Downhole optical fibre connection system

Abstract

Described is an optical fibre cable connection system. The system comprises a first connection part comprising a housing defining an internal space and an opening into the internal space, a first optical fibre cable having a termination end located within the internal space adjacent to said opening, a first sealing plate attached to the housing and sealing said opening whilst defining a first channel extending partially through the first sealing plate and being in alignment with said opening and a second channel extending completely through the first sealing plate and being spaced laterally apart from the first channel, a second sealing plate attached to the housing and spaced apart from the internal space by the first sealing plate, wherein the first sealing plate is movable laterally with respect to the second sealing plate and the housing, and a translation mechanism for causing lateral movement of the first sealing plate. The system further comprises a second connection part comprising a second optical fibre cable, and a shearable end cap fixed to a termination end of the second optical fibre cable and configured to puncture the second sealing plate for insertion into said first channel.

Description

[0001] DOWNHOLE OPTICAL FIBRE CONNECTION SYSTEM

[0002] FIELD

[0003] The present disclosure relates to systems for forming an optical connection, specifically an optical connection in a wellbore, and associated methods.

[0004] BACKGROUND

[0005] Optical fibres are commonly used within subsea / subterranean wellbores for monitoring and control functions, as they can transmit light over long distances with minimal signal loss. Transmission over optical fibres is also less susceptible to noise and other interference as compared for example with electrical transmission systems.

[0006] An optical fibre may be disposed within a wellbore with a production completion in order to transmit light to and from the surface, to help monitor wellbore conditions in order to optimise production, to ensure the well is in a safe working state; or detect other events in the well or its surroundings. As optical fibres may be in optical communication with sensors downhole, such fibres may provide a fast and reliable means for transmitting the data gathered by sensors to the surface, or other parts of the wellbore.

[0007] Optical fibres may also be used in the control of equipment downhole, such as for adjusting valves, controlling flow rates or manipulating various other tools within the wellbore. As optical fibres allow for precise and reliable optical communication, fibre optics may be the preferred means of transmitting control signals downhole.

[0008] Additionally, optical fibres themselves can be used as a distributed type sensor, detecting events or changes in downhole conditions; like pressure, temperature, flow and strain.

[0009] Traditionally, optical fibres cables used within wellbores are installed on an outer surface of a production completion. A production completion is typically installed in multiple stages, with a length of fibre optic cable installed on the outer surface of each completion section. Therefore, connection of each length of fibre optic cable to form a continuous optical communication path must be performed downhole. This is typically done in one of two ways. The first way is to allow for optical reading when landing a new completion section on the previously installed section. Such a method may take many attempts to form the connection between the optical fibres, given the small size of the optical fibre connectors, and how precisely the completion sections have to be aligned with one and other for the connection to be established. Therefore, multiple attempts may be required to establish connection of the optical fibre cables. The second way is to form the connection once a new completion section has landed on the previously installed section. In this method the connection is formed using a component of the completion assembly, such as packer, wherein setting the packer aligns and connects adjacent fibre optic cable lengths.

[0010] Given that these connections may need to be performed in liquid filled (e.g. water, oil, mud filled, etc.) environments (termed as ‘wetmate’ connections, for connections that can be made and broken in wet underwater conditions without compromising the integrity of the optical signals), and that a wellbore may be a high temperature / high pressure environment, further levels of complexity exist when forming reliable optical fibre connections within a wellbore. Therefore, known connection methods have typically proven to be unreliable.

[0011] SUMMARY

[0012] According to a first aspect of the present invention, there is an optical fibre cable connection system. The optical fibre connection system comprises; a first connection part comprising a housing defining an internal space and an opening into the internal space, a first optical fibre cable having a termination end located within the internal space adjacent to said opening, a first sealing plate attached to the housing and sealing said opening whilst defining a first channel extending partially through the first sealing plate and being in alignment with said opening and a second channel extending completely through the first sealing plate and being spaced laterally apart from the first channel, a second sealing plate attached to the housing and spaced apart from the internal space by the first sealing plate, wherein the first sealing plate is movable laterally with respect to the second sealing plate and the housing, and a translation mechanism for causing lateral movement of the first sealing plate; and a second connection part comprising; a second optical fibre cable, and a shearable end cap fixed to a termination end of the second optical fibre cable and configured to puncture the second sealing plate for insertion into said first channel. This optical fibre cable connection system may allow for precise and reliable optical fibre cable connections to be made with a single connection attempt. For example, such a connection system may be used in connecting two lengths of optical fibre cable downhole (e.g. in a wellbore). The second connection part may be installed on a completion section (such as a production tubular) disposed in the wellbore. The first connection part may be disposed on a further completion section (such as a further production tubular), to be connected to the completion section already disposed within the wellbore. After both lengths of tubular have been connected, the connection system may connect the first and second lengths of optical fibre cable. Therefore, the present optical fibre connection system may not require lengths of optical fibre cable to be connected at the same time as the production tubulars are connected. Further, connection of lengths of fibre optic cable using this system may be initiated only when the operator of the system is sure that the connection parts are correctly aligned; ensuring a reliable connection can be formed on the first connection attempt.

[0013] Provision of the first and second sealing plates seals the interior of the housing from the external environment, thus protecting the first length of optical fibre cable and its termination end from ingress of fluid or particulates. The sealing plates also help to maintain the interior of the housing at a balanced pressure level (while also preventing the interior of the housing being contaminated with the fluid of the external environment). Ingress of fluids or particulates may be damaging to the fibre optic cable and / or its termination end, or may prevent a reliable optical fibre connection being formed with the second length of optical cable.

[0014] Two sealing plates offer a robust debris barrier for the housing. For example, in the event that the integrity of one of the sealing plates is compromised, an additional sealing plate is provided to ensure the interior of the housing remains isolated from the external environment.

[0015] Additionally, the second sealing plate may be configured to seal against an outer surface of the second connection part during connection of the first and second optical fibre cables (e.g. after the second connection part has penetrated / punctured the second sealing plate). This may help to maintain the robust debris barrier for the housing, wherein the interior of the housing is still isolated from the external environment in the event that the integrity of the first sealing plate is compromised. The second sealing plate may be formed of Teflon. Teflon may be an advantageous material to use for the second sealing plate given its high heat resistance and chemical inertness. Teflon also exhibits low friction, which may assist lateral movement of the first sealing plate. Teflon is also highly durable, which may help to prevent damage and ensure the integrity of the second sealing plate in a downhole / wellbore environment.

[0016] The optical fibre connection system may further comprise a third sealing plate connected to the housing and spaced apart from the internal space by the first and second sealing plates. The third sealing plate may comprise a channel extending through the third sealing plate. The third sealing plate may help to protect the first and second plates. For example, if the optical fibre connection system is used with a completion system (as described above), and the first connection part is disposed on an outer surface of a production tubular, the third sealing plate may serve to protect the first and second sealing plates as the production tubular is disposed / transported in the wellbore. The channel extending through the third sealing plate may help to align the second connection part with the first, further helping a reliable connection between the first and second lengths of optical fibre cable be formed at the first attempt. The third sealing plate may be formed of any suitable material within the understanding of one skilled in the art, for example, steel.

[0017] The translation mechanism may comprise a profiled surface of the first sealing plate. Lateral movement of the first sealing plate may be induced when a force substantially perpendicular to the first sealing plate applied to the profiled surface. The profiled surface may be of any suitable configuration within the understanding of one skilled in the art that may induce lateral movement in the first sealing plate when a force substantially perpendicular to the first sealing plate is applied to the profiled surface. Therefore, when the optical fibre connection system is deployed in a wellbore, this may allow for a light intervention tool to be used to induce lateral movement of the first sealing plate.

[0018] The translation mechanism may further comprise an actuator, wherein the actuator is configured to act upon the profiled surface of the first sealing plate to laterally move the first sealing plate relative to the housing and second sealing plate. The actuator may be controlled by pressure. The actuator may be a hydraulic actuator. The actuator may be an electrical actuator. The actuator may be initiated or controlled by an operator; for example, when the connection system is disposed in a wellbore, the actuator may be controlled by personnel at surface.

[0019] An interior surface of the housing may comprise a slot, configured to axially align the first optical fibre cable with the housing. The inclusion of a slot may help to ensure that first length of optical fibre cable remains correctly aligned with the housing, further helping the first and second lengths of optical fibre cable be connected at the first attempt.

[0020] The second part may further comprise a tubular housing, housing the second length of fibre optic cable. The shearable end cap may be connected to the tubular housing of the second part. The shearable end cap may seal the interior of the tubular housing from the external environment. Sealing the interior of the tubular housing of the second part from the external environment may be advantageous for the same reasons as sealing the housing of the first part from the external environment.

[0021] The shearable cap may define a pointed surface, the pointed surface being configured to penetrate the second sealing plate. This may assist with puncturing the second sealing plate effectively.

[0022] The tubular housing of the second part may comprise a steel tube.

[0023] At least one of the first and second optical fibre cables may comprise at least one optical fibre disposed within a sheath, as is understood by one skilled in the art.

[0024] The optical fibre connection system may further comprise a pressure balance arrangement. The pressure balance arrangement may be in pressure communication with the interior of the sheath of at least one of the first and second optical fibre cables, configured to balance the pressure of the interior of the sheath of each cable an external environment pressure.

[0025] The interior of the sheath of each optical fibre cable may be liquid filled. The interior of each sheath may be filled with a liquid configured to protect the optical fibres disposed therein from damage. Any suitable liquid within the understanding of one skilled in the art may be used, for example, a liquid crystal polymer (LCP) due to its ability to withstand high temperatures and pressures, or a silicone gel or oil, due their ability to protect the fibre optic cable from moisture, chemicals or other contaminants, and high

[0026] The termination end of each of the first and second optical fibre cables may comprise a ferrule. The at least one of the ferrule of the first and second termination ends may be spring biased. As at least one of ferrules is spring biased, this will ensure that the termination ends of the first and second optical fibres are constantly urged into, and remain in contact, ensuring a reliable fibre optic cable connection.

[0027] A ferrule of one of the first and second optical fibre cables may comprise an alignment sleeve. Therefore, the other ferrule (i.e. the ferrule of either the first or second optical fibre cable that does not comprise the alignment sleeve) can be received within the alignment sleeve during connection of the first and second cables. Again, this helps to ensure a reliable connection of the first and second optical fibre cables, at a first attempt.

[0028] The connection system may comprise a plurality of first connection parts, and an equal number of corresponding second connection parts. Therefore, the connection system may allow for multiple connections between lengths optical fibre cable to be formed (between a first connection part and its corresponding second connection part). The translation mechanism of the plurality of first connection parts may be provided a common translation mechanism.

[0029] According to a second aspect of the present invention, there is a method of connecting first and second optical fibre cables using the optical fibre connection system as defined above. The method comprises: causing the shearable end cap to puncture the second sealing plate and enter the first channel; operating the translation mechanism to translate the first plate laterally, thereby shearing the end cap from the termination end of the second optical fibre cable and bringing the second channel into axial alignment with the now exposed termination end of the second optical fibre cable; translating the end termination of the second optical axially through the second channel and into optical communication with the termination end of the first optical fibre cable.

[0030] The method may further comprise puncturing the second plate seal by axially moving the second connection part towards the second sealing plate.

[0031] The method may further comprise, prior to penetrating the second sealing plate of the first connection part, balancing the pressure within the optical fibre cable of the first part with the pressure of the external environment.

[0032] The method may further comprise, prior to shearing the end cap from the termination end of the second optical fibre cable, balancing the pressure within the optical fibre cable of the second part with the pressure of the external environment.

[0033] It will be appreciated any of the features defined with respect to the first aspect of the disclosure may be used in combination with the second aspect of the disclosure, and vice versa.

[0034] BRIEF DESCRIPTION OF THE FIGURES

[0035] Embodiments of the present invention will now be described with reference to the accompanying drawings, in which:

[0036] Figures 1A and 1B show an embodiment of an optical fibre connection system, and a plan view of the connection system arranged with respect to a tubular;

[0037] Figures 1C and 1 D show an alternative embodiment of the optical fibre connection system, and a plan view of the connection system arranged with respect to a tubular; Figure 2 shows a further embodiment of the optical fibre connection system;

[0038] Figure 3 shows a pressure balance arrangement that may be used with the optical fibre connection system of Figure 1A;

[0039] Figures 4A and 4B show an example of optical fibre connectors which may be used with the optical fibre connection system of Figure 1A; and

[0040] Figures 5A to 5D show the steps of connecting two lengths of optical fibre using the connection system of Figure 1A. DETAILED DESCRIPTION

[0041] Figure 1A shows an embodiment of the optical fibre connection system 10. In this embodiment, the optical fibre connection system 10 is being used with a wellbore production system, wherein the system is disposed on the outer circumference of a production tubular 12, 14.

[0042] A first connection part 20 of the system 10 comprises a housing 22, defining an internal space and an opening 13 into the internal space. Disposed within the internal space of the housing 22 is first length of optical fibre cable 24, comprising a termination end 26. As understood by one skilled in the art, the optical fibre cable 24 may comprise an outer sheath formed of any suitable material, with one or more optical fibres disposed therein. Although not shown in Figure 1A, the housing 22 may define a slot or a groove on one of its inner surfaces; wherein the first length of optical fibre cable 24 and / or the termination end 26 is at least partially disposed within the slot or groove. This may help to axially align the first length of optical fibre cable 24 and / or termination end with the housing 22, and ensure the cable 24 and / or the termination end 26 are held in place for connection with a second length of fibre optic cable 32; thereby ensuring connection between the two can be made on the first attempt.

[0043] The first part further comprises a first 23 and second 25 sealing plate. This example also includes a third sealing plate 27, but this is not always required. The first sealing plate 23 is attached to the housing 22, and provides a barrier between the internal space of the housing 22 from the external environment, preventing the ingress of debris / particulates / fluids from the wellbore.

[0044] The first sealing plate comprises a first channel 21 which extends partially through the first sealing plate 23. Prior to connecting the first 24 and second 32 lengths of optical fibre cable, the first channel 21 is in alignment with the opening 13 of the housing. The first channel 21 may partially extend as far through the first sealing plate 23 as required, whilst still ensuring the first sealing plate 23 provides a barrier to the entry of debris / fluids / particulates from the external environment when the first channel 23 is in alignment with the opening 13.

[0045] The first sealing plate 23 may be a rigid plate, formed of any suitable material which can provide the necessary sealing and structural requirements. The first sealing plate also defines a second channel 28, the second channel extending completely through the second sealing plate. The function of second channel 28 will be described in greater detail below. When the second channel 28 is aligned with the opening 13 of the housing 22, entry may be permitted into the housing 22 via the opening.

[0046] As will be further described in the example of Figure 2, the first sealing plate 23 also comprises a translation mechanism, providing a means for lateral movement of the first sealing plate 23. Lateral movement of the first sealing plate 23 may be with respect to the opening 13 of the housing 22 of the first connection part 20 and the second sealing plate 25. The translation mechanism may be any suitable mechanism that can provide lateral movement of the first sealing plate 23. For example, the translation mechanism may comprise a profiled surface wherein, when a force substantially perpendicular to the first sealing plate 23 is applied to the profiled surface, lateral movement of the first sealing plate 23 is induced. Alternatively, the translation mechanism may be a mechanism that applies a substantially radial force to the first sealing layer 23, laterally moving the second sealing layer 23.

[0047] The second sealing plate 25 is also attached to the housing 22, and spaced apart from the housing 22 by the first sealing plate 23. The second sealing plate 25 may be a rigid plate. Alternatively, the second sealing plate 25 may be formed of a flexible material. During connection between the first 20 and second 30 parts of the connection system 10, the second sealing plate 25 must be punctured. Therefore, the second sealing plate 25 must be formed of a suitable material, and comprise any suitable dimensions, to allow it to be punctured by the second connection part 30. The second sealing plate 25 may also assist lateral movement of the first sealing plate 23 by being formed of a material that helps to reduce friction between the first 23 and second 25 sealing plates.

[0048] For example, the second sealing plate 25 may be formed of Teflon, which may be advantageous for the reasons outlined above.

[0049] The second sealing plate 25 may comprise a material that is configured to seal around the second connection part 30 when the second sealing plate 25 is punctured. Therefore, even when the second sealing layer 25 is punctured, it may still function as a barrier (for example, helping to prevent the ingress of debris / particulates / wellbore fluid into the interior of the housing 22).

[0050] In the example of Figure 1A, the first connection part also comprises a third sealing plate 29. The third sealing plate 27 is attached to the housing 22, and spaced apart from the housing by the first 23 and second 25 plates. The third sealing plate 27 also comprises a channel 29 extending therethrough. The channel 29 of the third sealing plate 27 is aligned with the channel 21 extending partially through the first sealing plate 23 and the opening 13 of the housing 22 when it is assembled to the first connection part 20. This may allow the second connection part 30 to extend through the third sealing plate 27 during connection with the first connection part 20.

[0051] The third sealing plate 27 may serve to protect the first 23 and second 25 sealing layers of the first connection part 20. For example, as this connection system 10 may be used within a wellbore, the connection system 10 may be susceptible to damage when being transported downhole. Damage to the first 23 and second 25 sealing plates may result in the first connection part 20 function incorrectly, preventing a fibre optic cable connection from being established in the wellbore. Therefore, the third sealing plate 27 may provide protection of the first 23 and second 25 sealing plates, ensuring connection system can function as intended in the wellbore. The third sealing plate 27 may be formed of any suitable material that can protect the first 23 and second 25 sealing layers from damage, such as steel.

[0052] It will be appreciated that the third sealing plate 27 is not required in every implementation of the invention.

[0053] Also shown within Figure 1A is the second connection part 30 of the optical fibre connection system 10. In this example, the second connection part 30 is disposed on the external circumference of production tubular 14 for use in a wellbore.

[0054] The second connection part 30 comprises a second optical fibre cable (which in this example is disposed within a tubular housing 32), and a shearable end cap 32 fixed to a termination end of the second optical fibre cable (and in this instance fixed to the tubular housing 32). The shearable end cap 34 is shearable via a weak point 36 formed between termination end of the optical fibre cable and the cap 34. Again, one skilled in the art that the second optical fibre cable will comprise a sheath, and at least one optical fibre disposed within the sheath.

[0055] The tubular housing 32 of the second connection part 30 may be formed of steel. This may help the second sealing layer 25 to seal against the second connection part 30 after it has punctured the second sealing layer 25, thereby maintaining the sealing integrity of the second sealing layer 25.

[0056] The second connection part 30 may be movable with respect to the tubular 14 upon which it is disposed, allowing the second connection part 30 to be moved towards the first connection part 20 during connection of the optical fibre cables of the first 20 and second 30 connection parts.

[0057] The shearable end cap 34 may isolate the interior of the tubular housing 32 from the external environment. This may help to protect the optical fibre cable and termination end of the optical fibre cable disposed therein from the external environment (e.g. protecting the optical fibre cable from damage from debris / particulates in the wellbore).

[0058] The shearable end cap 34 may define a surface configured to puncture of the second sealing plate 25. In the example of Figure 1A, the shearable end cap 34 defines two points, configured to puncture the second sealing layer 25. Alternatively, the shearable end cap 34 may be tapered to a single point, or may define any other surface suitable for puncturing the second sealing plate 25.

[0059] Figure 1B shows how the first 20 and second 30 connection parts of the optical fibre cable connection system 10 may be arranged on the production tubulars 12, 14 of Figure 1A. As outlined above, the first 20 and second 30 connection parts are arranged on the external circumferences of their respective tubulars 12, 14. Therefore, during connection of the production tubulars 12, 14 in a wellbore, the first 20 and second 30 connection parts may also be aligned, allowing for successful implementation of the optical fibre connection system 10.

[0060] Although the system 10 is described here as being used with wellbore production tubulars, it will be appreciated that this connection system may be used with any elongate component disposed in a wellbore; for example a casing string. Further, it will be appreciated that the connection system 10 does not need to be used within a wellbore, and may be used with tubular components which are assembled above ground level.

[0061] Although the first 20 and second 30 connection parts are shown as being circular in Figure 1 B, this is merely for illustrative purposes; and it will be appreciated that the first 20 and second components may be any suitable shape and configuration within the scope of the claims, which achieves the desired technical function.

[0062] Figure 1C shows an alternative optical fibre connection system 10 wherein multiple optical fibre cable connections can be established. The example of Figure 1C is generally the same as that of Figure 1A, except in that it comprises a plurality of first optical fibre cables 24 with the first connection part 20, and a plurality of second optical fibre cables 32 with the second connection part 30. The first and third sealing layers 23, 27 have also been adapted accordingly to provide the channels (21, 28, 29) required for connection of each pair of optical fibre cables (24, 32).

[0063] As will be appreciated by one skilled in the art, as this optical fibre connection system 10 functions in the same manner as that of Figure 1A, the example of Figure 1C allows for simultaneous connection between a plurality of first optical fibre cables 24 and their corresponding second optical fibre cables 32.

[0064] Similar to Figure 1 B, Figure 1 D shows how the first 20 and second 30 connection parts of the optical fibre cable connection system 10 may be arranged on the production tubulars 12, 14 of Figure 1C. As outlined above, the first 20 and second 30 connection parts are arranged on the external circumferences of their respective tubulars 12, 14. Therefore, during connection of the production tubulars 12, 14 in a wellbore, the first 20 and second 30 connection parts may also be aligned, allowing for multiple connections between lengths of optical fibre cables with the optical fibre connection system 10.

[0065] Figure 2 shows the optical fibre connection system 100 of Figure 1A, with an example translation mechanism 171 of the first sealing plate 123. Aside from the example translation mechanism 171 , the connection system 100 is identical to that of Figure 1A. In this example, the first sealing plate 123 comprises a profiled surface 172 on one of its edges. The profiled surface 172 extends in such a manner in which a force substantially perpendicular to the first sealing plate 123 can be applied to the profiled surface 171. In this example, the translation mechanism 171 further comprises an actuator 173, configured to provide a force on the profiled surface 172 to laterally move the second sealing plate. In some examples, the actuator 173 may not be provided, and the force to induce movement of the first sealing plate 23 may be provided by a tool extending to surface (e.g. a light intervention tool). The actuator 173 may be any suitable actuator type, such as a pressure controlled actuator, a hydraulic actuator or an electrical actuator, for example.

[0066] Figure 3 shows a pressure balance arrangement 40 that can be used with the optical fibre cables of either the first 20 or second 30 connection parts (or both) of the optical fibre connection system 10. The example of Figure 3 specifically shows a pressure balance arrangement 40 being used with the first connection part 20. Within this example, the pressure balance arrangement 40 also provides a junction (at the central unit 43) at which an optical control line 17 transitions into the first optical fibre cable 24 of the first connection part 20. Each optical fibre cable 17, 24 comprises at least one optical fibre 52, and a surrounding sheath 54.

[0067] Within the example of Figure 3, both optical fibre cables 17, 24 feed into a central housing 43. The interior of the sheath 54 of the first optical fibre cable 24 is in fluid communication with the central unit 43. Therefore, the at least one optical fibre 52 disposed within the sheath 54 of the optical fibre cable 24 may be surrounded by a fluid.

[0068] Also feeding into the central until 43 pressure balance arrangement 40 is a pressure cylinder 42. The pressure cylinder 42 comprises a first chamber 44 and a second chamber 48, wherein the first 44 and second 48 pressure chambers are separated by a piston 46. The first chamber is in fluid communication with the external environment (e.g. the wellbore environment). The second chamber may be filled with a ‘clean’ fluid for protecting the optical fibres 52 within the sheath 54 of the first optical fibre cable 24. The clean fluid may comprise an optical gel or oil, such as a silicon gel or oil, or a liquid crystal polymer (LCP) for example. Therefore, it can be said that the pressure cylinder 42 is in pressure communication with the interior of each of the optical fibre sheathes 54, and the interior of each of the optical fibre sheathes 54 may be equalised with wellbore pressure.

[0069] By using fluids such as silicon gels or oils, or an LCP, may also help protect the fibres 52 of the optical fibre cables 17 from high environmental temperatures, which may damage them.

[0070] Disposed within the central unit 43 is a pressure barrier 41, preventing the pressure cylinder 42 or the first fibre optic cable 24 being in pressure communication with the optical control line 17.

[0071] As outlined above, although the pressure balance arrangement 40 has been discussed for use with the first connection part 20 (wherein the output of the pressure balance arrangement 40 is the optical fibre cable 24 of the first connection part 20), the pressure balance arrangement 40 may also be used with the second connection part 30, wherein the output would be the second optical fibre cable 32; or wherein the pressure balance arrangement 40 is used in tandem with both the first 20 and second 30 connection parts, wherein the output of the pressure balance arrangement is both the first 24 and second 32 optical fibre cables of the first 20 and second 30 connection parts respectively.

[0072] Additionally, although only one optical fibre cable 17 is shown entering the central unit 43, and only one optical fibre cable 24 exiting the central unit 43, there may be multiple optical fibre cables in pressure communication with the central unit 43. For example, the pressure balance arrangement may have multiple optical fibre cables 24 of multiple first connection parts 20 in pressure communication with the pressure balance arrangement 40.

[0073] Figures 4A and 4B show detailed views of the termination ends 26, 60 of the first 24 and second 32 lengths of fibre optic cable respectively.

[0074] Within Figure 4A, the sheath 54 of the first fibre optic cable 24 is connected to the termination end 26 via a connection point 53. The connection point 53 may be formed by any suitable means within the understanding of one skilled in the art - for example gluing, melting / shrink fitting, friction fit, etc. At least one optical fibre 52 is shown within the sheath 54, and extending into the termination end 26.

[0075] The at least one optical fibre 52 is terminated at a ferrule 57. The ferrule 57 defines the connection point 59 for the first optical fibre cable 24 to the second optical fibre cable 32 of the second connection part 30. The ferrule may be of any suitable construction, and connected to the optical fibre of the first optical fibre cable 24, by any suitable means within the understanding of one skilled in the art. For example, the ferrule 57 may comprise a ceramic, polymer or stainless steel material (or any combination thereof), and / or comprise at least one polished surface.

[0076] At least partially surrounding, and axially extending from the ferrule 57, is an alignment sleeve 58. The alignment sleeve 58 extends beyond the connection point 59 of the ferrule 57. Therefore, the alignment sleeve 58 may act to guide a ferrule 67 of the second optical fibre cable 32 of the second connection part 30 into engagement with the ferrule 57 of the first optical fibre cable 24. The alignment sleeve 58 may also act to hold the ferrule 57 in contact with the corresponding ferrule 67 of the second optical fibre cable 32, ensuring a reliable connection is maintained, following connection of the first 24 and second 32 optical fibre cables.

[0077] A protective sleeve 51 surrounds the ferrule 57 and alignment sleeve 58 of the first termination end 26. The protective sleeve at least partially surrounds the alignment sleeve 58 and the ferrule 57, protecting the ferrule 57 and alignment sleeve 58 from collisions with the housing 22 of the first connection part 20. The protective sleeve 51 may also assist with aligning the ferrule 67 of the second termination end 60 with the ferrule 57 of the first termination end 26.

[0078] The first termination 26 end further comprises a spring 55. The spring is disposed between the ferrule 57 and a stop 56 of the first termination end 26. Therefore, the spring 55 acts to extend the ferrule 57 and alignment sleeve 58 axially through the protective sleeve 51. Use of a spring 55 to bias the ferrule 57 of the first termination end may help to ensure constant contact between the ferrule 57 of the first termination end 26 and the ferrule 67 of the second termination end 60; helping to maintain a reliable optical connection between the first 24 and second 32 optical fibre cables. Figure 4B shows the termination end 60 of the second optical fibre cable 32. This termination end 60 comprises a similar structure to the first termination end 67, save for an alignment sleeve disposed around the ferrule 67.

[0079] Figure 4B shows the sheath 64 of the second optical fibre cable 32 connected to the termination end 60 in the same manner as described above in relation to the connection between the first optical fibre cable 24 and its termination end 57. An at least one optical fibre 62 extends from the sheath 64 and into the termination end 60.

[0080] The termination end 60 of the second optical fibre cable 32 also comprises a ferrule 67, constructed and arranged within the termination end 62 in a similar manner to the ferrule 57 of the termination end 26 of the first fibre optic cable 24. The termination end 60 also comprises a protective sleeve 69 surrounding the ferrule 67. This protective sleeve 69 may also assist with the alignment of the ferrule 67 with the ferrule 59 of the termination end 26 of the first optical fibre cable 24, wherein the protective sleeve 67 may slot between the alignment sleeve 58 and the protective sleeve 51 of the termination end 26 of the first optical fibre cable 24; helping to maintain the ferrules 57, 67 of the termination ends 26, 60 in alignment, ensuring a reliable optical connection following connection of the first 24 and second 32 optical fibre cables.

[0081] The termination end 60 of the second optical fibre cable 32 also comprises a biasing arrangement similar to that of the termination end 26 of the first optical fibre cable 24; wherein the biasing arrangement (the spring 65 disposed between the ferrule 67 and the stop 66) acts to axially extend the ferrule 67 from the protective sleeve 69 of the termination end 60 of the second optical fibre cable 32. Again, this may help to ensure a contact surface 68 of the ferrule remains in contact with the contact surface 59 of the ferrule 57 of the termination end 26 of the first optical fibre cable 24, ensuring a reliable connection is maintained between the first 24 and second 32 optical fibre cables following connection.

[0082] Figures 5A to 5D show how the optical fibre connection system 10 may be used to form an optical fibre connection (between two optical fibre cables 24, 32). The optical fibre connection system 10 comprises all of the features as described within Figures 1A and 1B, so description of these features is omitted in relation to Figures 5A to 5D, for brevity. Further, the system is described as being used within production tubulars 12, 14 in a wellbore, but it will be appreciated that this connection system can be applied in other industries, both above and below ground.

[0083] Within Figure 5A, a production tubular 12 has been run into a wellbore (not shown). The production tubular 12 comprises the first connection part 20 (comprising a first optical fibre cable 24 disposed within a housing 22, wherein the housing is isolated from the external environment by a sealing arrangement 23, 25, 27) disposed on an outer circumference of the production tubular 12.

[0084] The production tubular 12 is aligned with (and subsequently connected to) a further production tubular 14, previously installed in the wellbore. The further production tubular 14 comprises the second connection part 30 (comprising a second optical fibre cable 32 with a shearable end cap 34 disposed at the termination end of the second optical fibre cable 32), disposed on the outer circumference of said production tubular 14.

[0085] When the sections of production tubular 12, 14 are connected, the opening 13 of the housing 22 of the first connection part 20 and the shearable end cap 34 of the second connection part 30 are aligned, to allow connection of the first 24 and second 32 optical fibres to commence.

[0086] Within Figure 5B, the second connection part is moved axially (as indicated by the arrows 38) towards the first connection part 20. Axial movement 38 of the second connection part 30 may be initiated by any suitable means within the understanding of one skilled in the art, such as the second connection part 20 further comprising an actuator to induce axial movement, or use of light intervention tools within the wellbore to move the second connection part 30 axially.

[0087] Within Figure 5B, axial movement 38 of the second connection part 30 has caused the shearable end cap 34 to puncture the second sealing plate 25 of the first connection part 20, with the shearable end cap 34 (and a portion 35 of the second sealing layer 25 displaced by the second connection part during puncture) now extending into the first channel 21 of the first sealing plate 23; ready for the shearable end cap 34 to be removed. As outlined above, the second sealing plate 25 may be configured to seal around the second connection part following puncture of the second sealing plate 25. This may ensure the sealing integrity of the second sealing plate 25 is maintained even after it has been punctured. This may be beneficial, as it provides a secondary seal to the first sealing plate 23, helping to still isolate the interior space of the housing 22 from the external environment.

[0088] To puncture the second sealing plate 25 and enter the channel 21 partially extending through first sealing plate 23, the second connection part 30 has also passed through the channel 29 of the third sealing plate 27. Therefore, in embodiments of the invention where a third sealing plate 27 is used, the channel 29 of the third sealing plate 27 must be substantially aligned with the channel 21 that extends partially through the first sealing plate 23.

[0089] Figure 5C demonstrates removing the shearable cap 34 from the second connection part 30. This is achieved by lateral movement 18 of the first sealing plate 23. Such lateral movement 18 may be achieved by any means within the understanding of one skilled in the art; for example, the first sealing plate 23 may comprise a profiled surface, and the lateral movement of the first sealing plate 23 may be induced by a force being applied to said profile surface (e.g. via an actuator or light intervention tool), as shown in the example of Figure 2.

[0090] The first sealing plate 23 is moved far enough laterally to align the second channel 28 of the first sealing plate 23 with the opening 13 of the housing 22 of the second connection part 20. Therefore, the second connection part 30 may now enter the housing 22 of the first connection part 20 to connect the first 24 and second 32 optical fibre cables.

[0091] As outlined above, the second part 30 may comprise a ‘weak point’ 36 between the shearable end cap 34 and the second optical fibre cable 32, to allow the end cap 34 to be sheared from second optical fibre cable 32 more easily.

[0092] Finally, as shown in Figure 5D, the second connection part 30 is axially moved 19 through the opening 13 of the housing 22 of the first connection part 20, and into engagement with the first optical fibre cable 24, establishing an optical communication path between the first 24 and second 32 optical fibre cables.

Claims

CLAIMS:

1. An optical fibre cable connection system comprising: a first connection part comprising a housing defining an internal space and an opening into the internal space, a first optical fibre cable having a termination end located within the internal space adjacent to said opening, a first sealing plate attached to the housing and sealing said opening whilst defining a first channel extending partially through the first sealing plate and being in alignment with said opening and a second channel extending completely through the first sealing plate and being spaced laterally apart from the first channel, a second sealing plate attached to the housing and spaced apart from the internal space by the first sealing plate, wherein the first sealing plate is movable laterally with respect to the second sealing plate and the housing, and a translation mechanism for causing lateral movement of the first sealing plate; and a second connection part comprising a second optical fibre cable, and a shearable end cap fixed to a termination end of the second optical fibre cable and configured to puncture the second sealing plate for insertion into said first channel.

2. The system of claim 1 , wherein the second sealing plate is configured to seal against an outer surface of the second connection part after the second connection part has punctured the second sealing plate.

3. The system of any one of claims 1 or 2, further comprising a third sealing plate connected to the housing and spaced apart from the internal space by the first and second sealing plates.

4. The system of claim 3, wherein the third sealing plate comprises a channel extending through the third sealing plate.

5. The system of any preceding claim, wherein the translation mechanism comprises a profiled surface of the first sealing plate.

6. The system of claim 5, wherein the translation mechanism further comprises an actuator, wherein the actuator is configured to act upon the profiled surface of the first sealing plate to laterally move the first sealing plate relative to the housing and second sealing plate.

7. The system of any preceding claim, wherein an interior surface of the housing comprises a slot, configured to axially align the first optical fibre cable with the housing.

8. The system of any preceding claim, wherein the termination end of each of the first and second optical fibre cables comprises a ferrule wherein the ferrule is spring biased.

9. The system of any preceding claim, wherein the shearable cap defines a pointed surface, the pointed surface being configured to penetrate the second sealing plate.

10. The system of any preceding claim and comprising a plurality of said first connection parts and a corresponding plurality of said second connection parts, the translation mechanisms of the plurality of first connection parts being provided by a common translation mechanism.

11. A method of connecting first and second optical fibre cables using the optical fibre connection system of any preceding claim, and comprising: causing the shearable end cap to puncture the second sealing plate and enter the first channel; operating the translation mechanism to translate the first plate laterally, thereby shearing the end cap from the termination end of the second optical fibre cable and bringing the second channel into axial alignment with the now exposed termination end of the second optical fibre cable; translating the end termination of the second optical axially through the second channel and into optical communication with the termination end of the first optical fibre cable.

12. The method of claim 11, and wherein puncturing of the second plate seal comprises axially moving the second connection part towards the second sealing plate.

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