GB2560708A

GB2560708A - Bore sensor insert

Info

Publication number: GB2560708A
Application number: GB1704059.3A
Authority: GB
Inventors: William Davis Mathew
Original assignee: Salunda Ltd
Current assignee: Salunda Ltd
Priority date: 2017-03-14
Filing date: 2017-03-14
Publication date: 2018-09-26
Also published as: WO2018167462A1; GB201704059D0

Abstract

A sensor insert 1 for a bore 2 comprises a tubular wall 10 of non-conductive material for lining the bore 2 and a plurality of sensing coils 11 arranged behind the inner surface of the tubular wall 10 that faces the bore 2, at different angular positions around the bore 2 to generate an electromagnetic field extending therethrough. A tubular shield 12 of conductive material is arranged outside the coils 11 providing a reference plane for the sensing coils 11. An annular cavity 14 is disposed between the tubular wall 10 and the tubular shield 12 and contains a liquid. The sensor insert 1 further comprises a pressure balancing unit 20, which may include a deformable container such as a bellows (23, fig 4) or bladder (31, fig 5), in fluid communication with the annular cavity 14 and the bore 2 to balance their pressures, thereby preventing distortion of the tubular wall 10 and tubular shield 12. The annular cavity 14 is preferably thicker than the tubular shield 12 and wall 10. An electrical circuit (40, fig 6) may be connected to the coils 11, generating oscillating EM fields in the bore 2.

Description

(71) Applicant(s):

Salunda Limited

Avonbury Business Park, Howes Lane, Bicester, Oxfordshire, 0X26 2UA, United Kingdom (72) Inventor(s):

Mathew William Davis (56) Documents Cited:

WO 2016/174439 A1 (58) Field of Search:

INT CL E21B, G01N, G01V Other: WPI, EPODOC

US 4651100 A1 (74) Agent and/or Address for Service:

J A Kemp

South Square, Gray's Inn, LONDON, WC1R 5JJ, United Kingdom (54) Title of the Invention: Bore sensor insert

Abstract Title: Insert with coils for generating EM fields to sense the contents of a bore (57) A sensor insert 1 for a bore 2 comprises a tubular wall 10 of non-conductive material for lining the bore 2 and a plurality of sensing coils 11 arranged behind the inner surface of the tubular wall 10 that faces the bore 2, at different angular positions around the bore 2 to generate an electromagnetic field extending therethrough. A tubular shield 12 of conductive material is arranged outside the coils 11 providing a reference plane for the sensing coils 11. An annular cavity 14 is disposed between the tubular wall 10 and the tubular shield 12 and contains a liquid.

The sensor insert 1 further comprises a pressure balancing unit 20, which may include a deformable container such as a bellows (23, fig 4) or bladder (31, fig 5), in fluid communication with the annular cavity 14 and the bore 2 to balance their pressures, thereby preventing distortion of the tubular wall 10 and tubular shield 12. The annular cavity 14 is preferably thicker than the tubular shield 12 and wall 10. An electrical circuit (40, fig 6) may be connected to the coils 11, generating oscillating EM fields in the bore 2.

Fig. 1

At least one drawing originally filed was informal and the print reproduced here is taken from a later filed formal copy.

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Fig. 5

Fig. 6

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Bore Sensor Insert

The present invention relates to a sensor insert comprising sensing coils that may be inserted into a bore for sensing of the contents of the bore.

The present invention may be applied to a bore used in oil and gas extraction and production, wherein there are a wide range of situations where it is necessary to sense the contents of a bore.

An example of such sensing in oil and gas extraction and production is to sense an elongate element such as a drill string or drill casing, in which case such sensing may be used to control a blow-out preventer (BOP). Various sensor systems for sensing the axial position along the bore of joint sections of a drill string in a well bore are known, many of these dating from the 1960s and 1970s when undersea drilling first became widespread. By way of example, each of US-3,103,976, US-3,843,923 and US-7,274, 989 disclose electromagnetic (EM) sensor systems for sensing the axial position of a joint section in a drill string.

Another example of such sensing is to sense the material properties of the contents of the bore. In oil and gas extraction and production, for example, there are a wide range of situations where it is advantageous to sense the EM properties of the contents of the bore, for example as discussed in WO-2012/007718, WO-2015/015150 and GB-2,490,685. In another example, WO-2012/153090 describes a fluid conduit fabricated from a composite material that incorporates sensors that sense the properties of the contents of the bore, in particular forming a cavity resonator packaged inside the fluid conduit.

WO-2016/174439 discloses a particular advantageous form of sensor system using a plurality of sensing coils arranged facing the bore for generating an EM field directed laterally into the bore. The sensor system may be arranged as an insert to be inserted into the bore, for example as a sealing insert, and provides for reliable and accurate sensing of the contents of the bore.

The present invention is concerned with the construction of a sensor insert for insertion in a bore and comprising a plurality of sensing coils for performing EM sensing of the contents of the bore.

According to the present invention, there is provided a sensor insert for insertion in a bore, the sensor insert comprising:

a tubular wall of non-conductive material for lining the bore; a plurality of sensing coils supported by the tubular wall, behind the inner surface of the tubular wall, at different angular positions and facing the inner surface of the tubular wall for generating an electromagnetic field extending therethrough;

a tubular shield of conductive material arranged outside the coils for providing a reference plane for the sensing coils;

an annular cavity disposed between the tubular wall and the tubular shield, the annular cavity containing a liquid;

a pressure balancing unit arranged in fluid communication with the annular cavity and the bore and to balance the pressures therewithin.

In such a sensor insert the plurality of sensing coils are supported by a tubular wall of non-conductive material for lining the bore, behind the inner surface of the tubular wall.. Thus, the tubular wall electrically isolates and protects the coils from the fluid within the bore. Use of a non-conductive material allows the EM field generated by the coils to penetrate laterally into the bore.

In addition, a tubular shield is arranged outside the coils. This provides a reference plane for the sensing coils, so that the coils may sense the contents of the bore without influence from material or components outside the bore.

It is desirable to separate the coils from the tubular shield, so far as is possible within the constraints of the location of the sensor insert in the bore. However, it has been appreciated that this creates a practical problem in providing such separation. This is due to the pressure within the bore, which is typically high in a well bore due to the use of pressurised well fluids. The pressure within the bore can create forces which may distort the tubular member and/or the tubular shield. Such distortion can alter the separation between the coils and the tubular shield, and thereby affect the sensing output in an unpredictable manner. In extreme cases, the distortion could potentially create mechanical failure of the tubular wall and/or tubular shield that renders the sensor insert inoperable.

There might be considered provision of a solid element to provide the separation, for example a solid tubular spacer or a potting compound. However, it has been appreciated that the bulk modulus of suitable materials is such that under the forces likely to be encountered in practice such a solid element will compress to an extent that is sufficiently great to affect the sensing output. Thus, this is not a suitable solution.

In order to tackle these problems, the separation is provided by disposing an annular cavity between the coils and the tubular shield. A liquid is disposed within the cavity and the sensor insert is provided with a pressure balancing unit which communicates with the annular cavity and the bore to balance the pressures therewithin. As a result of this arrangement, the pressure differential between the bore and the cavity is reduced, which in turn reduces forces that risk distorting the tubular member and/or the tubular shield.

With such an arrangement it is possible to maximise the separation of the coils and the tubular shield within the constraints of the location of the sensor insert by reducing the thickness of the tubular wall and the tubular shield. Thus, the annular cavity may typically be thicker than the tubular wall and/or may be thicker than the tubular shield.

Typically, the annular cavity has a thickness of at least 15mm.

Typically, the tubular wall has a thickness of at most 10mm.

Typically, the tubular shield has a thickness of at most 5mm.

The liquid preferably has a high a bulk modulus as possible, in order to minimise the volume change that needs to be accommodated by the pressure balancing unit on change of pressure within the bore. Typically, the liquid has a bulk modulus of at least 0.8 GPa.

Advantageously, the liquid may contain solid material having a higher bulk modulus than the liquid. By means of the cavity containing such solid material as well as the liquid, the overall volume change of the contents of the cavity is reduced, thereby reducing the volume change that needs to be accommodated by the pressure balancing unit.

The coils may be fixed to the outer surface of the tubular wall. In that case, they are easy to form on the tubular wall. However that is not essential and the coils may instead be embedded within the tubular wall, provided that they are behind the inner surface of the tubular wall.

Advantageously, the pressure balancing unit is disposed at an annular end of the cavity. This is a convenient arrangement because it allows the pressure balancing unit to be in close proximity to both the cavity and the bore, which simplifies the arrangement and reduces the risk of blockage associated with long fluid communication channels.

Furthermore, disposition of the pressure balancing unit is disposed at an annular end of the cavity permits the pressure balancing unit to comprise two interacting annular volumes extending around the annular end of the cavity and communicating with the annular cavity and the bore, respectively. Such an annular formation for the pressure balancing unit advantageously provides a relatively large pressure balancing unit, thereby reducing stroke and allowing relatively large volume changes to be accommodated.

Various different forms of pressure balancing unit may be applies. Advantageously, the pressure balancing unit may comprise a chamber containing a deformable container separating variable internal and external volumes, the two volumes communicating with the annular cavity and the bore, respectively. Suitable deformable containers include a bellows or a bladder. Another form of pressure balancing unit that may alternatively be used is a piston arrangement in which a piston is arranged between two volumes communicating with the annular cavity and the bore, respectively.

The sensor circuit may further comprise an electrical circuit connected to the plurality of coils. The sensor unit is particular suitable for use in a type of sensing wherein the electrical circuit comprises: an oscillator circuit arranged to drive electrical oscillations in the coils for causing the coils to generate oscillating electromagnetic fields; and a detection circuit arranged to output signals from each coil representing a parameter of the electrical oscillations generated therein that depends on the contents of the bore.

The sensor insert may advantageously be applied in a bore for oil and gas extraction and production. For example, the bore may be a bore for receiving a drill string or a drill casing.

The sensor insert may be configured to form a sealing insert for a joint assembly between sections of a tube defining the bore. This facilitates provision of the sensor insert in a pre-existing location within the bore.

Embodiments of the present invention will now be described by way of non-limitative example with reference to the accompanying drawings, in which:

Fig. lisa cut-away perspective view of a sensor insert;

Fig. 2 is a perspective view of a joint assembly in which the sensor unit may be inserted;

Fig. 3 is a perspective view of a tubular wall of the sensor insert;

Fig. 4 is a cross-sectional view of the pressure balancing unit of the sensor unit comprising a bellows;

Fig. 5 is a cross-sectional view of the pressure balancing unit of the sensor unit in an alternative form comprising a bladder; and

Fig. 6 is a diagram of an electrical circuit connected to the coils.

Fig. 1 illustrates a sensor insert 1 that is configured for insertion into a bore 2 used in oil and gas extraction or production. When so inserted, the sensor insert 1 lines part of the bore 2. The bore 2 may be a pipe bore, riser or flowline, or downhole. The bore 2 may be a casing, production tubing or a well bore in an ‘open-hole’ well. More generally, the sensor insert 1 may be applied to a bore in any type of pipe, tube or conduit, which may or may not be applied in an oil and gas application.

In this specific example, the sensor insert 1 is configured to form a sealing insert for a joint assembly 3 as shown in Fig. 2 for connecting two sections of a tube (not themselves shown) defining the bore 2. The joint assembly 3 comprises two flanges 4 which are connected together. The sealing insert 1 is inserted inside the joint assembly 3 extending across the boundary between the two flanges 4 to provide sealing therebetween.

Configuring the sensor insert 1 to form a sealing insert for a joint assembly 3 has the advantage of allowing the sensor system 1 to be quickly and easily implemented, simply by replacing the existing seal.

However, the sensor insert could equally be configured as an insert for any other part of the bore 2, for example to be inserted into a section of a tube forming the bore 2. In general terms, the sensor insert 1 may be inserted in any location inside the bore 2, including for example inside a riser or between a BOP stack and a riser, or inside a BOP stack. Such a sensor insert 1 may be mounted at multiple locations, for example at riser flanges, riser adapters and within the BOP stack itself. For ease of deployment, such a sensor insert 1 may be constructed in a format that corresponds to the dimensions of an industry-standard insert so that it can be conveniently mounted inside risers, riser adapters, flanges or BOPs, allowing for easy and quick retro-fitting to existing risers and BOPs in the field.

The sensor insert 1 is arranged as follows.

The sensor insert 1 comprises a tubular wall 10 which is arranged as the innermost component of the sensor insert 1 for lining the bore 2.

As shown in Fig. 3, a plurality of sensing coils 11 are supported by the tubular wall 10. In the example shown in Fig. 3, the coils 11 are fixed to the outer surface of the tubular wall 10. In that manner, the coils 11 are arranged behind the inner surface of the tubular wall 10 that faces the bore 2, and hence the tubular wall 10 electrically isolates and protects the coils 11 from the fluid within the bore 2. This is important due to the fluids within the bore 2 typically including various components which may prevent electrical operation and/or damage the coils 11, for example particles, debris, corrosive components, conductive components, etc.

However, this manner of support of the coils 11 on the tubular wall 10 is not essential, and the coils 11 may instead be embedded within the tubular wall 10, provided that they are behind the inner surface of the tubular wall 10 for electrical isolation and protection. The coils 11 may be embedded within the tubular wall 10 using any suitable technique, for example most simply by initially forming the coils 11 on an outer surface of the tubular wall 10 and then adding an outer layer to the tubular wall 10 outside the coils 11.

The coils 11 are at each arranged at different angular positions around the bore 2.

Each coil 11 is formed by multiple conductive turns. The turns of each coil 11 face the inner surface of the tubular wall 10. That is, in each coil 11 the turns are wound around a notional winding axis 13 that is directed laterally into the bore 2, perpendicular to the inner surface of the tubular wall 10. Thus, the coils 11 conform to the inner surface of the bore 2. As a result, the coils 11 each generate an EM field directed laterally into the bore 2. The EM field therefore interacts with the contents of the bore to provide sensing.

The tubular wall 10 is formed from a non-conductive material in order to allows the EM field generated by the coils 11 to penetrate laterally into the bore 2. The material of the tubular wall 10 is chosen having regard to the functions of protecting the coils 11 and allowing penetration of the EM field. The material of the tubular wall 10 is also selected to be chemically compatible (inert) both with fluids typically encountered within the bore 2 and the liquid within the cavity described below. A wide range of materials are possible. The material may be a plastic, for example polyether ether ketone (PEEK), or an elastomer, for example a rubber. The material may be a composite, such as carbon fibre or fibre glass. The material may be of a type known to be suitable for use as a lining of a bore 2 in oil and gas applications. Suitable materials include, without limitation: PEEK, PTFE (Polytetrafluoroethylene), FFKM (Perfluoroelastomer), polyisoprene, styrene butadiene rubber, ethylene propylene diene monomer rubber, polychloroprene rubber, chlorosulphonated polyethylene rubber, ‘Viton’ or nitrile butadiene rubber. The material may also be single material or a mixture.

The tubular wall 10 may be a single piece of material or may have a layered construction of multiple layers.

PEEK is a particularly advantageous material for the tubular wall 10 due to its high levels of chemical compatibility, high temperature performance and wide level of acceptance within the oil and gas markets.

The coils 11 are formed on the tubular wall 10 in any suitable manner, including without limitation the following. The coils 11 may be printed or etched onto a surface of the tubular wall 10. The coils may be formed in grooves formed in the surface of the tubular wall 10. The coils 11 may be formed on flexible PCB attached to the tubular wall 10.

In another construction, the coils 11 may be formed from wire or sheet metal fixed to the tubular wall 10. In that case, the coils 11 may be any suitable conductive material such as stainless steel, copper or Inconel.

In the example shown in Fig. 3, the coils 11 are spiral coils in which the turns are arranged in a common plane at different distances from the winding axis 13. As an alternative, the coils 11 may be formed as a planar coil formed by a stack of planar conductive sheets.

In the example shown in Fig. 3, there are a total of four, identically shaped rectangular coils 11 with equal angular spacing around the axis of the bore 2. However, this is merely by way of example and in general the coils 11 may have any other shape and/or configuration, in general any arrangement. By way of example, the coils 11 may be shaped in any of the configurations disclosed in WO-2016/174439 to which reference is made for further details, and which is incorporated herein by reference. The coils 11 may include differently shaped coils 11.

The coils 11 may have the construction disclosed in WO-2009/147385, which is incorporated herein by reference, so that they include for example features, discontinuities or notches that improve resolution when detecting the position of an object while also improving sensor stability and contracting drift and other environmental effects.

In addition, the sensor insert 1 comprises a tubular shield 12 arranged outside the tubular wall 10 and therefore outside the coils 11. The tubular shield 12 is made of conductive material and thereby provides a reference plane for the coils 11. This allows the coils 11 to interact with and sense the contents of the bore 2 without influence from material or components outside the bore 2.

It is desirable to separate the coils 11 from the tubular shield 12 so far as is possible within the constraints of the location of the sensor insert 1 in the bore 2 to reduce the influence of the tubular shield on the EM field generated by the coils 11. Typically, it a separation of 50mm or more may provide the most sensitive sensing, but that may be unachievable. In many locations, the sensor insert 1 may have a maximum overall thickness less than 50mm, for example say 30mm. In such cases, the separation between the coils 11 and the tubular shield 12 may be in a range of 10mm to 25mm, which provides reduced, but adequate, sensitivity.

The tubular shield 12 may be made of any suitable conductive material, typically a metal.

The sensor insert 1 also include an annular flange 17 protruding radially outwardly from the outside of the tubular shield 12. The annular flange 17 fits with the flanges 4 of the joint assembly 3 to assist with sealing.

The sensor insert 1 comprises an annular cavity 14 disposed between the tubular wall 10 and the tubular shield 12. The cavity 14 is formed by the sensor insert 1 including a first annular cap 15 (uppermost in Fig. 1) and a second annular cap 16 (lowermost in Fig. 1) each connected to both the annular wall 10 and the annular shield 12 and holding them spaced apart to define the cavity 14 therebetween. Thus, the first annular cap 15 and the second annular cap 16 form the annular ends of the cavity 14.

The thickness of the cavity 14 (together with the location of the coils 11 within the tubular wall 10 if the coils 11 are embedded) therefore defines the separation between the coils 11 and the tubular shield 12.

The cavity 14 is filled taking into account the following considerations.

In a low pressure application, the cavity 14 could simply be an air gap. However in an application where the fluid within the bore 2 is pressurised, for example in an oil and gas application, that would creates technical problems. A differential pressure would occur between the fluid within the bore 2 and the cavity 14. This pressure differential would apply a large forces to both the tubular wall 10 and the tubular shield 12 which can cause either of both of them to distort.

Even if the pressure differential is low enough that the hoop stress induced within the tubular wall 10 and the tubular shield 12 is below the yield stress of the materials used, then the distortion will cause the separation between the coils 11 and the tubular shield 12 to vary which would adversely affect the generated EM field and so influence the sensing results.

Furthermore, there is a risk that the pressure differential is sufficient to induce a level of stress in either or both of the tubular wall 10 and the tubular shield 12 that is sufficient to cause mechanical failure, which would be catastrophic to the sensor insert 1.

One might consider filling the cavity 14 with a solid material for example a potting compound, or equivalently by forming the sensor insert 1 entirely from solid material so that there is no cavity 14 as such. In that case, there would be no pressure differential by a problem arises from the compressibility of the solid material. Although solids and liquids are sometimes referred to as being “incompressible”, that is only correct relative to the high degree of compressibility of a gas. In fact, solids have a measurable level of compressibility which is represented by their bulk modulus. In the sensor insert 1 in the intended use in a bore 2 in oil and gas extraction and production, it is anticipated that the pressure levels would result in an approximate volume change of 4.5%. That would adversely affect the generated EM field and so influence the sensing results.

Furthermore, if providing solid material within, or in place of, the cavity 14, there would be practical difficulties ensuring no air gaps due to the level of compressibility of air, and it is questionable how the removal of gas could reliably be tested.

These issues are tackled in the sensor insert 1 by the annular cavity 14 containing a liquid, and further providing the sensor insert 1 with a pressure balancing unit 20 arranged to balance the pressure of the liquid within the annular cavity 14 with the pressure of the fluid in the bore 2.

In this example, the pressure balancing unit 20 is disposed at the annular end of the annular cavity 14 which is lowermost in Fig. 1 and is arranged as follows.

The pressure balancing unit 20 comprises an annular case 21 fixed to the second annular cap 16. The annular case 21 is hollow, so that the annular case 21 and the second annular cap 16 together define an internal, annular chamber 22.

A bellows 23 is disposed in the annular chamber 22. The bellows 23 is also annular and comprises inner and outer stacks 24 of annular metal diaphragms 25. In each of the inner and outer stacks 24, the diaphragms 25 are welded alternately at inner and outer edges in a concertina fashion. The bellows 23 further comprises an annular closure 26 attached to the end of the inner and outer stacks 24, so that the diaphragms 25 and the annular closure 26 together form a container which is deformable by extension and contraction of the stacks of diaphragms 25. Thus, the bellows 23 separates variable internal and external volumes 27 and 28 within the chamber 22 which interact with each other.

The volume 26 of the chamber internal to the bellows 23 is in fluid communication with the annular cavity 14 through a plurality of channels 29 formed in the second annular cap 16. The volume 27 of the chamber external to the bellows 23 is in fluid communication with the bore 2 through a plurality of openings 30 formed in the annular case 21.

As a result, the pressure balancing unit 20 balances the pressure of the liquid within the annular cavity 14 with the pressure of the fluid in the bore 2 by deformation of the bellows 23 to change the internal and external volumes 27 and 28. As a result, the pressure balancing unit 20 in use reduces the pressure differential between the bore 2 and the cavity 14. That in turn reduces the forces on the tubular wall 10 and tubular shield 12 and thereby prevents or reduces distortion thereof. In contrast, if the pressure balancing unit 20 were omitted, then the tubular wall 10 and tubular shield 12 would need to be extremely thick in other to restrain the applied pressure with minimal distortion and no risk of failure, for example of the order of 500mm which would not be practical for fitting the sensor insert 1 within the bore 2.

Thus, such an arrangement makes it possible to maximise the separation of the coils 11 and the tubular shield 12 within the constraints of the location of the sensor insert 1 within the bore by reducing the thickness of the tubular wall 10 and the tubular shield 12. Thus, the annular cavity 14 may typically be thicker than the tubular wall 10 and may be thicker than the tubular shield 12. For example in typical arrangements, the annular cavity may have a thickness of at least 15mm, the tubular wall 10 may have a thickness of at most 10mm, and the tubular shield 12 may have a thickness of at most 5mm.

The nature of the liquid within the cavity 14 is chosen as follows. The liquid is desirably non-conductive so as not to affect the EM field generated by the coils 11. The liquid desirably has a relatively low degree of thermal expansion. Typically, the liquid is chemically inert. A wide range of liquids have suitable properties. The liquid may typically be an oil, which may advantageously be a hydraulic oil.

The liquid preferably has a high a bulk modulus as possible, in order to minimise the volume change that needs to be accommodated by the pressure balancing unit 20 on change of pressure within the bore. Typically, the liquid has a bulk modulus of at least 0.8 GPa. For example, a hydraulic oil would typically have a bulk modulus of around 1.0 GPa.

To further reduce the compressibility of the contents of the cavity 14, the liquid within the cavity 14 may optionally contain solid material having a higher bulk modulus than the liquid. The solid material may take any suitable form, for example being particulate or being one or more blocks of relatively large volume compared to the volume of the cavity 14. In one simple form, such sold material may take the form of an annular block of nylon or other material. By providing solid material in the liquid, the overall volume change of the contents of the cavity under the application of pressure is reduced. That reduces volume change that needs to be accommodated by the pressure balancing unit 20.

The particular form of the pressure balancing unit 20 provides a number of advantages. The location at the annular end of the annular cavity 14 places the pressure balancing unit 20 in close proximity to both the cavity 14 and the bore 2, which simplifies the arrangement and reduces the risk of blockage which would otherwise be associated with long channels for fluid communication.

Also the annular form of the pressure balancing unit 20 and in particular of the internal and external volumes 27 and 28 provides the pressure balancing unit 20 with a relatively large active area, thereby reducing stroke and allowing relatively large volume changes to be accommodated.

However, this form of the pressure balancing unit 20 is not essential and could be varied, for example as follows.

The bellows 23 may take a different form or may be made of material other than metal. Similarly, the bellows 23 may replaced by some other form of deformable chamber. For example, in a modified form of the pressure balancing unit 20 shown in Fig. 5, the bellows 23 is replaced by a bladder 31 formed from a flexible sheet of material, for example an elastomer. In this case, the bladder 31 forms a deformable container that operates to provide pressure balancing in the same manner as the bellows 23.

The pressure balancing unit 20 may take any other suitable form, for example a dynamic piston arrangement.

Furthermore, notwithstanding the advantages of locating the pressure balancing unit 20 at the annular end of the annular cavity 14, the pressure balancing unit 20 may be located elsewhere, for example radially outside the tubular shield 12, by providing channels to provide fluid communication with the annular cavity 14 and bore 2.

Additionally, the cavity 14 may be provided with one or more pressure relief valves to allow liquid therewithin to exhaust from the cavity 14 should undesired thermal expansion occur.

The electrical arrangement of the sensor insert 1 is as follows.

The annular flange 17 has sockets 18 which are electrically connected to the coils 11. An electrical circuit 40 is housed in housings 19 provided outside the tubular shield 20 on the outside of the joint assembly 3. The electrical circuit 40 is connected to the sockets 18 for making an electrical connection to the coils 11.

The electrical circuit 40 is arranged as shown in Fig. 6 and includes an oscillator circuit 41 and a detection circuit 42 which may be implemented on a common circuit board.

The electrical circuit 40 also includes a switch arrangement 43 arranged to connect the oscillator circuit 41 selectively to any one of the coils 11. The oscillator circuit 41 drives electrical oscillations in the coil 11 to which it is connected. In use, the switch arrangement 43 is switched to connect the oscillator circuit 41 to each respective coil 11 in turn. The electrical oscillations in the coils 11 cause the coils 11 to produce oscillating EM fields that, due to arrangement of the coils described above, interact with the contents of the bore 2.

The oscillator circuit 41 and the coils 11 are designed to drive electrical oscillations that are radio frequency (RF) electrical oscillations. In general, the electrical oscillation may be any radio frequency, which as used herein, may in general be considered to be a frequency within the range from 3kHz to 300GHz.

Increasing the frequency of the electrical oscillation increases the sensitivity, for which reason the frequency may typically be at least 10kHz. Typically, the frequency of the drive signal may be at most 100MHz or at most 1GHz, as higher frequencies may require more complicated electronics.

The detection circuit 42 is arranged to detect one or more parameters of the electrical oscillations that is dependent on the interaction of the EM field generated by the coil 11 currently being driven with contents of the bore 2. The detection circuit 42 outputs output signal representing the one or more detected parameters. Parameters which may be detected by the detection circuit 42 include, without limitation, the frequency, the amplitude or Q factor of the electrical oscillations. Different parameters may be used to sense different aspects of the contents of the bore 2.

In general, the oscillator circuit 41 may be of any type but particular advantage is achieved by the oscillator circuit 41 being a marginal oscillator. A marginal oscillator provides high stability and sensitivity. The oscillator circuit 41 and the detection circuit 42 may be configured as described in more detail in WO-2016/174439 to which reference is made.

Alternatively, the oscillator circuit 41 may have the construction disclosed in WO-2015/015150 to which reference is made for further details, and which is incorporated herein by reference.

The electrical circuit 40 also includes a processing circuit 50 that is supplied with a the output signals from the detection circuit 42. The processing circuit 50 analyses the one or more detected parameters of the electrical oscillations. The processing circuit 50 may be any form of circuit that is capable of performing such an analysis, for example a dedicated hardware or a microprocessor running an appropriate program.

The processing circuit 50 also controls the operation of the oscillator circuit 41 and the switching of the switch arrangement 43 to connect the oscillator circuit 41 to each respective coil 11 in turn. This allows polling of the coils 11 over time. That is, as the switching occurs, the processing circuit 50 is supplied by the detection circuit 42 with the output signals from each respective coil 11 in turn. The processing circuit 50 processes the one or more detected parameters from all coils 11 to provide one or more measures of the contents of the bore 2. The processing circuit 50 may performed processing in the manner disclosed in WO-2016/174439, to which reference is made for further details.

The processing circuit 50 may output a measure of position of an object within the bore 2. For deriving such a measure may be a parameter which is detected and used may be the frequency of the oscillations. This will depend on the position of the object within the bore 2. In typical oil and gas applications, frequency shifts caused by the movement of an object in the bore are virtually unaffected by any fluctuations in the composition of the fluid in the bore 2. However, other parameters may alternatively be used.

For example, in some applications the object may be an elongate component in the bore 2. In an oil and gas application, the elongate component may be a drill string comprising a series of drill pipes connected by joint sections, a drill casing connected by a plurality of joint sections, tubing or tooling. For example, the elongate component, and sensed features thereof, may be any of: a section or ‘stand’ of drill pipe, pipe joint, tubulars, drilling tool, tool joint, casing, casing collar, logging tool, logging tool, cabling, wireline, electric line, slickline, logging while drilling (LWD) tools or measuring while drilling (MWD) tools, cameras, debris, wrenches or spanners, jars or jarring equipment, pigs or pigging devices, production tubing, perforators or perforation equipment, coiled tubing, hosing, umbilical, composite piping or tubing, well intervention tubing, cutting tools, fishing equipment or well intervention equipment.

In that case, the processing circuit 50 may output a measure of the lateral position within the bore 2 of the elongate component and/or a measure of the axial position within the bore 2 of a feature of the elongate component, for example a joint section. Generally the feature whose axial position is detected may be any element having a different interaction with the EM field of the coils from the remainder of elongate component. Typically, the feature will be an element having a different external shape from the remainder of elongate component.

More generally, the sensor insert 1 can be used to locate elongate components in any vertical or horizontal infrastructure used during drilling, exploration and production of hydrocarbons including but not limited to pressure control equipment, blow out preventer (BOP), BOP stack, Christmas trees (x-trees), subsea x-trees, ‘dry’ x-trees, horizontal or vertical x-trees, risers, flexible risers, articulated risers, well intervention systems, well caps, containment domes, seal-subs, riser adapters, composite risers, umbilical, casing, tubing, piping, flanges, production or injection flowlines, pipelines, pipeline networks, manifolds, separators, pumps, compressors, mouseholes, moon pools, jars and fingerboards.

The processing circuit 50 may derive such measures in the manner disclosed in WO-2016/174439, to which reference is made for further details.

In this case, the measures output by the processing circuit 50 may be used to control a BOP apparatus that operates shear rams in an emergency to cut through the elongate component with the intention of sealing the bore 2 and hence a well in which the BOP apparatus 2 is employed.

The processing circuit 50 may output a measure of material properties of the contents of the bore 2 in a region adjacent to the coil 11 from which an output signal is currently derived. The measures of material properties derived by the processing circuit 50 may be of various different types, depending on the nature of the contents of the bore 2 and the EM properties of interest. By way of non-limitative example, the measures of EM properties may be those described in WO-2012/007718, WO-2015/015150 or GB2,490,685.

For example, in the case of the contents being a slurry, or a fluid with particulate or 5 solid matter, the derived EM properties may be used to discriminate between the solid, water and oil content of a flowing matrix such as waste, brine, drilling cuttings, metallic particulate (in the case of lubrication or hydraulic fluid), mining waste, soil, plant matter (in the case of a fermentation process or biomass) or sewage.

Claims

1. A sensor insert for insertion in a bore, the sensor insert comprising: a tubular wall of non-conductive material for lining the bore;

a plurality of sensing coils supported by the tubular wall, behind the inner surface of the tubular wall, at different angular positions and facing the inner surface of the tubular wall for generating an electromagnetic field extending therethrough;

2. A sensor insert according to claim 1, wherein the annular cavity is thicker than the tubular wall.

3. A sensor insert according to claim 1 or 2, wherein the annular cavity is thicker than the tubular shield.

4. A sensor insert according to any one of the preceding claims, wherein the annular cavity has a thickness of at least 15mm.

5. A sensor insert according to any one of the preceding claims, wherein the tubular wall has a thickness of at most 10mm.

6. A sensor insert according to any one of the preceding claims, wherein the tubular shield has a thickness of at most 5mm.

7. A sensor insert according to any one of the preceding claims, wherein the liquid has a bulk modulus of at least 0.8 GPa.

8. A sensor insert according to any one of the preceding claims, wherein the liquid contains solid material having a higher bulk modulus than the liquid.

9. A sensor insert according to any one of the preceding claims, wherein the liquid is non-conductive.

10. A sensor insert according to any one of the preceding claims, wherein the liquid is an oil.

11. A sensor insert according to any one of the preceding claims, wherein the conductive material of the tubular shield comprises a metal.

12. A sensor insert according to any one of the preceding claims, wherein the coils are fixed to the outer surface of the tubular wall.

13. A sensor insert according to any one of the preceding claims, wherein the pressure balancing unit is disposed at an annular end of the cavity.

14. A sensor insert according to claim 13, wherein the pressure balancing unit comprises two interacting annular volumes extending around the annular end of the cavity and communicating with the annular cavity and the bore, respectively.

15. A sensor insert according to any one of the preceding claims, wherein the pressure balancing unit comprises a chamber containing a deformable container separating variable internal and external volumes, the two volumes communicating with the annular cavity and the bore, respectively.

16. A sensor unit according to claim 15, wherein the deformable container comprises a bellows or a bladder.

17. A sensor insert according to claim 15 or 16, wherein the pressure balancing unit is disposed at an annular end of the cavity, and the deformable container comprises a bellows comprising:

inner and outer stacks of annular metal diaphragms, the diaphragms in each stack being welded alternately at inner and outer edges, and an annular closure attached to the end of the stacks of diaphragms.

18. A sensor insert according to any one of the preceding claims, further comprising an electrical circuit connected to the plurality of coils.

19. A sensor insert according to claim 18, wherein the electrical circuit is disposed in housing arranged outside the tubular shield.

20. A sensor insert according to claim 18 or 19, wherein the electrical circuit comprises:

an oscillator circuit arranged to drive electrical oscillations in the coils for causing the coils to generate oscillating electromagnetic fields; and a detection circuit arranged to output signals from each coil representing a parameter of the electrical oscillations generated therein that depends on the contents of the bore.

21. A sensor insert according to any one of the preceding claims, wherein the bore is a bore for oil or gas extraction or production.

22. A sensor insert according to any one of the preceding claims, wherein the sensor insert is configured to form a sealing insert for a joint assembly between sections of a tube defining the bore.

Intellectual

Property

Office

Application No: GB1704059.3 Examiner: Eleanor Jones