules and ore.

Description

~075999 I 1 Thi~ invention relates to improvements in the

2~l transfer of materlals mined or conveycd to a location on or

3 1l below ~he bottom o~ a bo~y of watèx to above-surface recep-41 tacles and, more part~cularly, apparatus and method for transferlng ~uch material~ along a generally vertical path 6 through the body o~ water even under extreme wave and 7 ¦ weather cond~tion at the ~urface.

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In the handling of crude oil pumped from off~hore oil wells, a number of offshore terminal~ have been d~veloped 11 over the year~ for use in tran~ferring the production from 12 such wells to tankera at berth or to other receptacles or 13 ¦ vessels. Among these are the following: the artific~al 14 ¦ offshore island made up of ~te~l constructisn or preca~t 15 ¦ concrete pil~ngs fixed to the sea bottom and supporting 16 steel, precast or cast-in-place concrete structures; thQ
multiple-buoys-mooring sy~tem consi~ting of several moor~ng 18 buoys anchored around a tanker berth; the tower mooring 20 ~ system con3isting of a steel structure f~xed to the ~ea bottom by pilea and having a turntable fitted on the top of 211 the 3tructure from which a mooring rope is connected to a tanker at berth ad~acent thereto; and the single point 23 ¦ mooring ~ystem which can be of one of two types, namely, a ¦i catenary-chain type, single buoy mooring system or the single anchor leg mooring unit, both of which allow a tanker to rotate freely and to take the posit~on o~ lea~ rQslstance 1~ to combined external ~orces, such as those due to waves, sea !! currents, wind and other types of rotating mooring All of - I the~e various sy3tems can only be compared by select~ng a 30lj 31l , 32l 1 :
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i i ~L~7S9~9 1~ partlcular ~ite where such ~ystem~ may be installed. At any 2 ~uch site, water depth and qea and weather conditions are to 3 be conRiderad along wlth the moorihg forces between each

4 system and a vessel to be as~oclat2d therew~th.

5 I All of the foregolng ~y9tem3 have certsin drawbacks,

6 I especlally when the same are used in region~ of the ~aa

7~ whlch have extreme wave actlon at certain times of the year.
8l For instance, at certain locatlon3 in the North Sea where 9 much offshore drilling now take~ place, a 100-y~ar wave i~
estimatad to have a height o~ 95 to 105 feet but such esti-11 mates have latoly been ~hought to be erroneous in that a 12 more correct e~timat~ is lS0 feet. Under such extreme wave 13¦~ conditions, it is virtually impossible to maintain a moorlng 14 I between a ves~el and any one of the aforesaid offshore 15 ~ terminal~ without causing damage to both ~he vessel and the 16~ terminal. A1YO, to disengage and re-engage the vessel 17l relative to the terminal in ~uch extreme wave conditions, 181 special ~tructures and time con~uming procedure~ are required.
19~ The above-ment~oned offshore terminals also have 20¦ other drawback~ including restrictive water depth and excessive 21~ cost3 of con~truction and maintenancQ due to their complexity 221 o~ ~tructural detail. For instance, the artificial offshore 23l island i~ 80 c08tly that lts use seems ju~tified only when 24 ¦I tha oil production handled thereby or throughput i9 very 25~ high, such a~ above 200,000 barrels per day, and only when 26l very large va~sel~ are available for u3e with lt. Also, the 27 1I water~ around the i31and ~hould be well protected; otherwice, 28 1ll a breakwater ha~ to be constructed at high co~t. Furthe~more, 291 the depth at which the aforesaid svstems are operable do not 30l exceed about 300 feet.

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1~)75999 1, .
The multiple-buoy~-mooring ~ystem finds it appli-~I cation only in protected shallow waters ox exposed locations j~ with m~ld wave climate and or relàtively small tankar~. It othe~ise too ea~ly damased; thus, it cannot withstand ~I the extre~e weather conditions mentioned above whlch occur 76j ln the North Sea.
The tower mooring system i~ c03tly to erect and to

8 operate and presents collision ris~s. It is believed to find it~ best application only in relatively shallow waters which are proteated from extreme wave action; thus, it i8 11 not suitable at all for the open North Sea opexations discu3sed above.
43 The ~in~l~ point mooring sy~tem i~ not suitable for use under extreme wave conditions because, in the case o~ the ~ingle buoy mooring system, the hawsexs which anchor 16 the tanker or vessel break due to i~pact tension caused by 17 ~ wave forces exerted on tho system. These waves also cau3e 1 1 the buoy to separate from the vessel and then to slam into 19 it to cause damage to either or both of them. In the case I o f the single anchor leg mooring system, an anc~or chain 22 connects a buoy body to a generally rigid ~ertical riRer ¦ standing upwardly from the sea bottom but this chain al30 ¦~ breaks due to extreme wave action and separates the ~uoy i from the riser, causing sufficient damage to the system to il re~uire replacement of the buoy, all of which requires a Il long shutdown time for repair3.
27 1l In view o~ the problems associated with the off-I ~hore oil terminals mentioned above, a need has arisen for I --~i-- I
., an improved offshore terminal which is simple and rugged in construction, is relatively inexpensive to produce and maintain, can be easily moved to other locations, can be used to keep a vessel coupled thereto even under extreme wave conditions yet the vessel can safely engage with and disengage from the terminal without special assistance or procedures, and can operate at depths of up to 2,000 feet or more.
The present invention satisfies the aforesaid need by providing an improved materials delivery system for transporting materials from the bottom of a body of water to the surface and to a receptacle, such as a vessel coupled with the system itself. The present invention is especially suitable for handling offshore oil well production although it is suitable for other applications as well. For instance, it can be used to deliver natural gas from such offshore wells, and it can also deliver particle material, such as manganese nodules and ore, and can also deliver refrigerated fluids and slurries of various types. In the case of slurries, ocean mining can be carried out which would allow dredging marine deposits of tin, diamonds, gold or high value commodities under sea conditions in which conventional dredges are impractical or impossible for use.
More specifically the present invention is a materials delivery system for the transfer of mined materials from the bottom of a body of water to the water surface comprising: a spar having means at one end thereof for mounting the same in a generally upright position on the bottom of said body of water with the spar having a length sufficient to permit it to extend to a location adjacent to the water surface, there being a material delivery line capable of transporting said materials and extending along the spar from a location adjacent to said mounting means to a location adjacent to the upper end of the spar, said delivery line adapted to be coupled to a materials receiver near the water surface when the spar is in said position;
and means coupled with the spar near the upper end thereof for coupling the spar to the materials receiver and for applying a generally upward force to the spar when the spar is in said position, the upper end of the spar being movable laterally when the spar is mounted in said upright position and as said upward force is applied thereto, whereby the spar can move laterally with the materials receiver.
The materials delivery system of this invention may use a spar having a relatively small cross section and provided with means for applying an upward tension force thereon when the lower end of the spar is anchored by a suitable mass anchor base or is pile anchored or hydro-anchored to the bottom of a body of water. The coupling between the mass base and the spar can be a ball joint, a U-joint, an elastic joint or other structure permitting articulation of the spar relative to the base so that the spar, when coupled to a vessel on the surface of the water, can move with the vessel due to wave action without becoming separated from the vessel. It is also possible to make the spar flexible and to attach it by a rigid connection to the anchor base. This latter feature would be advantageous in deep water. The base can either be permanent or of a removable type, the latter being much more economical to relocate to another site than presently existing structures.
Tension is applied at all times to the spar by, for example, a buoyancy chamber carried by the spar adjacent to but below the upper end thereof. When a vessel is adjacent to the spar, it is coupled by tensioning means to the spar, and the tensioning means applies an additional tension force to the spar in a manner such that a lateral tension component is exerted on the spar at all times during the vessel-spar connection to hold the spar against the vessel. This feature virtually assures that they will not separate from each other even during periods involving extreme wave and wind conditions on the water surface. This will prevent impacting of the spar and the vessel together to thereby eliminate any structural damage to either or both of them due to this cause. The connection of the tension means to the spar is by way of a swivel so that the vessel can windvane without causing rotation of the spar about its longitudinal axis. Any of several embodiments of the tensioning means can be used to carry out the teachings of the present invention.

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llj The nor~al or rcst pO3itiOIl will ordinarily be 2I generally vertlcal. ~owever, it can ~e normally tiltcd by 3 !! ad~usting the amount of buoyancy ~rovided by either or both 4~l of the buoyancy chamber and the tenqioning means.
5 11 The spar c~n be provided with ono or more exter~al 6¦ or intornal material deliv~ry lines, Ruch as fluld flow 7 llnes or conveyors for particle matorial, coupled at their 8l lower end6 to a materi~ls source near tho ma~s anchor base, 91¦ the delivery lines extending to swivel means near the upper 10l end of the spar, whereby the material delivery from the 11 ¦ delivery lines can be transferred by material delivery means 12¦ to the vessel or other receptac~es regardless of the locat~on 13~ of the vesQel or receptacle about the spar. Control means 14i can also extend through the core and the spar to operate 151 control equipment on the bottom of the body of water. If 16 ! the delivery lines are comprised of fluid flow lines, the 17l buoyancy chamber itself can be provided with a manifold to 18 I permit a decrea~e ~n the fluid pressure of the flow lines 19 ll and to reduce the number of flow lines to swlvel cou~led to 20 ~ he delivery hoses connected to the vessel.
21 1l If material conveyors are used, they c~n be bucket 22 ll conveyors or hydro-pneumatic (airlif~) or pneumatic conveyor3, 23 11 'or delivery of particle materi~l, such as ~anganesa nodules 24 1 or ore, to ~he water ~urface. Such materials can be raised 25 ll in slurry form through ~luid flow lines as an alternative 26 ~ approach. I
27 'I The system i-~ suitable for depths f.om 250 feet to 28l more than 2,000 feet below the water surface and can be used 29 to r~place all existing offshore terminals of the conventional 3 2 ~ - 8 -" .

" 1C1 75999 types described above. It is simple in construction, readily installable in place, and requires a minimum of maintenance.
The swivel at the top of the spar can be con-structed to handle segregated products, such as crude oiland natural gas or particle materials of several different ~inds. Such products would not be co-mingled at the swivel and they could be transferred by respective flexible delivery hoses or conductors to a vessel or other receptacles and into segregated storage areas thereon.
Thus this invention provides materials delivery apparatus and method for the transfer of mined materials from the bottom of a body of water to a receptable on the water surface wherein a spar having tension exerted thereon is used to support material transfer means extending from the bottom of a body of water to the water surface in a manner to permit transfer of materials to the receptable even during extreme wave action on the water surface, yet the spar can be engaged with and disengaged from the recep-tacle under such conditions without the need for special assistance or procedures to carry out this purpose.
Several embodiments of the invention are illus-trated, by way of example, in the accompanying drawings, in which:

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1~7~g99 2 ~11 Fi8. 1 i~ a ~che~tic view of the artlcul~ted 3 1I te~810~ spar of thii3 invenelon showing one of saveral ui~e~

4l of the sa~e, n3~Qly, for trani3ferrlng crudc oll from an 5l; ~nderwator wcll to a ves~Ql at bcrth near the uppcr ~nd of I the spar;

7 I Fig. 2 i8 a ~ide clevatlonsl view of the upper ent 8, of the spar, sho~ing the way in whlch tens1on ig applied Il there~o when the same i8 coupled to laterally proJecting lO,j horns on the bow of the veqsel;

Flg. 2a i~ a fragmentasy view of the ~psr and 2,~ tensio~ing synte~ when tne &par i~ in lts vertical po~itlon;

! Fig. 3 i0 a top plan view of the spar tens~oning 14 syste~ of Fig. 2;
I! Fig, 4 i3 a fro~t elevat~onal view of the spar 16~ tenslonlng system of Fi8. 2;

171¦ F~g. 5 18 a perspectlve vlew of a ?referred I embodlment of the mass anchor base for the spsr;

19l Fl~ 6 i8 a alde elevatlonal view~ partly ln 201, section, of the mass anchor base when the same 18 embedded in the botto~ of a body of wster, showlng the spsr mountet Il by a ball Jolnt on the base; - I
23 11 Flg. 7 19 a view slmllar to Flg. 6 but ~howlng 24 11 anoth~r embodlment of the base ~ul~able for use whcn thc bottom of the body of water ls covered by a lsyer of soft ,I mud;
27i1 ~ot75999 . I
l ll 1 I Fig. 7a i~ a view ~imilar to Flg8 . 6 and 7 but 2 ~ ~howing another way in whlch the spar 1 coupled to the 3 base;
4 1I Fig. 7b i~ a view similar to Fig. 7a but showing a 5 1I tripod or a pyramidal ~tructure coupling the spar and the 6~ base;
71 Fig. 8 i~ an enlarged, fragmentary, view of the 8 upper end of the ~par showing the way in which fluid flow

9 I line~ through the spar are coupled by mean~ of ~wivels to a

10 ~ fluid swivel core and one or more deli~ery ho~e~ or con-

11 ductor~ ts a vessel or other xeceptacle;

12 I Flg. 9 is a cross-sectional view taken along line

13 9-9 of Fig. 8;

14 Fig. lO i8 a view similar to Fig. 2 but Rhowing

15¦ another tensloning system between the spar and a vessel with

16¦ the spar in a substantial windvane position relative to the

17¦ vessel;
181 Fig. ll is a view ~imilar to Fig. lO but ~how$ng 19l the spar in a sub~tantial override position;
20~ Fig. 12 i3 a top plan vlew of the ~ystem of Fig.
21~ 10;
l Flg. 13 is a view similar to Figs. 2 and 10 but 23~ showing a third embodiment of the tensioning sy~tem between 24~ the ~par and the ve~el, the spar being in a substantial 25l~ windvane position relat~ve to the ve~sel;
26l F$g. 14 is a view similar to F~g. 13 but showing 27l the ~par in a ~ub~tant$al override po~ition;
i 311;
321~ 1 f '\ l ~ 107599g 1 Fig. 15 is a top plan view of the system of Figs.
23~ 13 and 14;
l Fig. 16 is a schematic vlew of the spar and vessel 4~ of Figs. 13-15 at the crest of a wave;

6 ~ig. 16a is a fragmentary view of the spar showing l the wave and tension forces exerted thereon at the crest of 7j a wave when the wave moves in the direction shown in Fig.
8~ 16;
9¦ Fig. 16b iq a ~iew similar to Fig. 16a but showing 10¦ the forces on the spar at the trough of a wave when the wave 11 ¦ moves in the direction shown in Fig. 16; and 12~ Fig. 17 is a view similar to FigO 16 but showing 13l the spar and vessel at the trough of a wave.

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Il i ,i ~ ~ For purpo~es of illustration only, the material~
3 delivery system of the present invention will hereinafter be 4 described as a mean~ for transEerring cruda oil or gas through fluid flow lines from a base manifold coupled to one or more wells drilled into the bottom of a ~ody of water to a ves~el floating on the surface at a location above the wells. Crude oil wlll hereinaf~er be described as the fluid l to be handled ~y the system of the present invention. The 91 invention is, however, broader in ~cope than this illustrative example, since it can be used to ral3e partlcle material, 2 such as manganese nodules or ore, to the surface of a ~ody 13 of ~ater by the use of conveyors.
I ~he concept of the present invention is illustrated 141 schematically in Fig. 1 wherein the delivery system, denoted 16~ by the numeral lO, includes an elon~ated, tubular, spar 12 17~ mounted on a base 14 on the bottom l6 o~ a body of water

18~ which will hereinafter be considered a~ a sea so that

19 bottom 16 will be referred to as the sea bottom. Spar 12 extands upwardly from the base to and above the upper surface 21 18 of the ~ea and terminates near the bow 20 of a vessel 22, which will hereinafter be described as a tanker, although 22l ~uch a vessel can include any type of marine craft, such as 23l a barge, ore ship, floating pier and the like.

25¦ Base 14 is positioned on the sea bottom in the 26 vicinity of one or more oil wells, typically six in number, 27 which may be spaced from each other a~ varying distances.
I! Fluid flow llnes from the various we~ls and the associated 28ll equipment, such a~ valves, regulators, controls, p~nps and !! the like, are provided ~o direct the crude oil from the well I headq to a ba~e manifold 27 and then into spar 12 for transit 31l I through one or more fluid flow linas extending through the 1075~5~9 spar to its upper end and then, by way of other conduit means, to the tanker as hereinafter described.
sase 14 is shown in its preferred embodiment in Figs. 5 and 6. The base can have any suitable shape but~
for purposes of ill~stration~ it comprises a generally square, octagonal or round hollow housing 24 having a top 26 provided with a pair of tubes 28 and 30 communicating with the interior thereof. Tubes 28 and 30 extend either into spar 12 or extend upwardly to upper surface lô along the outer surface of the spar. They are used for directing a ballast into housing 24 when it is desired to anchor the same on sea bottom 16.
A typical ballast is a slurry of iron ore, magnetite, sand, or some other heavy material in slurry form to he pumped from the surface into housing 24. This type of ballast will allow good control of the submergence of base 14 since no compressible gas or fluid is used for this purpose. Also, by using tubes 28 and 30, the ballast can later be fluidized within housing 24 and ejected if it becomes desirable to move base 14 to another job site.
Typically base 14 is made slightly positive in buoyancy to facilitate its transport to a job site. A typical ballast weight is lS00 tons or more.
Housing 24 may be of one or several compartments either connected to or independent of each other. In the latter case, each independent compartment would have its own tubes 28 and 30. The compartments may be tubular and may be set up in the particular geometric configuration to suit the sea and soil conditions of the site.
Housing 24 has a continuous penetration skirt 32 secured to and extending from the bottom of the housing as shown in Figs. 5 and 6. This skirt is adapted to penetrate 107S9~

the sea bottom to provide a positive anchor for the base.
The skirt provides a hydraulic seal for the bottom of housing 24, and relief tubes 34 and 36 extending outwardly from opposite side of the housing and through the bottom thereof can be used to provide a reduced pressure or suction in the space surrounded by the skirts to permit differential, hydraulic pressure to force skirt 32 into the sea bottom.
Tubes 34 and 36 are connected to a suitable suction force, such as on the vessel which is used during installation of the base.
To disengage housing 24 from the sea bottom, the region below the bottom of the housing can be pressurized through tubes 34 and 36 to assist skirt 32 to move out of the sea bottom. Then, by ejecting the ballast from housing 24, the base can then be moved to a new job site. The ballast can be ejected from the housing through either the bottom of the housing or other tubes through the housing by conventional means.
In some cases, the sea bottom in deep water comprises a layer 38 (Fig. 7) of soft, fine sand and silt bottom, the layer being 15 or more feet thick and resting on a good bearing bottom 40. In such a case, the footing of layer 38 is too weak to support base 14. In such a case, the base will have a different construction from that shown in Figs.
5 and 6 and will include a continuous sidewall 41 (Fig. 7) secured to a housing 43 and extending downwardly therefrom.
A continuous penetration skirt 42 will extend downwardly from the sidewall 41 as shown in Fig. 7, housing 43 being hollow and provided with tubes 44 and 46 for the same purpose as tubes 28 and 30 of Figs. 5 and 6. Continuous sidewall 41 10~$~

is used to increase the pressure on layer 38 so that skirt 42 can more effectively penetrate the layer and then extend into the good bearing material 40 below the layer. The interior of the space surrounded by sidewall 41, denoted by the numeral 48, can be exhausted by a pair of tubes 50 connected to a suitable suction source. Space 48 can be pressurized when it is desired to remove base 14 from the sea bottom and to move it to another job site.
One way of mounting spar 12 on base 14 is by the use of a ball joint 54 (Figs. 6 and 7) with the ball of the joint being mounted on a suitable pedestal 56 on top 26 of base 14 and with spar 12 having a socket member 58 at its lower end for coupling the spar with the ball. The spar is thus able to articulate relative to the base 14 in all directions about hori~ontal axes through the ball; however, the coupling is provided with means (not shown) for preventing rotation of spar 12 about its longitudinal axis relative to the ball joint. In lieu of a ball joint, a universal joint can be used for this same purpose.
Other embodiments of the action between the spar and the base are shown in Figs. 7a and 7b. In Fig. 7a, pedestal 56 is provided with an elastic ring or elastic blocks 60 which rest upon and are connected to the flat upper surface 62 of the pedestal and which support and are connected to the bottom of spar 12. To limit the compression of blocks 60 when spar 12 has a tendency to tilt with respect to the vertical, a number of limit bars or springs 64 may be used and, if used, are secured between pedestal 56 and re-spective lateral ears 66 on the lower end of spar 12. Limit 1~759~Y~

bars 64 prevent the deformation of blocks 60 beyond its elastic limit. In any case, blocks 6Q allow spar 12 to articulate relative to base 14 in all directions about generally horizontal axes through the block, and limit bars 64 prevent spar 12 from rotating about its longitudinal axis relative to the base.
To enhance the structural behavior and the economics of a very long spar in deep waters, base 14 could be fabricated to contain a tripod or a pyramidal structure of three or more legs 67 as shown in Fig. 7b~ All of the flow lines could be made to extend through the base and legs 67 and into spar 12. At the top of the pyramid is a platform 69 to mount pedestel 56, 54, and socket member 58. This feature will allow the use of a relatively short spar since legs 67 can be made relatively long.
Spar 12 is of relatively thin-wall steel construc-tion, such as a 2-inch wall thickness, and is relatively small in diameter, typically about 10 feet in diameter. In the alternative, the spar could be of concrete and steel or other suitable material. The length of the spar typically is from 250 to 450 feet but can be as long as 2,000 feet or more. The length will be such that the upper portion of the spar will extend upwardly from upper surface 18 and through the space 70 (Fig. 3) between a pair of spaced, generally parallel bow horns 72 mounted in any suitable manner on bow

20 of tanker 22. The upper end of the spar terminates above the bow horns as shown in Figs. 1 and 2~ for instance.

~75g~?'3 Spar 12 has a buoyancy tank 74 (Fig. 1) mounted thereon near the upper end thereof and below surface 18.
Tank 74 provides buoyancy for spar 12 and provides a tension force which is exerted on the spar in an upward, axial direction at all times even when tanker 22 is separated from the spar. Thus, the spar can be of relatively small diameter.
When the tanker is in berth, the spar is further tensioned by a spar tensioning system in a manner hereinafter more fully described.
Buoyancy tank 74 can be designed with either or both air and buoyant material-filled buoyancy chambers.
Also, it can be somewhat enlarged so that it can enclose one or more flow line manifolds to allow reduction in flow line pressures from about 3,000 psi to about 300 psi. When a large number of flow lines are being brought into the spar, one or more manifolds at this location will reduce the output lines to one or more from the spar to the tanker.
Under certain conditions, spar 12 may have a ballast tank 75 (Fig. 1) near its lower end for receiving ballast to assist in putting the spar in place. Ballast tank 75 reduces the upward forces on base 14 and assists in keeping spar 12 in an upright position if, for some reason, the spar separates from the base. Ballast tank 75 can have a number of compartments and can be helpful in towing the spar to a job site since tank 75 will be buoyant with no ballast in it and can cooperate with base 14 when the latter is free of ballast to provide a buoyant force on the lower -18_ 1075~

end of the spar so that the spar can be towed in a generally horizontal position, the front end of the spar being buoyed by tank 74.
a first embodiment of the spar tensioning system is shown in Figs. 2-4. In this embodiment, the spar has a collar 76 rotatably mounted thereon at a location either above or below the surface of the water. A pair of tension members 78, such as cables or chains, couple collar 76 to the tanker. Specifically~ one end of each tension member 78 is connected to an eyelet 80 near the outer end of the corresponding bow horn 72 and the opposite end of the tension member is coupled to a constant tension device 82 mounted on the tanker near the rear end of the corresponding bow horn. Each tension member 78 passes down and about a sheave 84 mounted on a respective side of collar 76 (Fig. 4);

-18a-~(~'7S9~

thus, the two portions of each tension member extending upwardly from the corresponding sheave 84 are at acute angles relative to the longitudinal axis of spar 12. Also, members 78 extend upwardly and laterally outwardly (Fig. 4) to provide equal and opposite lateral force components on the spar to keep it substantially centered between the bow horns to prevent impact therewith.
Under maximimum storm conditions, a typical tension applied to the spar by tension members 78 is 300 ~ons. Such a load requires a heavy-duty construction for each tension member. A suitable chain for this purpose is 4-inch, super-strength, Di-Lok. Each link of such a chain is 24 inches long and 15 inches wide. Proof tests of this chain include the application of loads up to 600 tons. All sheaves used with this type of chain will be shaped to fit these links as commonly used in a wildçat windlass. This chain size should be satisfactory for resident tanker service3 i.e., where the tanker remains permanently connected to the spar by way of the chains. If a transit tanker is to be coupled to the spar, the chain will need only a small fraction of the strength required for resident tanker service since a transit tanker will be in berth only under less severe sea conditions.
Also, the average transit tanker will be smaller than the average resident tanker.
As wave loads exerted on the spar increase, the tanker, because it is coupled to the spar by tension members 78, puts a greater load on the spar which, in turn, becomes more resistant to transverse wave loads to minimize bending of the spar. ~nis spar design tends to compensate for wave loads on the spar itself and reduces resulting stresses ~ ~759~

thereon. Moreover, the spar tends to remain upright because of the buoyancy of buoyancy tank 74 and the geometry of the tension system. When the spar is in its upright position ~Fig. 2a), the portions of each tension member 78 extending away from the corresponding sheave 84 make substantially the same angle with the longitudinal axis of the spar so that the resultant tension force T is generally vertical.
The main purpose in allowing spar 12 to articulate is to allow it to follow horizontal movements of the tanker rather than moving relative to and out of phase with the tanker and then impacting with it which would cause damage to either or both of them. For instance, if the spar is caused to articulate or tilt slightly toward the tanker as shown in Fig. 2, sheaves 84 will move a short distance along respective tension members 78 so tha~ there will be an unbalanced force in the forward direction, i.e., to the right when viewing Fig. 2, which will contribute to the buoyant force of buoyancy tank 74 to return the spar to its normally upright position~ Similarly, if the spar tilts in the direction opposite to that of Fig. 2, the opposite effect will occur.
The tensioning system of Figs. 2-4 also operates to position and keep the spar centrally between and spaced from bow hor~s 72 and forwardly of and spaced from bow 20.
The tensioning system also allows the tanker to pitch rela-tive to the spar yet the tanker and spar remain coupled together and the spar remains substantially centered between the bow horns~ Also, the spar can be disengaged from and re-engaged with the ~anker without assistance from additional ~075999 marine craft. Differential vertical forces exerted on the tanker are compensated for by the tension system supplied by tension members 78.
The spar needs both anchorage and buoyancy to keep it in an upright position. Base 14 provides the anchorage as mentioned above to achieve the desired negative buoyancy. By balancing the buoyancy force of the buoyancy tank 74 and the anchorage supplied by ballast in base 14, the spar can be designed for towing, submerging and final positioning with little or no recourse to air chambers.
While the tensioning means 82 has been described as a con-stant tension device, this is only for purposes of illustration because there are other ways of providing the constant tension for tension members 78. For instance, a counterweight can be mounted on the tanker bow or spar and coupled to tension members 78 so as to provide the desired tension thereon, such as about 300 tons. This value of tension should be adequate to deal with 50-year recurrence storms but is far in excess of normal requirements. The counter-weight could possibly be of the variable type, such as one filled with seawater or other fluid so that it could be adjusted to changing sea conditions.
A variable tension could be applied to tension members 78 by way of one or more air cylinder and piston assemblies. Such an assembly might typically be about 50 feet long, 30 inches in diameter, and operate under a pressure of 1,000 psi under extreme weather conditions.

-21-10~759~

Motion compensators are also commercially available for applying constant tension to tension members 7~. These devices a}e commercially available from suppliers to the offshore drilling industry. Some types of motion compensators involve multiple cables and sheaves; thus, they are not as practical for use as constant speed winches or a counterweight.
Under the constant motion of a tanker in the open sea, the movement of cables over sheaves would possibly result in excessive wear of the sheaves and the cables. However, cable type motion compensators might possibly be suitable or adequate.
In some instances, heavy nylon hawsers could be used to maintain tension on the spar. The overall length of nylon hawser would be such that maximum elongation does not exceed 25 percent. Within this limit, nylon is resilient.
A swivel unit 90 (Figs. 8 and 9) is mounted on the upper end of spar 12 to allow rotation of tanker 22 about spar 12. Swivel unit 90 includes an elongated tubular swivel core 92 mounted by spaced upper and lower bearings 94 and 96 to the upper part of spar 12 so that core 92 can rotate relative to the spar. A number of delivery hoses 98 (only one af which is shown in the drawings) communicating with the interior of core 92 are connected to a support 100 (Fig. 2) mounted on the bow of the tanker. The support has flow lines (not shown) coupled to hoses 98 to direct crude oil from respective flow lines on the spar to the gas-oil process facilities on the tanker or to a storage tank therein.

-22-- ~ ( l 1~7599~

1 A well-control condule 102 exte~ds downwardly 2 through the center of core 92 a~d can carry as many as 60 or 3 more high-pres~ure, ~mall diameter hydraulic line~ and 8iX
4 electrlc downhole pressure lndicator llnes. Condult 102 1~ ¦
flxed relatlve to the spar BO that core 92 rotate~ about 6 conduit 102. A well-control ~wivel 104 i~ ~ounted on the 7 upper end of conduit 102 and has an umbllicsl cable 106 8 whlch extends to the tanker. Cable 106 i~ coupled to the 9 varlous llnes ln conduit 102.
There may be ~everal flow lines from subsea wells 11 extend~ng upwardly through the spar to a reglon ad~acent to 12 core 92. Typlcally, there wlll be seven hydraulic flows 13 through the swivel, slx of which wlll be for use in dlrecting 14 crude oll upwardly and lnto core 92 for translt through plpe 98 to the tanker. The seventh llne wlll be used for well 16 test purpo~es and wlll be used to dlrect natural ~as or 17 crude oil back down the spsr and then to a nearby transit 18 tanker berth or by plpellne to a recelvlng ter~lnal on the 19 shore. For purposes of lllustration, three such flow lines are coupled by respective swlvels to core 92 at corre~pondln8 21 locatlons along the len~th of the core. As shown in Fig. 8, 22 there 18 an upper swivel 108, a mlddle ~wlvel 110 and a

23 lower swlvel 112, all three swlvels belng rotatably mounted

24 on core 92 and havlng sultable seals at the core-swivel Junctions to assure a fluidtlght connectlon eherebetween.
26 Any number o f flow systems can be accomodated uslng thi~
271~ general arrangement. Flow llnes 114, 116 snd 118 are coupled 28 1I to respectlve swlvels 108, 110 and 112.
291' 32 -23- i ~1 I

~(~7~

Core 92, for purposes of illustration, is divided into three compartments, 120, 122 and 124, compartment L24 communicating with flow line 118 as shown in Fig. 9. Flow lines 114 and 116 are similarly in tommunication with com-partments 120 and 122? respectively~ Well-head pressure, if sufficient, will cause crude oil to be pumped through flow lines 114, 116 and 118. Pumps can also be used for this purpose. There will be respective delivery hoses 98 in fluid communication with the three compartments 120, 122 and 124. Thus, regardless of the angular position of the tanker relative to the spar, there will be a flow of crude oil through hoses 98 to the tanker. In the alternative, the spar could have a flow line manifold. In such a case, only one hose 98 would be required.
An access man-way 126 is provided in the upper end of the spar as shown in Figs. 8 and 9. The depth to which the man-way extends generally will be at least to buoyancy tank 74 and possibly below the same.
Another embodiment of the tensioning system of the present invention is shown in Figs. 10-12 wherein the upper portion of the spar is provided with a morring swivel 130 rotatably mounted thereon above buoyancy chamber 74 on spar 12 as shown in Fig. 10. The spar also has a slip ring 132 rotatably mounted thereon between a pair of bow horns 134 on the bow 20 of the tanker. A first pair of tension members 136 are secured at their lower ends to respective sides of mooring swivel 130, and tension members extend upwardly to and over a common sheave 138 on bow 20 and then pass to a -24_ 1(~'7S5'~5~

constant tension device 140, such as a constant tension winch. Thus, members 136 exert a tension force on spar 12.
The location of mooring swivel 130 along the length of spar 12 is such that angle A (Fig. 10) between each tension member 136 and the longitudinal axis of spar 12 is quite shallow, such as 10 to 15~ Tension members 136 are located at this angle relative to the spar so that there will always be a lateral component 137 of the tension force T exerted along each tension member 136 to urge the spar toward the tanker. In this way, the spar and tanker are kept from moving out of phase with each other so as to avoid damage due to impacting of the two together.
A second pair of tension members 142 is coupled at the front ends thereof to respective sides of slip ring 132, then to respective sheaves 144 near the outer ends of respective bow horns 134, then to respective constant tension devices 146 on opposite sides of the bow as shown in Fig.
12. Tension members 142, when cooperating with slip ring 132, maintains the spar centrally located between bow horn 134 and spaced forwardly of the bow of the tanker to prevent impact of the spar and the tanker itself. Also, tension members 142 allow the tanker to pitch relative to the spar.
The buoyancy force of buoyancy tank 74 is aided by the tension force of tension members 136 to bias or urge the spar into its normally upright position.
Fig. 10 shows a substantial windvane position of the spar relative to the tanker~ and Fig. 11 shows a substantial override position of the spar relative to the tanker~

-25-~ l-1~75999 l Typlcally~ ~he inclination of the gpar ln the wlndvane 2 posltlon 19 about 20 and ln the overrlde position 18 about 3 10-. In both ca~es, the spar r,emains centered between and 4 spaced from the bow horn~ by te~nslon members ~42 and tenslon members 136 continue to be at an angle relael~e to the 6 longltudlnal 8xi8 of the ~par.
7 The embodiment of Flgs. 13-lS 18 very slmllar to 8 that of Flgs. 10-12 ln that lt has a rotatable ~oorlng 9 swivel 130 above buoyancy tank 74 and a palr of tenslon members 136 whlch extend upwardly to snd over a common ll sheave 138 on the bow of the tanker and then to a constant 12 tension devlce 140. Inetead of slip ring 132 and ten~ion 13 membQrs 142 of Figs. 10-12, the embodiment of Flgs. 13-lS
14 has a motlfled bow horn structure 148 in whlch a V-~haped notch or recess 150 (Flg. 15) i8 provlded at the forward l6 extremlty and three or more angularly spaced rollera 152 are l7 mounted on structure 148 near the rearmost portlon of the l8 notch for rotatlon about respective horlzontal axes. The l9 rollers operate to engage the ad~acent part of the spar at 20~ all times. Spar 12 1Q held in rolling contact with rollers 21~ 152 by the lateral component 137 of ehe tension force T
22¦ applied by angled tension member~ 136 to ~ooring swlvel 130, 23~ yet the spar i~ biased in a normally npright po~itlon by the 241 buoyancy force of buoyancy tank 74. Flg. 13 ~how3 a a~bstan-251 tlal windvane posltion of the spar relative to the tanker;

26 and ~ig. 14 sho~is a substantial override posltion of the

27 spar.

3~ -~6-1~75~

The way in which wave action affects the relative positions between the spar and the tanker is illustrated in Figs. 16, 16a, 16b and 17. The tensioning system of Figs.
10-12 is assumed to be the coupling means for purposes of discussion hereinafter. In Figs. 16 and 16a, the effects will be considered at the crest of a wave, and Figs. 16b and 17 illustrate the effects at the trough of a wave.
The crest of the wave (Fig. 16) is denoted by the numeral 210 and the direction of the wave is from right to left as indicated by arrow 208. Thus, as conventionally considered~ the wave particle motion will be circular as indicated by circles 214, 216 and 218 and of progressively decreasing diameter as the circles extend downwardly and away from crest 210.
In practice, the wave will have its greatest force at the surface 18, the wave force being less intense as the water depth increases. The force of the wave action will be exerted at various locations along the spar, the individual forces at such locations being denoted by arrows 220 extending to the left.
Fig. 16a shows the resolution of the various forces exerted on the spar when the spar is in the inclined attitude of Fig. 16, assuming the wave crest is passing and wave direction is from right to left as denoted by arrow 208. In this case, the forces exerted on the spar by the wave action and the component 137 of the tension force of each tension member 136 exceed the lateral component of force 139 due to the buoyancy force 141 of buoyancy tank 74.

t--~ 7S999 2 Thus, th~ ~par 1~ malntained ln lts normal coupled relstlon-3 shlp with the bow of the tanker and there is substant1ally 4 . no problem of tanker separaeion from the spar due to wave actlon (Flg. 16~.

6 When che wave trough i~ passing and wave directlon 7 ¦ 1~ ln the dlrection of arrow 208, the wave forces on the 8 ~ spar are in the dlrectlon of arrows 222 (Fig. 16b) and the 9 spar may a~sume the inclined attitude opposlte to that of 10 ~ Flg. 16a. In the alternative, the spar may remain gen~rally 11 I uprlght althou~h, in general, it will be sllohtly inclined in one direc~ion or another. Assumlng that the incllnaelon 23 ¦ f the ~pa~ i~ a~ shown in ~ig. 16b, lateral co~ponent~ 137 14 ¦ of the tenslon force due to tension members 136 and lateral 15 ¦ component~ 139 of the buoyancy force 141 of buoyancy tank 74 16 ~ must be at lea~t as great as the sum of the force~ of the 17 I wave actio~ denotPd by arrow 222. Since the tension of the 18 I ten~lon memberR 136 1~ relatively large, such as 300 tons or 19 ¦ ~ore, the lateral component 137 will be relatively large ~o 20 ¦ as to keep the spar effectively coupled to the tanker e~en 21 ~ during e~treme conditlon3, such as being subJected to the 22 ¦ trough of a 60-foot wave in the dlrectlon of arrow 208 of 23 ¦ Fig. 16. Even assumlng thst the spar i9 in a generally 24 ¦ upri~ht position when the wave strikes the ~par, lateral 25 ~ component 137 will continue to counterbalance the force of 26 the wave or even exceed the force of the wave wlthout the 27 assistance of component 139, for in the uprlght po~itlon,

28 co~ponent 139 will not exist becau~e the buoyancy force 141

29 will be coincident wlth the }ongitudinal a~is of the spar.

2 -2~-Il ~

.

1 I In considerlng the rlelatlonshlp to the tanker and 2 ¦ the Qpar at the trough 230 of R wave moving ln the dlrectlon 3~ of arrow 208 (Flg. 17~, the wave action i9 assumed to rotate 4 ~n the d~rection of srrow 232 and thereby exert lsteral 5 ¦ fQrces 234 along varlous locntlons of the spar. ln sueh a 6 case, the lateral component 137 of the tenslon due to member 7 136 must counterbalance the~e force~ 234 as well as the 8 later~l component 139 of buoyancy force 141 If ~par 12 i~
9 lnclined to the left as shown in Flg. 16a. If incllned to the rlght a~ shown in Fig. 16b, lateral components 137 and 11 139 are ln the ~ame dlrectlon and are addltlve, the sum of 12 these co~ponents then serving to counterbalance wa~e forces 13 234. The tension of members 136 wlll be sufflclently great 14 such that component 137 will have a magnltude st least equal to or greater than the sum of the forces comprlsed of com-16 ponent 139 and forces 234 due to the wave aetion.
17 For wave actlon at the trough for waves moving ln 18 the dlrectlon opposlte to arrow 208, the lateral forces 236 19 will be the forces due to wave action and these lateral 20 ¦ forces wlll be in the same dlrection a~ lateral component 21 137. Thus, thls will be a condltion ln whlch there wlll be 22 substantlslly no tanker separatlon problems and the spar and 23 the tanker wlll remaln effectively coupled together. This 24 conflguratlon allows the tanker to dlsengage from the mooring 25 ~ under severe weather condltion~ wlthout as~lctance from 26 ¦ other marlne craft and without ha~lng workmen exposed on the 27 tanker bow by slmply releasing the connectlng csble.

., .

Claims (12)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A materials delivery system for the transfer of mined materials from the bottom of a body of water to the water surface comprising: a spar having means at one end thereof for mounting the same in a generally upright posi-tion on the bottom of said body of water with the spar having a length sufficient to permit it to extend to a location adjacent to the water surface, there being a material delivery line capable of transporting said materials and extending along the spar from a location adjacent to said mounting means to a location adjacent to the upper end of the spar, said delivery line adapted to be coupled to a materials receiver near the water surface when the spar is in said position; and means coupled with the spar near the upper end thereof for coupling the spar to the materials receiver and for applying a generally upward force to the spar when the spar is in said position, the upper end of the spar being movable laterally when the spar is mounted in said upright position and as said upward force is applied thereto, whereby the spar can move laterally with the materials receiver.

2. A system as set forth in Claim 1, wherein the delivery line extends through at least a major portion of the spar and is carried thereby.

3. A system as set forth in Claim 1, wherein the delivery line is externally of at least a major portion of the spar and is carried thereby.

4. A system as set forth in Claim 1, wherein the mounting means comprises a base having means for anchoring the same to the bottom of said body of water, and including means defining a connection between the spar and the base to permit articulation of said spar and thereby lateral move-ment of the upper end of the spar relative to said base.

5. A system as set forth in Claim 4, wherein said connection defining means comprises a ball joint.

6. A system as set forth in Claim 4, wherein said connection defining means comprises a U-joint.

7. A system as set forth in Claim 4, wherein said connection defining means comprises an elastic joint.

8. A system as set forth in Claim 1, wherein the force applying means comprises a buoyancy tank near the upper end of the spar for applying a first force thereon at a first location below and adjacent to the upper end thereof, and flexible means coupled to the spar at a second location between said upper end and the first location and adapted to be coupled with said receptacle for exerting a second force on the spar with the second force having a component extending transversely of the longitudinal axis of the spar.

9. A system as set forth in Claim 8, wherein said flexible means includes structure for applying a constant tension force to said spar.

10. A system as set forth in Claim 8, wherein is included a swivel mounted on the spar at said second location, said flexible means being coupled to said swivel.

11. A system as set forth in claim 1, wherein the delivery line comprises a fluid flow line, said spar having a tubular core rotatably mounted thereon adjacent to the upper end thereof, said core being rotatable about the longitudinal axis of the spar and having means for transferring a fluid therefrom to the receptacle, and means coupling said fluid flow line to the core and permitting the core to rotate relative to said fluid flow line.

12. A system as set forth in claim 11, wherein said means for coupling the fluid flow line to the core includes a swivel mount having a fluid passage therethrough for placing the fluid flow line in fluid communication with the core.