GB2223074A - Swivel connection system with flexible pipes and moveable carriages - Google Patents

Abstract

A system is described for connecting hoses and other lines from the sea bed up to a floating unit, such as a ship, of the type intended to be able to rotate - according to the direction of the weather - around an element which is rotatably mounted in the floating unit and moored relative to the sea bed, and for facilitating conduction and fixation of said hoses and lines. Between the ship (10) and the moored element or turret connector hoses (5) and swivels (6) are arranged, and mounted in the floating unit is an annular body (1) which supports two or more carriages (3) which may be driven relative to the body and relative to each other, the annular body (1) having coupling points (2) for the connector hoses (5). If the ship rotates beyond a certain angle, e.g. 45 DEG , the other carriage (3') with the corresponding set of hoses (5') is connected to the production system via a different coupling point (2d) and production can continue uninterrupted. This arrangement provides a considerable unobstructed space in the centre of the turret, for other equipment. <IMAGE>

Description

OFFSHORE CONNECTION SYSTEM The present invention relates to a connection system suitable for the type of moored ships for production, storage and loading of hydrocarbons offshore where the attachment of mooring and connecting lines (pipes, hoses and cables) between the ship and the sea bed is achieved by means of a cylindrical/conical hollow structure (hereinafter referred to as a turret). The turret is moored with respect to the sea bed but is so arranged in the ship that the ship may rotate in order to weathervane with respect to the wind and wave direction. To simplify matters, the following description only refers to a production ship. Nevertheless, the principle of the invention would apply to other installations, e.g. a loading buoy and/or offshore storage tank.

The relative turning movement between the ship and turret makes it necessary to build into each of the connecting lines between the ship and sea bed a device permitting a corresponding turning while concurrently providing sufficient safeguarding against leakage.

There are two known principles for such turning compensating devices, one consisting of one or more swivels and the other consisting of coils or resilient spirals incorporated as a part of the lines.

In the first case the compensators are arranged in the central portion of the turret and therefore prevent the turret from being used for any other purpose than as a connector. The second case involves a complicated and bulky arrangement in and around the same area, with corresponding drawbacks.

According to the present invention there is provided a system for connecting hoses or other lines from the sea bed up to a floating unit, comprising first and second units, one moored to the sea bed and the other floating and able to rotate around an element of the moored unit, at least one flexible connector hose between the floating unit and the moored unit, an annular body mounted on the first unit and having connection means for the or each hose, and at least one carriage arranged to move around the annular body, wherein each connector hose extends between a carriage and the second unit and the carriage has coupling points for connection to the connection means on the annular body, so that if the floating unit rotates round the moored unit the carriage can be disconnected from the connection means on the annular body and a fresh connection can be made between the same or another carriage and the connection means.

With embodiments of the present invention the deficiencies and drawbacks of the prior art systems can be avoided because the central portion of the turret is completely free from connecting lines and, furthermore, access to the centre of the turret from the ship is made possible. The central portion of the turret may therefore be used for well drilling, BOP (blowout preventer) installation, and well services and workover. This is particularly interesting when the wells are situated directly below the production ship.

Large expenditures for special drilling rigs and service ships may therefore be avoided.

Advantageously at least two carriages, each with at least one hose, are provided so that one carriage can be connected before the other carriage is disconnected, enabling a continuous connection between the moored and floating units. This facilitates a remotely controlled (automatic) and operator-friendly conduction of the necessary lines for transfer of well flow, injection, services and control between the turret and the production ship during well workover or drilling operations, while at the same time allowing production to continue uninterrupted without endangering the safety of personnel, the environment or equipment.

Advantageous embodiments of the invention thus display a mechanical arrangement of pipe lay-outs, valves, mechanical/hydraulic couplings, flexible hoses and swivels which make it possible to convey one or several media uninterrupted between the turret and the production ship, while at the same time the area at the centre of the turret (moonpool) remains open.

This characteristic, viewed in conjunction with the fact that a turret-moored production ship permits loading directly into a tanker on site, represents an optimal and competitive development solution.

A production ship can be used in three phases of the development of a field: the test phase, early production and the permanent production phase. In the first phase usually only one well is connected to the ship, often by means of a flexible pipeline and control lines. In this connection it is known to use a simple arrangement of "jumpers", i.e. hoses which manually and by means of wires, sheaves and winches are moved from one connecting point to the other as the ship is turning.

In the next phase, wherein e.g. 4-6 wells are producing for a period of 2 to 5 years, and in the last phase, with up to 20 wells directly below the production ship to be drilled and maintained, embodiments of the present invention will be particularly relevant.

Simultaneous operations through a turret and several risers/wells connected up through the turret, pose stricter requirements as to safety, design and routines. The present invention is intended to satisfy the new requirements in this respect and to provide an integrated production vessel with cost optimisation.

For a better understanding of the invention embodiments will be described more closely with reference to the appended drawings, in which: Figure 1 illustrates the principle of a turretmoored production ship with a plurality of wells directly below the ship; Figure 2 shows a vertical section through the ship and turret; and Figures 3 and 4 show plan and side views, respectively, of details of the connection mechanism.

Figure 1 shows the general arrangement envisaged where a production ship 10 is moored to a turret so as to rotate round it. Oil rises from wells 11 into a manifold system (not shown) on the sea bed or the turret and passes via transfer stations4 (Figure 2), each connected to a suitable set of pipes 5, to the ship.

Figure 2 shows an annular body 1 arranged on the production ship 10 in a position above and around the centre of the turret, i.e. coaxially with the rotation of the ship. Connector stations 2 are positioned on the annular body 1, each having direct connections to the ship's production system via a permanent network of pipes, and constitute a connection means for the flexible pipes 5. As can be seen in Figure 3, there are four stations 2a,2b,2c and 2d spaced evenly round the annular body 1. Each connector station 2 includes a number of remotely controlled mandrels or male couplings, equalling the number of lines to be conducted between the turret and the production ship, in this case four. These may comprise, for example, two production pipes, one water injection pipe and one gas injection/lift pipe. Corresponding female couplings for a set of pipes are arranged on movable carriages 3 which are supported by the annular body 1, one set per carriage. The couplings could of course be arranged the other way round with respect to the connector stations and carriages. The male couplings are fitted in a manner so as to allow them to be remotely controlled so as to slide into or be retracted from the female couplings.

Each of the carriages 3 has its own propulsion system which can drive the carriages round the annular body 1, e.g. by means of a rack and pinion power transmission. In this embodiment at least two carriages 3 are required in order that they may alternate in being connected to one of the connector stations 2 as the production ship turns about the turret, thus providing continuous connection. The further connection between the carriages 3 and the transfer stations 4 on the turret is achieved through an arrangement of flexible pipes 5 and swivels 6 enabling the production ship to revolve round the turret within a sector of for instance 900, i.e. 450 in either direction, as can be seen in Figure 3.

Both the connector stations 2 on board the production ship and the transfer stations 4 on the turret have shut-off valves fitted which can be both locally and remotely operated. Separate test lines (not shown) are provided for each of the pipelines to enable these to be pressure tested after being connected and before being placed in service. Lines which have been shut off can be relieved of pressure and emptied into a collecting tank through a discharge valve.

As can be seen from Figure 2, the annular body 1 allows room for equipment 7 of substantial size in the central portion of the turret, such as subsea well head equipment, "Christmas trees", BOP's, tools, riser completion and workover equipment.

In operation, the set of hoses 5 fitted to one of the two carriages 3 is coupled to one of the connector stations 2 on the annular body 1, e.g. station 2a in Figure 3. The ship starts at a position given by the arrows FWD, with, for example, the connector station 2a in position thwartships, as shown in solid lines. The ship can rotate about the turret within a sector corresponding to for example + 450 without it being necessary to perform a switch to the opposite side in order to rotate the ship further (see Figure 3).

If a further rotation is required then the ship is rotated about the turret, e.g. by means of its own positioning equipment, which is activated after the friction force and/or any locking mechanisms between the ship and the turret have been released. When the ship has rotated in this case 450 from its starting position and the friction force and any locking mechanisms between the ship and turret have been reestablished, a switch is made to the opposite side, i.e. the pipes 5 of the other carriage 3' are connected, and the ship may now be rotated further about the turret. The way this is achieved is by placing the opposite carriage 3' in a position e.g. 450 from the thwart ship direction and connecting the coupling of this carriage to the appropriate connector station, in this case 2d, on the annular body 1 - see the dashed lines in Figure 3.The new connector is pressure tested, and the production is transferred to the opposite side, i.e. via carriage 3' and connector station 2d, by opening and closing the appropriate valves. The previous connection is pressure relieved, and the "old" carriage 3 is shut off, disconnected from connector station 2a and rotated back to a desired position. The ship may now be rotated further to any desired position within a sector of e.g. 900. In this way the connection is unbroken during the rotation of the ship.

Any further rotation from the new position beyond 900 will necessitate another switching and is performed by repeating the procedure as described above.

A collecting receptacle 8 is fitted underneath the mechanism to collect any liquid that might escape from the couplings upon opening or closing. The collecting receptacle is emptied to a tank in the stationary platform for further transport and processing.

While the embodiment described has four connector stations and two carriages, it is clear that other combinations are possible. For instance, if the swivel range of the pipes is + 600 then only three connector stations are necessary with two carriages. The carriages may be arranged oppositely, as above, with the connector stations evenly spaced. It would further be possible in principle to have three carriages and two connector stations.

While in general at least two carriages will be required in order to provide continuous connection, as explained above, arrangements are conceivable in which only one carriage is used, or two carriages and fewer than four connector stations, there being a gap in transmission while the carriage is transferred from one connector station to another. This may be acceptable in some circumstances.

In principle the arrangement of the embodiment shown could be reversed in that the annular body could be arranged stationary with respect to the turret, connection to the ship being made via hoses extending between the ship and carriages travelling on the annular body.

Claims (14)

CLAIMS:

1. A system for connecting hoses or other lines from the sea bed up to a floating unit, comprising first and second units, one moored to the sea bed and the other floating and able to rotate around an element of the moored unit, at least one flexible connector hose between the floating unit and the moored unit, an annular body mounted on the first unit and having connection means for the or each hose, and at least one carriage arranged to move around the annular body, wherein each connector hose extends between a carriage and the second unit and the carriage has coupling points for connection to the connection means on the annular body, so that if the floating unit rotates round the moored unit beyond a certain angle the carriage can be disconnected from the connection means on the annular body and a fresh connection made between the same or another carriage and the connection means.

2. A system according to claim 1 and having at least two carriages, each with at least one hose, so that one carriage can be connected before the other carriage is disconnected, enabling a continuous connection between the moored and floating units.

3. A system according to claim 1 or 2, wherein the first unit (with the annular body) is the floating unit and the second unit is the moored unit.

4. A system according to claim 3, wherein the connection means on the annular body comprises at least two connector stations, each with its own set of couplings, which are directly connected to a production system on the floating unit.

5. A system according to claim 4 and having two carriages and three connector stations.

6. A system according to claim 4 and having two carriages and four connector stations.

7. A system according to claim 4, 5 or 6, wherein the coupling points of the carriages are positionable at a selected connector station so as to be connected to the couplings fitted on the annular body.

8. A system according to any preceding claim, wherein the carriages are movable relative to the annular body by means of a propulsion system mounted on the carriages.

9. A system according to any preceding claim, wherein a collecting receptacle is fitted below the couplings on the carriages which will collect any liquid escaping from the couplings upon opening or closing.

10. A system according to any of claims 4 to 9, wherein a separate test line is provided for testing the couplings before they are put in service.

11. A system according to any preceding claim, wherein the connector hoses are provided with swivels at the ends where they are attached to the second unit.

12. A system according to any of claims 3 to 11, wherein shut-off valves are fitted at the outlet from the moored element and at the inlet to the annular body.

13. A system according to any preceding claim, wherein an open area of substantial magnitude is provided through the central portion of the annular body, for handling equipment.

14. A system substantially as described herein with reference to the accompanying drawings.