DE2206929A1 - Watercraft, in particular drilling ship, with variable draft - Google Patents

Description

Patent attorney patent attorneys

Dr. phil. Gerhard Henkel Dr. rer. nat. Wolf-Dieter Henkel

D-757 bottom-bottom bellows Di pi.-1 ng. Ralf M. Kern

Te ₁ TK ⁸ A Dr. rer. nat. Lothar Feller

T »» «gr-A * .: BMp» okiBecl »irted ·· D-O ΜϋΠΟΙΘΠ 90

Eduard-SdwnW-Str. 2 'ρ -j ΤΛ: (0811) 663197

T, l * if necessary-A *. ι EIHiMOici MOndwa ! • tar .. ^ ___ ""

Santa Fe International

Corporation

Orange, Calif ,, V.St.A. 2206929

L- -J & FEB. 1972

•• «mi watercraft _f in particular drilling ship _f with variable depth

The invention relates to a variable draft watercraft and, more particularly, to a variable draft deep water drilling vessel Draft, which has double hulls and a single, central column that supports a drilling platform.

In the search for new oil fields, the drilling is increasing and made to a significant extent in coastal waters and in similar places where the oil field is of a sizable nature Amount of water is covered. This resulted in a great interest in near-coast, both in shallow and deep water, research drilling carried out and significant expenditures for them. The current coastal drilling is in general limited to comparatively shallow water depths, deep water research wells have heretofore been using specially designed and constructed watercraft or drilling rigs, which various, even closer to there are explanatory disadvantages and limitations. A brief discussion of the coastal exploration drilling practices that have been carried out to date and the watercraft or drilling equipment used may serve for a better understanding of the invention and

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a clear distinction between the shallow water and deep water drilling used drill ships or drilling rigs enable.

An earlier, still used method of drilling in coastal waters provides for the construction of a self-contained, fixed platform that rests on piles driven into the seabed and on which a drilling rig, additional equipment and crew quarters are arranged. After the drilling work has been completed, a tractor or a crane frame is brought in to dismantle the drilling rig and move it away; In the case of a dry, ie unsuccessful, drilling, the entire, self-contained platform is dismantled and removed. A modification of this method provides for the use of a somewhat smaller platform which rests in a similar manner on piles and carries a drilling rig, while the additional equipment and the crew quarters are on a tugboat lying alongside. After the drilling work has been completed, the platform is either left in place for oil production or, in the event of an unsuccessful borehole, dismantled and removed. The two methods described last are mainly used for production drilling and not for research drilling. In another method, a self-lifting swimming cream is used, which is towed to the drilling site and is provided with pillars or feet, which are then lowered and embedded in the seabed. Then the pram is heaved up so that it comes free from the surface of the water, and then serves as a platform on which the drilling rig, the crew quarters and the additional equipment for carrying out the drilling work are then arranged. After completion of the drilling work, in the event of a successful borehole, a fixed plate is generally

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form for further oil production, while the self-lifting floating cream was towed to another drilling location will. The aforementioned methods are suitable for use in comparatively shallow waters with a depth normally not exceeding about 90 m. The factors which make the construction and operation of such one of the arrangements described above Determining swimming equipment only affects stability, movement and other problems like them in a secondary position occur when drilling from a swimming platform, for example for deep water drilling, because the aforementioned Drilling and floating devices are designed for seabed contact "

So far, deep-water research drilling has been carried out using drilling ships floating on the surface of the water, which are either tugged or self-propelled to the drilling site and which form a self-contained system in that the drilling rig, additional equipment and crew quarters all form part of the ship. These floating drill ships are anchored above the drilling site and are usually provided with a central opening through which the drilling rig operates. The drilling operations carried out from such drilling vessels, however, are severely restricted by the prevailing sea conditions, since excessive ship movements during lifting, pitching and rolling can easily damage the drilling equipment and also increase the difficulty of anchoring the ship directly above the drilling location. The stability and movement properties of such a monohull drilling ship therefore in no way favor the effective implementation of the oil drilling work. A catamaran or double-hull drilling ship has also been built; although such a vessel is more stable than a single hull ship, it throws

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nevertheless considerable difficulties in terms of excessive ship movement due to wave action, an only insignificant one Motion damping property, including over-stability lower natural or natural period and the resulting "fast" effect through which the Crew is exposed to unexpected shocks which can endanger the drill string and other equipment. While such craft are not geographically limited to coastal water drilling operations, they are Use restricted in sheltered or calmer waters

For deep-water drilling work, semi-submersible platforms have also been used, which, like the floating watercraft, form completely self-contained systems.In this latter type, the platform rests on a number of load-bearing members including stabilizing columns which, at their lower ends, are connected to a substructure Floating structure are connected, which in the ballast-free state carries the entire structure in a state of shallow draft on the water surface, the substructure being largely freeboard. The columns are spaced apart and usually arranged practically symmetrically around the outer ends of the platform has been dragged with freeboard to the drill site, the floating base is weighted with ballast so that it is immersed, together with parts of the column, after which the ship ¹ assumes a state of large draft. the drilling platform is at this deep draft through the Ve The displacement of the submerged column sections and the remaining displacement of the substructure are kept above water. The platform stability. around the pitch and roll axes is ensured by the righting moments, which are generated by the water plan surfaces of the pillars located outside the center of the platform,

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In one embodiment of this earlier semi-submersible Platforms form the stabilizing columns practically symmetrical equilateral polygons with at the tips of the respective Polygons of usually square or triangular shape lying pillars. The equilateral symmetrical The polygonal arrangement ensures practically identical erecting moments around the roll and ram axes as well as around all of them Intermediate axles, regardless of the shaft direction * Another embodiment of a similar, semi-submersible Drilling ship has a number of stabilizing columns interconnected near their upper ends, only these columns float in the water and are again arranged in the form of a symmetrical equilateral polygon. If" like such known semi-submersible drilling ships generally have sufficient stability for the drilling work have, they are subject to the disadvantage of very poor transportability between the different drilling locations due to the large frontal area of the in Columns or pillars and / or arranged in the form of a polygon of the substructure, so that their towing speed is often not more than two knots.

A drilling ship with a variable draft has also already been constructed and has been used which provides sufficient stability for drilling operations in a state of great depth and the serious drawbacks of very little mobility between drilling locations such as that of the earlier semi-submersible Platforms are common, turns off. This drill ship is disclosed in patent 1,781,202.1 which is a development of the subject matter of patent 1,781,292.1. As disclosed in these patents, this drilling vessel is characterized by two spaced apart, practically parallel hulls, each supporting a number of upright columns, at the upper ends of which a drilling platform

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shape is arranged. Special merlanale of this drilling ship '' are the high mobility and maneuverability between. the drilling locations, sufficient stability in a state of great draft above the drilling location and properties that greatly reduce ship movements, with the drilling ship practically not responding to the excitation forces caused by the action of wind and waves. This drillship has proven successful at various drilling locations around the world.

Although the pillars of the drill ships described above offer reduced areas in the deep draft condition which the stimulating forces act in this state of great depth, call these forces when they hit the pillars act, a certain hoIl-, stamping and lifting movement of the drilling ship. Mark in the state of great draft These drillships are also characterized by positive righting moments caused by the around the outer edges of the drillship spaced columns are generated. This means that the location of the pillars is around the outer edges of the drilling vessel around as well as the considerable VVasser plan areas defined thereby ensure the only righting moments required for the stability of the vessel in a state of great draft are. The position and the size of the pillars of these well-known drilling ships are therefore the most important criteria which determine their stability properties in the state of great draft.

The object of the invention is therefore primarily to create a novel double-hull variable watercraft Draft, which, compared to the known drilling rigs and drilling ships of this type, has various advantages in terms of construction, It offers working method and result by greatly reducing it, especially when swimming with a great draft

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Sefaiff movement is guaranteed as a result of the excitation forces caused by the action of the waves, which in the following is referred to as ^M Bfcw © gungs ~ DampungsveriHö'gen ^u , but maintains adequate stability "

This drilling ship should be maneuverable quickly and in large Water depths can work as a self-contained drilling ship.

Here, a drilling platform is to be arranged on a deck of the double-hull ship and the drilling ship is in the state great draft improved motion damping properties as well as a reduced water plane surface in the drilling condition with a large flow passage.

Another feature of the invention is that the draft of this drilling ship varies by floods and bilges- * is bar, so that the drill ship can either go into one state, wrestle Draft in which the hulls have freeboard, and a state of great draft can be brought into which because it swims stabilized.

This drilling ship should furthermore have a draft which is variable between a state of large and such a shallow draft, the center of gravity being above the center of buoyancy in the case of a low draft and below the center of the buoyancy in the case of a deep draft; This property is characterized by the fact that the main cause of the overall ^{stability of the drilling ship at great drafts is a "pendulum n} -stability", which is ensured by placing the center of gravity far below the buoyancy zone, while the water position dea * central column contributes only minimally to the overall stability of the drilling ship.

2.0.9 84 8/058

In a further embodiment, the invention creates a deep water Do ppelrumpf drilling ship with a variable draft, the one Number of columns arranged substantially around its lateral outer edges, which it during the initial part of the transition from low to high draft as well as during the last part of its transition give stability from the great draft to the shallow draft.

The draft should be variable between a low driving draft and a large drilling draft, with in an almost shallow draft stability is ensured by the erecting moments of the pillars, which is essentially are arranged around the lateral outer edges of the ship, while at almost or very deep draft the stability is mainly guaranteed by righting moments, which are caused by the ship's center of gravity is below the center of buoyancy.

According to a further feature of the invention is the deep water drilling ship of variable depth, comprising a number of stabilizing columns arranged substantially around its outer edge as well as having a central column carrying a drilling platform above a pair of hulls, characterized in that that the middle waterline at great draft between the drilling platform and the upper ends of the fully submerged Stabilizing pillars, whereby in the state of great draft the area exposed to the excitation forces of wind and waves of the ship is greatly reduced.

The following are preferred embodiments of the invention explained in more detail with reference to drawings. Show it:

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Fig. 1 is a perspective view of a large state Draft double-hulled watercraft of variable draft with the features of the invention,

2 shows a side view of the watercraft according to the invention, on a slightly enlarged scale,

Fig. 3 is a front view of the same,

Fig. If a horizontal section essentially along the Line / Hf in Fig. 2,

5 shows a section through the platform essentially longitudinally the line 5-5 in Fig. 2 showing the general arrangement the platform illustrates

6 shows a vertical section, on an enlarged scale, through the central column,

Figures 7, 8 and 9 are cross-sections along lines 7-71, 8-8 and 7-7, respectively. 9-9 in Fig. 6,

Fig.10 is a schematic representation of a fuselage of the Watercraft to illustrate a ballast system for this,

Flg.Π a perspective view of a modified ,;,., AusfUhrungsform of a double-hulled watercraft with variable draft according to the invention, which is shown in the towing state of low draft,

Fig. 12 is a perspective view of the watercraft according to FIG. 11 in the drilling condition of great depth,

13 shows a side view of the watercraft according to FIG. 12,

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Fig _# 1if a front view of the same and *

Fig.15 shows a horizontal section essentially along the Line 15-15 in Figure 1Z *.

The embodiment shown in FIGS. 1 to 3 In the following, for the sake of simplicity, the variable draft watercraft designated as drilling ship 10 has two in the transverse direction spaced apart elongated hulls 12, which are parallel to each other and have sufficient displacement to the drill ship 10 in one To carry swimming state of low draft, in which the hulls, as indicated at f in Fig. 2, have freeboard. The hulls 12, which are practically identical to one another, each have a substantially rectangular cross-section, as shown in FIG. Each fuselage 12 has hydrostatic and hydrodynamic properties in terms of construction, including a streamlined one Shape to ensure minimal resistance to movement through the water. Each hull 12 has a bow 1 / +, a stern 16 and a central body lying therebetween. The aerodynamic shape of the hulls 12 reduces resistance to travel and through the water as the shallow draft drillship 10 is fully supported by the hulls 12, wherein the latter have freeboard f (Fig. 2). Between the hulls 12 and the terminal pairs of columns to be described 26 extend longitudinally spaced box-shaped beams 18 as structural connections which the Keep hulls practically parallel to each other at a distance.

A platform or a main deck 20 is supported by a vertical central column Ξ.Ι + at a distance above the hulls 12, the platform side parts 25 projecting beyond the column 2if. This is connected at the upper end to the platform 20 and arranged on the underside at a distance above the hulls 12, and they are supported by box-shaped support members

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28 of substantially rectangular cross-section extending from the hulls 12 diagonally inward and upward extend to the bottom of the column. More precisely, these elements 28 provide a structural connection between the hulls 12 and the column 2Zf, the amidships is arranged so that its vertical axis is in the middle between the hulls 12 and is practically in the middle between the two ends of the drilling ship 10.

For reasons to be explained in more detail, there are from each trunk 12 on its outboard side a plurality of columns 26 distributed over longitudinal distances upwards, the supports 18 with their ends are attached to the inboard sides of the transversely aligned pillars 26.

6-9, the central column 2Zf has a larger diameter portion 30 which forms the lower end or base of the column 2Zf. The column 2Zf also has a central shaft 32 which extends coaxially over its entire length. According to Fig. 1, the deck 20 carries in a central position on the drilling ship 10 a derrick 38, so that a not shown underwater riser pipe from the derrick 38 through the central shaft 32 of the column 2Zf and between the hulls 12 can be passed to still carry out drilling work to be described in more detail. The central column 2h has several decks located at different heights, the upper decks comprising an anchor deck ZfO (spider deck) and storage decks Zf2 for storing drilling accessories. The lower, diametrically widened part 30 of the column 2Zf forms a sludge system deck AfZf, which can be seen to accommodate sludge pumps, sludge mixing pumps, reserve sludge tanks, etc. In the embodiment shown, passenger and freight elevators Zf6 and Zf8 are provided, which allow access to these decks. The main deck 20 is formed in the shape of a segment of a circle at the front and rear ends, wherein

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its sides merge into chord lines of the circle circumscribing the front and rear ends of the deck 20. The deck 20 forms a so-called Texas deck with several deck superstructures 50 for accommodating machines 51 »crew quarters 53 ₁ various additional equipment etc. On the deck 20 several pipe racks 55 are provided for the storage of drill pipes provided for the various offices and for further additional equipment, which is located near the front section of the drilling ship 10, above it a helicopter deck 5 * t is present.

The drilling equipment provided on deck 20 preferably includes an automatic drill pipe receiving machine, indicated generally at 56 to plumb the drill pipes from their storage location for connection to the drill string To spend position in the derrick. On both sides of the drilling ship 10 is a crane 58 of conventional design, i.e. with the usual boom 60 and crane operator's cab 62, mounted. The cranes can have any desired lifting capacity, for example one of 100 t, and are preferably mounted on bases 6 * f.

In a preferred embodiment, the pillars 26 are along the outboard sides of the torso . arranged such that the centers of mass of their cross-sectional areas are outboard of the center lines of the associated hulls. In this way, the columns 26 generate greater moments of inertia of the water planar surfaces around the roll and pitch axes in order to give the drilling ship 10 greater stability during its transition between large and shallow drafts, which will be described later, than would be the case if the columns 26 were to the center lines of the hulls 12 would be arranged. The pillars 26 protrude from the hulls 12 a predetermined amount upwards, the

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depends on the predetermined characteristics of the drilling vessel when transitioning between shallow and deep drafts, such as this will also be explained later

The drilling ship is provided with permanent ballast, ie each hull 12 has a layer of very dense concrete along the bottom, which has a very high specific weight of about 3 _f 5 to ij. and gives the ship permanent ballast in addition to the water ballast, which is used in a manner to be described to change its draft between large and shallow drafts.

According to FIG. 10, each hull 12 is divided into a number of spaces, the ballast chambers 70 for changing the ship's draft form. Likewise, according to FIG. 3, the columns are also subdivided into a plurality of spaces serving as ballast chambers 72. All chambers 70 and 72 are optional and independent of one another Can be flooded and drained so that the draft can be changed between a high and a low value, the deck 20 but remains practically horizontal at every draft. The ballast chambers can also be used to adjust the trim position of the drilling ship 10 are used around the roll and pitch axis, while the ship dives into and is held in the state of great draft. Furthermore, flood and bilge operations are carried out when the drilling ship is in the state of great draft in order to achieve its own period, i.e. natural oscillation number can be changed at will when lifting, tamping and rolling. In Fig. 10 is the starboard hull shown with its ballast system; evidently the port hull is accordingly, even if it is reversed, and is ballasted in a similar manner. The ballast chambers 72 in the two of the associated fuselage 12 supported transition columns 26 are not shown, but their flood connections are shown.

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The ballast chambers 70 and 72 are selectively and independently flooded and drained so that the drilling ship can also be partially submerged within a range between large and shallow drafts, but with the platform 20 remaining practically horizontal during such a change in draft. To carry out this flooding and bilging, several lines 7h run from a pump space P arranged centrally in each hull 12 in the longitudinal direction opposite to the various ballast chambers 70 in the hulls. For the sake of simplicity, four ballast chambers are shown in the bow and stern sections of each fuselage 12, although, it should be noted, in practice a larger number of ballast chambers are normally provided. Furthermore, several lines 76 also run from the two fuselage pump chambers P to the ballast chambers 72 in the columns 26. Two further lines 7 & run backwards from the pump chamber P and open into two chambers 80, which are used as additional ballast chambers or as Can serve chambers for receiving drilling water. Two bilge water lines 82, which are not part of the ballast system itself, go from the pump room P to the front and back into the bilges of the hulls and are connected to the ballast pumps in a manner to be described below.

The pump room has a seawater inlet indicated at 8 / f and an overboard outlet 86 indicated at 86, both of which are provided by corresponding power operated slide valves 88 and 90 are controlled; the hulls are rare indicated in Fig. 10 by the dashed lines. Two Pumps 92 and 9 * f suck through inlet 8 ^ - and valve 88 Seawater and then convey it via lines 96 or 98 and check valves 100 or 102 into a line 10Zf, which communicates with a main ballast line 106. The two ends of the main line 106 are via optionally open, power-operated valves 108 with the front and

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the rear ballast line 7k ″ or 76 in connection, the lines 7h being arranged in parallel at both ends of the main line 106. When the valves 88, 100 and 102 are open, both the fuselage ballast chambers and those shown, three each Column ballast chambers can be flooded with seawater by selectively actuating the valves 108. Preferably, only at most two chambers are flooded at the same time in order to keep the drilling ship more easily keel-alive when flooding at a great depth.

In order to allow the drill pipe 10 to float again with the hulls on the freeboard, the valve 88 is closed and the valves *? 0 _? 108 and 110 are opened. The pumps 92 and 9 ^ - deliver dos water in the same direction as before and thus suck off the main line 106 via line 112. By selectively actuating the valves 108, the ballast water can be drained from the ballast chambers via line 10Zf, open valve 90 and outlet 86. Preferably, a maximum of two ballast chambers are drained at the same time, so that the drilling ship can be kept keel-life when draining at a low-draft.

A line 11 if connects the port and starboard sides Pump rooms with each other and communicates with the ballast line 106 · By actuating the appropriate valves, including of valve 116 in line 11 ^, ballast water can of a. Trunk to be transferred to the other. If a pump room is flooded as a result of major damage, this can Ballast system can be kept under control after opening valve 116 with the help of the pumps in the other fuselage.

The Bailast / Bohrwasser lines 78 are also on the Valves 108 corresponding valves 118 parallel to the rear Connected to the end of the main line 106 »As a result, the ballast / drilling water chambers 80 can be operated optionally

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supply of the valves 118 and the aforementioned valves 88, 90 and 110 in a similar manner to the chambers 70 and 72. can be flooded and drained jointly and optionally.

A fresh water inlet or feed line 120 connected to the deck 20 via a riser 122 and a fresh water suction line 12Zf connected to a ship's fresh water pump 126 are each connected to a fresh water chamber 128 located at the rear of the hull inboard side. A line \ 2 $ establishes a connection between the fresh water pump 126 and the deck 20 via a riser 130. Two fuel suction lines 132 are connected to a fuel tank 134 located in front of the pump chamber on the inboard side of the fuselage and deliver the fuel oil to the engine deck by means of a fuel pump 138 via a riser 136.The drilling water is drawn from a rear drilling water chamber IZfO and from the ballast / Drilling water chambers 80 conveyed by a pump 1Zf8 via lines 1Zf2 or 78, l ^ fif into a drilling water main line 1 Zf6, the pump 1 Zf8 the drilling water via a valve and a riser \ ^ 2. promotes to deck 20. A drilling water line 154 communicates with a forward drilling water chamber 156 and delivers drilling water to deck 20 via pump 1Zf 8 and line 152. Valves 158 are provided in lines 1Zf2 and 11 + 1 + , which together with valve I56 in the line 151+ can optionally be operated to fill and empty the chambers 80, IZfO and I56, whereby drilling water can be conveyed to and from the drilling rig and used to flood and drain the drilling vessel

When the drilling ship 10 is in the low draft state as shown in FIG. 1 and the hulls are open air level f, is its center of lift under its center of gravity, the hulls 12 of the drilling ship 10 in the low-draft position

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Give stability. In the state of great draft according to FIG. 2, however, the orientation of these two points is reversed to one another, ie the center of lift of the drilling ship is located above its center of gravity. In particular when flooding the drilling ship 10 for the purpose of transitioning from the low to the great draft, ie when the ship's draft is gradually increased from the shallow draft, its center of buoyancy shifts upwards and its center of gravity downwards. If, on the other hand, the drilling ship is pumped for the purpose of changing from a large to a shallow draft, that is to say in the case of a gradual reduction in draft, then its center of buoyancy shifts downwards and its center of gravity upwards. During this transition, at a certain draft, an orientation of the ship is reached in which its center of lift and also its center of gravity are practically on a straight horizontal plane or at the same height. To give the drill ship stability during its transition between the two draft states and also, as will be explained in more detail _? To keep the area of the ship exposed to the effects of wind and waves as small as possible, so that the drilling ship responds much less to the excitation forces caused by the effects of wind and waves when the draft is large, the stabilizing columns 26 protrude beyond the lumps 12 a predetermined distance above, in which they provide the drilling ship with righting moments at the transition between the two draft states and especially with such drafts in which the upwelling zone is below the center of gravity or at the same height. If the drilling ship is flooded in the manner described earlier, the columns are capable 26 after submerging the hulls 12 righting moments to ensure the roll and pitch axes and thereby maintain the stability of the drilling ship as the draft increases.

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In the interest of shortening the description, the following definitions are given: "Motion damping properties" are those properties of the drilling ship which greatly reduce its movement as a result of the excitation forces caused by wind and wave action and which the drilling ship in the state of great draft by special design of the cross-sectional area and the configuration of the columns, by weight distribution in the drilling ship and by shaping the submerged ship parts at great drafts, so that the ship has a natural period outside of the period range of the waves to be expected and a reduced area in terms of lifting, pitching and rolling movements mean waterline has »" State of low draft "means the draft ^{at which the ship swims with hulls with freeboard:} c, " State of great draft "is the draft at which the ship swims so that its mean waterline is between de m deck 20 and the head ends of the pillars 2.6 and where the drilling work is also carried out The top of the trunk collapses or lies above it. Finally, the "near-great draft area" is the draft area in which the center of buoyancy of the ship is above its center of gravity and does not include the actual "great draft state".

As mentioned, the center of buoyancy in the low-draft state and in the near-low-draft area is below the ship's center of gravity. If the ship's draft increases from the shallow draft beyond the aforementioned near-low draft range, the center of lift and the center of gravity relstxv to the ship shift towards one another. This shift continues over a ship's position in which the two points pass each other, ie. the ship's draft

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exits the near-shallow draft range and enters the near-great draft area. The arrangement of the Columns 26 and the water plan areas defined by them when the draft was enlarged in the near-low-draft area are chosen so that they generate sufficient righting moments to ensure the stability of the ship. at further weighting of the ship, i.e. when its draft enters the near-great draft area and yourself approaches the state of great draft, the center of lift and the center of gravity shift apart again, with the former comes to rest over the latter. When the draft is beyond the near-great draft range in the direction of the state When the draft increases, the righting moment increases of the pillars 26 ensured contribution to the overall stability of the drilling ship compared to the contribution to the overall stability by the increasing vertical distance between the center of gravity and the center of lift is guaranteed because the former is below the latter. at This "pendulum type U" stability with the center of gravity below the center of buoyancy finally provides even further increasing draft the main contribution to the overall stability of the drill ship, At a certain draft in the near-great-draft range the columns 26 are completely submerged and no longer contribute to stability.

The stability properties described above are graphically illustrated in the following table, in which: the stability properties of the drilling ship during the transition from the low to the large draft by means of the standard formula GM = (KB - KG) + BM are expressed. Here, GM is the metacentric height, KB and KG are the vertical heights of the Buoyancy center or the center of gravity above the lowest point of the drilling ship (determined by one of the undersides the plane containing the hulls) and BIi the metacentric radius - (with I = the transverse moment of inertia of the waterline and

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V a the displaced volume up to the relevant water line).

Draft condition

(KB - KG)

BM

GM

Low-low gear

Negative value

Big positive
value

Positive value + BM (KB-KG)

Nearly-

Low-low

aisle area

Nearly-

Large-deep

aisle area

Greater
Draft

Negative value and size that decreases to zero as the draft increases

Positive value, increasing with increasing draft

Great positive value

Positive value

Positive value small if central column is the only one
Water plane area
specifies

Smaller positive
value

Positive value

+ BM +

Positive value

+ BM +

Positive value + (KB-KG) ♦ BM

In addition, the diametrically enlarged lower part 30 is the central one Column 2 / f arranged so that it raises the center of lift when the draft is over the near-great draft area the state of great draft increased. This extended part takes effect after the center of lift is above the center of gravity has shifted beyond "pendulum type" stability is. Since the righting moment caused by this predominates and, in order to reduce the response of the drilling vessel to excitation forces, the pillars 26 terminate sufficiently at the top well below the position of the mean waterline when the drillship is in a deep draft state. More precisely, the columns 26 end at the top at a height which coincides with the mean waterline when the Ship is in the near-great draft area in which it is given enough "pendulum-type" stability to maintain its maintain required stability. The columns 26 are thus capable of ship righting moments about the roll and pitch axis to ensure around at least at such a depth,

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at which the center of lift is below the center of gravity and is at the same height as it, i.e. over the entire near-low-draft range away. The ship's stability is therefore in the near-great-draft range and in the large state Draft guaranteed by the large righting moment, which is ensured by the center of gravity under the center of lift is caused, while the central column contributes little or very little to the stability.

To facilitate the transition between a draft of the drilling ship, which gives him stability through the pillars 26 alone is awarded, i.e. from the low-draft to the near-low-draft range away, and a draft in which the ship's stability is primarily derived from the pendulum-type stability exists (with a focus below the center of buoyancy and only slightly promoted by the planar water surface of the central column (i.e. over the near-great-draft area and in the state of great draft), the tops of the Columns 26 designed so that their cross-sectional areas gradually decrease in the direction of the deck 20. These Reduction in cross-section begins at a height above the hulls 12, which is practically the mean waterline at one Ship draft coincides with which the influences of the relative position of the center of lift to the center of gravity and the The water planar area of the central pillar jointly gives the drillship sufficient stability when it is fully loaded State. More specifically, the upper inner surfaces 27 of the pillars 26 are truncated to form wedges beveled outwards and upwards so that the column cross-sectional area gradually reduced in size towards the deck 20, the columns 26 are obviously in the direction of the Trunk axes extended, which means that when the draft changes greater righting moments are generated than in the case where the paws had a circular cross-section, and their mass

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Center would be closer to the ship's inclination axis. aside from that the pillars 26 are completely submerged in the deep draft state, i.e. the mean waterline is between the top of the pillars 26 and the bottom of the deck 20.

According to FIG. 2, anchoring rope pulleys 180 arranged in pairs are provided around the upper end of the central column Z1. Anchor lines 182 are guided over the rope pulleys 180 and rolled up on double-drum winches 1 S ^ f, which are arranged on the deck located below the anchor deck / fO (FIG. 6). Each pair of anchor lines 182 runs over rope pulleys 184-a provided at the upper end of the column 2 ^ and over guide rollers 185 on the upper sides of the stabilizing columns 26 Location is held. Two dynamic positioning and propulsion thrust drives 186 are attached near the two ends of each hull 12, which are rotatable over a full 360 ° and serve to hold the drilling ship precisely above the drilling location. The thrust drives are controlled by signaling devices, which can either have an acoustic system using transponders located on the seabed or tension indicators located on the anchor lines; however, these devices are neither described nor shown in detail. It can be seen that the dynamic thrust drives 186 can be used in conjunction with the anchor system, for example, at water depths of up to approximately 180 m, while the drilling ship is held at the station solely by the dynamic positioning devices at greater water depths. Movable rubber fenders 137 on wire rope guides 189 stretched between deck 20 and hulls 12 may be provided along the ship's waterline.

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Pas according to KLg. 11 to 15 trained drill ship is similar in most details, with the exception of the differences indicated below, the first described embodiment - Carrying the deck 220 at a distance above it · The hulls 212 and the central column 22h are constructed in the same way as the hulls 12 and the column 2h of the first-described embodiment. The hulls 212 are connected to one another by box-shaped supports 218 and supports 228 which, similar to the first embodiment described, converge upwards from the hulls 212 and support the column 22h . The deck 220 carries a number of deck superstructures 250 for accommodating the machines, the crew quarters, the various additional equipment, etc. On it, pipe racks 251 are also arranged for the storage of drill pipes} the deck 220 also carries a deckhouse 252 for accommodating the various Offices and other additional equipment, while a helicopter deck 254 is provided on deckhouse 252. The drilling device arranged on deck 220 includes an automatic drill pipe picking machine 256 as well as cranes 258 with booms 260 and cabins 262 mounted on bases 26if.

The main difference between the embodiment according to FIGS. 11-15 and the first described embodiment is the rectangular outline of the deck 220 and its direct support on the hulls in contrast to the cantilevered support of the deck 20 on the central column 2h of the first described embodiment. More precisely, the deck 220 is substantially rectangular in plan, and it rests not only on the central column 22 ^, but also on a number of supports 222, which in turn consist of elongate members which extend between the deck

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220 and the hulls 212 extend perpendicularly on their outboard sides. As shown, three supports ZZZ are provided along the side edge of each of the hull, which support the deck 220 on its outer sections. As in the embodiment described first, a plurality of stabilizing columns 226 distributed at longitudinal distances protrude upright on the outboard sides of the hulls 212 # In the modified embodiment, however, each column encompasses a lower part of the associated vertical support 222 or completely encloses it. The central beams 222 bisect the intermediate columns 226 on each fuselage, while the columns 226 located at the two ends of the fuselage are arranged opposite the assigned beams ZZZ in such a way that the majority of these columns are in front of or behind the assigned front or rear beam 222 . As in the first-described embodiment, the upper ends of the pillars 226 gradually decrease in cross-section towards the deck 220. This decrease in cross-section begins at a similar level above the hulls 212 as was described in connection with the first embodiment, and is carried out by chamfering the inner surfaces of the pillar outwards and upwards so that wedge truncations are formed. In addition, the upper edges of the pillars are also bevelled forwards and backwards, creating a further gradual transition in the draft of the drilling ship between its two types of stability, which, as explained above, give it a draft on the one hand near-low and on the other hand near-large -Draft range as well as in the state of great draft are guaranteed. More precisely, the outboard-side sections of the upper ends of the columns arranged at the two ends of the hulls, as indicated at 266, are progressively beveled with respect to the transverse center line of the ship. The upper ends of the central pillars 226 of both hulls are also sloping progressively towards the associated carrier ZZZ. In all other respects the drillships are according to the two

209848/0584

The illustrated and described embodiments are identical to each other · Obviously, however, the water level surfaces ■ of the upper sections of the supports 222 are practically insignificant with regard to the righting ^{moments generated by them, in comparison to the righting moment generated by the "pendulum type n} " stability, as is the case with the almost large - Draft level and in the state of great draft of the drilling ship is achieved.

For the sake of simplicity, the method of operation of a drilling ship according to the invention is explained below with reference to the preferred embodiment according to FIGS. 1 to 10, unless otherwise stated, but the description also applies equally to the embodiment according to FIGS the invention is that the drilling ^! ship 10 can be towed from drilling location to drilling location at speeds on the order of 8 knots, giving it considerable mobility between drilling locations. In the pailed condition the hulls have such displacement that they support the weight of the drilling ship in the low draft condition in which they have freeboard. In the floating state, the drilling ship 10 therefore has the upright stability and the roll angle characteristic of a double-hulled ship. It goes without saying that the girder strut is located between the hulls on their upper side and therefore above the waterline, so that it does not offer the waterfront any frontal area that would cause drag. In the swimming state of low draft, only the two hulls 12 displace water, whereby the drag in the water is reduced due to their hydrodynamic properties, in particular their practically aerodynamic bow shape, as well as the foal of support structures lying in the water, so that the drilling ship is at significantly higher speeds can be towed than was previously the case with halbt also capable drilling platforms, with the exception of drilling ships according to the patents mentioned at the beginning.

209848/0584

When the drilling ship 10 reaches the drilling site, the anchoring system and thrust drives are operated to level and hold the ship above the drilling site. In the case of comparatively shallow water depths, for example those of at most about 180 m, the anchors are ejected with the anchor lines in order to keep the drilling ship directly above the drilling location. The hulls 12 are then flooded to bring them below the waterline. If during this flooding and submersion of the hulls the draft increases over the near-shallow draft range, the moment of inertia of the water planes of the columns 26 keeps the drilling vessel 10 stable, while the center of lift and center of gravity from their initial position in the low-draft state with the center of gravity lying below the center of gravity To move the center of lift relative to the ship on each other. When the drillship increases its draft and enters the near-great draft area, the center of lift and the center of gravity pass each other and the former is the upper of the two. As mentioned earlier, the stability is as long as the ship's draft is such that the center of lift either smells below the center of gravity or is up to the same level with it, ensured by the righting moments generated by the columns 26. If the draft increases and the drilling ship enters the near-great draft area, the center of lift rises considerably above the ship's center of gravity, in particular because of the widening of the base of the central column, and the ship's stability is increasingly ensured by the constantly increasing righting moment , which results from the position of the center of gravity below the center of buoyancy, ie the drilling ship receives ^M pendulum-type "stability. This type of stability becomes predominant over the righting moments generated by the columns 26 and, with increasing draft, is sufficient to maintain the ship's uncertainty in the state of great draft. To facilitate the transition between the stability form in the low and

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in the near-low-draft condition and the stability form in the near-large and in the large-draft range, the cross-sectional area of the upper parts of the columns 26 decreases, so that their contribution to the ship's stability gradually decreases and then becomes zero when the drilling ship reaches a draft, in which the central waterline is above the tops of the pillars 26. The contribution made by the water planar surfaces of the girders 222 of the second embodiment to the overall stability of the drilling ship is insignificant in comparison to the "pendulum type" stability of the ship, which is required by the rearrangement of the center of lift and center of gravity in the near-great draft range and in the state of great draft If the drilling ship reaches a draft at which the central waterline lies between the deck 20 and the upper ends of the columns 26, the surface against which the wave excitation forces can act consists, in the first embodiment, practically exclusively of that of the central one Column Zhg and, in the second embodiment, that of the central column 22 * t and the supports 222 · This circumstance contributes significantly to the greatly reduced ship movement. It can be seen that the deep draft condition of the drill ship becomes ideal when the central waterline is practically midway between the upper ends of the pillars 26 and the underside of the deck 20. In addition, in the state of great draft, the distance from the upper ends of the columns 26 to the underside of the deck 20 exceeds the height of the largest wave to be expected from wave crest to wave trough. When using anchors, as the draft of the drilling ship increases, the anchor lines are of course kept under a predetermined tension by operating the winches in order to keep the drilling ship above the drilling location.

With the predetermined large draft, the displacement of the submerged columns and the remaining displacement of the hulls are sufficient in order to keep the drilling ship in its floating state at great depth

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In this state, not only is this displacement sufficient and ^II pendulum type ^u -stability guaranteed, but the drilling ship also shows minimal response to excitation forces, which considerably slows down its movements and thus becomes a stable platform To avoid waves and ship movement and thus to further reduce the overall movement of the ship, the drilling ship is shaped in such a way that its undamped natural oscillation periods during lifting, pitching and rolling in the state of great draft are greater than the peak periods that occur in practically all sea areas in which currently Drilling work is being carried out or may be planned to be carried out in the future. The fully damped natural periods of the drilling ship are of course significantly higher than the peak oscillation periods of the lakes in practically all parts of the world. The undamped natural periods are defined as follows: When lifting about 28 seconds; when stamping and knocking about 51 seconds.

The drilling work is carried out in the state of great draft of the ship shown in FIG. The underwater riser pipe and the drill string are passed through the shaft 32 of the central column. The drillship can be kept on station above the drilling site by the dynamic Thrust drives 186 actuated or optionally the anchor lines tightened and loosened as required and possible will.

After completion of the drilling, the drilling ship 10 is pumped to put it in the shallow draft state. Here the ballast chambers are pumped anhydrous in the manner described above. When the drilling ship is pumping, his will be Draft over the near-great draft area, in which the center of lift and the center of gravity converge move; the former is in a state of great draft initially

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borrowed above the center of gravity. Decreased with decreasing draft the ship's stability is limited to a certain extent as a result of this relative positioning of the center of buoyancy and the center of gravity. At which center of lift and center of gravity are at the same height along the ship, the beveled ends dive of the pillars 26, and their flat surface area and their location on board the roll and ramming axes of the drilling ship generate righting moments, the size of which gradually increases with decreasing draft, until the entire surface of the water is flat of the pillars is effective to ensure these lifting moments # Before the center of buoyancy shifts downwards and the center of gravity upwards to such an extent that both points are on reach the same height, therefore the columns are fully surfaced, so that their maximum water surface area is effective for the drilling ship Able to give stability · If the draft then decreases further with further bilge, the center of lift will pass and center of gravity on each other, and the drill ship nearly kicks in e-low-draft area in which the center of gravity is above the center of lift. In this area, the Stability only offered by the righting moments generated by the columns 26 until the hulls 12 emerge, whereupon the stability corresponds to that of a double hull ship.

In the preferred, illustrated and described embodiment of the invention according to FIG. 1, the drilling ship has a total length of about 110 m on the hulls 12, each of which is 16.75 m wide and is spaced about 12.2 m from one another on the inside, so that the total width of the drilling ship is about A-5.70 m. The height of the decks above the hull bottoms is about 33 _t km. Each hull is about 7.6 m high, and the height of the pillars 26 above the hull tops is about 2f, 2 |. The columns 26 have a length of about 13.7 m in the longitudinal direction and a width of about 7.6 m.

-30- 2098Λ8 / 058Λ

the. The waterline is about 1.53 m below the topside of the hull in the low draft state and about 12.2 m below the underside of the deck 20 in the high draft state, ie about 10.7 m above the upper ends of the columns 26, as can be seen in this way that the greatest waves to be expected act neither on the deck 20 nor on the upper ends of the columns 26. The deck 20 has a total length of about 65.3 m and a width of about 53 "1 m". The central column Zh has a total height of about 33 m and a diameter of about 15.9 m, and in the extended lower part 30 it is about about 2.l \. _t k ^m · The shaft 32 passing through it has a diameter of about 5 »5 m. According to Fig. 6, the lower end of the column 2.1 \ widens from a diameter of about 15.9 m over a distance of about 2, if m obliquely upwards to one of about 2.1 + 1 h M at the widened part 30 which from then on extends vertically upwards from about 9 »15 ßi.

Of course, the invention can be implemented in other special embodiments without their Framework or its essential properties is deviated. The embodiments shown and described above are therefore intended in all respects as illustrative and illustrative only In no way should the invention be viewed as limiting, rather the invention is intended to all fall within the extended scope of protection Include lying changes and modifications.

In summary, the invention therefore creates a watercraft, in particular a drilling ship, with two transversely spaced apart, elongated hulls, along their outboard sections several upright columns spaced apart are distributed. In a preferred embodiment carries a central Column a working platform spaced above the hulls. The hulls carry the drilling ship through buoyancy in one

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Low draft condition in which the hulls are freeboard. The hulls and the marginal pillars are provided with ballast chambers for flooding and bilging the drilling ship, on the one hand the hulls, the outer columns and to submerge part of the central column and to bring the ship into a state of great draft, in which the middle waterline is in the middle of the height of the central column and between the platform and the upper one Ends of the outer pillars, and on the other hand to bring the drilling ship back to a state of shallow draft. The outer pillars provide stability to the drillship during the initial portion of its transition from low on the great draft as well as in the end section of his Transition from a large to a shallow draft · The stability at a great draft is primarily thereby ensures that the center of gravity is placed under the center of lift. Drilling work is done at great draft passed through the central column which also contains decks for sludge handling, storage, etc.

209848/0584

ORIGINAL INSPECTED

Claims (1)

Claims (Yasser vehicle, in particular drilling ship, with variable draft, characterized in that it has a load-bearing floating structure (12, 212), a work platform (20, 220), a device (28, 30, 2k or 228, 230, 22 / f, 222), which carries the platform (20, 220) at a distance above the floating structure (12, 212), and several of the drilling ship (10, 210) between the floating structure (12, 212) and the platform (20 , 220) has carried elements, of which at least one (28, 30, Zk or 228, 23O, ZZk) represents at least a part of the connecting device, that these elements are a central, practically vertical column (24, ZZk , etc.) and have a plurality of stabilizing members (26, 226) arranged transversely at a distance from this and from one another, the upper parts of which are spaced below the platform (20, 220) so that the floating structure (12, 212) has such a displacement that it pushes the drilling ship (10 , 210) in a low draft state s is able to carry, and that means (70, 72, etc.) for flooding and bilging the drilling vessel (10, 210) are provided around the floating structure (12, 212), the stabilizing members (26, 226) and part of the central Column (24, ZZk , etc.) to submerge and to create a state of great depth in which the waterline in the middle of the central column (Zk _t 22 ^. etc.), and to return the drillship (10, 210) to the shallow draft condition, the stabilizing members (26, 226) being arranged and having water planar surfaces such that the drillship during at least part of its transition between the shallow and the great depth is given stability, and the displacement of the submerged floating structure (12, 212), the stabilization 209848/0584 sierglieder (26, 226) and part of the central column (2Z {-, 22i +, etc.) is sufficient, the drill ship (10, 210) in State of great draft to keep buoyant " 2. Drilling ship according to claim 1, characterized in that the supporting floating structure has two elongated, practical has floating bodies (hulls) (12, 212) arranged parallel to one another and next to one another, the overall displacement of which is large enough to keep the drilling vessel (10, 210) in the low draft state in which the floats (12, 212) have a freeboard (f), to keep it buoyant, 3. Drilling ship according to claim 2, characterized in that the stabilizing members have columns (26, 226) which protrude upright from the floats (12, 212), and that the central column (2 ^ -, 22Jf) at the top with the Platform (20) is connected and with its lower end below the upper ends of the stabilizing columns (26, 226) lies. Zf. Drilling ship according to claim 3 »characterized in that the cross-sectional areas of the stabilizing columns (26, 226) on one above the floating bodies (12. 212) and also including part of the central column (2if, 22 ^ ·) Remove the point facing towards the platform (20, 220). 5. drilling ship according to claim 1, characterized in that its center of buoyancy below its center of gravity in the low draft state and above its center of gravity in the high draft state the same is that the stabilizing members of the floating bodies (12, 212) by so much upwardly projecting columns (26, 226) are that they are planar areas of water during the transition between the states of low and great draft 209848/0584 for drilling ship drafts between a draft at which the mean waterline is practically the same Height with the lower ends of the pillars (26, 226), and set a mean draft at which The center of lift and the center of gravity are practically at the same height, and that the central column (2 / f, 22 ^) is connected at the upper end to the platform (HO, 220) and at its lower end below the upper ends of the stabilizing columns (26, 226). 6 · Drilling ship according to claim 5, characterized in that the cross-sectional area of the pillars (26, 226) downstream of the platform (20, 220) at at least one of the aforementioned elevations corresponding height between platform (20, 220) and floating bodies (12, 212) decreases, 7. Drilling ship according to claim 1, characterized in that the load-bearing floating structure has two elongated floating bodies (212) arranged side by side at a distance and practically parallel, the total displacement of which is large enough to keep the drilling ship (210) in the low draft state with freeboard (f ) floating bodies, that the stabilizing members are columns (226) protruding upright from the floating bodies (212), that the central column (22 ^ ·) is connected at the upper end to the platform (220) and at its lower end below of the upper ends of the columns (26, 226), that the connecting means are beams (222) extending from the upper ends of the columns (226) to the platform (220) and that their water plane surface compared to that of the central column (2.2. 1+) is small when the drilling ship (210) is in the great draft state. 8 · Drilling ship according to claim 1, characterized in that the central column (2 ^, 22 ^) has one near its lower end having enlarged part (30, 230). -35- 209848/0584 9. drilling ship according to claim 1, characterized in that the platform (20, 220) carries a drill (38, 238), the central column (2if, 22if) with a stretching over its entire length extending opening (e.g. shaft 32) and the drilling device above the central column (2if, 22 £ f) is arranged and drilling through this opening (e.g. 32) is able to carry out through it. 10. Drilling ship according to claim 3 »characterized in that at least one of the on each floating body (12, 212) arranged columns (26, 226) has a cross section which is pralitisch parallel to the longitudinal axes of the float is elongated. 11. Drilling ship according to claim 3 »characterized in that the centers of mass of the columns (26, 226) in the transverse direction with respect to perpendicular planes are spaced apart which through the longitudinal center lines of the floating bodies (12, 212) run. 12 · Drilling ship according to claim 3 »characterized in that the flooding and bilge devices at least two ballast chambers (e.g. 70, 72) in each float (12, 212) have, which are spaced from one another in the horizontal direction, and that means for optional flooding and bilges of the two chambers in each floating body are provided to the natural period of oscillation of the drilling ship (10, 210) to change. 13 · Drilling ship according to claim 1, characterized in that the central column (2if) is the only load-bearing connection between the floating structure (12) and the platform (20) represents. 209848/0584 1Zf. Drill ship with variable draft, especially after one of the preceding claims, characterized by a load-bearing floating structure (12, 212), one above same spaced-apart work platform (20, 220), devices (28, 30, 2Zf or 228, 230, 22Zf, 222) for establishing a connection between the working platform (20, 220) and the floating structure (12, 212), to keep the former at a distance from the latter, with a central, practically vertical column (2Zf, 22Zf etc.), facilities (70, 72) for flooding and draining the drilling ship (10, 210) to change its draft between a low and a high draft state, where the middle waterline in the latter state is at the middle of the central column (2Zf, 22Zf) and where in the low draft state, the center of gravity of the drilling ship (10, 210) is above its center of buoyancy, while the center of lift in the state of great draft is above the center of gravity, and means (26, 226) for Stabilizing the drilling ship during at least part of its transition from shallow to deep draft, 15 · Drilling ship according to claim 1Zf, characterized in that the floating construction has two elongated floating bodies (12, 212) arranged practically parallel to one another at a distance, the total displacement of which is large enough to keep the drilling ship (10, 210) in the low draft state to float while the floats (12, 212) have freeboard (f). ^v 16. Drilling ship according to claim 1Zf, characterized in that the one delivered by the water plane surface of the central column (2Zf, 22Zf) in the state of great draft of the drilling ship (10, 210) Contribution to the overall stability of the drilling ship is small compared to the much larger contribution 209848/0584 for overall stability, which is ensured by the fact that in the state of great draft the center of gravity is below the Buoyancy center is placed. 17. Drilling ship according to claim 1Zf, characterized in that the floating construction has two elongated floating bodies arranged parallel to one another at a distance pralitically (12, 212) and the stabilizing devices several from the floating bodies (12, 212) are upright columns (26, 226). 18. Drilling ship according to claim 17, characterized in that the stabilizing _{columns protrude so far over the floating body (12 3} 212) upwards that they define during the transition of the drilling ship (10, 210) between large and shallow drafts of the water plane surfaces for drafts between a draft at which the mean waterline is practically level with the lower ends of the columns (26, 226) and an intermediate draft at which the center of buoyancy and emphasis on practical ■ lie at the same height. 19 · Drilling ship according to claim 18, characterized in that the floating bodies (12, 212) have an overall displacement which is large enough to make the drilling ship (10, 210) buoyant in the low draft state in which the floating bodies have freeboard to keep that the platform (20, 220) carries a drilling device (38} - &&) , the central column (2Zf, 22Zf) is provided with an opening extending over its entire length (e.g. shaft 32.) and the drilling device is above the central column (2Zf, 22Zf) is arranged and is able to carry out the drilling work through this opening. 2098A8 / 058A 3O
ϋ - 20. Drilling ship according to claim 18, characterized in that at least one of the columns (26, 226) arranged on each floating body (12, 212) has a cross section, which is elongated practically parallel to the longitudinal axes of the float, and that the centers of mass of the columns (26, 226) in the transverse direction have a distance from perpendicular planes which are defined by the longitudinal center lines of the Floats (12, 212) run. 21. Drilling ship with variable draft, in particular according to one of the preceding claims, characterized by a load-bearing floating structure (12, 212), a working platform (20, 2.2.0) arranged above the same at a distance, between the latter and the floating structure (12, 212) inserted devices (28, 30, 2i \ or 228, 230, 22 ^, 222) to keep the platform (20, 220) at a distance above the floating structure (12, 212), with a central, practically vertical arranged column (2 ^ ·, 220 »means (70, 72 etc.) for flooding and bilging the drilling ship (10, 210) for the purpose of changing its draft between a state of low and a state of great draft, the mean waterline in the latter state in mid-height of the central pillar (2 ^ ·, 22 ^), and means for stabilizing the drilling vessel (10, 210) during at least part of its transition between the low and high draft states, with its stability inherent Shafts are characterized by the formula GM = (KB-KG) + BM, in which GM is the metacentric height, KB and KG are the vertical heights of the center of lift or the center of gravity above the lower outline of the ship and BM is the metacentric radius, and where the drilling ship (10, 210) is designed so that in the low draft state a positive value of GM is obtained from the sum of a positive value of BM and a negative value of (KB-KG), while in the high draft state a positive -39- 209848/0584 tive value of GM is obtained from the sum of a positive value of Bl-i and a positive value of (KB-KG). 22. Drill ship with variable draft, especially after one of the preceding claims, characterized by a load-bearing floating structure (12, 212), one above the same working platform (20, 220) arranged at a distance, between the latter and the floating structure (12, 212) inserted facilities (28, 30, 24 or 228, 230, 224, 222) to keep the platform at a distance above the floating structure (12, 212), a central, practically perpendicular arranged column (24, 224) extending from the platform (20, 220) to the floating construction (12, 212), several of the floating construction (12, 212) so far above protruding stabilizing columns (26, 226) that sections of them with part of the central column (24, 224) on at the same height, with the stabilizing columns in the transverse direction at a distance outward from the central column (24, 224) are arranged, and means (70, 72 etc.) for flooding and bilge the drilling ship (10, 210) for the purpose of modification its depth. 23. Drill ship according to claim 22, characterized in that the lower end of the central column (24, 224) at a distance is arranged above the floating structure (12, 212). 24 · Drill ship according to claim 22, characterized in that the upper end sections of the stabilizing columns are spaced apart lie under the platform (20, 220). 25 · Drilling ship according to claim 24 »characterized in that the lower end of the central column (24, 224) at a distance is arranged above the floating structure (12, 212). 209848/0584 26. Drill ship according to claim 22, characterized in that the connecting devices only the central column include. A drilling ship according to claim 22, characterized in that the lower end section (30, 230) of the central column (Zk, ZZk) has a larger cross-section than the part of the central column located between the platform (20, 220) and this lower end section . 28 · Drilling ship according to claim 27, characterized in that the widened lower end section (30, 230) of the central column (Zk, 22 / f) is at the same height as sections of the stabilizing columns (ZG _{1 ZZG).} 29 · Drilling ship according to claim 22, characterized in that devices (28, 228) are provided for connecting the central column (Zk, ZZk) to the floating structure (12, 212). 30. Drill ship according to claim 22, characterized in that means for connecting the central column (2 ^ -, 22 ^ ·) with at least two stabilizing columns (26, 226) are provided. 31 · Drilling ship according to claim 22, characterized in that devices (222) are provided for connecting the stabilizing columns (226) to the platform (220). 32 drilling ship according to claim 22, characterized in that the floating structure (12, 212) has two floating bodies, which extend practically parallel to one another at a distance and at least two at both ends Carry upright stabilizing columns (26, 226). 209848/0584