Downhole connection

Abstract

A downhole tool connection comprises (i) a tool intended for downhole use and including a connection section protruding therefrom in use in an uphole direction, the connection section supporting two or more first connectors spaced from one another and operatively connected to the tool; and (ii) a cable carrier moveable in an in-use downhole direction towards the connection section. The cable carrier supports (a) one or more cables and (b) two or more second connectors spaced from one another and operatively connected to at least one cable. Pairs of the first and second connectors are mutually connectable, on movement of the cable carrier towards the connection section to increase the proximity of the connectors of the pairs, in a manner effecting electrical transmission between the connectors of each pair. At least one pair of the connectors connects inductively, and at least one pair of the connectors connects conductively.

Claims

1. A downhole tool connection comprising: (i) a tool intended for downhole use and including a connection section protruding therefrom in use in an uphole direction, the connection section supporting two or more first connectors that are spaced from one another and operatively connected to the tool; and (ii) a cable carrier that is moveable in an in-use downhole direction towards the connection section, the cable carrier supporting (a) one or more cables and (b) two or more second connectors that are spaced from one another and operatively connected to at least one of the one or more cables, pairs of the first and second connectors being mutually connectable, on movement of the cable carrier towards the tool connection section so as to increase the proximity of the first and second connectors of the pairs, in a manner effecting electrical transmission between the first and second connectors of each pair, wherein at least one of the pairs of the first and second connectors connects inductively and at least one of the pairs of the first and second connectors connects conductively.

2. A downhole tool connection according to claim 1 wherein the connection section is or includes an elongate mandrel protruding from the in-use uphole end of the tool.

3. A downhole tool connection according to claim 2 including a plurality of the first connectors defining a series extending along the elongate mandrel.

4. A downhole tool connection according to claim 3 wherein at least one of the first connectors of the series that lies nearest the tool connects inductively, and wherein at least one of the first connectors that lies furthest from the tool connects conductively.

5. A downhole tool connection according to claim 4 including a plurality of the first connectors that connect inductively defining a first series extending along the elongate mandrel away from the tool; and a plurality of the first connectors that connect conductively defining a second series extending along the elongate mandrel away from the first series.

6. A downhole tool connection according to claim 5 wherein the first series comprises six of the first connectors; and wherein the second series comprises two of the first connectors.

7. A downhole tool connection according to claim 2 wherein at least one of the first connectors encircles the mandrel.

8. A downhole tool connection according to claim 1 wherein the cable carrier includes one or more socket for receiving the connection section therein.

9. A downhole tool connection according to claim 8 including a semi-solid, essentially non-conducting medium occupying the cross-section of the interior of the socket at least in the vicinity of a given one of the second connectors that connects conductively.

10. A downhole tool connection according to claim 8 wherein the connection section is or includes an elongate mandrel protruding from the in-use uphole end of the tool; and wherein the socket is or includes an elongate hollow cylinder.

11. A downhole tool connection according to claim 10 wherein at least one of the second connectors includes an annulus extending about the interior of the hollow cylinder.

12. A downhole tool connection according to claim 11 wherein the connection section is or includes an elongate mandrel protruding from the in-use uphole end of the tool; wherein at least one of the first connectors encircles the mandrel; and wherein the diameter of the at least one second connector including the annulus extending about the interior of the hollow cylinder that connects inductively is greater than the outer diameter of the at least one first connector of the pair of which the at least one second connector forms part.

13. A downhole tool connection according to claim 11 wherein the connection section is or includes an elongate mandrel protruding from the in-use uphole end of the tool; wherein at least one of the first connectors encircles the mandrel; and wherein the diameter of the at least one second connector including the annulus extending about the interior of the hollow cylinder that connects conductively results in contact with the at least one first connector of the pair of which the at least one second connector forms part when the at least one first and second connectors are in proximity.

14. A downhole tool connection according to claim 8 including a plurality of the second connectors defining a series extending along the interior of the socket.

15. A downhole tool connection according to claim 14 wherein at least one of the second connectors of the series that in use lies nearest the tool connects inductively, and wherein at least one of the second connectors that lies furthest from the tool connects conductively.

16. A downhole tool connection according to claim 15 including a plurality of the second connectors that connect inductively defining a third series extending in use along the interior of the socket away from the tool; and a plurality of the second connectors that connect conductively defining a fourth series extending along the interior of the socket away from the first series.

17. A downhole tool connection according to claim 1 wherein the cable carrier includes an elongate, cylindrical body supporting on its exterior one or more swab cups permitting pumping of the cable carrier along a borehole.

18. A downhole tool connection according to claim 1 wherein the cable carrier includes an elongate, hollow cylindrical body inside which at least one of the one or more cables supported by the cable carrier extends.

19. A downhole tool connection according to claim 18 including one or more flexible weights supporting at least one of the one or more cables inside the cylindrical body.

20. A downhole tool connection according to claim 1 wherein at least one of the one or more cables supported by the cable carrier in use connects to one or more sources of electrical power located uphole of the tool.

21. A downhole tool connection according to claim 1 wherein at least one of the one or more cables supported by the cable carrier that connects to the second connector that connects inductively is connected to one or more sources of electrical power in a range of 8-15 Watts each.

22. A downhole tool connection according to claim 1 wherein at least one of the one or more cables supported by the cable carrier that connects to the second connector that connects conductively is connected to one or more sources of at least 200 Watts of electrical power.

23. A downhole tool connection according to claim 1 wherein the cable carrier is or includes a side entry cable sub.

24. A downhole tool connection according to claim 1 including one or more shock absorber acting between the connection section and the tool.

25. A downhole tool connection according to claim 24 wherein the shock absorber includes one or more resiliently deformable member defining an elongate column, whereby the column is resiliently compressible on being subjected to compressive force in the direction of elongation of the column.

26. A downhole tool connection according to claim 24 wherein the resiliently deformable member is formed as two or more regions of the material or materials of the column that are interconnected by resiliently deformable interconnecting elements.

27. A downhole tool connection according to claim 26 wherein at least one of the resiliently deformable interconnecting elements is formed from the material or materials of the column.

28. A downhole tool connection according to claim 24 wherein the shock absorber includes at an in-use uphole end one or more landing surfaces from which the connection section protrudes in a manner exposing part of the landing surface for engagement by the cable carrier on movement of the cable carrier towards the tool connection section so as to increase the proximity of the first and second connectors of the pairs.

29. A downhole tool connection according to claim 1 wherein the connection section includes a cylindrical body that includes one or more fluid flow passage extending therethrough and defining a fluid flow path.

30. A downhole tool connection according to claim 29 wherein the fluid flow path includes one or more openable and closeable valves for opening and closing the fluid flow path.

31. A downhole tool connection according to claim 1 when included in or forming part of a downhole tool selected from the list including logging tools, testers, and sampling tools.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) There now follows a description of a preferred embodiment, by way of non-limiting example, with reference to the accompanying drawings in which:

(2) FIG. 1a illustrates a logging tool inside drill pipe and having a protruding connection section;

(3) FIG. 1b illustrates a cable carrier supporting one or more cables for movement inside the drill pipe in a manner permitting connection to the connection section;

(4) FIG. 2 is an enlargement of part of the connection section of FIG. 1a and the cable carrier of FIG. 1b when they are spaced from one another inside drill pipe such that connection between them is not established; and

(5) FIG. 3 shows the parts of FIG. 2 following movement together of the connection section part and the cable carrier part to a state of increased proximity amounting to connection between the connection part and the cable carrier part.

DETAILED DESCRIPTION

(6) Referring to the drawings a logging tool 10 intended for downhole use is illustrated in a downhole location in a borehole secured at the end of drill pipe 11. The nature of drill pipe is well known in the downhole exploration discipline and is not described in full herein.

(7) The logging tool 10 may take any of a wide variety of forms and non-limitingly may be e.g. a resistivity logging tool or a pulsed neutron generator type, these logging tools being illustrative of kinds of logging tool that have mixed electrical power requirements. In particular such logging tools require a high power connection that powers an energy source forming part of the logging tool that energizes a rock formation surrounding the borehole; and they also have one or more relatively low power needs for purposes of telemetering log data to a surface (uphole) location, transmission of deployment and activation commends from the surface location to the logging tool and so on as indicated herein.

(8) It is known to deploy logging tools such as logging tool 10 protruding from the end of drill pipe 11 that is fed into the borehole from the surface location. Drill pipe is manufactured in discrete lengths that may be connected one to another at the surface location and that when connected together in short lengths are called “stands”. The addition of drill pipe stands one by one in this way repeatedly extends the resulting drill pipe string into the borehole until the protruding logging tool reaches a depth in the borehole at which logging is to commence.

(9) Subsequent logging takes place typically while the stands or the individual lengths of drill pipe one by one are removed from the uphole end of the drill pipe string, with the consequence that the logging tool is gradually withdrawn along the borehole in an uphole direction.

(10) Many logging tool designs must be connected to wireline so that (a) power for energizing the rock can be transmitted to the downhole logging tool; (b) deployment, activation and other commands can be transmitted to the logging tool; (c) the logging tool can transmit signals to an uphole location in order to indicate its status, correct or incorrect deployment, the start and finish of logging activities and so on; and (d) log data signals generated by the logging tool can be telemetered to an uphole location for processing, analysis, display, storing, printing and transmitting purposes.

(11) It is however in many instances impossible to deploy the logging tool protruding from the drill pipe with the wireline connected. Therefore it is necessary to arrange connection of the wireline to the logging tool after the latter has been deployed to the depth in the borehole at which logging is to commence. As explained, prior art arrangements for effecting such connection are in various ways sub-optimal.

(12) The logging tool 10 of FIG. 1a includes protruding from its in-use uphole end 10a in an uphole direction a connection section 12 that forms one element of a downhole logging tool connection according to the disclosure hereof.

(13) The connection section 12 in the illustrated embodiment includes an elongate mandrel 13 that protrudes from a shock absorber 14, that is described in more detail below, forming a further part of the connection section 12 and interconnecting the mandrel 13 and the uphole end 10a of the logging tool 10.

(14) Mandrel 13 is in the illustrated embodiment a rigid, elongate cylindrical member. Such an element is relatively easy to manufacture and its shape promotes good connection with a cable carrier 26 described below. However other forms of the connection section 12 may include e.g. mandrels of non-circular cross-section (such as but not limited to ellipses, regular polygonal shapes or irregular polygonal shapes). Partly hollow or perforated members also are possible, as are many further design variants of kinds that will occur to the person of skill in the art. The mandrel 13 does not have to be of constant or regular cross-section, although a circular cross-section is preferred.

(15) The mandrel 13 supports a plurality of first electrical connectors 16, 17, 18, 19, 21, 22, 23, 24. These are presented as a series of mutually equally spaced elements extending in a line along the mandrel 13.

(16) As explained in more detail below, first connectors 16, 17, 18, 19, 21 and 22 are relatively low power connectors (e.g. that non-limitingly are designed to transmit 8-15 Watts each) that connect inductively; and first connectors 23, 24 are relatively high power connectors (e.g. intended to transmit 200+ Watts each) that connect conductively.

(17) Each of the first connectors 16, 17, 18, 19, 21, 22, 23, 24 is formed as an annulus that is secured to and encircles the shaft of the mandrel 13. Each of them is insulated from the material of the mandrel 13 and is connected e.g. inside the mandrel 13 to at least one cable that electrically communicates with one or more operative parts of the logging tool. The person of skill in the art readily will be able to envisage such insulation and cable connections inside the mandrel 13.

(18) Other forms and numbers of the first connectors 16, 17, 18, 19, 21, 22, 23, 24 are possible within the scope of this disclosure. Thus for example it is not essential that the first connectors 16, 17, 18, 19, 21, 22, 23, 24 in each, or indeed any, case encircle the mandrel 13 and instead for instance one or more of them may be formed as interrupted annuli, strips, buttons or blocks. As indicated the numbers of first connectors 16, 17, 18, 19, 21, 22, 23, 24 may differ from the eight illustrated; and it is not essential that the spacings between each adjacent pair of first connectors is the same as described. Combinations of different first connector types are possible within the scope of the disclosure.

(19) The downhole logging tool connection also includes a cable carrier 26 supporting one or more cables 27 and a plurality of second connectors 28, 29, 31, 32, 33, 34, 36, 37.

(20) The cable carrier 26 is intended for deployment inside the drill pipe 11 in a manner described below and includes at an in-use downhole end an elongate, hollow cylindrical socket 38 that is open at an in-use downhole end and closed at its opposite end as illustrated. As described in more detail below socket 38 is in use of the downhole logging tool connection located and dimensioned to receive inserted therein the mandrel 13.

(21) The second connectors 28, 29, 31, 32, 33, 34, 36, 37 are located in a series extending along the inside of the socket 38.

(22) Each second connector 28, 29, 31, 32, 33, 34, 36, 37 is in the illustrated embodiment an annulus extending about the circular cross-section interior of the socket 38; but this need not necessarily be the case. Thus for example it is not essential that the second connectors 28, 29, 31, 32, 33, 34, 36, 37 in each, or indeed any, case encircle the mandrel 13 and instead for instance one or more of them may be formed as interrupted annuli, strips, buttons or blocks. The numbers of second connectors 28, 29, 31, 32, 33, 34, 36, 37 may differ from the eight illustrated; and it is not essential that the spacings between adjacent pairs of second connectors is the same as described. Combinations of different second connector types are possible within the scope of the disclosure.

(23) In like manner to the mandrel 13 it is not essential that socket 38 exhibits the regular, circular cross section illustrated in FIG. 1b. Thus it is possible for the socket 38 to have a non-circular and/or irregular cross-section, for example adopting one or more of the shapes listed above in relation to the mandrel 13. When the downhole logging tool connection is embodied in a form as illustrated including a mandrel 13 and socket 38 however it is important that the dimensions and/or shapes of these parts are such as to permit the insertion of the mandrel 13 into the socket 38 in a manner promoting electrical connection between the respective first 16, 17, 18, 19, 21, 22, 23, 24 and second 28, 29, 31, 32, 33, 34, 36, 37 connectors.

(24) To this end in the embodiment of FIGS. 1a and 1b the locations, diameters and spacings of the second connectors 28, 29, 31, 32, 33, 34, 36, 37 are such that on insertion of the mandrel 13 into the socket 38 as described below each respective first connector 16, 17, 18, 19, 21, 22, 23, 24 is in register with an associated second connector 28, 29, 31, 32, 33, 34, 36, 37.

(25) In a similar manner to the series of first connectors 16, 17, 18, 19, 21, 22, 23, 24, the second connectors 28, 29, 31, 32, 33, 34 are relatively low power connectors that connect inductively and the second connectors 36, 37 are relatively high power connectors that connect conductively.

(26) As is apparent from the figures the six first conductors 16, 17, 18, 19, 21, 22 supported on the mandrel 13 closest to the logging tool 10 connect inductively and the two first conductors 23, 24 furthest from the logging tool 10 connect conductively. The second connectors 28, 29, 31, 32, 33, 34, 36, 37 are similarly arranged so that on insertion of the mandrel 13 into the socket 38 each inductive first connector is in register with an inductive second connector; and each conductive first connector is in register with a conductive second connector. Thus, overall, there are four series of connectors: two made up of first connectors supported on the mandrel and consisting respectively of inductive and conductive connectors; and two supported in the socket and also consisting respectively of inductive and conductive connectors.

(27) The cable 27 is in the illustrated embodiment non-limitingly shown as wireline the nature and characteristics of which are well known in the logging tool art. The design of the cable 27 therefore is not described in detail herein, except to note that within an outer, armored, semi-rigid casing 39 the wireline is constituted as a plurality of individual cables some of which are relatively high-power cables and some of which are relatively low-power cables.

(28) As shown in FIG. 1a the individual cables 27a-27h extend beyond the termination of the armored casing 39 inside the cable carrier 26 uphole of the closed end of the socket 38. The individual cables 27a-27h connect respectively to the second connectors 28, 29, 31, 32, 33, 34, 36, 37 by passing along passages formed in the material of the socket 38. The armored casing 39 is clamped in one or more clamping blocks 41, 42 inside the cable carrier 26 in order to stabilize the wireline at the end of the armored casing 39.

(29) In FIG. 1b the individual cables are illustrated as being the same as one another but in embodiments it is likely that at least the individual cables intended to carry relatively high currents will be of differing specifications and designs than individual cables intended to carry relatively low currents. In the illustrated embodiment six of the individual cables 27a-27f are low power cables and are connected to the respective inductively connectable second connectors 28, 29, 31, 32, 33, 34; and two of the individual cables 27g and 27h are relatively high-power cables that connected to the conductively connectable second connectors 36, 37.

(30) More or fewer of the relatively low-power and relatively high power individual cables may be provided, depending on the nature of the logging tool 10 and its operational requirements. The numbers of first connectors correspond to the numbers of second connectors that are in turn determined by the number and nature of individual cables.

(31) At least one of the individual cables 27a-27h is in use of the downhole connection connected at an uphole or surface location to a source of electrical power. At least a pair of the individual cables 27a-27h may be provided as a twisted cable pair.

(32) The cable carrier 26 extends as a plain cylindrical body in an uphole direction for several meters and encloses the wireline over this length extending along the cable carrier 26 within a hollow interior. The wireline 27 enters the interior of the cable carrier by way of an aperture 43 formed in the uphole end of the cable carrier. A side entry sub, i.e. a separate sub placed higher in the drill string to allow the cable to enter the inside of the drill pipe may be provided in order to permit the cable 27 to enter the illustrated tool string at a relatively uphole location. Side entry sub designs are familiar to the person of skill in the art. Separately a female pump down/weight bar assembly may be provided on the end of the wireline (cable 27). For example, this may take the form of one or more flexible weights 19 supporting at least one of the one or more cables inside the cylindrical body, a possible location for which is schematically illustrated in FIG. 1b.

(33) The interior of the socket 38 in a typical use application would be filled with a semi-solid, non-conducting medium such as a grease. This prevents the ingress of borehole fluid into the interior of the socket 38 during deployment of the cable carrier from an uphole location. The precise specification of the grease may be selected by the person of skill in the art depending on the nature of e.g. the borehole fluid.

(34) In practice it is relatively straightforward to fill the entire socket with the semi-solid medium, but the disclosure also includes within its scope arrangements in which the socket is partially filled with such a medium, or empty of medium.

(35) Each of the second connectors 28, 29, 31, 32, 33, 34 that connects inductively is of a greater diameter than that of the respective first connector 16, 17, 18, 19, 21, 22 with which it is in register on insertion of the mandrel 13 into the socket 38. Thus the inductively connectable second connectors 28, 29, 31, 32, 33, 34 and the inductively connectable first connectors 16, 17, 18, 19, 21, 22 pass one another essentially without contact during movement of the connection section 12 and the socket 38 from a position of relative separation downhole to a position of greater proximity that brings the respective first and second connectors into register with one another.

(36) This minimizes the effect of the first and second connectors abrading one another, or causing abrasion by reason of the trapping of borehole fluid between the inductively connectable first and second connectors.

(37) Moreover since the first and second inductively connectable connectors do not need to contact one another in order for an electrical connection to be made, they can be protected (e.g. through the application of polymeric or other durable covers or coatings that prevent or at least minimize abrasion and chemical attack by the borehole fluid).

(38) On the other hand the diameter of each of the second connectors 36, 37 that connect conductively are such as to contact the exterior of the first, conductively connectable connector 23 or 24 with which it is in register when the mandrel 13 is fully inserted into the socket 38. This gives rise to the conductive connection and also causes wiping of the conductively connectable connectors in a manner removing grease, borehole fluid and other media that might otherwise interfere with the conductive connection.

(39) The cylindrical exterior of the cable carrier 26 includes encircling it at least one, and in the illustrated embodiment two, swab cups 44, 46.

(40) A swab cup is known per se in the downhole tool deployment art and typically consists of a circular or annular cup-like structure formed of a resiliently deformable material. In the case of the illustrated embodiment the exterior diameter of the cup is such that the resiliently deformable material of the swab cup 44, 46 seals against the inner surface of drill pipe 11 inside which the swab cup 44, 46 is deployed. An inner annulus of the swab cup seals on to the exterior of the cable carrier 26.

(41) As a result of this arrangement when borehole fluid is circulated by pumping in the drill pipe 11 it is possible to convey the cable carrier along the interior of the drill pipe 11. This is known as “pump down” deployment, and is familiar to the person of skill in the art.

(42) The connection section 12 includes a shock absorber 14 extending between the mandrel 13 and the logging tool 10. The shock absorber 14 in the illustrated embodiment is constituted as a collapsible column defined by a series of resiliently deformable elements 47 seriatim interconnecting respective, intermediate incompressible members 48 that may be formed e.g. as discs of rigid material. In the illustrated embodiment the resiliently deformable elements 47 and the incompressible members 48 are formed by machining or other material removal methods from an initially solid column of a rigid material such as a metal. However a variety of other ways of forming the shock absorber are possible and the disclosure is not limited to the arrangement shown. As one non-limiting variant one may consider a stack of resiliently deformable (e.g. polymeric) tubes.

(43) The uphole end of the shock absorber 14 adjacent the downhole end of the mandrel 13 is formed as a disc-like landing surface 49. The landing surface is dimensioned to be engageable by the open end of the socket 38 on insertion of the mandrel 13 thereinto. The lengths of the mandrel 13 and the socket 38 are chosen to permit such engagement without the end 13a of the mandrel engaging the closed end of the socket 38.

(44) A fluid flow passage 51 is formed in the material of the logging tool 10 in a manner interconnecting the uphole side of the logging tool 10 and its downhole side that protrudes downhole beyond the drill pipe 11. As a result the fluid flow passage 51 defines a fluid bypass allowing fluid under pressure inside the drill pipe 11 to escape in a downhole direction.

(45) The fluid flow passage 51 includes a valve 52. This may take a variety of forms and in the illustrated embodiment is a spring-loaded flapper valve formed in a valve chamber 53 of greater dimensions than the passage 51.

(46) The spring loading of the flapper valve 52 maintains it in a normally closed position blocking the flow of fluid in the passage 51. When the pressure of fluid in the passage 51 is sufficient to overcome the biasing of the flapper valve 52 the valve opens and permits fluid bypass.

(47) The biasing of the valve 52 to a normally closed position means that in the event of well kicking causing a pressure pulse that travels in an uphole direction (typically at high speed) the valve prevents transmission of pressure-induced forces uphole that might damage equipment or cause injury to operators in the vicinity of the borehole. Biasing of the flapper valve 52 may be effected in a per se known way using one or more springs or in a variety of alternative ways.

(48) In use of the illustrated downhole connection the logging tool 10 is initially secured onto the downhole end of a stand of drill pipe 11 that is then fed from an uphole (surface) location in to a borehole. Successive drill pipe stands are then added at the uphole location, thereby progressively lengthening the drill pipe string with the logging tool protruding from its downhole end.

(49) During this process the logging tool 10 must remain disconnected from wireline and is depowered.

(50) When the logging tool 10 reaches a location at which logging is to commence the cable carrier 26, supporting the wireline 27 as described and having its socket 38 filled with non-conducting grease also as described, is pumped down the borehole inside the drill pipe 11. Such pumping is effected by circulating borehole fluid in the drill pipe, using per se known pumping and valve control techniques to cause the swab cups 44, 46 to drive the cable carrier 26 in a downhole direction. During this process pressurized borehole fluid driven ahead of the cable carrier 26 passes via the passage 51 to open valve 52 and vent to the downhole side of the drill pipe 11.

(51) The relative positions of the mandrel 13 and the socket 38 just before making of the required downhole connections occurs is shown in FIG. 2. The dimensions and shape of (a) the open end of the socket 38 and (b) the end 13a of the mandrel 13 are such that as long as the cable carrier 26 is largely centered in the drill pipe (as would be assured through appropriate swab cup design) the mandrel 13 is aligned for entry into the socket 38.

(52) Further pumping of the cable carrier 26 in a downhole direction results in the situation shown in FIG. 3, in which the mandrel is fully inserted into the socket 38. As the insertion completes the various pairs of connectors align with one another to form the described inductive or conductive connections as appropriate. During this part of the connection action at least some of the grease (or other semi-solid medium) in the socket 38 is displaced and passes along the outside of the mandrel 13 to escape into the drill pipe.

(53) The open end of the socket 38 engages the landing surface 49 before the end 13a of the mandrel collides with the closed, uphole end of the inside of the socket 38. As a result the energy driving the cable carrier 26 in a downhole direction is transmitted to the shock absorber 14 and attenuated.

(54) The inductively connectable connector pairs achieve connection without contacting one another; and the conductively connectable pairs engage as illustrated. As mentioned this wipes the connectors of each pair, clearing grease, borehole fluid and other non-conducting materials in order to ensure good electrical connection.

(55) The described arrangement gives rise to a reliable connection in which the conductive connector pairs are protected against damage by reason of being located deep inside the socket 38 and by reason of the presence of the semi-sold medium. The inductively connectable connector pairs may as described be protected by shielding on their exteriors, which do not make contact with other parts of the connection and therefore require protection only in respect of the effects of borehole fluid.

(56) A releasable latching mechanism that is not shown in the drawings is then activated to retain the connector parts in their connected configuration. Such a latching mechanism may readily be envisaged by the person of skill in the art, and may be of a type that releases if a threshold tension is exceeded.

(57) Although the described embodiment is a highly reliable design, numerous variants are possible. Thus for example it is not necessary to embody the cable carrier 26 so as to include a socket per se. On the contrary, the mandrel may be caused to pass through one or more guiding rings to ensure it aligns with a cable carrier that may take the form of a plate on one or more surfaces of which the second connectors are supported.

(58) As noted the numbers of the conductively and inductively connectable connectors may vary, it being a requirement herein simply that there is at least one connector of each type.

(59) The mandrel and socket components may be inverted in the arrangement, such that the cable carrier includes a protruding mandrel and the uphole end if the logging tool may include an elongate socket. However in this arrangement it may be hard to be sure an adequate quantity of non-conducting semi-solid medium exists inside the socket.

(60) As explained although the described embodiment is of a logging tool, the downhole tool may take a variety of other forms and may be (or may include) a tester or sampling tool. Combination/hybrid tools also are possible. The person of skill in the art may embody such tools, following as necessary modifications of the parts described and illustrated herein.

(61) The listing or discussion of an apparently prior-published document in this specification should not necessarily be taken as an acknowledgement that the document is part of the state of the art or is common general knowledge.

(62) Preferences and options for a given aspect, feature or parameter of the invention should, unless the context indicates otherwise, be regarded as having been disclosed in combination with any and all preferences and options for all other aspects, features and parameters of the invention.