Process And Installation For The Connection Of A Cable Or Flexible Pipe To An Underwater Guide Column

Abstract

This invention concerns a submerged installation for the connection of a guide cable or flexible hydraulic pipe to an underwater well-head guide column, from a floating structure. The invention comprises a process and equipment for laying the cable or flexible pipe, stored in a drum inside a module with a guide cone, which is lowered near the guide column and propelled into its final position by propulsion gear controlled from the floating structure on the basis of locating signals transmitted by detectors on the module.

Description

This invention concerns an installation for the automatic connection of guide cables, electric cables, flexible hydraulic pipes or similar pipes to an underwater well or similar guide column, from a floating structure, possibly a ship, by means of a module, the lower part of which consists of an inverted funnel, with the end of the cable or flexible pipe to be connected to the guide column held at the narrow end of it, and which is also fitted with devices such as sonar equipment to detect the guide column, and means of propelling the module horizontally through the water.

In one existing process, a drill string re-entry device is lowered together with the guide cable, until the end of the cable can be connected to the guide column. The whole drill string then has to be raised to the ship and the re-entry device detached, after which any other equipment required can be lowered along the guide cable.

In this method, the end is guided to the correct position entirely by hand : in other words the operator on board the floating structure orientates the "jet" propelling the end of the cable, on the basis of information transmitted to the surface by the sonar equipment, by controlling the rotary table and pumps on the platform.

Furthermore, because of the slight flexibility of the drill string, its point of suspension on the floating support has to be very nearly vertically above the guide column to which the connection is to be made.

This invention offers a different method, in which the flexible hydraulic cable or pipe is stored inside a module, preferably on a revolving drum, the module containing the cable is lowered as far as the guide column, to which the end of the cable is connected automatically, and the module is then raised to the surface, while the cable unwinds as it leaves the base of the module, the other end remaining connected to the module.

This procedure means that at any point between the guide column and ship only one cable is being unwound at once : during the lowering phase, the whole cable for connection is on the drum inside the module, while the cable from which the module is suspended unwinds; during the raising phase, after the actual connection operation, the connected cable unwinds from the module, remaining underneath it, while the suspension cable, as the module rises, remains above it. This means that there is no risk of several cables becoming entangled.

The invention also concerns an installation to apply this process, im which the module, which is negatively buoyant, comprises a structure suspended by the upper end from a cable carried on the floating structure, and containing means of housing the guide cable or pipe, which ends in a connector designed to be held elastically in the narrow part of the funnel, on the same axis as the module suspension cable, which incorporates the cables or pipes to link the detectors and means of horizontal propulsion with the floating structure.

The fact that the funnel and suspension cable area on the same axis makes handling easier : in particular, when the module is raised and loaded on to the ship, it can simply be laid on the funnel, which provides a completely stable base. The negative buoyancy of the module allows it to be lowered steadily, without any special cables being required. Since the whole structure is centred on the axis of the suspension cable, there is no risk of couples forming, and hindering proper positioning of the connector on the guide column.

In one recommended embodiment, the sides of the funnel contain large apertures, improving the stability of the module during lowering.

According to another feature of the invention, the detectors are fitted to the end of a retractable arm formed of two hinged sections, the first projecting horizontally from the module and the second projecting vertically downwards from the end of this first section. This ensures greater accuracy in determining the angular position of the module by means of the sonar equipment, and when the arm is folded back the equipment is protected from blows during handling.

According to one particular feature, the module is propelled horizontally by means of separate and individually controlled propellers for linear and pivotal movements, the linear propellers preferably fitted to the module approximately level with the point of connection between the module and its suspension cable, to ensure maximum stability, and the pivotal propellers fitted to the arm carrying the detectors, to ensure more effective determination of the pivotal couple without creating any significant linear component.

According to yet another feature, the module is equipped with a drum for the cable or pipe for connection, fitted with a braking system, preferably remote-controlled from the floating structure by means of lines or pipes incorporated in the suspension cable.

It will be easier to understand the invention from the following description, illustrated by the accompanying drawings, showing one of many possible embodiments of an installation for the automatic connection of a cable to an underwater guide column, as defined in this invention, which is however in no way confined to this embodiment.

FIG. 1 is a cross-sectional view of the whole installation, with an underwater well-head guide column, and a ship forming the floating structure.

FIG. 2 is a larger-scale view of the main part of the module seen in FIG. 1.

FIG. 3 is a front view corresponding to FIG. 2.

FIG. 4 is a vertical cross section, showing a system to disconnect the cable from the guide column.

The installation shown in FIG. 1 is being used to connect a guide cable 1 to the upper end of the guide column 2 of an underwater well-head 3, from a floating structure, consisting in this example of a ship 4.

The same installation could be used to connect any flexible component similar to the guide cable, such as an electric cable or even a flexible hydraulic pipe. The floating structure, instead of being a ship, could equally well be a drilling platform or other suitable unit, and the guide column need not necessarily form part of an underwater well.

The main feature of this installation is a module 11, comprising a structure, made of welded tubes for instance, suspended by the upper end from a cable 12, which is stored on a winch 13 on the ship 4.

The lower end of the module 11 which, when fully equipped, is negatively buoyant, is fitted with an inverted funnel-shaped re-entry cone 16, the sides of which may be formed of welded strips of iron, set apart to leave large apertures, so that lowering of the module is not hindered by any resistance from the water. Initially, the whole guide cable 1, which can also be seen in FIGS. 2 and 3, is inside the module, preferably coiled on a drum 14, on a horizontal shaft 18, attached to the module framework and fitted with a braking device 19, preferably remote-controlled from the ship 4 by means of electric cables incorporated in the suspension cable 12.

At the end of the guide cable 1, there is a connector 21, with a neck 22, held elastically in the module by radial push rods 23, which are kept against the neck by means of springs 24. The upper edges of these rods slope upwards and outwards, so that they can be pushed back, as will be described further on, by a wider truncated conical section 26 above the neck.

The lower end 31 of the connector 21, which can also be seen in FIG. 4, has a projecting rim, which is held by radial bevelled stops 32 fitted with springs 33, in the upper end of the guide column 2.

To keep the whole module vertical during lowering, despite the lateral imbalance resulting from the weight of the length of guide cable 1 on the drum 17, the suspension cable 12 is connected to the module by means of a slide 36, which can be seen in FIG. 3, the position of which can be adjusted in relation to the module, in a direction parallel to that of the drum shaft 18, by any standard regulating device (not shown here).

The guide column detectors, in particular a sonar device 41, which can be seen in FIG. 1, are fitted to the end of an arm 42, formed of two sections, the first 42A projecting horizontally from the module and the second 42B projecting vertically downwards from the end of this first section. This arm, which is hinged on two axles 44 and 45, can be folded back against the module framework, as shown by the arrows f1 and f2.

Horizontal movements of the module, to position it accurately above the guide column over which the funnel 16 is to fit, are produced by propulsion gear consisting of propellers to provide linear movement 46 and others 47 which cause the module to pivot on the axis of the suspension cable 12.

These two sets of propellers perform completely separate functions, and are controlled separately from the surface by pipes which are incorporated in the suspension cable. In the example shown here, there are two linear propellers 46, to move the module horizontally through the water in the direction shown by the arrow in FIG. 1 f4, in other words in the opposite direction to that of the arm 42 carrying the sonar equipment, and two pivotal propellers 47 facing in opposite directions on the arm 42, so that the module can be made to pivot in either direction, by using the appropriate propeller.

Retraction and extension of the arm carrying the sonar equipment and pivotal propellers are also remote controlled from the surface, by means not shown here.

FIG. 4 also shows a device to detach the connector 21 from the guide column 2, consisting of a tube 51 which can be lowered over the connector 21 and the bevelled lower rim of which 52 fits against the bevelled edges of the stops 32, pushing them apart sufficiently to let the wider part 31 of the connector be withdrawn upwards.

The installation functions as follows.

The module can be piloted manually from the ship 4, or automatically, particularly when it is close to the target formed by the guide column 2 to which the cable is to be attached. In the case of automatic piloting, the sonar equipment sends up data for processing in a specialized computer on the ship, which works out the orders to be sent to the linear and pivotal propellers. These are transmitted by cables or pipes incorporated in the suspension cable 12.

Connection is done as follows.

When the ship reaches the zone where the guide column 2 is located, the cable 12 on which the module is suspended is unwound until the module is near the seabed. Automatic piloting of the pivotal movement starts, so that the module turns in the direction of the target. On the basis of the data supplied by the sonar equipment, the ship is brought directly over the target, with the linear propellers still not in operation. When the module is near the target, the distance depending on the depth involved, the ship is stabilized and the automatic piloting unit brought into operation, for both linear and pivotal movements. Eventually, the funnel 16 is located directly above the guide column 2, and after checks have been made the module is lowered abruptly. Because of its negative buoyancy, the funnel fits exactly over the guide column, and the connector 21 is inserted into the top of the guide column 2, and held there, as shown in FIG. 4. The module is then raised slowly. The sprung rods 23 are pushed apart by the wider section 26 of the connector 3, and the drum, with its braking system, lets the guide cable 1 unwind as the module rises. When it reaches the surface, it is loaded on to the ship, and placed on the funnel, which provides a convenient wide base. The guide cable 1 is shifted on to a winch, preferably one providing uniform tension.

Later, if the connector 21 is to be removed from the guide column 2 a tube 51, shown in FIG. 4, is lowered along the guide cable 1 until it reaches the guide column, when its bevelled lower edge 52 pushes the stops 32 outwards, releasing the wider lower end 31 of the connector. This can then be raised by pulling the guide cable 1, which also raises the tube 51.

The negative buoyancy of the module ensures stable horizontal trim, making it easier to fit the connector on to the guide column, through the simple effect of gravity.

The large funnel or cone forms a heavy part of the module, so that the centre of gravity of the unit is quite low. The funnel contains large perforations, reducing its resistance to movement through the water to a minimum, and facilitating launching.

The presence of the re-entry cone makes handling easier, and avoids the risk of accidental penetration of the guide column into the module during final guiding operations. Furthermore, this design allows clean connection, without stray couples, since the centre of gravity of the module is almost on the same vertical as the cone access.

Since the sonar equipment is suspended vertically from the end of the remote-controlled retractable arm, it can be kept away from the axis of the cone, and consequently from the guide column, during the final phase. In this way, there is less risk of damaging it during connection, and its effective precision is greater. In addition, this arrangement allows the transducer-hydrophone unit to be placed during guiding at a certain distance, for instance 2 metres, below the base of the cone, allowing vertical displacement of the module by the same distance, as the result of the ship heaving. When the arm carrying the sonar equipment is folded back against the module, the whole unit becomes conveniently compact for launching and storage, and the sonar equipment is protected.

The fact that the point at which the suspension cable is attached to the module is roughly in the same horizontal plane as the linear propellers almost completely eliminates any pitching couple caused by these propellers.

The male connector described in the example shown here can be replaced by any standard connector suitable for flexible hydraulic pipes or electric cables.

Naturally, the invention is in no way confined to the embodiment described and illustrated here : many modifications are possible, depending on the applications involved, without any departure from the spirit of the invention.

For instance, the example shows a male connector for attachment to a female guide column, whereas the opposite arrangement could be adopted, with a female connector fitting on to a male guide column.

Claims

What is claimed is:

1. An installation to connect a guide cable or similar appliance, such as an electric cable or flexible hydraulic pipe, to an underwater well-head or similar guide column, from a floating structure such as a ship, by means of a module, the lower part of which consists of an inverted funnel, with the end of the guide cable held in the narrow end of it, and which is also fitted with devices such as sonar equipment to detect the guide column, and means of propelling the module horizontally through the water, characterized by the fact that the module, which is negatively buoyant, comprises a structure suspended by the upper end from a cable carried on the floating structure, and containing means of housing the guide cable or pipe, which ends in a connector designed to be held elastically in the narrow part of the funnel, on the same axis as the module suspension cable, which incorporates the cables or pipes needed to link the detectors and means of horizontal propulsion with the floating structure.

2. An installation as defined in claim 1, in which the sides of the funnel contain large apertures.

3. An installation as defined in claim 1, in which the detectors are fitted to the end of a retractable arm formed of two hinged sections, the first projecting horizontally from the module, and the second projecting vertically downwards from the end of this first section.

4. An installation as defined in claim 1, in which the module is propelled horizontally by means of separate and individually controlled propellers for linear and pivotal movements.

5. An installation as defined in claim 4, in which the linear propellers are fitted to the module approximately level with the point of connection between the module and its suspension cable.

6. An installation as defined in claim 4, in which the pivotal propellers are fitted to the arm carrying the detectors.

7. An installation as defined in claim 1, in which the connector is held elastically in the module by radial sprung rods which push against a neck in the connector.

8. An installation as defined in claim 1, in which the lower end of the connector has a projecting rim, which is held by radial bevelled stops fitted with springs, at the upper end of the guide column.

9. An installation as defined in claim 8, in which a bevelled tube can be lowered over the connector, with a bevelled lower rim which pushes the bevelled edges of the stops apart, releasing the connector from the guide column.

10. An installation as defined in claim 1, in which the cable or pipe for connection is stored on a drum mounted on a shaft and fitted with a braking system, remote-controlled from the floating structure by means of lines or pipes incorporated in the suspension cable.

11. An installation as defined in claim 1, in which the suspension cable is connected to the module by means of a slide, the position of which is adjustable in a direction parallel to the horizontal axis of the drum shaft.

12. An installation as defined in claim 1, comprising means of detecting and transmitting data to a computer concerning the relative position of the guide column in relation to the module, and means of controlling the linear and pivotal propellers on the basis of the data processed by the computer.

13. A process for connecting a guide cable or similar appliance, such as an electric cable or flexible hydraulic pipe, to an underwater well-head or similar guide column, from a floating structure such as a ship, by means of a module carrying the cable or pipe for connection, which is lowered near the seabed, guided to the guide column by means of detectors and propulsion gear on the module, and dropped on to the guide column, characterized by the fact that the whole guide cable is inside the module, preferably stored on a revolving drum, the module containing the cable is positioned vertically over the guide column, dropped on to it, and then raised to the floating structure, while the cable unwinds as it leaves the module, where the other end of the cable remains attached.

14. A process as defined in claim 13, in which the module is positioned vertically over the underwater guide column by means of detectors which instantaneously measure the relative positions of module and guide column and transmit their data in the form of electrical signals, to a computer on board the floating structure, which processes the data and works out the orders to be sent to the horizontal propulsion gear on the module, and by means of this horizontal propulsion gear.

15. A process as defined in claim 13, in which the module is lowered near the seabed by means of a suspension cable, the position of an inverted funnel in relation to the guide column is measured by detectors and data concerning this transmitted to the computer on the floating structure, the pivotal propellers are then started up to orientate and keep the sonar-equipment/funnel-centre axis pointing in the direction of the guide column, until the distance between module and guide column is considered suitable, upon which the computer, on the basis of the data received, transmits automatic guiding orders to the pivotal and linear propellers, and when the funnel on the module is vertically above the guide column the computer orders the abrupt release of the suspension cable, so that the funnel fits over the guide column.