NL1025708C2 - Device for connecting two offshore units. - Google Patents

Description

Title: Device for connecting two offshore units

The invention relates to a device for connecting two offshore units and provided with a coupling element which can be connected to the one offshore unit via a first set of coupling means and via a second set of coupling means to the other offshore unit, further restoring provisions being present are for absorbing movements between the two offshore units.

Such a connecting device is used, for example, in connecting a tender drilling unit and a wellhead platform or a production platform. Such connecting devices are generally relatively rigid and rigid, so that they can only be used under relatively mild environmental conditions.

In order to obtain a more flexible connection, it is known to use stretchers, that is to say lines with a lot of elongation which are applied under bias between the two offshore units. A consequence of this is that the two offshore units are pulled towards each other. To prevent this, the pre-stressing in the stretchers must be compensated by the positioning systems of the offshore units, for example anchor or thruster systems. This often leads to additional anchor lines having to be provided, which requires additional investments and installation time.

Another possibility of establishing a flexible connection between two offshore units is the use of a yoke construction with a ballast weight. A relatively heavy ballast weight is needed for this. Such a connecting device is used, inter alia, for coupling tankers to offloading stations. The counterweight is suspended from hinges connected to an offshore unit. With this solution the load capacity of the offshore unit is considerably reduced.

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Moreover, the size of the ballast weight is such that the installation thereof cannot take place at sea, but must already take place in advance in the port.

The object of the invention is to improve a connecting device of the type described in the preamble in such a way that it can also be used under relatively rough environmental conditions and is not subject to the disadvantages and problems described above.

This is achieved in accordance with the invention in that the coupling element comprises a frame, both sets of coupling means connecting the frame to the one or the other offshore unit in a manner that allows pivoting and rotation, at least one set of coupling means is provided with a first and a second elongated element, wherein each elongated element is connected to one of the offshore units via a first pivot and rotation-permeable construction and, at a distance from that first, via a second pivot and rotation-permissible construction to the frame, the first elongated element extending between the frame and said one offshore unit at a distance from the second elongate element, and the resetting means comprise a first and a second resilient element, which resilient elements are each stationarily connected to said one offshore unit and whether the first or the first second elongated element to a substantially vertical advanced position.

Due to these measures, a heavy ballast weight and additional anchor lines for the offshore units can be omitted, because a displacement of the two offshore units relative to each other via the frame will result in a pivoting and / or rotation of the elongated elements in their expression. substantially vertically extending position. This leads to the generation of resetting forces in the resilient elements, which 1025708 want to push the elongated elements back to their substantially vertical position, so that horizontal reaction forces are exerted on the frame which are opposite to the direction of the relative displacement which the two offshore units. These reaction forces therefore force the offshore units back through the frame to the neutral starting position.

A special advantage of this construction is that, in contrast to the known connecting devices with stretchers, additional anchor lines and baast loads can be omitted, so that no forces act on the connecting device in the neutral starting position and therefore also do not act between or on the two offshore units. to be. An additional advantage is that the connection device is relatively simple, fully controllable and can be installed on site.

The device can further be embodied such that the frame is provided with a first pair of engagement points for the elongated elements of the first set of coupling means and with a second pair of engagement points for the elongated elements of the second set of coupling means, wherein the frame then is preferably rectangular, with an elongate element 20 engaging at each corner point. In this way both offshore units can be equipped with receiving and resetting facilities. However, according to a further embodiment of the invention, it is preferred that the frame is a triangular frame and one of the sets of coupling means is a coupling member comprising a ball joint which is situated at a first corner point of the triangle frame, while first elongated element of the other set of coupling means engages a second angular point and the second elongated element at a third angular point of the triangle frame. Such an embodiment of the device has the advantage that in one of the offshore units the provisions to be arranged can be limited to a minimum, for instance only a ball joint or even only the possibility of connecting a ball joint to the offshore unit . This is particularly advantageous for offshore units that only need to be connected to another offshore unit once during use. During the other, normal use, no provisions need then be present for connecting, which provisions could disturb that other, normal use.

In order to be able to accommodate the various relative displacements of the offshore units in the most efficient and effective manner, according to a further embodiment of the invention, it is provided that the pivot and rotational structures allow a pivot about three mutually perpendicular axes.

A relatively simple, but extremely efficient embodiment can be obtained if at least the elongated elements consist of a steel cable, wherein it is then further preferred that each steel cable is connected to the relevant offshore unit via a winch 15. This, in combination with the resilient element, offers the possibility of simply tuning the device by shortening or extending the steel cable to the relevant application case, both with regard to positioning, that is to say dimensions of the two offshore units and the manner of collection. of mutual displacements between the units, i.e. the bias of the biasing force in the resilient elements, in other words the spring characteristic of the connecting device. In order thereby to shorten and lengthen the steel cable as well as the intended pivotal movement thereof about its vertical position in order to be able to preferably carry out three mutually perpendicular horizontal axes as optimally as possible, it is preferred according to a further embodiment of the invention that the steel cable be connection to the other offshore unit, via, for example, a winch, first runs over a, preferably hinged, wire guide before it starts to extend substantially vertically.

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In order to be able to install the connecting device easily and quickly, it is further proposed that the steel cable is provided with pivoting and rotation-permitting connecting means for coupling to the frame and with connecting means for coupling to a resilient element. Furthermore, if the connecting means for coupling the steel cable to the frame are spaced apart from those with the resilient element, the part of the steel cable which is situated between the two connecting means being connected over a preferably hinged to the offshore unit wire guide, it is simple to effect the vertical extension of the steel cable in the neutral position, while at the same time the pivoting of the steel cable is accurately controlled and guided when moving the offshore units.

If, for example, the frame is connected to the one offshore unit at the start of the installation of the connecting device, the coupling thereof with a steel cable can be carried out quickly and efficiently if the steel cable is interrupted at the location of the connecting means with the frame.

Another possible embodiment of the invention can be obtained if an elongated element is formed by a hinge connected to a relevant hinge via a hinge pivotable about at least three mutually perpendicular axes, which rod is furthermore pivotable via a hinge pivoting about at least three mutually perpendicular axes is connected to the frame and optionally via an intermediate element, preferably a steel cable, to the resilient element.

In order to generate a damping and a restoring force, according to a further embodiment of the invention, it is preferable that a resilient element is formed by a resilient plastic cable. If the resilient plastic cable is connected to the relevant offshore unit via a winch, then a further advantageous adjustment option for the bias and thus the receiving and resetting action of the device according to the invention is obtained. This adjustment option can, if desired, be combined with the adjustment option discussed above for a steel cable 5 originating from a customer.

Another possible embodiment of the invention can be obtained if at least one resilient element is formed by a hydropneumatic clamping unit. This can also be used in both the version with steel cables and those with hinged rods.

10 The offshore units to be connected, where platforms, barges and ships can be considered, can both be floating units. There may also be a floating unit and a unit standing on a bottom. For example, the connecting device can be used to connect a floating tender drill unit to a wellhead platform. The wellhead platform can then be both a floating unit, which is held in place by means of an anchor system or tension-laying system, and a structure submerged on a bottom. The floating tender drilling unit can be held in place either by means of an anchor system or a dynamic positioning system with propellers or by a combination of both. Other possibilities where the connecting device according to the invention can be applied are, for example, the connection between a floating tanker and a floating or an offloading station or production platform standing on a bottom of water, or more generally where offshore units, such as a offshore platform, a barge or a ship, for the execution of work, often temporarily, relatively close to each other. This includes units designed as a work, crane, drilling, tender, accommodation, storage, production or transport unit and the like.

According to a preferred embodiment of the invention, if the one offshore unit is a bottom-standing unit and the other offshore unit is a floating unit, it is preferable for the frame to be arranged with the bottom-end hinge offshore unit and to be connected to the floating offshore unit by the resetting By taking these measures, the provisions on the offshore unit standing on the bottom need only be minimal, for instance only the provision of the ball joint with a triangle frame, or even only provisions for securing the ball joint.

With reference to an embodiment shown in the drawing by way of non-limiting example only, the connecting device according to the invention will now be further elucidated. It shows:

FIG. 1 is a side view of a wellhead platform and a tender unit 15 coupled by a connecting device according to the invention;

FIG. 2 is a top view of FIG. 1;

FIG. 3 is a perspective view of the wellhead platform according to FIG. 1 and 2;

FIG. 4 is a side view of the connecting device in a neutral position, wherein the wellhead platform and the tender unit are in a desired, predetermined mutual position;

FIG. 5 is a side view of the connecting device in a position where the wellhead platform and the tender unit are moved relative to each other with respect to the neutral position; FIG. 6 is a side view of the connecting device in a position where the wellhead platform and the tender unit are moved apart relative to the neutral position;

FIG. 7 is a top view of the connecting device in a neutral position, wherein the wellhead platform and the tender unit are in a desired, predetermined mutual position; 1025708 8

FIG. 8 is a top view of the connecting device in a position in which the wellhead platform and the tender unit are rotated relative to each other from the neutral position; and FIG. 9 is a top view of the connecting device in a position in which the wellhead platform and the tender unit are displaced from the neutral position relative to each other, whereby a shifted position is assumed.

In FIG. 1 to 3, a floating, anchored offshore unit in the form of a wellhead platform 1 is shown, which is provided with a deck 2 and is anchored to a subsurface in a manner not shown. Furthermore, FIG. 1 3 a floating offshore unit moored near the wellhead platform 1 in a manner not shown, in the form of a tender unit 3.

The wellhead platform 1 and the tender unit 3 are mutually coupled by a connecting device 4, which is provided with a relatively rigid triangle frame 5, for example formed by a rod construction, a first corner point of which carries a ball joint 6, which is also fixed on the deck 2 of the wellhead platform 1, with which the coupling between the connecting device 4 and the wellhead platform 1 is established. The two other angular points of the triangle frame 5 are connected via pivoting and rotation-permitting connecting means 7 to a steel cable 8, which initially runs substantially horizontally from a winch 9 secured to the tender unit 3 to a wire guide in the form of a wire conductor also on the tender unit 3 hinged wire disk 10 and from there extends substantially vertically downwards to the connecting means 7. A further steel cable 12 extends substantially vertically from the connecting means 7 to a wire guide in the form of a hinged wire disk 11, where a bending of the further steel cable 12 takes place in substantially horizontal direction.

At some distance beyond the wire disc 11, the further steel cable 12 is coupled by connecting means 13 to a resilient plastic cable 14, which comes from a winch 15, which is again secured to the tender unit 3. With the aid of the winches 9, the positioning in height of the triangle frame 5 and with the help of the winches 15 the pre-tensioning in the steel cables 8 and 12 as well as the resilient plastic cables 14 to be accurately adjusted and adjusted to the relevant situation of use.

The coupling of the tender unit 3 with the wellhead platform 1 by means of the connecting device 4 can be achieved in various ways. One possibility is to attach the connecting device 4 to the tender unit 3, wherein the coupling to the wellhead platform 1 is effected by the corner point of the triangle frame 5 carrying the ball joint 6 with the aid of a wire to the fixing point of the ball joint 6 on to pull the wellhead platform 1. In this case, only one possibility for securing the ball joint 6 must be present on the deck 2 of the wellhead platform 1. Another possibility is to attach the triangle frame 5 and the ball joint 6 to the wellhead platform, the coupling of the wellhead platform 1 to the tender unit 3 taking place via the connecting device 4 by attaching the elaborated steel cables 8 and 12 of the tender unit 3 to the connecting means 7 on the triangle frame 5. After this, the steel cables 8 and 12 as well as the resilient plastic cables 14 are threaded into the tender unit 3 by means of the winches 9 and 15 to the correct length. This latter way of working is preferred because the steel cables 8 and 12 with the resilient plastic cables 14 can offer more clearance through the winches 9 and 15 when coupling the possibly moving tender unit and wellhead platform.

If desired, it is possible to provide additional spring elements 30 between the triangle frame 5 and the offshore unit on which the ball joint 6 is mounted, such as with a dashed line in FIG. 2 spring elements 1025708 10 16, which can be formed by stretchable plastic wires or a wire or rod with a hydropneumatic clamping unit.

In FIG. 4 shows the neutral position of the connecting device 4, in which the steel cables 8 and 12 extend substantially straight downwards vertically. The tender unit 3 is then at the desired location relative to the wellhead platform 1.

In FIG. 5 shows the situation that arises when, for example, environmental influences (waves, wind, current, etc.) have moved the wellhead platform 1 and the tender unit 3 towards each other. The triangle frame 5 herein has pressed the initially straight steel cables 8 and 12 to a V-shape. Because gentlemen 9 and 15 (see Fig. 1) are blocked in their position taken in the neutral position (see Fig. 4), the V-shaped deformation of the steel cables 8 and 12 has been effected by stretching the plastic cables 14 Moving the wellhead platform 1 and the tender unit 3 towards each other is thus absorbed and counteracted by exerting a resetting force in the direction of the neutral position.

FIG. 6 shows the situation in which the wellhead platform 1 and the tender unit 3 have moved apart. Here too the steel cables 8 and 12 are again deformed from their initial straight position to a V-shape, albeit opposite to that according to FIG. 5. For similar reasons as was the case with the situation according to FIG. 5, moving the wellhead platform 1 and the tender unit 3 away from each other is absorbed and counteracted by the resetting action of the connecting device 4.

FIG. 7, the connecting device 4 is shown in top view in the neutral position. From this position, for example, due to environmental influences, a mutual rotation can occur between the wellhead platform 1 and the tender unit 3, for example as far as in Figs. 8 position. The steel cables 8 and 12 will herein be deformed in a V-shape while tensioning the plastic cables 14. In a similar manner as described in the foregoing, the steel cables 8 and 12 with subsequent plastic welding cables 14 will have a resetting force in the direction of generate the neutral position.

In addition to rotation, displacement may also occur, resulting in a combined displacement which, for example, may result in the displacement shown in FIG. 9, mutually shifted position of the wellhead platform 1 and the tender unit 3 shown in Fig. 9. Also in this position, a cooperating, counteracting and resetting action will occur as a result of the cooperation of the steel cables 8 and 12 with the plastic welding cables 14, as in the foregoing. discussed and explained.

In the embodiment discussed above and shown in the drawings, the connecting device is provided with a triangular frame which is connected to one of the offshore units via a ball joint. If desired, the frame can also have a shape other than triangular, such as, for example, rectangular, square, polygonal, whether or not provided with bent, protruding or recessed peripheral parts. With such a differently configured frame, it may be preferable to replace the ball joint with line joints, universal joints and the like. It is likewise possible to replace the ball joint with a coupling means similar to that on the other side of the frame, which is then preferably rectangular. Such a construction requires more materials and investments, but offers additional collection and resetting possibilities, such as, for example, doubling them or a system with two different spring constants.

It is self-evident that within the scope of the invention, as laid down in the appended claims, many further modifications and variants are possible. For example, a winch 9, a hinged wire disc 10 and the part of a steel cable 8 to the connecting means 7 can be replaced by a rod which is for instance connected by a ball joint to the tender unit 3 at the place where the hinged wire 1025708 12 wire disc 10 is currently located. is located. Furthermore, a resilient plastic cable 14 can be replaced by a hydropneumatic tensioning unit or steel cables can be replaced by plastic cables. It is also possible to opt for a number other than two steel cables and two plastic cables 5 or the steel cables can be connected to the tender unit without the intervention of winches and wire conductors. Although two steel cables 8 and 12 have been discussed, it will be clear that this could also be a continuous steel cable. Finally, it is noted that it is of course also possible to reverse the connecting device, that is to say fix the ball joint on the tender unit and the steel cables with associated elements on the wellhead platform. Furthermore, it will be obvious that the coupling of, for example, a floating offshore unit and an offshore unit standing on a bottom can be carried out in a similar manner as discussed above for two floating offshore units.

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Claims (17)

1. Device for connecting two offshore units and provided with a coupling element that can be connected to the one offshore unit via a first set of coupling means and via a second set of coupling means to the other offshore unit, further restoring provisions being present for receiving of movements between the two offshore units, characterized in that the coupling element comprises a frame, both sets of coupling means connecting the frame to the one or the other offshore unit in at least one set of coupling means in a manner that allows pivoting and rotation a first and a second elongated element, wherein each elongated element is connected to one of the offshore units via a first pivot and rotation-permeable construction and remote from that first, via a second pivot and rotation-permitting construction to the frame, wherein the first elongated element extends away from the second elongated element extends between the frame and said one offshore unit, and the resetting arrangements comprise a first and a second resilient element, which resilient elements are each stationarily connected to said one offshore unit and whether the first or the second elongate element is connected to a substantially vertically extending position. 1025708 2. Device as claimed in claim 1, characterized in that the frame is a triangle frame and one of the sets of coupling means is a coupling member which comprises a ball joint which is situated at a first corner point of the triangle frame, while the first elongated element of 5 the other set of coupling means engages a second corner point and the second elongated element at a third corner point of the triangle frame. Device as claimed in claim 1, characterized in that the frame is provided with a first pair of engagement points for the elongated elements of the first set of coupling means and with a second pair of engagement points for the elongated elements of the second set of coupling means. 4. Device as claimed in claim 3, characterized in that the frame is of rectangular design, wherein at each corner point an elongate element engages in each case. | 5. Device as claimed in any of the foregoing claims, characterized in that characterized in that the pivotal and rotational construction allows movement around three mutually perpendicular axes. 20 Device as claimed in any of the foregoing claims, characterized in that at least the elongated elements consist of a steel cable. 7. Device as claimed in claim 6, characterized in that each steel cable is connected to the relevant offshore unit via a winch. 8. Device as claimed in claim 6 or 7, characterized in that the steel cable runs from its connection to an offshore unit first over a wire guide before it starts to extend substantially vertically. 1025708 9. Device as claimed in any of the claims 6-8, characterized in that the steel cable is provided with pivoting and rotation-permitting connecting means for coupling to the frame and with connecting means for coupling to a resilient element. 10. Device as claimed in claim 9, characterized in that the connecting means for coupling the steel cable to the frame are spaced apart from those with the resilient element, wherein the part of the steel cable which is situated between the two connecting means over a wire conductor connected to the offshore unit. Device as claimed in any of the claims 8-10, characterized in that the wire guide is pivotally connected to the offshore unit. Device as claimed in claim 10 or 11, characterized in that the steel cable is interrupted at the location of the connecting means with the frame. Device as claimed in any of the claims 1-5, characterized in that an elongated element is formed by a hinge connected to the relevant offshore unit via a hinge pivotable about at least three mutually perpendicular axes, which rod is furthermore connected via an at least three mutually perpendicular pivotable hinge with the frame and connected to the resilient element, whether or not via an intermediate element, preferably a steel cable. 14. Device as claimed in any of the foregoing claims, characterized in that a resilient element is formed by a resilient plastic cable. 10257 G. Device as claimed in claim 14, characterized in that the resilient plastic cable is connected to the relevant offshore unit via a winch. 5 Device according to one of claims 1 to 13, characterized in that at least one resilient element is formed by a hydropneumatic clamping unit. 17. Device as claimed in any of the foregoing claims, characterized in that one offshore unit is a bottom-standing unit and the other offshore unit is a floating unit, wherein the frame is adapted to pass through a ball joint with the offshore standing on the bottom. unit and by the resetting facilities to be connected to the floating offshore unit. 1025708