GB2111099A

GB2111099A - Well head equipment

Info

Publication number: GB2111099A
Application number: GB08136994A
Authority: GB
Inventors: Henry Weston
Original assignee: Individual
Current assignee: Individual
Priority date: 1981-12-08
Filing date: 1981-12-08
Publication date: 1983-06-29
Also published as: GB2111099B

Abstract

An underwater well head and riser installation comprises a narrow riser 7, a flexible joint 5 between the riser and the well head valve block 1, providing direct vertical communication to the well, and one or more flexible flow conduits 9 extending from the well head valve block 1 to and along the riser, in parallel with and independent of the flexible joint. This enables the riser to remain connected to the well head and to remain operative for production and in-well operations in a wide range of weather conditions with the riser appreciably tilted. <IMAGE>

Description

SPECIFICATION Well head equipment This invention relates to underwater well head equipment.

At the present time, it is usual to connect an underwater well head to an installation at the surface, by a substantially rigid riser. In the case of a floating installation, there are severe restrictions on the range of weather conditions in which the floating installation can remain connected to the well head, and in particular it is usually possible to tolerate a departure of only a few degrees of the riser from the vertical. This problem is particularly acute in the case of a riser provided with a multiplicity of flow pipes, as it is impossible to provide a reliable multiple connection to the well head that will tolerate inclination of the riser.

According to the present invention, the riser is connected to the well head (in particular, to a christmas tree or a quick-release coupling) in a non-rigid manner so that at least the major part of the length of the riser can be inclined from the vertical relative to the stationary well head, and at least one non-rigid flow line extends from a flow inlet below the non-rigid region to a flow duct on or in the riser above the flexible region.

By means of such an arrangement, the riser can remain connected to the well head over a much wider range of angles of inclination, and therefore of weather conditions, than is the case with existing well head/riser arrangements. Consequently, a floating rig or platform can remain connected to the well head for extended initial production testing, for other operations by wirelining or TFL (through flow line) tools, and for production, in a wider range of weather conditions than is possible at present. It is anticipated that such operations will be able to continue over a range of weather conditions comparable to those in which it is at present possible to carry out drilling operations.

In a preferred arrangement, there is direct axial access through the riser to the stationary well head equipment, to allow TFL or wire line operations. The tools used for such operations can be run on relatively narrow tubing capable of passing from the riser to the well head through the non-rigid region even when the riser is appreciably off vertical.

The riser itself will in general be relatively narrow for example similar to a drilling riser, and may even be the drilling riser, therefore being inherently more flexible than conventional production risers. A slip joint may be provided at the top of the riser.

In the case of a well head with multiple access points, for example multiple flow lines, the riser and its coupling to the well head preferably provide direct access for a running tool capable of selecting a desired access port at the top of the well head, for example in a quick-release coupling.

The accompanying drawings illustrate a preferred embodiment of the invention.

Figure 1 shows the upper part of a sub-sea well head coupled to a riser. A valve block 1 is connected to a conventional christmas tree (not shown). The valve block has access ports connected to one or more flow lines and to the well annulus The valve block provides for connections to the flow lines and to the annulus at the top face of the valve block, but also has lateral access points 2 for the flow lines, and stop valves 3 above these to close off the flow lines from the top of the valve block.

Above the valve block is a quick-release coupling assembly 4, the upper part of which carries a flexible joint 5. The illustrated flexible joint comprises curved rnetal/rubber lamination stacks 6, but other forms of flexible joint can be used, for example ball joints, and stacks of spools separated by elastomeric spacers.

The top of the flexible joint is connected to the bottom of a narrow riser 7 which can be, or can be similar to, a drilling riser. Because of the use of a narrow riser and a flexible joint on the well head, it is possible to tolerate substantial movement of the surface rig off station.

The riser carries flow lines 8 which are connected to the side access points 2 on the valve block, by flexible coils 9. The lower ends of these are provided with suitable releasable stabs 10 for coupling to and uncoupling from the valve block, so that the riser together with the flexible joint, flexible coils and upper part of the quick release coupling can be uncoupled from the well head. Because the flow lines at the well head are connected to those on the riser by flexible coils, production flow can be maintained despite substantial tilting of the riser relative to the well head and production can therefore be maintained in weather that would require uncoupling of a conventional production riser, as these can tolerate very little departure from strict vertical aligment.

The valve block 1 also provides vertical access to the flow lines and well annulus.

Vertical access to these is provided through the lower part 11 of the quick-release coupling. The upper part 1 2 of the quick-release riser coupling provides communication between the interior of the riser 7 (through the flexible joint 5) and a number of access ports in the bottom of the part 12, these ports providing communication by way of the lower coupling part 11 with the access ports in the top of the valve block 1. A running tool on a narrow pipe or drilling sleeve can be lowered through the riser to make connection with a selected port in the quick release coupling. It is convenient if the ports in the coupling are at equal radii from the coupling axis and at equal angular intervals, but this is not essential.To orient the tool, the quick-release coupling has an internal cam 1 3 to engage and guide an exernal key on the tool.

By way of example only, Fig. 2 shows a suitable tool. The tool body 20 is of somewhat smaller diameter than the riser 7 and the internal passage through the flexible joint 5, so that the tool can be run through the riser and joint into the quick-release coupling even when the riser is not vertical. The tool is run on relatively narow tubing 21 which communicates with an eccentric bore or pipe 22 leading through the tool to an eccentric spigot or stab 23 projecting from the tool bottom and placed to engage the selected access port in the quick-release coupling, depending on the selected position on the tool body of an orientation key 24 which engages the cam 1 3. The tool body can be provided with multiple key locations so that the same tool can be used to couple with any selected access port in the quick release coupling, simply by moving the orientation key.Alternatively single-purpose tools can be provided, one for each access port. The tool is provided with any suitable locking and release gear for example hydraulically releasable locking segments 25.

Although the insertion of the tool may require that the flexible joint 5 be relatively straight, once the tool is in position flexing can occur substantially without restriction, because only the narrow tubing 21 is within the flexible joint 5.

The running tool can be used for example to provide vertical connection to one or other of the flow lines in the valve block, or for access to the well annulus. It can be used for testing or production flow, for wire line operations, or for TFL operations.

Should vertical access to the flow lines not be required, the multiple-orientation tool facility can be omitted. It would be possible to omit entirely the vertical access facility, access being provided only through the flexible flow lines 9.

The illustrated system can also be used for circulation of fluids using the flexible lines 9, whether or not vertical access to the valve block is also provided.

Numerous different running tool designs are possible, for example incorporating a ball and sleeve lock for the running pipe or tubing to enable the lower end of this to be retracted into and extended from the bottom of the tool.

Claims

1. An underwater well head installation for connection of a well head to a riser, comprising a well head connection element for connection to a well head, a flexible joint attached to said connection element and adapted to be connected to the lower end of a riser, and at least one non-rigid flow duct disposed in parallel with said joint and extending between a flow duct of said riser and a flow connection below said joint for providing fluid-flow communication between said well head and said riser.

2. The installation of claim 1 wherein said joint is hollow for providing through communication between said riser and well head.

3. A riser assembly for connection to an underwater well head comprising in combination a riser provided with at least one flow duct and having a lower end, a flexible joint attached to said lower end, a well head coupling assembly attached to said joint whereby said riser can tilt relative to said coupling assembly, said coupling assembly being adapted to engage with a well head, and at least one flexible flow conduit having an upper end connected to a said flow duct and having a lower end mounted on said coupling assembly for connection thereby to said well head.