The present invention relates to a downhole tool. In particular, but not exclusively, the invention relates to an annular valve or sliding sleeve assembly for a tool used in oil and water/gas well applications.

Sliding sleeves are known in the industry. A typical sleeve is described by patent GB2247481 (Well Tool with Sealing Means). In certain well bores, where the environment is particularly hostile, due to temperature or chemical attack, sliding sleeves with conventional elastomeric or plastic seals are not suitable. In certain oilfield locations, conventional downhole tools such as sliding sleeves cannot be used due to the very high temperatures used in, for example, steam assisted gravity drainage (SAGD). The inability of conventional downhole tools to perform in this environment is causing concern to the safety authorities, so there is now a commercial requirement to extend the performance of down hole tools into these environments.

Furthermore, the sliding sleeve may include a piston or pistons, so that it may by operated remotely by hydraulic lines, through which fluid is pumped. The pumped fluid acts on the piston or pistons imparting a motive force to components in the tool, which then open, close or operate a choke to control oil or gas flow in the well bore.

It is desirable that a sliding sleeve can operate in severe environments, such as using a flexible metal seal as described in PCT WO2005/022012. In sliding sleeves it is known to position seals on either side of a port or ports of an outer housing. An internal axially sliding member also has a port or ports, which in a first position align with the ports on the outer housing, between the two seals. In this first position, the sliding sleeve is open. In a second position the ports in the member are on the opposite side of one of the seals. In this second position, the sliding sleeve is closed. The sliding sleeve is placed within the well tubing string. When open, the sliding sleeve allows fluids or gas to pass between the annular space formed by the borehole or well casing and the outside of the sliding sleeve and the bore of the well tubing string, normally termed the production string.

The internal axially sliding member may be moved mechanically, via a shifting tool, which is placed in the well bore for the purpose of operating the sliding sleeve. Alternatively, a hydraulic piston integral to the sliding sleeve itself may move the internal axially siding member.

In one embodiment, the invention uses the flexible metal seal and hence allows the sliding sleeve to operate in severe environments.

A common problem with metal seal devices is that they can only operate in static applications, i.e. the sealing surfaces cannot easily move in relation to the seal. With a sliding sleeve, it is essential that one of the sealing surfaces move, when manipulating the tool. According to an aspect of the present invention there is provided a downhole tool comprising: a tool body defining a longitudinal bore and having one or more transverse ports extending from the bore to the outer surface of the tool body; a movable sleeve member which is movable relative to the tool body between a first position in which the or each transverse port is open and a second position in which the or each transverse port is closed; and at least one sealing member adapted to sealingly close the or each transverse port, wherein the or each sealing member is adapted to be disengaged from a surface of the tool body when the sleeve member is at the first position and to be engaged with a surface of the tool body when the sleeve member is at the second position.

Preferably the sealing member comprises a flexible seal, such as a flexible metal seal. Preferably the sealing member is disengaged from the tool surface while the tool is operated. Preferably the sealing member is engaged with the tool surface only when the sleeve member is substantially at the end of its travel to the second position.

Preferably the sealing member is deformable, most preferably in a controlled manner. Preferably the sealing member is adapted to deform and thus engage with the tool surface when the sleeve member is at the second position. Preferably the sleeve member includes an abutting member which acts upon the sealing member to deform the sealing member. Preferably the movable sleeve member is axially movable. Aternatively the movable sleeve member may be rotationally movable.

Preferably either the downhole tool includes adjustment means to allow manufacturing tolerances to be accommodated when the sealing member is engaged.

Preferably the downhole tool includes a locking mechanism adapted to activate the sealing member. Alternatively or in addition, the locking mechanism may be adapted to retain the sleeve member in the closed position.

Particular embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 shows a first embodiment of a downhole tool with the sliding sleeve in the open position, and with the seals disengaged.

Figure 2 shows the tool of Figure 1 with the sliding sleeve in the closed position, and with the seals and locking mechanism disengaged.

Figure 3 shows the tool of Figure 1 with the sliding sleeve in the closed position, and with the seals and locking mechanism engaged.

Figure 4 shows a metal-to -metal seal used in the tool of Figure 1. Figure 5 shows a detail of sleeve 6 of the tool of Figure 1 and a further detail of sleeve 6 fitted inside housing 15, with locking keys 7 shown in the expanded position, 7B.

Figure 6 shows a second embodiment of a downhole tool and including a sliding sleeve with an integral hydraulic piston, used to operate the tool via two hydraulic lines.

In figure 1, a downhole body has a tool body which comprises a first housing 1 threaded to second housing 2 by thread 16. The tool body includes transverse ports, which when aligned with ports on mandrel 9, allow fluid or gas to pass from the inner to the outer annular space, or vice versa. Housing 2 is threaded to lower housing 3 by thread 16. The extremities of housings 1 and 3 are in turn connected to the well tubing string. Upper seal 4A and lower seal 4B are uncompressed, meaning that the outer surface of mandrel 9 is free to move inside the inner surfaces 18 of seals 4 A and 4B.

A key or keys 7 are held within a housing 5, with a movable sleeve member or expander sleeve 6 A, aligned so groove 14 in the said expander sleeve is aligned with the keys 7A. The expander sleeve is held in the position as shown in figure one, by means of collet fingers 13, which align with a location groove 12A on the sleeve 5 A, allowing the keys to be in collapsed state. Sleeve 5 is threaded to mandrel 9 by adjustable thread 15. Seal 4A is restrained between stop ring 8 and a shoulder on the ported sub 2. Shoulder 17 and the major diameter of end stop 10 are not engaged with the seals 4 A and 4B. The tool is operated using industry standard downhole shifting tools, such as an Otis BO shifting tool, interacting with the internal grooves on the expander sleeve 6. Other such tools are known.

As shown in figure 2, the shifting tool engages with the upper groove in the expander sleeve 6 A, which is mechanically linked to the key housing 5 B by keys 7 A, which cannot expand until they meet groove 11 in housing 1. By moving the assembly, the ports on mandrel 9 are now positioned on the other side of the seal 4 A, with shoulder 17 abutting seal 4 A and shoulder on stop ring 10 abutting seal 4B. Thread 15 allows the relative position between shoulder 17, the key window on key housing 5B and groove 11 to be adjusted to suit manufacturing tolerances. The end stop 10 is further adjustable in relation to the said position to align the major diameter on the stop ring 10 with seal 4B to suit manufacturing tolerances.

As shown in figure 3, further movement of the expander sleeve 6B expands the keys 7B into groove 11. This in turn causes shoulder 17 to compress seal 4C and stop ring 10 to compress seal 4D. The expander sleeve 6B now supports the keys 7B and is held in place by collet fingers 13 aligning with groove 12B.

With reference to figures 3 and 4, the seal 4 is compressed between faces 20 and 21. The seal deforms in a controlled manner, such that face 19 forms a seal against the respective face on housing 1 and lower housing 3. Seal face 18 forms a seal against the surface of mandrel 9. With the seal 4C and 4D sealing on mandrel 9, gas or fluid is prevented from passing from the inner to the outer annular space, or vice versa.

Figure 6 shows a second embodiment, operated via two hydraulic lines 22 and 23. Housing IA is connected to piston housing 29 and with expander sleeve 6C forms two chambers 24 and 25 bounded by dynamic seals 26, 27 and 28. Application of hydraulic pressure via port 22 acts between seals 26 and 27, causing expander sleeve 6C to move down, releasing keys 7. Application of hydraulic pressure via port 23 acts between seals 27 and 28, causing expander sleeve 6C to move upwards, engaging keys 7.