GB2638973A

GB2638973A - Improved downhole safety valve

Info

Publication number: GB2638973A
Application number: GB2403088.4A
Authority: GB
Inventors: Haavik Kjetil; Skovgaard Kristiansen Steffen; Vinje Lars
Original assignee: Equinor Energy AS
Current assignee: Equinor Energy AS
Priority date: 2024-03-04
Filing date: 2024-03-04
Publication date: 2025-09-10
Also published as: WO2025188192A1; WO2025188192A8; GB202403088D0

Abstract

A method of determining the state of a downhole safety valve (DHSV) (Fig. 1), wherein the valve comprises a sleeve (107), and wherein the sleeve is moveable within a housing (105), the method comprising: operating the valve to change the state of the valve by moving the sleeve; monitoring an optical output of an optical fibre (113), wherein the optical fibre is arranged in the longitudinal direction of the DHSV; detecting an optical signal as a result of a signal generated by the movement of the sleeve during said step of operating. The monitoring system may include a distributed acoustic sensor (DAS) utilising either Rayleigh scattering or Fiber Bragg Grating (FBG) to detect the acoustic signal. The valve may be a sleeve actuated flapper valve, with the actuator being teeth (Fig. 2A; 115), permanent magnets (Fig. 3; 117) engaging a resiliently deformable arm (Fig.2; 116 and Fig. 3; 118 respectively), or grooves (Fig. 4; 404) engaging a ball (Fig. 4; 405) and spring (Fig. 4; 406), with the ball biased against said grooves.

Description

Improved downhole safety valve

Technical field

The invention relates to diagnostics of hydrocarbon producing wells, and in particular to determining the state of a downhole safety valve.

Background

Downhoie safety valves (DHSVs) are valves that can be used to isolate part of a wellbore. A flapper valve is opened by applying hydraulic pressure to one or more pistons in the DHSV, whereby the pistons move a sleeve acting on the valve. The valve closes under the influence of downhoie pressure when the hydraulic pressure is reduced or removed. A fluid column may need to be provided above the valve to equalise the pressure on both sides of the flapper valve before the valve can be opened by the hydraulic pressure. A downwards pressure of fluids entering the well will push the flapper valve open. The flapper valve will isolate the well, unless the flapper is opened by the hydraulic; pressure onto the piston.

The only communication to downstream equipment takes place via a hydraulic pressure communication channel arranged to drive the opening or closing of the DHSV. The state of the valve may not be known, or may be difficult to derive from the hydraulic signal alone. The valve may also suffer malfunction as a result of debris becoming lodged in a part of the valve and thereby partially or completely blocking movement of one of the moving parts. It is challenging to detect such malfunction from the hydraulic pressure alone, while leaks from the well need to be avoided.

Other valves than DHSVs also make use of a sliding sleeve. An example is WO 2016/186519, which uses a sleeve to selectively open fluid ports to a packer.

Statement of invention

According to a first aspect of the invention, there is provided a method of determining the state of a downhole valve, wherein the valve comprises a sleeve, and wherein the sleeve is moveable within a housing, the method comprising: operating the valve to change the state of the valve by moving the sleeve; monitoring an optical output of an optical fibre, wherein the optical fibre is arranged in the longitudinal direction of the DHSV; detecting an optical signal as a result of a signal generated by the movement of the sleeve during said step of operating.

The signal may be an acoustic signal, or a heat signal. The step of operating the valve to change the state of the valve may comprise changing the state from open to closed or from closed to open.

The step of operating the valve may comprise actuating the valve by increasing or decreasing hydraulic pressure in a hydraulic driving fluid to change the state of the valve, wherein the hydraulic pressure drives said sleeve, and wherein the sleeve acts on a flapper valve to open or close the flapper valve.

The optical fibre may comprise a distributed acoustic sensor, DAS.

The acoustic wave may be generated by one or more of: the sleeve of the valve engaging with a shoulder within the valve; a flapper valve of the valve engaging with a valve seat within the valve; and at least one actuator acting on a receptor.

The at least one actuator may comprise one or more teeth and the receptor may comprise a resiliently deformable arm, and the one or more teeth may be arranged to engage with a resiliently deformable arm during movement of a movable part of the valve.

The at least one actuator may comprise one or more permanent magnets, and the receptor may comprise a resiliently deformable arm, or an electronic detector for detecting the one or more permanent magnets, and the electronic detector may be electrically connected to a microphone for generating an acoustic signal.

The at least one actuator may comprise one or more grooves, and the receptor may comprise a ball and spring, wherein the ball is biased against the grooves by the spring.

The method may further comprise calibrating the step of detecting prior to carrying out the steps of the first aspect, wherein calibrating comprises carrying out a known change of state of the valve, detecting a corresponding acoustic signal and storing the acoustic signal together with a reference for the change of state.

The known change of state may be one of: the sleeve of the valve engaging with a shoulder within the valve; a flapper valve of the valve engaging with a valve seat within the valve; and at least one actuator acting on a receptor.

The method may further comprise comparing the stored acoustic signal with the detected acoustic signal, and deriving a state of the valve.

The method may further comprise raising an alert when the stored acoustic signal does not correspond to a measured acoustic signal.

According to a second aspect, there is provided a downhole valve assembly comprising: a downhole valve comprising a sleeve and a housing; an acoustic sensor comprising an optical fibre; wherein the acoustic sensor is arranged along the downhole valve.

The downhole valve assembly may further comprise a hydraulic pressure chamber containing a hydraulic fluid arranged to act on the sleeve; a flapper valve, wherein the sleeve is arranged to open the flapper valve when hydraulic pressure is applied by the hydraulic fluid.

The downhole valve assembly may further comprise one or more actuators arranged on one of the sleeve and the housing, and a receptor for generating an acoustic signal arranged on the other one of the sleeve and the housing.

The one or more actuators may comprise one or more teeth, and the receptor may comprise a resiliently deformable arm, and the one or more teeth and the arm may be arranged to cooperate to generate an acoustic signal when the sleeve moves with respect to the housing.

The one or more actuators may comprise one or more permanent magnets, and the receptor may comprise a resiliently deformable arm, the resiliently deformable arm may comprise a magnetisable material or a permanent magnet to generate an acoustic signal when the sleeve moves with respect to the housing.

The one or more actuators may comprise one or more permanent magnets, and the receptor may comprise a sensor, the sensor may be coupled to an electric signal generator to generate an acoustic signal when the sleeve moves with respect to the housing.

The one or more actuators may comprise one or more grooves arranged on the sleeve, and the receptor may comprise a sliding member, wherein the sliding member is biased onto the sleeve by a resiliently deformable member.

According to a third aspect, there is provided a downhole valve comprising a sleeve, a housing, one or more actuators arranged on one of the sleeve and the housing, and a receptor for generating an acoustic signal arranged on the other one of the sleeve and the housing.

The downhole valve may further comprise: a hydraulic pressure chamber, the hydraulic pressure chamber containing a hydraulic fluid arranged to act on the sleeve, a flapper valve, wherein the sleeve is arranged to open the flapper valve when hydraulic pressure is applied by the hydraulic fluid; The one or more actuators may comprise one or more teeth, and the receptor may comprise a resiliently deformable arm, and the one or more teeth and the arm may be arranged to cooperate to generate an acoustic signal when the sleeve moves with respect to the housing.

The one or more actuators may comprise one or more permanent magnets, and the receptor may comprise a resiliently deformable arm, wherein the resiliently deformable arm comprises a magnetisable material or a permanent magnet to generate an acoustic signal when the sleeve moves with respect to the housing.

The one or more actuators may comprise one or more permanent magnets, and the receptor may comprise a sensor, wherein the sensor is coupled to an electric signal generator to generate an acoustic signal when the sleeve moves with respect to the housing.

Figures Some embodiments of the invention will now be described by way of example only and with reference to the accompanying drawings, in which: Fig. 1 is a perspective view of a cut-open schematic of a downhole safety valve; Fig. 2 is a vertical cross section of a downhole safety valve; Fig. 3 is a close up schematic drawing of an acoustic signal generator; Fig. 4 is a schematic drawing of a different acoustic signal generator in a downhole safety valve; Fig. 5 is a cross section of different arrangements of a downhole safety valve with acoustic signal generators; and Fig. 6 is a flow diagram.

Specific description

Fig. 1 is a schematic illustration of a standard downhole safety valve (DHSV). The DHSV 101 comprises a tubing 102 with threaded ends 103 and 104 for attaching to standard tubing sections respectively below and above the DHSV. A housing 105 is contained within the tubing 102. A flapper valve 106 is received within a valve seat defined by the housing. The flapper valve is illustrated as being closed. A biasing mechanism such as a spring biases the flapper valve to the closed position. A sleeve 107 is contained within the housing and reciprocates in the longitudinal direction of the tubing between a retracted position, as illustrated, and an extended position. In the extended position, the sleeve pushes the flapper valve open. The hollow sleeve defines a bore through which fluids can flow without interruption when the flapper valve is in the open position. The sleeve is biased to a closed position by a helical spring 108. A hydraulic piston 109 acts opposite to the spring 108. The hydraulic piston is driven by hydraulic fluid within a hydraulic chamber 110. The hydraulic fluid is controlled through a control line 111. Hydraulic seals 112 are provided to avoid the hydraulic fluid leaking out of the chamber and control line.

The inventors have appreciated that a fibre optic sensor, in particular a distributed acoustic sensor (DAS) 113, can be used to remotely determine the state of the DHSV. The DAS comprises an optical fibre arranged to carry an optical signal. The optical signal is coupled into the fibre using an optoelectronic device, typically including a laser source. The DAS is arranged alongside the DHSV or within the DHSV, and is configured to detect an acoustic signal emitted by the DHSV. The acoustic signal causes strain on the fiber and modulation of the refractive index, which in turn causes a change in Rayleigh backscattering of the light the propagates through the fibre.

Although Rayleigh backscattering is the dominant contribution, there are also other effects which could be used to detect acoustic signals, such as Brillouin scattering or Raman scattering. A DAS relies on Rayleigh backscattering, but more generally a fibre optic sensor can be used to detect an acoustic signal. A Fiber Bragg Grating (FBG) is another option for a fibre-based detection method. In an FBG, a periodic variation of the refractive index acts like a grating, which reflects a particular spectral portion. An acoustic or heat signal causes a variation in the grating constant, thereby changing the reflected spectrum.

The fibre optical cable 113, acting as a distributed acoustic sensor (DAS) is arranged in the longitudinal direction of the DHSV. Although illustrated for clarity as the cable being parallel but not in direct contact with the DHSV, it is preferable that the cable is in direct contact to improve the transfer of acoustic signals from the tubing 102 to the fibre. The cable may also be arranged through the body of the DHSV, but that option may be less preferable given that the cable channel may cause a leak path.

The DAS is arranged to pick up distinct signals from the DHSV, which can be used to determine remotely the state of the DHSV. The motion of the sleeve is limited on either side by a part of the housing that acts as stops: inwards protruding shoulders 113 and 114. When the sleeve hits either stop, an acoustic signal is generated. The sound of each stop will be slightly different, and provide thereby a unique acoustic signature of the position of the sleeve. Further, the process of the flapper valve 106 landing against the valve seat will also generate a distinct acoustic signal which can be detected by the DAS.

The signatures will depend on the design and materials of a particular DHSV, and a calibration process can be carried out at the surface for the DHSV before installation.

Although a distributed acoustic sensor is illustrated to be used for detecting acoustic signals generated by a DHSV, the skilled person will appreciate that an acoustic sensor can also be used for detecting acoustic signals from other valves, in particular sliding sleeve valves. A DHSV is typically a valve installed on the tubing, and is therefore tubing-retrievable, but the acoustic sensor can also be used for a smaller wireline retrievable valve that includes a sleeve. Another example is the sliding sleeve used in WO 20161186519.

Figure 2 illustrates an embodiment of a DSHV whereby additional features are included for generating an acoustic signal of other stages of the closing process besides the end points of the sleeve hitting the stops and the valve hitting the seat. The additional features are an actuator and a receptor, which interact with each other to generate a sound. A cross section is illustrated, whereby the same (or equivalent) elements as in Fig. 1 are assigned the same reference numbers. The sleeve 102 is illustrated as resting against a shoulder 114 of the housing. The spring 108 is compressed by the hydraulic pressure within the hydraulic chamber 110. A series of teeth 115 extend outwards from the outer wall of the sleeve 107. The teeth engage with a flexible arm 116 attached to an inner wall of the housing when the sleeve changes position. The actuator is the set of teeth, while the receptor is the flexible arm. The arm is resiliently deformable, so that one of the teeth bends the arm when moving past, and so that the arm bounces back again after the tooth has moved past, thereby generating an acoustic signal. The teeth otherwise do not change the working of the DSHV, but only cooperate with the flexible arm to generate an acoustic signal while the sleeve is moving. Fig. 2A shown an enlarged detail of the DSHV with teeth 115 and arm 116.

Multiple embodiments of the teeth and arm system are provided. The teeth may all be of the same shape and size, or may differ in size. The teeth may successively increase in size towards the end of the sleeve, for example. If the teeth increase in size, the signal generated by the arm will also increase because the deformation of the flexible arm will be larger. The distance between the different teeth may be the same, as illustrated, or may vary.

In a different embodiment, a magnetic interaction replaces the mechanical interaction between the teeth and the arm. In a magnetic system, each of the teeth may be replaced by a small permanent magnet. This embodiment is illustrated in Fig. 3. A series of magnets 117 is illustrated, which are the actuators. A resiliently deformable arm 118 is arranged along the longitudinal direction of the sleeve, which is the receptor. The arm may be made of a magnetisable material, in which case the arm may be attracted by each magnet. The arm will be bent towards the magnets, and may impact on a rigid receiving member 119 to generate an acoustic signal. Alternatively, or in addition, a rigid receiving member 120 may be arranged away from the magnets and the resiliently deformable arm 118 may comprise a permanent magnetic material that is repelled by the permanent magnets 117 when they travel past. The arm 118 will then impact on member 120 when the magnets travel past. As set out in relation to teeth 115, each of the magnets could have the same or different size and strength. A mixture of teeth and magnets may also be provided.

The receptor may be a battery powered detector arranged to detect the magnetic actuators when they move past the receptor. The detector is coupled to an acoustic signal generator arranged to generate a signal for the DAS to detect.

In an alternative embodiment, the receptor is arranged to generate a heat signal. For example, an infrared signal may be emitted, or a chemical reaction may generate heat. A chemical reaction could be generated by bursting a capsule with a reagent, although that would be a single use embodiment. A fibre optical sensor is sensitive to heat changes, because the heat will locally change the refractive index and thereby the optical return signal. If a heat signal is used, the separation between the fibre optical sensor and the heat source is preferably minimised. A large separation between emitter and sensor or a thick portion of metal from the housing between emitter and sensor will dissipate the heat signal and decrease the signal to noise ratio.

The position of the teeth, or magnets, and the arm within the DSHV can also be varied, as long as the teeth (or magnets) are on one of the static or moving part, and the arm is on the other one of the static or moving part.

The actuator and receptor are described in connection with a DHSV, but the inventors have realised that they can also be provided on other sliding sleeve valves. For example, the actuators and receptor can be used on the device of W02016/186519. A channel may be arranged on the housing of the sleeve in the direction of the main longitudinal axis. The channel provides the space for arranging the actuators and receptor. The DAS is preferably arranged alongside the valve, or can be embedded within the using of the device.

A further embodiment is illustrated in Fig. 4. The housing 105, flapper 106 and sleeve 107 are arranged as discussed in connection with the previous embodiments. The actuators are a set of grooves 404 cut into the sleeve. The receptor comprises a sliding member, which is biased onto the sleeve by a resiliently deformable member, such as a spring. The sliding member may be a ball 405 that is pushed by a spring 406 onto the sleeve with the grooves. The spring rests on a base 407. The ball 405, spring 406 and base 407 are received within a cavity 408 in the housing. When the sleeves moves within the housing, the ball will generate an acoustic signal each time a groove passes the ball. Each of the grooves passes the ball when the sleeve moves over the full length. The grooves may be arranged closer together if the stroke length is shorter. The acoustic signal is detected by a DAS arranged against the housing or outside the housing.

As an optional further feature of the embodiment illustrated in Fig. 4, a battery powered microphone 409 is connected to the base 407 via a wire 410. The base includes a battery powered sensor arranged to sense the movement of the ball and spring, and emits a signal to the microphone 409 to generate a signal. A similar microphone arrangement may be provided in the embodiments discussed before.

As an alternative embodiment, magnetic bands are provided instead of grooves 404, similar to the Fig. 3 embodiment. An electronic detector, signal processor and microphone are arranged in the cavity 408 detect the magnetic bands when they pass the cavity during movement of the sleeve. The signal processor sends a signal to the microphone to generate an audible signal for the DAS.

As discussed previously, each band or groove can have a unique shape such that a corresponding unique signal is generated, and the position of the sleeve is known in real time. Alternatively, the grooves can be the same as illustrated.

During typical use of a conventional DHSV, the sleeve moves relatively fast when hydraulic pressure is applied or released compared to the sample speed of the DAS. In order to improve the signal quality, the hydraulic pressure can be slowed down during opening or closing of the DHSV.

Fig. 5 illustrates the same principle as illustrated in the previous embodiments, but with a slightly different layout of the DHSV and a different location of the actuator and receptor for generating the acoustic signal. A sleeve 501 reciprocates within a housing 502, between a first shoulder 503 and a second shoulder 504. A piston 505 driven by hydraulic fluid within a hydraulic chamber 506 pushes the sleeve downwards to open a valve 507. A spring 508 pushes the sleeve upwards.

Fig. 5A illustrates actuators 509 arranged on the housing and receptor 510 arranged on the sleeve 510. The actuators may be any of the previously discussed examples: mechanical teeth and arm, magnets and an arm, magnets and an electronic detector, a set of grooves and a ball and spring or any combination thereof.

Fig. 5B illustrates actuators 509 arranged on the sleeve, while the receptor 510 is arranged on the housing. As yet a further variation, a single actuator may be provided which is arranged to act on a plurality of receptors. Each of the plurality of receptors may have a unique design to generate a corresponding unique acoustic signal.

Figs. 5A and 5B illustrate the DHSV in the closed position, while Fig. 5C illustrates the DHSV in the open position.

The method of determining the state of a DHSV can be summarised by the following steps, illustrated in Fig. 6: S1, actuating a downhole safety valve, S2, monitoring output of an optical cable, and S3 detecting an optical signal as a result of the step of actuating.

The illustrated embodiments enable a user to monitor the acoustic signal by way of the DAS, and thereby monitor the state of the valve. The detected signal can further be correlated with the applied hydraulic pressure. If a particular hydraulic pressure is applied, but a deviation of the acoustic signal is detected when compared to an expected acoustic, then it could be an indication of malfunctioning of the DHSV. For example, debris can be present between the sleeve and the housing, which causes friction and a diminished response to hydraulic pressure.

Although the invention has been described in terms of preferred embodiments as set forth above, it should be understood that these embodiments are illustrative only and that the claims are not limited to those embodiments. Those skilled in the art will be able to make modifications and alternatives in view of the disclosure which are contemplated as falling within the scope of the appended claims. Each feature disclosed or illustrated in the present specification may be incorporated in the invention, whether alone or in any appropriate combination with any other feature disclosed or illustrated herein.

Claims

CLAIMS: 1. A method of determining the state of a downhole valve, wherein the valve comprises a sleeve, and wherein the sleeve is moveable within a housing, the method comprising: operating the valve to change the state of the valve by moving the sleeve; monitoring an optical output of an optical fibre, wherein the optical fibre is arranged in the longitudinal direction of the downhole valve; detecting an optical signal as a result of a signal generated by the movement of the sleeve during said step of operating; wherein the signal is an acoustic signal, or a heat signal generated by one or more actuators acting on a receptor, wherein the one or more actuators are arranged on one of the sleeve and the housing and wherein the receptor is arranged on the other one of the sleeve and the housing.LU
2. The method of claim 1, wherein said step of operating the valve to change the Ostate of the valve comprises changing the state from open to closed or from closed to open.
3. The method of any one of claims 1 to 2, wherein said step of operating the valve comprises actuating the valve by increasing or decreasing hydraulic pressure in a hydraulic driving fluid to change the state of the valve, wherein the hydraulic pressure drives said sleeve, and wherein the sleeve acts on a flapper valve to open or close the flapper valve.
4. The method of any one of the preceding claims, wherein the optical fibre comprises a distributed acoustic sensor, DAS.
5. The method of claim 1, wherein the at least one actuator comprises one or more teeth and wherein the receptor comprises a resiliently deformable arm, and wherein the one or more teeth are arranged to engage with a resiliently deformable arm during movement of a movable part of the valve.
6. The method of claim 1, wherein the at least one actuator comprises one or more permanent magnets, and wherein the receptor comprises a resiliently deformable arm, or an electronic detector for detecting the one or more permanent magnets, and wherein the electronic detector is electrically connected to a microphone for generating an acoustic signal.
7. The method of claim 1, wherein the at least one actuator comprises one or more grooves, and wherein the receptor comprises a ball and spring, wherein the ball is biased against the grooves by the spring.
8. The method of any one of claims 1 to 7, further comprising calibrating the step of detecting prior to carrying out the steps of claim 1, wherein calibrating comprises carrying out a known change of state of the valve, detecting a corresponding acoustic signal and storing the acoustic signal together with a reference for the change of state, wherein the known change of state may be one of: the sleeve of the valve engaging with a shoulder LO within the valve; a flapper valve of the valve engaging with a valve seat within the valve; and at least one actuator acting on a receptor.
9. The method of claim 8, comprising comparing the stored acoustic signal with the detected acoustic signal, and deriving a state of the valve.
10. The method of claim 9, further comprising raising an alert when the stored acoustic signal does not correspond to a measured acoustic signal.
11. A downhole valve assembly comprising: a downhole valve comprising a sleeve and a housing; one or more actuators arranged on one of the sleeve and the housing, and a receptor for generating an acoustic signal or a heat signal when acted on by the one or more actuators, wherein the receptor is arranged on the other one of the sleeve and the housing an acoustic sensor comprising an optical fibre; wherein the acoustic sensor is arranged along the downhole valve.
12. The downhole valve assembly according to claim 11, further comprising a hydraulic pressure chamber containing a hydraulic fluid arranged to act on the sleeve; a flapper valve, wherein the sleeve is arranged to open the flapper valve when hydraulic pressure is applied by the hydraulic fluid.
13. The downhole valve assembly according to claim 11, wherein the one or more actuators comprise one or more teeth, and wherein the receptor comprises a resiliently deformable arm, and wherein the one or more teeth and the arm are arranged to cooperate to generate an acoustic signal when the sleeve moves with respect to the housing.
14. The downhole valve assembly according to claim 11, wherein the one or more actuators comprise one or more permanent magnets, and wherein the receptor comprises a resiliently deformable arm, wherein the resiliently deformable arm comprises a magnetisable material or a permanent magnet to generate an acoustic signal when the sleeve moves with respect to the housing.
15. The downhole valve assembly according to claim 11, wherein the one or more actuators comprise one or more permanent magnets, and wherein the receptor Ocomprises a sensor, wherein the sensor is coupled to an electric signal generator to generate an acoustic signal when the sleeve moves with respect to the housing.
16. The downhole valve assembly according to claim 11, wherein the one or more actuators comprise one or more grooves arranged on the sleeve, and wherein the receptor comprises a sliding member, wherein the sliding member is biased onto the sleeve by a resiliently deformable member.
17. A downhole valve comprising: a sleeve; a housing; one or more actuators arranged on one of the sleeve and the housing, and a receptor arranged to generate an acoustic signal or a heat signal when acted on by the one or more actuators, wherein the receptor is arranged on the other one of the sleeve and the housing.
18. The downhole valve according to claim 17, further comprising: a hydraulic pressure chamber, the hydraulic pressure chamber containing a hydraulic fluid arranged to act on the sleeve, a flapper valve, wherein the sleeve is arranged to open the flapper valve when hydraulic pressure is applied by the hydraulic fluid;
19. The downhole assembly according to claim 17 or 18, wherein the one or more actuators comprise one or more teeth, and wherein the receptor comprises a resiliently deformable arm, and wherein the one or more teeth and the arm are arranged to cooperate to generate an acoustic signal when the sleeve moves with respect to the housing.
20. The downhole assembly according to claim 17 or 18, wherein the one or more actuators comprise one or more permanent magnets, and wherein the receptor comprises a resiliently deformable arm, wherein the resiliently deformable arm comprises a magnetisable material or a permanent magnet to generate an acoustic signal when the sleeve moves with respect to the housing.
21. The downhole assembly according to claim 17 or 18, wherein the one or more actuators comprise one or more permanent magnets, and wherein the receptor Ocomprises a sensor, wherein the sensor is coupled to an electric signal generator to generate an acoustic signal when the sleeve moves with respect to the housing.
22. The downhole assembly according to claim 17 or 18, wherein the one or more actuators comprise one or more grooves arranged on the sleeve, and wherein the receptor comprises a sliding member, wherein the sliding member is biased onto the sleeve by a resiliently deformable member.