OA17246A - Method for installing an offshore arrangement on the sea bed, and offshore arrangement. - Google Patents

Abstract

The invention relates to a method for installing an offshore arrangement on the seabed, wherein the offshore arrangement has a support structure, at one end of which support means are provided for supporting an above-water structure, and at the other end of which founding means are provided for establishing the offshore arrangement on the seabed, wherein the founding means comprise at least one floodable float body, and wherein at least one float body is provided that is likewise floodable and movable along the support structure, wherein the method comprises the following steps: the offshore arrangement, lying floating, is pulled and/or pushed to the installation site, wherein the floodable float bodies provide the buoyancy of the offshore arrangement, at the installation site the float body of the founding means is flooded at least to some extent so that the offshore arrangement is uprighted while the founding means is sinking, wherein the movable float body moves along the support structure in the direction of the support means, until the offshore arrangement is completely upright, and is held floating above the seabed at least by the movable float body, a final alignment of the floating offshore arrangement is performed at the installation site, if necessary, then, if it has not occurred already, the float body of the founding means is completely flooded, wherein the offshore arrangement sinks to the seabed and the movable float body is fully flooded, wherein the movable float body moves into an end position, remaining there permanently, near the likewise flooded float body of the founding means, and the offshore arrangement is established with the founding means on the seabed. The invention also relates to an offshore arrangement.

Description

Method for Installing an Offshore Arrangement on the Seabed and Offshore Arrangement

The invention relates to a method for installing an offshore arrangement on the seabed and an offshore arrangement for installing on the seabed, wherein the offshore arrangement comprises a support structure, al onc end of which support means are provided for supporting an above-waler structure, and at die other end of which founding means arc provided for cstablishing die offshore arrangement on the seabed.

I0 The above-water structure can be, for example, a platform, particularly oil or gas drilling platform.

The transport of such offshore arrangements to an installation site al sca and die installation of die offshore arrangement on die seabed is typically complcx. Thus, 15 frequently many parts of the offshore arrangement must still bc asscmblcd al the installation site al sca. For this purpose, heavy equipment is required at die installation site. Additional ly, offshore arrangements are typically large and must bc towed in un expensive manner to Uic installation site. From the document WO 99/51821 Al, for example, il is known to use so-callcd suelion piles for cstablishing such offshore 20 arrangements. Thèse bave a chamber, to which a négative pressure is applied such that the suelion piles are sunk in the seabed.

The document WO 2008/030689 A2 discloses a meüiod for installing an offshore arrangement in which die offshore arrangement is towed to the installation site lying 25 horizontally. This results in simplifying the transportation of die offshore arrangement to the installation site. Al the installation site, widi the known methods, massive ballast bodies are attached to tlie end of a support structure of lhe offshore arrangement so that this end sinks under water and die offshore arrangement is uprighted. Columns of lhe support structure arc flooded with water in order to set a defined sinking deplh of the 30 offshore arrangement. Aldiough the installation of tlie offshore arrangement with the known mediods is simplified bccause no heavy equipment is required for this purpose,

- 2 uprighling lhe offshore arrangement is costly and hardly flexible due to lhe massive ballast bodies to be attached.

Starting from the stated prior art, the object of the présent invention is to provide a 5 method and an offshore arrangement of the initïally named type, wherein the installation of the offshore arrangement is simplcr and more flexible, and wherein the offshore arrangement is suited particularly for shallow water deplhs.

The invention solves üiis object by the subject matter of the claims I and 19. 10 Advantagcous embodiments are found in lhe dépendent claims, the description and the drawings.

The invention solves Lhe objective on the one hand by a method for inslalling an offshore arrangement on the seabed, wherein the offshore arrangement has a support 15 structure, at one end of which support means are provided for supporting an abovewater structure, and al the Ollier end of which founding means are provided for establishing the offshore arrangement on the seabed, wherein the founding means comprise at least one floodable floal body, and wherein at least one float body is provided that is likewise floodable and movable along the support structure, wherein the 20 method comprises the following steps: the offshore arrangement, lying floating, is pulled and/or pushed lo the installation site, wherein the floodable float bodies provide lire buoyancy of the offshore arrangement, al lhe installation site the float body of lhe founding means is flooded at leasl to some extenl so thaï the offshore arrangement is uprighted while the founding means is sinking, wherein lhe movable float body moves 25 along the support structure in the direction of the support means, untii lhe offshore arrangement is completely upright, and is held floating above the seabed at leasl by the movable float body, a final alignaient of lhe floating offshore arrangement is performed al the installation site, if necessary, then, if it lias not occurrcd already, Lhe float body of the founding means is completely flooded, wherein the offshore arrangement sinks to

n

-3the seabed and lhe movable floal body is fully floodcd, wherein the niovable floal body moves inlo an end position, rcmaining lherc permanenlly, near the likewise floodcd float body of the founding means, and the offshore arrangement is established with die founding means on the seabed.

On lhe other hand, the invention solvcs the objective by an offshore arrangement for installation on the seabed, comprising a support structure, at one end of which support means are provided for supporling an above-water structure, and at the oüicr end of which founding means arc provided for establishing the offshore arrangement on die 10 seabed, characterized in Üiat die founding means comprise at least one floodable float body, diat al least one float body is provided that is likewise floodable and movable along the support structure, that die floodable float bodies arc designed for the purposc of providing die buoyancy of the offshore arrangement during a transportation lying floating to the installation site, and that die float body of die founding means is further 15 designed for lhe purpose of uprigliting the offshore arrangement while sinking the founding means by flooding at least to some extent, wherein the movable float body is designed for the purpose of moving along the support structure in die direction of die support means until the offshore arrangement is completely upright, and is lield floating above the seabed al least by the movable float body, and sinks to the seabed due to the 20 complété flooding of die floodable float body, wherein the movable floal body is designed for reinaining permanenlly in a completely floodcd state in an end position near the likewise floodcd floal body of the founding means.

The enlire offshore arrangement according to die invention can be assembled, or 25 rcspcctivcly built already lying on land, preferably in a dock, particularly in a so-callcd drydock having a shallow to normal depth. The offshore arrangement can lhen be floaled and towed from lhe drydock to the installation site al sea. The above-water structure to be atiaclied onto lhe offshore arrangement according to the invention can be, for example, a platform, such as a gas or oil drilling platform. However, odier above17246

-4walcr structures arc also possible. The offshore arrangement is pulled and/or pushed in a lying statc floating to the installation site al sea. This can be performed by means of suitable towboats or similar walercraft. The offshore arrangement according to the invention has al least two float bodies which are pumped empty during the transport of 5 the offshore arrangement to the installation site, and providing the necessary buoyancy for the flotation of the offshore arrangement. At tire installation site, they can be flooded in a targeted and flexible manner. In this manner, a sclf-actuated uprighting of the offshore arrangement is achieved in a particularly simple manner. Separate ballast bodies to be attached arc not necessary.

According to the invention, furthermare, one of the float bodies is movable, particularly slidablc, along the support structure, thus particularly in the longitudinal direction of the support structure, in a defined région between the support means and the founding means. The movable floal body moves particularly driven by buoyancy force or 15 gravitational force along the support structure, depending on the fill level of the float body. Thus, separate drives for moving the movable float bodies arc not rcquired. The movable float body ensures a reliablc and defined uprighting of the offshore arrangement and maintains tire flotation of the upright offshore arrangement al a defined distance above the seabed. By suitable adjustment of the end positions of the movable 20 float body, the height of the offshore arrangement above the seabed can be modified in a targeted manner to the respective conditions al the installation site. Subsequently, or if necessary, there can also bc a final positioning of the offshore arrangement before uprighting the offshore arrangement. Additionally il should bc noted that the (complété) flooding of the float body of the founding means can occur before the (complété) 25 flooding of the movable floal body. Howcvcr it is also possible thaï the (complète) flooding of these float bodies occurs intermiitcnlly or complctcly in parallel.

The support structure can in principle comprise complété means for lying up boats, or al least an attachment structure for such means. The support structure can also alrcady

-5comprise ail risers nccessary for the installation and the operation of the offshore arrangement (for exampie, ballast and suclion pump lines, grout lines, import and export risers, conduclor guides).

It is fundamcntally possible to preassemble the offshore arrangement lying on land, or respcctivcly lying in a dock, as described above, to tlic greatest extenl possible, and then to transport the offshore arrangement to the installation site. In addition, the installation is simple because the movable float body is sunk after the installation by complète flooding to the grounding means, and reinains there permanent!y. Thus, after installation 10 the movable float body does not need to bc decouplcd and transported away in an costly manner.

A secure establishment of the offshore arrangement on the scabed occurs using the founding means. The founding means according to a particularly practical design can 15 comprise at least one suction pile, which in the course of complète flooding of the float body sinks into the seabcd at least to some extenl duc to gravitational force, and for founding Lhc offshore arrangement, is subscquently driven further into the seabed by creating a négative pressure in the suclion pile. Using such suction piles, founding is possible in a particularly easy manner. The suction pile comprises at least one pressure 20 chamber, to which a négative pressure can be applied by attaching a suitable vacuum pump. As a resuit, the suclion pile is sunk into the seabed. After founding, the vacuum pump can be decoupled, controlled remotcly, and brouglil to the surface. The suction pile can serve as a temporary founding, based for exampie on a once a year storm condition at the installation site. The suclion pile can be divided into a plurality of 25 pressure chambers, for example four, each having ils own négative pressure line, ln this manner, it is possible to oplimally align the offshore arrangement vcrlically by suitable évacuation of the individual pressure chambers. If pipes are guidcd through the suclion pile, appropriate sealing rings can be provided al the entry site, ln spécifie cases,

-6permanent founding of the offshore arrangement can also be provided using lhe suction piles. Naturally, it is also possible lo provide a plurality of such suction piles.

The support means can also comprise al least one float body, which together with the float body of the founding means and the movable float body, provides the buoyancy of the offshore arrangement during the transport of lhe offshore arrangement to the installation site. The float body of the support means can also, in principle, be floodable.

The support body of the offshore arrangement according to the invention can be a lattice framework structure, particularly a tubular lattice framework structure. Thus, with this design, there arc no closed towers having buoyancy compartmcnts or ballast cells in the support structure itself. The lattice framework structure can be a three or four leg structure for example. The lattice framework structure itself can also hâve or provide buoyancy. Il can hâve guidance devices for the conductors or risers. it can also comprise support devices for grouting lines, hydraulic devices for controlling lhe floaling bodies or hydraulic devices for vacuum pumps of the grounding means. The risers can also bc preinstalled on land. The risers can be floatable, or for example flooded, in order to influence in this manner, lhe angle of the offshore arrangement being transported floating and lying horizontally. The lattice framework structure also represents a guidance for the movable float body for example when il is sunk during the installation of the offshore arrangement.

The movable float body can be moved, using glide or roi 1er bcarings, along lattice legs of the support structure ronning in lhe longitudinal direction between the founding means and the support means. Thus, guidance occurs along the main legs of lhe lattice framework structure. The movable float body can be moved along the support structure in the course of the installation of lhe offshore arrangement driven by buoyancy force or gravitational force. Upper and lower end positions can be specified for the movable float body using stop means. The stop means are attached particularly to the support

-7struclurc, on the legs of the support structure for exampie. In this regard, according to a further design, llie stop means can bc slidable along the support structure. Furtlicrinorc, during transport of the offshore arrangement to the installation site, the movable float body can bc secured against moving along the support structure using sccuring means.

Using the stop means, an upper end point of the mobility of the movable float body can be determined in a flexible manner, whcrcby in tum, the height of the uprîght offshore arrangement above the seabcd can bc determined before lhe founding. A suitable drive can bc provided for moving lhe stops. However, it is also possible to manually move the 10 stops in adapting to the particular conditions of the respective installation site. The movable float body is sccured in a floating position suitable for horizontal transport of the offshore arrangement, thereby excluding undesired movement of the movable float body during transport of the offshore arrangement. The securing means can comprise chain tensioning devices and pad-eyes for example.

As alrcady cxplained, lhe movable float body is an object used teinporarily for lhe transport and installation of lhe offshore arrangement which serves particularly for uprighting and holding the offshore arrangement vertical ly for founding. It can hâve a lightweight construction, which after uprighting the offshore arrangement is lloodcd 20 using valves thaï can bc operated from lhe surface, for exampie hydraulic valves, and thus is sunk to a lower stop surface. SuiLable damping means can be provided on lhe support structure and/or the movable float body in order to prevent damaging llie float body or the support structure during movement of lhe float body. In fact, ail floodablc float bodics can be flooded, for example, using valves thaï can be operated from lhe 25 surface, for exampie, hydraulic valves.

After founding the offshore arrangement, starting from the support means, borcholcs can be introduced through guide tubes integrated al least into the founding means, into llie seabed. An intermediate space formed rcspeclively in llie wall of lhe guide tubes can

-8be filled for a final founding using a curing filler material, particularly with mortar (grouting). The support means and the support structure can also hâve corresponding guide openings and/or guide tubes through which borcholes can be introduced, The guide tubes in the installed state of the offshore arrangement can project into the seabed.

A suitable boring apparatus (drilling rig) is used for introducing the boreholes. The subséquent filling of the intermediate spaces can also be performed using the drilling apparatus or using a separate device, for exampie from a separate watcrcraft. Il is also possible, in addition to a founding, to anchor the offshore arrangement lemporarily at the seabed using a suction pile, if a subséquent founding using grouting is not possible 10 for a longer time.

According to a further design, before introducing the borcholes, a central section of the support means can be removed, and a drilling apparatus can be placed on the support means for introducing boreholes from the side into the position of the removed central I5 section on the support means. For this purpose, the support means can hâve side walls, and possibly also upper walls or covers that can be disassemblcd. Thus after removal of the central section, the support means simultancously form a working plane and guidance for the drilling apparatus. The removed central section, alone or in combination with the rcmaining sections, can also providc die buoyancy of the support 20 means. The size of the support means dépends on the depth of the water at the installation site and contributes overall to the buoyancy of the offshore arrangement. The removed central section of the support means can be particularly lighter than die rcmaining section. The remaining section can hâve a U-shapcd cross-section, so that the lower section bounded by the two legs of the U-shapc forms the working plane for üic 25 drilling apparatus. As expiained, guide tubes for the boreholes can also be installed in the support structure. A possibly required sump vessel for the platform can also be integrated into the support structure. Additionally, the support structure has suitable fastening means for fastening the above-water structure.

-9Thc abovc-walcr structure can be disposed on die support means at the installation site. Thus, in this design, die offshore arrangement is transported initially to the installation site without the above-water structure, and the above-water structure is placed only at the installation site onlo llie offshore arrangement thaï is typically already founded. For 5 this purpose, the above-water structure can be placed onto the support means instead of the removed central section of tlic support means after introducing die borcholes and possibly removing the drilling apparatus. In fact, the drilling apparatus can also bc used for the installation of the above-water structure. Howcver, it is also possible to install the above-water structure only at a later time, when die drilling apparatus has already 10 been removed. If the drilling apparatus is used for installation of the above-water structure, die above-water structure can be pushed onlo the support means using, for exampie, suitable guide rails, and faslened there. As an alternative, other suitable devices, for instance water crânes, can bc used for lliis purpose. The installation of die above-water structure only at tlic installation site of the offshore arrangement lias die 15 advanlage that die offshore arrangement can be transported lying horizontally in the water. In particular, at this time dierc is no above-water structure présent at the offshore arrangement thaï must kept oui of the water as much as possible. Thus, the offshore arrangement, floating lying horizontally, can be pullcd and/or pushed in the water to die installation site, so thaï both the support means and die founding means are lying at least 20 to some extent below sea Ievel.

According to an alternative design, the above-water structure can already be disposed on die support means before transporling the offshore arrangement to die installation site, wherein die offshore arrangement is pullcd and/or pushed lying floating to the 25 installation site such that the above-water structure is located above water at ail limes.

Thus, in this example dicre is no horizontal lying position of the offshore arrangement during the transport to the installation site, rather a tippcd position, for example, wherein the above-water structure is hcld above sea Ievel. Whiie the effort for transporting tlic offshore arrangement is increased somewhat by this, this design has die

- ÎOadvantagc thaï lhe above-water structure can be already preasscmblcd onto the offshore arrangement on land. Thus, costly measures for installing lhe above-water structure at the installation site arc omitted. This design lends ilself particularly to very small abovewater structures. If large above-water structures arc already preasscmblcd on land, the 5 above-water structure can lie on a floating pontoon, for example, during transport to the installation site, so lhat it is guaranlccd thaï the above-water structure is held above sca level.

Basically, the above-water structure for the offshore arrangement according to lhe invention can vary with respect to lhe size thereof and the weight thereof depending on the respective requircments. The invention is suilcd particularly for relatively small above-water structures having a weight of less than 600 tons. Smaller oil or gas platforms as above-water structures, can hâve a weight in the range of 300 to 350 tons, for example. Larger above-water structures, for example, larger oil or gas drilling platforms with integrated water injectors can hâve a weight of more than 500 tons.

The method according to the invention is suited particularly for installing offshore arrangements in régions with a comparativcly shallow water depth of less than 100 m, particularly in a range of 40 to 80 m.

The device according to the invention is suitable for carryîng out lhe method according to lhe invention. Correspondingly, the method according to llie invention can bc performed using the device according to lhe invention.

Example embodiments of the invention are explained in lhe following in more detail using the drawings. They show schcmatically:

Fig. 1 an offshore arrangement according to the invention in a first operating state in a side view according to a first example embodiment,

- U Fig. 2 tlie offshore arrangement from Fig. I in a second operaling state,

Fig. 3 the offshore arrangement from Fig. I in a third opcraling state,

Fig. 4 the offshore arrangement from Fig. I in a fourth operaling state,

Fig. 5 the offshore arrangement from Fig. I in a fifth operating state,

Fig. 6 the offshore arrangement from Fig. 1 in a sixLh operaling state,

Fig. 7 the offshore arrangement from Fig. 1 in a seventh operaling state,

Fig. 8 the offshore arrangement from Fig. 1 in an eighth operating state,

Fig. 9 the offshore arrangement from Fig. 1 in a ninth operating state,

Fig. 10 the représentation from Fig. 9 in a perspective view, and

Fig. 11 the offshore arrangement according to the invention in a first operating state in a side view according to a second example embodiment.

The same référence numbers refer to the same objccls in the figures unless indicated otherwise. The figures schcmatically show the seabed, with rcferencc number 10, upon which the offshore arrangement shown in the figures is to be installed. The figures schematically represent the sca level with rcferencc number 12. Fig. 1 represents an offshore arrangement according to the invention, lying horizontally and fioating on tlie surface of the sca, and particulariy having a jackel structure. The offshore arrangement comprises a latticc Framework support structure 14, which has a plurality of tubular legs

-1216, four in the exemple shown, running in the longitudinal direction of the support structure 14. Support means 18 for supporting an above-water structure, not shown in Fig. 1, for example a platform such as an oil or gas drilling platform, are provided al die left end in Fig. 1 of the support structure 14. Founding means 20 for establishing the 5 offshore arrangement on the seabed 10 arc disposed at the opposite end of the support structure 14. The founding means 20 comprise a suclion pile 22 and a floodable float body 24. A floodable float body 26, mounted movably along the main legs 16 of the support structure using glide or rollcr bcarings for example, is also shown.

In the operaling state shown in Fig. 1, die movable float body 26 is secured against moving using suitable sccuring means on the support structure 14 in the floaling position show in Fig. 1. The support means 18 together with the movable float body 26 and the float body 24 of the founding means 20 provide sufficicnt buoyancy for the offshore arrangement, so that the arrangement floals on the surface of the sca 12 in the horizontally lying state shown in Fig. 1. In this state, the offshore arrangement, prcassembled on land, or respectively lying in a dock, can bc transporlcd to an installation site at sca, particularly puslied or pullcd using suitable towboats or similar watcrcraft. For this purposc, Lhe offshore arrangement can be launched from land into water in a simple manner, using a suitable crâne, for example. The float bodics 24, 26 and lhe support means 18 are designed so thaï llic offshore arrangement floals lying substantiaily horizontally in the water. The immersion depth of the offshore arrangement can be set preciscly by suitable sélection, or respectively by suitable flooding of lire float bodies.

After reaching the installation site, initially Lhe float body 24 of the founding means 20 is flooded so that the founding means 20 begins to sink below lhe surface of the sca 12, wherein the offshore arrangement is slowly uprighled, as shown in the Figs. 2 to 4. The float body 24 of lhe founding means 20, and incidentally also of the movable float body 26, can be flooded by means of remotely actuated hydraulic valves, for example. Before

- 13sinking the founding means 20, as shown in the Figures 2 to 4, the securing means of the movable float body 26 is also released, for example, likewise rcmotely actuatcd. Because the float body 26 is not yet flooded al this time, it is pushed by the buoyancy force along the uprighting support structure 14 in the direction loward the support 5 means 18, as also seen in the Figures 2 to 4. The completely upright state of the offshore arrangement is shown in Fig. 5. The movable float body 26 lies against an upper stop al the support structure 14, whereby in the state shown in Fig. 5 the offshore arrangement is held floaling at a defined height above the seabcd 10.

In lhe state shown in Fig. 5, the offshore anangement can be finally aligned for founding, by a suitable lowboat, for example. Naturally, lhe final alignaient of the offshore arrangement can also occur before starting lhe uprighting, thus in the state shown in Fig. 1. After altaining the final position, the float body 24 of the founding means 20 is completely flooded, whereby the offshore arrangement with the suction pile

22 sinks into Lhe seabed 10 duc to gravity, as shown in Fig. 6. Then, the movable float body 26 is also flooded, for example, whereby due to gravitational force the body sinks downward along lhe main legs 16 of lhe support structure 14 up to a stop formed by the founding means 20, as shown in Fig. 7. The movable float body 26 remains permanenlly in this sunken state.

Finally, négative pressure is applied to Üic suction pile 22 by means of a vacuum pump, not shown. The suction pile 22 can have particularly a plurality of négative pressure chambers, to which négative pressure can bc applied also independently of each other. Applying négative pressure causes die suction pile 22 to sink into lhe seabed 10. In 25 particular, llie suction pile 22 sinks automatically into lhe seabed 10. In this state, the offshore arrangement is established at least initially on the seabed 10. As further seen in Fig. 7, a central section 28 of the support means 18 was removed from the support means 18. This removed central section 28 can, for example, bc a section 28 which significantly contributes to die buoyancy. A work surface 30 remains on the support

- 14mcans 18 having a U-shaped cross-section, upon which now a drilling apparatus can bc driven from lhe front over die work surface 30 by means of a separately standing socalled drilling rig, in Fig. 7. The drilling apparatus makes boreholes through die support structure 14 and die founding structure 20, parLicularly using suitable guide tubes of die support structure 14 and die founding structure 20, into die seabed 10, as shown schematically with reference number 34, Intermediate spaces formed in lhe walls of the guide tubes can be filled with a curing material, for example, mortar (grouting), in order to cause die final grounding of lhe offshore arrangement on lhe seabed 10. Later, oil or gas, for example, can bc conveycd using the boreholes 34. After introducing die boreholes 34 and the installation of die conductors, valve crosses (so-called X-mas trees widi blow oui preventer BOP), shown with reference number 32, are attached.

Finally, as seen in Fig. 9, an above-water structure 36 is disposed on lhe support means 18 from a suitable watcrcraft. The above-water structure 36 can bc an oil or gas drilling platform 36, for example. As seen in Fig. 9, die valve crosses 32 romain on the support means 18. The offshore arrangement is now ready for operation.

Fig. 11 shows a second example embodiment of the invention. Here, an offshore arrangement according to the invention is shown in an operating state, which corresponds to die operating state according to Fig. 1. In this case, an above-water structure 36' was disposed on the support means 18 already on land. In order to prevent die above-water structure 36' from plunging into the seawater during transport to the installation site, the offshore arrangement lies on a floaling pontoon shown schematically in Fig. 11 widi the reference number 38. Tlie installation of lhe offshore arrangement, particularly lhe uprigliting and founding, can dien occur as described above with die first example embodiment.

Tlie offshore arrangement according to die invention and the installation dicreof arc particularly simple and therefore cost-effective. Costly heavy equipment is not required

- 15al die installation site because the offshore arrangement is largely self-installing and self-founding. Il is comparatively light weight and at lhe saine time, il can be used for a plurality of applications. Il is particularly suited for comparatively small above-water structures having a weight of less than 600 tons, and for comparitively shallow water 5 depths of less dian 100 m, particularly in a range of 40 to 80 m.

Claims (29)

1. L A method for installing an offshore arrangement on the seabed (10), wherein the offshore arrangement has a support structure (14), at onc end of which support means (18) arc provided for supporting an above-walcr structure (36, 36'), and al the ollicr end of which founding means (20) arc provided for establislling the offshore arrangement on the seabed (10), wherein the founding means (20) comprise at least one floodable float body (24), and wherein al least one float body (26) is provided that is likewise floodable and movable along the support structure (14), wherein the method comprises the following steps:

   the offshore arrangement, lying floating, is pulled and/or pushed to the installation site, wherein the floodable float bodies (24, 26) provide the buoyancy of the offshore arrangement,

   - at the installation site the float body (24, 26) of the founding means (20) is flooded at least to some extent so thaï the offshore arrangement is uprighted while the founding means (20) is sinking, wherein the movable float body (26) moves along the support structure (14) in the direction of the support means (18), until the offshore arrangement is completely uprighl, and is held floating above die seabed (10) al least by the movable float body (26),

   - a final alignmcnt of the floating offshore arrangement is performed at the installation site, if necessary,

   - subsequently, if it has not occurred already, the float body (24) of the founding means (20) is completely flooded, wherein the offshore arrangement sinks to the seabed (10) and the movable float body (26) is fully flooded, wherein the movable float body (26) moves into an end position, remainîng there permanently, near the likewise flooded float body (24) of the founding means (20), and

   - the offshore arrangement is established with tlic founding means (20) on the seabed (10).
2. 2. The method according lo claim l, characterized in that the founding means (20) comprises al least onc suction pile (22), which in the course of complète flooding of the float bodics (24, 26) duc to gravilational force sinks into the scabed (10) at least to some extent, and for founding the offshore arrangement, is subsequently driven further into the seabed (10) by creating a négative pressure in the suction pile (22).
3. 3. The method according to one of the preceding claims, characterized in thaï the support means (l 8) also comprise al least one float body, which together with the float body (24) of the founding means (20) and the movable float body (26), provides the buoyancy of the offshore arrangement during the transport of the offshore arrangement to the installation site.
4. 4. The method according to onc of the preceding claims, characterized in that the support structure (14) is a latlice framework structure.
5. 5. The method according to claim 4, characterized in that the movable float body (26) moves by means of glide or roller bearings, along latlice legs (16) of the support structure (14) running in the longitudinal direction between the founding means (20) and the support means (18).
6. 6. The method according to one of the preceding claims, characterized in thaï in the course of the installation of the offshore arrangement, the movable float body (26) moves along the support structure (14) driven by buoyancy force or gravilational force, wherein upper and/or lower end positions are preset for the movable float body (26) by stop means.
7. 7. The method according to claim 6, characterized in that the stop means are movable along the support structure (14).
8. 8. The method according to one of the preceding claims, characterized in that during transport of the offshore arrangement to the installation site, the movable float body (26) is secured against sliding along lhe support structure (14) by means of securing means.
9. 9. The method according lo one of lhe preceding claims, characterized in that after founding lhe offshore arrangement, starting from lhe support means (18), boreholcs (34) arc introduced through guide tubes integrated at leasl into lhe founding means (20) into the seabed (10),
10. 10. The method according lo claim 9, characterized in thaï each iniermediatc space formed respectively in die walls of the guide lubes is filled with a curing fill material, particularly with a mortar malcriai.

    15
11. 11. The method according lo one of lhe claims 9 or 10, characterized in that before introducing lhe boreholcs (34) a central section (28) of the support means (18) is removed, and lhat a drilling apparatus for introducing the boreholcs (34) is placed onto the support means (18) from the side into lhe position of the removed central section (28).
12. 12. The method according to one of the preceding claims, characterized in that the above-water structure (36, 36') is disposed on lhe support means (18) at the installation site.

    25
13. 13. The method according lo one of the preceding claims, characterized in lhat üic offshore arrangement, floating lying horizontally, is pulled and/or pushed to the installation site, wherein both the support means (18) and also the founding means (20) are located at least lo some extent below sea level (12).

    30
14. 14. The method according to one of the claims 1 lo 11, characterized in that the above-water structure (36, 36’) is disposed on Lhe support means (18) already

    - 19before transport of the offshore arrangement to the installation site, wherein the offshore arrangement, lloaling lying, is pulled and/or pushed to the installation site such that the above-water structure (36, 36') is locatcd above water al ail times.
15. 15. The method according to claim 14, characterized in thaï the above-water structure (36, 36’) lies on a floaling pontoon (38) during the transport to die installation site.
16. 16. The method according to one of the preceding claims, characterized in thaï the offshore arrangement is already asscmbled lying horizonlally, preferably in a dock.
17. 17. The method according to one of the preceding claims, characterized in that the above-water structure (36, 36') has a weight of less than 600 tons.
18. 18. The method according to one of the preceding claims, characterized in that the offshore arrangement is inslalled in a water depth of less than 100 m.
19. 19. An offshore arrangement for installation on the seabed (10), comprising a support structure (14), at one end of which support means (18) are provided for supporting an above-water structure (36, 36'), and al tire other end of which founding means (20) arc provided for cstablishing the offshore arrangement on the seabed (10), characterized in that

    - the founding means (20) comprise at least one floodable float body (24),

    - that at least one float body (26) is provided, likewise floodable, and movable along llte support structure (14), that the floodable float bodies (24, 26) arc designed for the purpose of providing die buoyancy of die offshore arrangement during a transportation lying floaling to the installation site, and thaï die floal body (24) of the founding means (20) is further designed for die purpose of uprighting the offshore arrangement while sinking the founding means (20), by flooding al it least to some exlent, wherein the

    -20movable float body (26) is designcd to move along the support structure (14) in the direction of lhe support means (18) until lhe offshore arrangement is completely upright, and is held floating above the seabed (10) at least by the movable float body (26), and sinks lo the seabed (10) duc to the complété flooding of tlie floodable float bodies (24, 26), wherein lhe movable float body (26) is designed for remaining permanenlly in a completely flooded state in an end position near the likewise flooded float body (24) of lhe founding means (20)

    - Lhe support means (18) also comprise at least onc float body, which is designcd lo providc, together with tlie float body (24) of the founding means (20) and the movable float body (26), the buoyancy of the offshore arrangement during tlie transport of the offshore arrangement to tlie installation site,
20. 20. Tlie offshore arrangement according lo claim 19, characterized in thaï the founding means (20) comprise at least one suction pile (22) which is designed to sink, due lo gravitational force, al least to some extent into tlie seabed (10) in the course of the complété flooding of the float bodies (24, 26), and subsequenlly by applying a négative pressure to tlie suction pile (22) to be driven further into lhe seabed (10) for founding lhe offshore arrangement.
21. 21. The offshore arrangement according lo one of tlie claims 19 lo 20, characterized in thaï tlie support structure ( 14) is a lattice framework structure.
22. 22. The offshore arrangement according to claim 21, characterized in that die movable float body (26) can be moved by means of glide or roller bcarings along lattice legs (16) of the support structure (14) running in the longitudinal direction between the founding means (20) and lhe support means (18).

    -2l -
23. 23. The offshore arrangement according to one of the claims I9 to 22, characterized in thaï lhe movable float body (26) is designed to be moved in lhe course of die installation of the offshore arrangement, driven by buoyancy force or gravitalional force, along die support structure (14), wherein stop means are provided for defining an upper and/or lower end position for the movable float body (26).
24. 24. The offshore arrangement according to claim 23, characterized in tliat the stop means can be moved along die support structure (14).
25. 25. The offshore arrangement according to one of claims 19 to 24, characterized in that sccuring means are provided for securing the movable float body (26) against movement along lhe support structure (14) during the transportation of die offshore arrangement to lhe installation site.
26. 26. The offshore arrangement according to one of the claims 19 to 25, characterized in diaL guide tubes arc provided al least in the founding means (20), wherein intermediate spaces formed rcspcctively in die walls of the guide tubes arc filied with a fill material, particularly with a mortar material.
27. 27. The offshore arrangement according to claim 26, characterized in thaï a central section (28) of die support means (18) is formed to be removed from lhe support means (18), and that for introducing boreholes (34) through lhe guide tubes into die seabed (10) a drilling apparatus is provided which is designed to be moved from the side into the position of die removed central section (28) onto lhe support means (18).
28. 28. The offshore arrangement according to one of die claims 19 to 27, characterized in that die above-water structure (36, 36') has a weight of less than 600 tons.
29. 29. The offshore arrangement according to one of die claims 19 to 28, characterized in that the offshore arrangement is designed for the purpose of installation in water depths of less than 100 m.