APPARATUS AND METHOD FOR SIGNALLING BETWEEN DOWNHOLE AND UPHOLE LOCATIONS

Abstract

An apparatus can include a downhole tool having a fluid outlet connectable to a fluid inlet to define a flow path via a hollow interior of the tool, and a valve member capable of opening and constricting or closing the flow path. The apparatus further includes pipe within which a part of the tool is located, the tool being sealed with an interior of the pipe, preventing fluid flow in the pipe via the part of the tool. The pipe includes an openable valve for permitting flow of fluid from the pipe interior via another flow path interconnecting the pipe interior and outside. The valve is normally closed. When the valve member constricts or closes the first flow path, fluid pressure in the pipe increases to cause opening of the valve and venting of pressurized fluid from within the pipe to the outside via the second flow path.

Claims

1. Apparatus for signalling between downhole and uphole locations in a borehole comprising a downhole tool having a hollow interior; a fluid inlet; a fluid outlet that is connectable to the fluid inlet to define a first fluid flow path via the hollow interior; and a moveable valve member that is capable of selectively opening and constricting or closing the first fluid flow path, the apparatus further including pipe within which at least part of the downhole tool is moveably located, the downhole tool being peripherally sealed to the interior of the pipe in a manner preventing fluid flow in the pipe via part of the exterior of the downhole tool; the downhole tool being constrained to lie at least partially within the pipe; and the pipe including an openable valve permitting flow of fluid from the interior of the pipe via at least one second fluid flow path interconnecting the interior of the pipe and the outside, wherein the openable valve is normally closed and wherein when the moveable valve member constricts or closes the first fluid flow path fluid pressure in the pipe increases to cause opening of the openable valve and venting of pressurised fluid from within the pipe to the outside via at least one said second fluid flow path.

2. Apparatus according to claim 1 wherein the downhole tool is or includes a logging tool.

3. Apparatus according to claim 1 wherein the fluid inlet and the fluid outlet are respective apertures that are spaced from one another along the length of the downhole tool and that each perforate a wall of the downhole tool whereby the hollow interior interconnects the fluid inlet and the fluid outlet.

4. Apparatus according to claim 1 wherein the fluid inlet in use lies uphole of the fluid outlet.

5. Apparatus according to claim 1 wherein the moveable valve member is or includes a piston that is moveable in the hollow interior between a valve open position in which it is spaced from the fluid inlet; and a valve closed position in which the piston lies adjacent to and constricts or closes the fluid inlet.

6. Apparatus according to claim 1 wherein the moveable valve member is or includes a piston that is moveable in the hollow interior between a valve open position in which it is spaced from the fluid inlet; and a valve closed position in which the piston lies adjacent to and constricts or closes the fluid inlet, the apparatus including one or more actuator for effecting movement of the piston between the valve open position and the valve closed position when the downhole tool protrudes partially from the pipe.

7. Apparatus according to claim 1 wherein the downhole tool includes extending about its exterior at least one sealing member that effects a fluid-proof seal between the downhole tool and the interior of the pipe.

8. Apparatus according to claim 1 wherein the downhole tool includes extending about its exterior at least one sealing member that effects a fluid-proof seal between the downhole tool and the interior of the pipe and wherein the at least one sealing member permits movement of the downhole tool along the pipe.

9. Apparatus according to claim 1 wherein the interior of the pipe includes one or more inwardly directed projection and the pipe includes one or more outwardly directed projection that is engageable with a said inwardly directed projection, and wherein mutual engagement of the inwardly and outwardly directed projections constrains the logging tool to lie partially within the pipe with a length of the downhole tool protruding from the pipe in a downhole direction.

10. Apparatus according to claim 1 wherein the interior of the pipe includes one or more inwardly directed projection and the pipe includes one or more outwardly directed projection that is engageable with a said inwardly directed projection, wherein mutual engagement of the inwardly and outwardly directed projections constrains the logging tool to lie partially within the pipe with a length of the downhole tool protruding from the pipe in a downhole direction: wherein the one or more inwardly directed projections is or includes an annular projection secured to and protruding inwardly from an interior surface of the pipe; and wherein the one or more outwardly directed projections is or includes an annular projection secured to and protruding outwardly from an outer surface of the downhole tool and being located uphole of the inwardly directed annular projection, the outwardly directed annular projection being too large to pass through the inwardly directed annular projection on movement of the downhole tool in a downhole direction causing the inwardly directed annular projection to approach the outwardly directed annular projection.

11. Apparatus according to claim 1 wherein the interior of the pipe includes one or more inwardly directed projection and the pipe includes one or more outwardly directed projection that is engageable with a said inwardly directed projection, wherein mutual engagement of the inwardly and outwardly directed projections constrains the logging tool to lie partially within the pipe with a length of the downhole tool protruding from the pipe in a downhole direction: and the apparatus including one or more shock absorbing element that is retained relative to the downhole tool in a region between the one or more outwardly directed projection and the one or more inwardly directed projection thereby permitting indirect engagement between the one or more inwardly directed and outwardly directed projections in order to buffer impulses arising on mutual approach of the one or more inwardly and outwardly directed projections during movement of the downhole tool in a downhole direction.

12. Apparatus according to claim 1 wherein the interior of the pipe includes one or more inwardly directed projection and the pipe includes one or more outwardly directed projection that is enaaaeable with a said inwardly directed projection, wherein mutual engagement of the inwardly and outwardly directed projections constrains the logging tool to lie partially within the pipe with a length of the downhole tool protruding from the pipe in a downhole direction: the apparatus including one or more shock absorbing element that is retained relative to the downhole tool in a region between the one or more outwardly directed projection and the one or more inwardly directed projection thereby permitting indirect engagement between the one or more inwardly directed and outwardly directed projections in order to buffer impulses arising on mutual approach of the one or more inwardly and outwardly directed projections during movement of the downhole tool in a downhole direction: and wherein the one or more shock absorbing element encircles the downhole tool in a region between the one or more inwardly directed projection and the one or more outwardly directed projection.

13. Apparatus according to claim 1 wherein the one or more shock absorbing element is or includes a crushable tube that encircles the downhole tool.

14. Apparatus according to claim 1 wherein the one or more shock absorbing element includes a swage element that lies externally of the downhole tool; and wherein the apparatus includes a swage member that is fixable relative to the downhole tool and is moveable in engagement with the swage element on movement of the downhole tube beyond a predetermined position in a manner dissipating kinetic energy of the downhole tool.

15. Apparatus according to claim 1 wherein the one or more shock absorbing element includes a swage element that lies externally of the downhole tool; wherein the apparatus includes a swage member that is fixable relative to the downhole tool and is moveable in engagement with the swage element on movement of the downhole tube beyond a predetermined position in a manner dissipating kinetic energy of the downhole tool; and wherein the swage element is or includes a tube that encircles the downhole tool.

16. Apparatus according to claim 1 wherein at least one said second fluid flow path is or includes one or more aperture perforating a wall of the pipe.

17. Apparatus according to claim 1 wherein the openable valve includes a moveable tubular valve member that lies within the pipe and a biasing arrangement that causes the tubular valve member normally to close the or each second fluid flow path.

18. Apparatus according to claim 1 wherein the openable valve includes a moveable tubular valve member that lies within the pipe and a biasing arrangement that causes the tubular valve member normally to close the or each second fluid flow path; and wherein the biasing arrangement includes an inwardly directed valve bias projection that protrudes inwardly from a wall of the pipe at a location downhole of the tubular valve member; and a hollow spring extending between the inwardly directed valve bias projection and a location uphole thereof whereby the hollow spring acts on the tubular valve member and biases it to a position closing the or each second fluid flow path.

19. Apparatus according to claim 1 wherein the openable valve includes a moveable tubular valve member that lies within the pipe and a biasing arrangement that causes the tubular valve member normally to close the or each second fluid flow path; and wherein the biasing arrangement includes an inwardly directed valve bias projection that protrudes inwardly from a wall of the pipe at a location downhole of the tubular valve member: a hollow spring extending between the inwardly directed valve bias projection and a location uphole thereof whereby the hollow spring acts on the tubular valve member and biases it to a position closing the or each second fluid flow path; and a spring core tube lying inside and supporting the hollow spring.

20. Apparatus according to claim 1 wherein the openable valve includes a moveable tubular valve member that lies within the pipe and a biasing arrangement that causes the tubular valve member normally to close the or each second fluid flow path; wherein the biasing arrangement includes an inwardly directed valve bias projection that protrudes inwardly from a wall of the pipe at a location downhole of the tubular valve member: the apparatus including a hollow spring extending between the inwardly directed valve bias projection and a location uphole thereof whereby the hollow spring acts on the tubular valve member and biases it to a position closing the or each second fluid flow path; and a spring core tube lying inside and supporting the hollow spring; wherein the tubular valve member and the spring core tube define respective hollow interiors the sizes of which are such as to permit passage of the downhole tool within and along the tubular valve member and the spring core tube.

21. Apparatus according to claim 1 wherein the openable valve includes a moveable tubular valve member that lies within the pipe and a biasing arrangement that causes the tubular valve member normally to close the or each second fluid flow path and the apparatus includes a space between the tubular valve member and the pipe, the space being bounded at either end respectively by an inwardly directed protuberance protruding towards the interior of the pipe and an outwardly directed protuberance protruding from the tubular valve member whereby to define an essentially closed chamber, the tubular valve member being perforated in the vicinity of the space whereby fluid pressure acting within the tubular valve member acts on the inwardly and outwardly directed protuberances to urge them apart from one another and cause movement of the tubular valve member to open the openable valve.

22. Apparatus according to claim 1 wherein the openable valve includes a moveable tubular valve member that lies within the pipe and a biasing arrangement that causes the tubular valve member normally to close the or each second fluid flow path and the apparatus includes a space between the tubular valve member and the pipe, the space being bounded at either end respectively by an inwardly directed protuberance protruding towards the interior of the pipe and an outwardly directed protuberance protruding from the tubular valve member whereby to define an essentially closed chamber, the tubular valve member being perforated in the vicinity of the space whereby fluid pressure acting within the tubular valve member acts on the inwardly and outwardly directed protuberances to urge them apart from one another and cause movement of the tubular valve member to open the openable valve and wherein the space is annular and the inwardly directed and outwardly directed protuberances are shaped accordingly.

23. Apparatus according to claim 1 wherein the openable valve includes a moveable tubular valve member that lies within the pipe and a biasing arrangement that causes the tubular valve member normally to close the or each second fluid flow path and the apparatus includes a space between the tubular valve member and the pipe, the space being bounded at either end respectively by an inwardly directed protuberance protruding towards the interior of the pipe and an outwardly directed protuberance protruding from the tubular valve member whereby to define an essentially closed chamber, the tubular valve member being perforated in the vicinity of the space whereby fluid pressure acting within the tubular valve member acts on the inwardly and outwardly directed protuberances to urge them apart from one another and cause movement of the tubular valve member to open the openable valve; wherein the space is annular and the inwardly directed and outwardly directed protuberances are shaped accordingly: and wherein the tubular valve member includes plural perforations defining an annular pattern that corresponds to the annular shape of the space.

24. Apparatus according to claim 1 wherein the openable valve includes a moveable tubular valve member that lies within the pipe and a biasing arrangement that causes the tubular valve member normally to close the or each second fluid flow path and the apparatus includes a space between the tubular valve member and the pipe, the space being bounded at either end respectively by an inwardly directed protuberance protruding towards the interior of the pipe and an outwardly directed protuberance protruding from the tubular valve member whereby to define an essentially closed chamber, the tubular valve member being perforated in the vicinity of the space whereby fluid pressure acting within the tubular valve member acts on the inwardly and outwardly directed protuberances to urge them apart from one another and cause movement of the tubular valve member to open the openable valve, the apparatus including a liner tube extending between the tubular valve member and the pipe, the space being defined between the tubular valve member and the liner tube and the liner tube supporting one or more nozzles each forming part of a said second fluid flow path.

25. Apparatus according to claim 1 wherein the apparatus includes or supports one or more sensor elements that are secured relative to the pipe and wherein the downhole tool includes one or more sensors, the one or more sensors detecting the one or more sensor elements on movement of the downhole tool to a deployed location and generating one or more signals indicative of such movement of the downhole tool.

26. Apparatus according to claim 1 including at an uphole location one or more detectors of a pressure pulse that arises at the time of venting of pressurised fluid from within the pipe to the outside via the or each second fluid flow path, the one or more detectors generating one or more signals indicative of such a pressure pulse.

27. Apparatus according to claim 1 including at an uphole location one or more detectors of a pressure pulse that arises at the time of venting of pressurised fluid from within the pipe to the outside via the or each second fluid flow path, the one or more detectors generating one or more signals indicative of such a pressure pulse and wherein the uphole location is a surface location.

28. Apparatus according to claim 1 wherein the apparatus includes or supports one or more sensor elements that are secured relative to the pipe and wherein the downhole tool includes one or more sensors, the one or more sensors detecting the one or more sensor elements on movement of the downhole tool to a deployed location and generating one or more signals indicative of such movement of the downhole tool, the apparatus including one or more processor for processing one or more signals generated by the one or more sensors and generating one or more control commands based on the said signals.

29. Apparatus according to claim 1 wherein the apparatus includes or supports one or more sensor elements that are secured relative to the pipe and wherein the downhole tool includes one or more sensors, the one or more sensors detecting the one or more sensor elements on movement of the downhole tool to a deployed location and generating one or more signals indicative of such movement of the downhole tool, the apparatus including one or more processor for processing one or more signals generated by the one or more sensors and generating one or more control commands based on the said signals and wherein the downhole tool is configured to respond to the one or more control commands by one or more of initiating an action, continuing an action, ceasing an action and/or modifying an action.

30. Apparatus according to claim 1 wherein the apparatus includes or supports one or more sensor elements that are secured relative to the pipe and wherein the downhole tool includes one or more sensors, the one or more sensors detecting the one or more sensor elements on movement of the downhole tool to a deployed location and generating one or more signals indicative of such movement of the downhole tool, the apparatus including one or more processor for processing one or more signals generated by the one or more sensors and generating one or more control commands based on the said signals and wherein the downhole tool is configured to respond to the one or more control commands by one or more of initiating an action, continuing an action, ceasing an action and/or modifying an action: and wherein the said action is selected from the list including deploying one or more deployable components; commencing logging activity; terminating logging activity; adjusting a parameter of logging activity; processing one or more signals resulting from logging activity; requesting diagnostic information and/or responding to one or more requests for diagnostic information.

31. Apparatus according to claim 1 wherein the apparatus includes or supports one or more sensor elements that are secured relative to the pipe and wherein the downhole tool includes one or more sensors, the one or more sensors detecting the one or more sensor elements on movement of the downhole tool to a deployed location and generating one or more signals indicative of such movement of the downhole tool; the apparatus including one or more processor for processing one or more signals generated by the one or more detectors and generating one or more indications based on the said signals.

32. Apparatus according to claim 1 wherein the apparatus includes or supports one or more sensor elements that are secured relative to the pipe and wherein the downhole tool includes one or more sensors, the one or more sensors detecting the one or more sensor elements on movement of the downhole tool to a deployed location and generating one or more signals indicative of such movement of the downhole tool; the apparatus including one or more processor for processing one or more signals generated by the one or more detectors and generating one or more indications based on the said signals: and wherein the one or more indications include one or more selected from the list including an indication of deployment of the downhole tool; an indication of failure of the downhole tool to deploy; and/or diagnostic information received from the downhole tool.

33. Apparatus according to claim 1 wherein the apparatus includes or supports one or more sensor elements that are secured relative to the pipe and wherein the downhole tool includes one or more sensors, the one or more sensors detecting the one or more sensor elements on movement of the downhole tool to a deployed location and generating one or more signals indicative of such movement of the downhole tool; the apparatus including one or more processor for processing one or more signals generated by the one or more detectors and generating one or more indications based on the said signals, the apparatus including one or more display devices for displaying the one or more indications.

34. A method of signalling between downhole and uphole locations in a borehole, the method comprising conveying to a downhole location inside pipe a downhole tool having a hollow interior; a fluid inlet; a fluid outlet that is connectable to the fluid inlet to define a first fluid flow path via the hollow interior; and a moveable valve member that is capable of selectively opening and constricting or closing the first fluid flow path, the pipe including an openable valve permitting flow of fluid from the interior of the pipe via at least one second fluid flow path interconnecting the interior of the pipe and the outside, wherein the openable valve is normally closed and the downhole tool is peripherally sealed to the interior of the pipe in a manner preventing fluid flow in the pipe via part of the exterior of the downhole tool; causing the moveable member to constrict or close the first fluid flow path and effect an increase in the pressure of fluid in the pipe and thereby cause opening of the openable valve and venting of pressurised fluid from within the pipe to the outside via at least one said second fluid flow path.

35. A method according to claim 34 wherein the downhole tool is or includes a logging tool.

36. A method according to claim 34 including the step of causing the downhole tool to move in the pipe to a position partially protruding from the pipe; and subsequently causing the moveable valve member to constrict or close the first fluid flow path and effect an increase in the pressure of fluid in the pipe.

37. A method according to claim 34 including the step of causing the downhole tool to move in the pipe to a position partially protruding from the pipe; and subsequently causing the moveable valve member to constrict or close the first fluid flow path and effect an increase in the pressure of fluid in the pipe and wherein the interior of the pipe includes one or more inwardly directed projection and the pipe includes one or more outwardly directed projection that is engageable with a said inwardly directed projection, the method including causing mutual engagement of the inwardly and outwardly directed projections that constrains the logging tool to lie partially within the pipe with a length of the downhole tool protruding from the pipe in a downhole direction.

38. A method according to claim 34 including the step of causing the downhole tool to move in the pipe to a position partially protruding from the pipe; and subsequently causing the moveable valve member to constrict or close the first fluid flow path and effect an increase in the pressure of fluid in the pipe and wherein the interior of the pipe includes one or more inwardly directed projection and the pipe includes one or more outwardly directed projection that is enaaaeable with a said inwardly directed projection, the method including causing mutual engagement of the inwardly and outwardly directed projections that constrains the logging tool to lie partially within the pipe with a length of the downhole tool protruding from the pipe in a downhole direction and further including causing one or more shock absorbing element that is retained relative to the downhole tool in a region between the one or more outwardly directed projection and the one or more inwardly directed projection to absorb impact energy on mutual engagement of the inwardly and outwardly directed projections.

39. A method according to claim 34 wherein the openable valve includes a tubular valve member that lies within the pipe and a biasing arrangement that causes the tubular valve member normally to close the or each second fluid flow path; and wherein the method includes causing or permitting the biasing arrangement to bias the openable valve to a normally closed position.

40. A method according to claim 34 wherein the openable valve includes a tubular valve member that lies within the pipe and a biasing arrangement that causes the tubular valve member normally to close the or each second fluid flow path; wherein the method includes causing or permitting the biasing arrangement to bias the openable valve to a normally closed position: and wherein the apparatus includes a space between the tubular valve member and the pipe, the space being bounded at either end respectively by an inwardly directed protuberance protruding towards the interior of the pipe and an outwardly directed protuberance protruding from the tubular valve member whereby to define an essentially closed chamber, the tubular valve member being perforated in the vicinity of the space and the method including causing fluid pressure acting within the tubular valve member to act on the inwardly and outwardly directed protuberances to urge them apart from one another and cause movement of the tubular valve member to open the openable valve.

41. A method according to claim 34 wherein the openable valve includes a tubular valve member that lies within the pipe and a biasing arrangement that causes the tubular valve member normally to close the or each second fluid flow path; wherein the method includes causing or permitting the biasing arrangement to bias the openable valve to a normally closed position: and wherein the apparatus includes a space between the tubular valve member and the pipe, the space being bounded at either end respectively by an inwardly directed protuberance protruding towards the interior of the pipe and an outwardly directed protuberance protruding from the tubular valve member whereby to define an essentially closed chamber, the tubular valve member being perforated in the vicinity of the space and the method including causing fluid pressure acting within the tubular valve member to act on the inwardly and outwardly directed protuberances to urge them apart from one another and cause movement of the tubular valve member to open the openable valve wherein the said movement of the tubular valve member opposes the biasing effect of the biasing arrangement.

42. A method according to claim 34 wherein the apparatus includes or supports one or more sensor elements and wherein the method includes operating one or more sensors that are secured relative to the downhole tool to detect the one or more sensor elements on movement of the downhole tool to a deployed location and generate one or more signals indicative of such movement of the downhole tool.

43. A method according to claim 34 including activating at an uphole location one or more detectors of a pressure pulse that arises at the time of venting of pressurised fluid from within the pipe to the outside via the or each second fluid flow path, and causing the one or more detectors to generate one or more signals indicative of such a pressure pulse.

44. A method according to claim 34 including activating at an uphole location one or more detectors of a pressure pulse that arises at the time of venting of pressurised fluid from within the pipe to the outside via the or each second fluid flow path, and causing the one or more detectors to generate one or more signals indicative of such a pressure pulse; wherein the uphole location is a surface location.

45. A method according to claim 34 including operating one or more processor for processing one or more signals generated by the one or more sensors and generating one or more control commands based on the said signals.

46. A method according to claim 34 including operating one or more processor for processing one or more signals generated by the one or more sensors and generating one or more control commands based on the said signals, the method further including causing the downhole tool to respond to the one or more control commands by one or more of initiating an action, continuing an action, ceasing an action and/or modifying an action.

47. A method according to claim 34 including operating one or more processor for processing one or more signals generated by the one or more sensors and generating one or more control commands based on the said signals, the method further including causing the downhole tool to respond to the one or more control commands by one or more of initiating an action, continuing an action, ceasing an action and/or modifying an action and wherein the said action is selected from the list including deploying one or more deployable components; commencing logging activity; terminating logging activity; adjusting a parameter of logging activity; processing one or more signals resulting from logging activity; requesting diagnostic information and/or responding to one or more requests for diagnostic information.

48. A method according to claim 34 including activating at an uphole location one or more detectors of a pressure pulse that arises at the time of venting of pressurised fluid from within the pipe to the outside via the or each second fluid flow path, and causing the one or more detectors to generate one or more signals indicative of such a pressure pulse, the method including causing one or more processor to process one or more signals generated by the one or more detectors and generate one or more indications based on the said signals.

49. A method according to claim 34 including activating at an uphole location one or more detectors of a pressure pulse that arises at the time of venting of pressurised fluid from within the pipe to the outside via the or each second fluid flow path, and causing the one or more detectors to generate one or more signals indicative of such a pressure pulse, the method including causing one or more processor to process one or more signals generated by the one or more detectors and generate one or more indications based on the said signals and wherein the one or more indications include one or more selected from the list including an indication of deployment of the downhole tool; an indication of failure of the downhole tool to deploy; and/or diagnostic information received from the downhole tool.

50. A method according to claim 34 including activating at an uphole location one or more detectors of a pressure pulse that arises at the time of venting of pressurised fluid from within the pipe to the outside via the or each second fluid flow path, and causing the one or more detectors to generate one or more signals indicative of such a pressure pulse, the method including causing one or more processor to process one or more signals generated by the one or more detectors and generate one or more indications based on the said signals, wherein the one or more indications include one or more selected from the list including an indication of deployment of the downhole tool; an indication of failure of the downhole tool to deploy: and/or diagnostic information received from the downhole tool; and the method additionally includes including one or more of (a) causing one or more display devices to display the one or more indications; (b) causing one or more printing devices to print indicia representing the one or more indications; (c) causing one or more memory devices to record data characteristic of the one or more indications; or (d) generating one or more visible or audible alert.

Description

[0096] There now follows a description of preferred embodiments, by way of non-limiting example, with reference being made to the accompanying drawings in which:

[0097] FIG. 1 is a schematic, partly-sectioned view of apparatus according to the disclosure hereof and illustrating in part the method disclosed herein;

[0098] FIG. 2 is a similar view to FIG. 1, showing the apparatus after completion of method steps disclosed herein;

[0099] FIG. 3 shows a downhole tool that may form part of the FIG. 1/FIG. 2 apparatus, partly in phantom, illustrating a moveable valve member in a first position giving rise to an open first fluid flow path;

[0100] FIG. 4 is a similar view to FIG. 3, showing the moveable valve member in a second position closing the first fluid flow path;

[0101] FIG. 5 shows in perspective view part of a downhole tool, illustrating a seal and projection section;

[0102] FIG. 6 shows in cross-sectional view an enlargement of drill pipe forming part of apparatus according to the disclosure, and illustrating an openable valve formed in the drill pipe;

[0103] FIG. 7 is a partly sectioned view showing further embodiments, including a number of optional features;

[0104] FIG. 8 is an annotated plot of pressure, rotational motion and sensor outputs detected in the vicinity of the downhole tool during deployment operations; and

[0105] FIG. 9 is an annotated plot that is similar to FIG. 8 illustrating the signals generated at a surface location while the operations represented in FIG. 8 take place.

[0106] Referring to the drawings, apparatus 10 for signalling between downhole and uphole locations in a borehole represented schematically by numeral 11 includes a downhole tool 12 that in the illustrated embodiment is a logging tool but as mentioned may take any of a range of other forms. FIGS. 1 and 2 illustrate a logging tool in a generic manner. In practical embodiments the logging tool may be of any of a range of types, and may be a multi-purpose tool having sections intended to perform various different functions (not all or indeed any of which need be connected with logging). Equally the downhole tool may be of a dedicated type that performs only a single function.

[0107] Frequently it is a requirement of a downhole tool such as that illustrated that it effects communication from a downhole location in an uphole direction, to e.g. a surface location, when there is no direct communication connection, as would be provided by wireline, between the downhole tool and the uphole location. When the downhole tool is a logging tool as in preferred embodiments it may be of the battery-memory type mentioned above that functions autonomously following detachment and withdrawal of wireline also as described above.

[0108] Regardless of its precise design the downhole tool 12 is a rigid elongate cylinder that as shown in FIGS. 1 and 2 is contained inside hollow, rigid (typically steel) drill pipe 13. As is conventional the downhole tool is made up of a series of tool sections that are secured together in a per se known manner not requiring a detailed explanation herein. As explained herein other types of pipe alternatively may be used instead of drill pipe.

[0109] The drill pipe 13 may be of largely constant internal diameter as shown; or it may have a variable internal diameter. One way in which the latter arrangement may be effected is by connecting one or more lengths of e.g. wash pipe in series with one or more drill pipe lengths. As mentioned, moreover, the drill pipe may be entirely replaced by wash pipe although it is more likely that only a small number of pipe sections (such as one or two sections at the downhole end of the pipe) are formed as wash pipe, as is conventional in the bottom hole assembly and similar arts.

[0110] At its uphole end the illustrated downhole tool 12 is formed with a wireline neck 15 of a per se known kind permitting releasable attachment of wireline that as explained is connected to the downhole tool during running in. The downhole tool 12 however is not limited to such an arrangement, and other types of neck (including but not limited to fishing neck types) may be provided in addition to or as alternatives to the illustrated wireline neck 15. The precise design of the downhole tool 12 will depend on its features and intended use.

[0111] The downhole tool 12 is moveable in the drill pipe 13 except at times when as described herein it is restrained against movement relative to the drill pipe 13.

[0112] At least one section 12a of the downhole tool 12 includes an elongate, cylindrical hollow interior 14 best illustrated in FIGS. 3 and 4. The hollow interior 14 extends longitudinally centrally along the tool section 12a.

[0113] In practical embodiments there may exist more than one section, such as section 12a, of downhole tool 12 having a hollow interior 14. For simplicity the remainder of this description assumes the presence of only a single such section 12a.

[0114] The drill pipe 13 in use is filled with a fluid schematically represented by fluid flow arrows 17 that normally is pumped in a downhole direction inside its hollow interior, circulated out of the open downhole end of the drill pipe and returned back to a surface location via the approximately annular gap between the exterior of the drill pipe 13 and the boundary of the borehole 11. Surface-located pumping systems are routinely used for this purpose. The nature and operation of such pumping systems are well known in the art.

[0115] The fluid 17 may take any of a range of forms, and may include drilling mud, fluid such as water or hydrocarbons that flows under pressure from a formation perforated by the borehole 11, chemicals intentionally added to perform a function downhole, water introduced from a surface location, mineral and other debris, and undissolved gas bubbles. The fluid 17 may be for example conducting or non-conducting, may be water-based or oil-based and may be highly saline or of low salinity as is familiar to those having knowledge of drilling engineering. Almost without fail the fluid 17 will be a complex mixture the precise make-up and properties of which are likely to vary over time and from one instance to another.

[0116] A fluid inlet, in the form of at least one and in practice typically plural apertures 16, perforates the wall of the downhole tool section 12a to permit communication of fluid 17 surrounding the downhole tool 12 from the exterior of the downhole tool 12 to the hollow interior 14.

[0117] A fluid outlet, in the form of at least one and in practice typically plural apertures 18, perforates the wall of downhole tool section 12a at a location downhole of the fluid inlet apertures 16. The fluid outlet apertures permit the flow of fluid from the hollow interior 14 of tool section 12a to the exterior of the downhole tool 12. The hollow interior 14 thus connects the fluid inlet 16 and the fluid outlet 18 to define a first fluid flow path. As explained below such connection may selectively be opened and closed during operation of the disclosed apparatus 10.

[0118] The apparatus 10 includes a moveable valve member in the form of a piston 19 (FIGS. 3 and 4) that is moveable longitudinally along the hollow interior 14 of the downhole tool section 12a.

[0119] In the illustrated embodiment the piston 19 is supported on a rod 21 that extends part of the way along the hollow interior 14 and is itself supported for stable longitudinal movement. The diameter of the piston 19 is slightly less than that of the hollow interior 14. This in combination with the stabilising effect of the rod 21 means that the piston may be caused to slide from a first position, illustrated in FIG. 3 and described further below, in which the first fluid flow path is open and a second position illustrated in FIG. 4 in which the first fluid flow path is constricted or closed. The rod 21 is connected to an actuator mechanism for the purpose of selectively effecting such movement of the piston 19.

[0120] The actuator mechanism in the illustrated embodiment includes a motor sub 20 included in the downhole tool that is arranged to cause selective rotation of a drive screw 25 drivingly received in a nut assembly 30 that causes extension and retraction, as desired, of the rod 21 in the longitudinal direction of the interior of the downhole tool. The rod 21 is at its downhole end supported in a manner permitting such movement with the result that the piston 19 may be caused selectively to move along the hollow interior 14. Such movement is apparent from comparison of FIGS. 3 and 4.

[0121] The motor 20 may be of a range of types and typically would be an electric or hydraulic motor.

[0122] As shown in FIG. 3 the piston 19 may normally be held on the rod 21 at a location slightly uphole of the fluid inlet apertures 16 whereby the first fluid flow path is open and essentially uninterrupted. The piston 19 may at times when it is required to close the first fluid flow path be moved on the rod 21 a short distance in the downhole direction to a location immediately adjacent the fluid inlet apertures 16 so as to block them and thereby prevent the flow of fluid via the first fluid flow path. The purpose of such closing is explained further below.

[0123] The moveable valve member need not adopt the piston form illustrated and may instead take a variety of other forms. As a non-limiting example in this regard one may consider a flap valve that as desired occupies or is clear of the hollow interior 14. Moreover although it is desirable that the moveable valve member is capable of completely blocking the first fluid flow path it is believed possible to construct working embodiments of the apparatus 10 in which the moveable valve member constricts the first fluid flow path, without closing it entirely.

[0124] The downhole tool 12 includes extending about its outer periphery a sealing member 22. This may form part of a seal and projection section 23 of the downhole tool 12 that is shown schematically in FIGS. 1 - 4 and illustrated in one embodiment in more detail in FIG. 5.

[0125] The sealing member 22 is a resiliently deformable annulus that encircles and is a tight fit on the exterior of the downhole tool 12 at a location lying intermediate the fluid inlet apertures 16 and the fluid outlet apertures 18. As needed the exterior of the downhole tool may be formed with projections and/or recesses that co-operate with the sealing member to secure it in a desired location along the length of the downhole tool 12. A non-limiting example of such an arrangement is the formation of an annular bead projecting radially inwardly from the sealing member 22 that is received in a complementary annular recess formed in the surface of the downhole tool 12 in the seal and projection section 23. Numerous other ways of securing the sealing member 22 in position are possible and will occur to the person of skill in the art. Fasteners such as clips or screws may for example be employed, as may adhesive compounds, either in replacement of or to augment a projection and recess combination described. Other combinations of retention means are also possible.

[0126] The sealing member 22 includes one or more flanges 24, 26 that are spaced from one another along the length of the sealing member 22 and that extend outwardly away from the surface of the downhole tool 12. The flanges 24, 26 are continuous, circular structures that are dimensioned such that when the downhole tool 12 is positioned in the drill pipe 13 as illustrated they engage the inner wall of the drill pipe 13 in a sealing manner that prevents the flow of fluid via the part of the exterior of the downhole tool 12 in the vicinity of and beyond the seal and projection section 23. This in turn means that any fluid flowing in a downhole direction is forced to follow the first fluid flow path when this is not closed through operation of the moveable valve member.

[0127] The sealing member 22 preferably is made from a resiliently deformable compound such as a polymer or copolymer or a composite including a polymer or copolymer. A range of polymers and copolymers is suitable for this purpose, as will be known to the person of skill in the art. Different parts of the sealing member 22 may have differing stiffnesses and other properties and may be formed as composite structures including internal and/or external reinforcing elements.

[0128] As mentioned, in FIG. 5 the sealing member 22 includes two radially outwardly extending flanges 24, 26 but this number is not mandatory. More or fewer than the illustrated number of flanges may be provided; and indeed the sealing member 22 may adopt an entirely different design that does not rely on the presence of flanges if desired, it being sufficient that the sealing member 22 substantially or entirely prevents the flow of fluid in a downhole direction via the exterior of the downhole tool 12.

[0129] The apparatus 10 includes various means for constraining the downhole tool 12, which otherwise would be moveable out of the open, downhole end of the drill pipe 13, to lie at least partially within the drill pipe 13.

[0130] If the downhole tool 21 is as described of a kind requiring conveying in a downhole direction protected inside the drill pipe 13 it is necessary during such conveying to ensure that the downhole tool 12 is recessed entirely within the drill pipe 13 in order to protect it against damage that may occur as the tool 12 is conveyed.

[0131] This is achieved in the illustrated embedment through the use of one or more latch arms 27, 28 that as shown are positioned towards the uphole end of the downhole tool 12 and are capable of selectively extending from and retracting into the downhole tool 12. On assembling of the downhole tool 12 in the drill pipe 13 ready for conveying downhole the latch arms, which may be of a per se known design, are caused to extend from the surface of the downhole tool 12 to engage in respective recesses 29, 31 formed in a latch sleeve 32.

[0132] One way of effecting movement of the latch arms 27, 28 between the retracted and extended positions is through a mechanism that is coupled to and driven by the drive screw 25. Mechanisms of this kind are known in the art and familiar to the person of skill in the art. Therefore they are not described further herein. One advantage of using the drive screw 25 to cause movement of the latch arms 27, 28 is that such movement is timed to coincide with movement of the piston 19. A timing ratio may as desired be built in to the components for example through the choice of screw thread pitch and/or the incorporation of meshing gears or similar ratio-based drive parts in the mechanism.

[0133] Other means of effecting movement of the latch arms may alternatively be employed. Examples include but are not limited to dedicated drive motors.

[0134] The latch sleeve 32 is fixed inside the interior of the drill pipe 13 such that engagement of the latch arms 27, 28 in the recesses 29, 31 fixes the downhole tool 12 in position recessed within the drill pipe 13.

[0135] When so fixed the downhole tool 12 lies completely within the drill pipe 13. As a result extending of the drill pipe 13 in a downhole direction, in a per se known manner involving adding sections or “stands” of drill pipe sequentially at the surface termination of the borehole 11, causes the downhole tool 12 to be carried to the part of the borehole where it is required to function, in a manner protecting it against damage. Such damage otherwise probably would occur, as a result of the harsh borehole environment and the significant forces imparted to the drill pipe 13 while it is being extended along the borehole 11.

[0136] In the illustrated embodiment the latch sleeve 32 is such as to define an optional annular gap between its exterior and the interior wall of the drill pipe 13. Such a gap is not visible in the drawings but is represented schematically by the fluid flow arrows 17 in FIG. 1 in the vicinity of the latch sleeve 32 passing close to the wall of the drill pipe 13.

[0137] Other arrangements however are possible, including designs in which the fluid may pass between protruding latch arms such as arms 27 and 28 instead of bypassing the arms via the annular gap. The annular gap arrangement however is advantageous because it minimises damage to the latch arms 27, 28 as may be caused by debris in the fluid 17.

[0138] A distance uphole of the latch sleeve 32 the drill pipe 13 includes an openable valve 33 shown in schematic form in FIGS. 1 and 2 and in more detail in FIG. 6.

[0139] Openable valve 33 consists primarily of a hollow tubular valve member 34 that is a sliding fit inside a modified length or section 36 of the drill pipe 13. The tubular valve member 34 is biased by a biasing arrangement 39 described below normally to close one or more valve apertures 37, 38 formed in and perforating the cylindrical wall of modified drill pipe section 36. The tubular valve member 34 extends for part of the length of the modified drill pipe section 36. The tubular valve member 34 is caused to move to open the valve apertures 37, 38 when pressure of fluid inside the modified drill pipe section 36 increases to a degree that overcomes the effect of the biasing arrangement 39 in maintaining the tubular valve member in a position closing the valve apertures.

[0140] The exterior dimensions of the tubular valve member 34 are not constant along its length. As a result an uphole portion 34a is a sliding fit relative to a liner tube 41 that is described in more detail below and is fixed so as to lie within and line the interior of the modified drill pipe section 36.

[0141] Downhole of the portion 34a a recessed portion 34b is of reduced external diameter and terminates in an outwardly directed protuberance in the form of protruding ring 34c that in like manner to the portion 34a is a sliding fit relative to the liner tube 41. Downhole of the protruding ring 34c the tubular valve member 34 defines a further length 34d that is of reduced external diameter compared with the portions 34a and 34c. The further portion 34d extends for the remainder of the length of the tubular valve member 34 to its downhole termination.

[0142] The liner tube 41 is of constant internal diameter over approximately half its length at the uphole end; and of enlarged internal diameter over the remainder of its length defining a space between the liner tube 41 and the tubular valve member 34. The liner tube thus defines an inwardly directed protuberance in the form of a shoulder 42 that when the openable valve 33 is closed lies opposite and slightly uphole of the protruding ring 34c. As a result the shoulder 42, protruding ring 34c and the overlap of section 34b with the constant internal diameter section of the liner tube 41 define an essentially closed, annular chamber 43. A number of o-ring seals are provided received in recesses as illustrated and ensure the fluid-tightness of the boundaries of the annular chamber 43.

[0143] The tubular member 34 is perforated in an annular region lying adjacent the shoulder 42 and the protruding ring 34c by an annular series of through-going apertures 44. The apertures 44 permit fluid pressure inside the tubular valve member 34 to act in the closed annular chamber 43.

[0144] The tubular valve member 34 is open at each end. The in-use downhole end of the tubular valve member 34 is received in the open upper end of a hollow, open-ended spring core tube 46 that forms part of the biasing arrangement 39. Spring core tube 46 terminates at its uphole end in a cup section 46a of relatively large internal and external diameters that accommodates the downhole end of the tubular valve member and is a sliding fit inside the modified drill pipe section 36.

[0145] Downhole of the cup section the spring core tube 46 is of reduced internal and external diameter. A coiled spring 47 encircles the spring core tube 46 over the major part of its length and lies between the spring core tube 46 and the interior wall of the drill pipe section 36. At the downhole end of the coil spring 47 the modified drill pipe section 36 defines a reduced internal diameter portion 48 that presents an upwardly facing shoulder 49. The coiled spring 47 acts between the upwardly facing shoulder 49 and a downwardly facing shoulder 51 defined by the underside of the cup section 46a.

[0146] At least one optional spacer ring 52 may be provided to encircle the spring core tube 46 at its lowermost end and transfer force between the spring 47 and the upwardly directed shoulder 49. The number and dimensions of the spacer ring provision may be varied in order to adjust the degree of pre-load of the coiled spring 47 as further described below. A similar spacer ring arrangement may be provided in addition or as an alternative at the uphole end of the spring 47.

[0147] The spring core tube 46 constrains the coiled spring 47 to retain a cylindrical shape and protects the coiled spring 47 against damage that might otherwise be caused by the flow of fluid in the modified drill pipe section 36.

[0148] The liner tube 41 as noted is fixed relative to the modified drill pipe section 36 and is radially perforated to define one or more, and in practice an annular series of, valve apertures 37, 38. Each of the valve apertures 37, 38 forms part of a respective second fluid flow path and is lined by a respective nozzle 53. The nozzles 53 extend radially relative to the longitudinal axis of the modified drill pipe section 36 and are supported by the liner tube 41. The nozzles 53 are shaped to produce desired flow characteristics when fluid flows via the second fluid flow paths as described below.

[0149] When as illustrated in FIG. 6 the openable valve 33 is closed the coiled spring 47 urges the cup section 46a of spring core tube 46 into engagement with a fixing ring 54 secured e.g. using one or more screws 56 adjacent the downhole end of the liner tube 41. Any increase in fluid pressure inside the modified drill pipe section 36 however acts via the through-going apertures 44 and pressurises the annular chamber 43. This urges the inwardly directed shoulder 42 and the protruding ring 34c apart from one another with the consequence that if the fluid pressure increase is sufficient the tubular valve member 34 is driven in a downhole direction against the effect of the biasing arrangement 39 and in particular the coiled spring 47.

[0150] This effect arises when the pressure of fluid inside the modified drill pipe section 36 exceeds a threshold that is equivalent to the force applied by the spring 47. The spring is pre-loaded by the spacer ring 52. The insertion of further spacer rings, that may be the same as that visible in FIG. 6 or may be of differing designs, optionally adds to the pre-load with the consequence that a higher pressure increase then is required to open the openable valve 33.

[0151] As is apparent in FIG. 6 the tubular valve member 34 and the spring core tube 46 present an essentially constant internal diameter of their contiguous hollow interiors. This is desirable in order to confer good fluid dynamic characteristics on the interior of the modified drill pipe section 36. However in other embodiments a non-constant internal diameter may be desired and such arrangements lie within the scope of the disclosure.

[0152] As illustrated in FIG. 7 the drill pipe 13 supports one or more sensor elements that in the preferred embodiment illustrated are magnets 55. In the illustrated embodiment two such magnets 55 are visible at diametrically opposite locations on the interior wall of the uphole end of a rigid, hollow, cylindrical swage member 59 the nature and operation of which are described further below. In other embodiments more or fewer than the two illustrated magnets 55 may be provided, for example in a circular array extending about the inside surface of the swage member.

[0153] The swage member 59 is positioned inside the drill pipe 13 before deployment of the downhole tool 12 occurs, and typically would be assembled in position as illustrated before the length 13 of drill pipe supporting it is run in to the borehole 11. As a result the magnets 55 are pre-located near to the downhole end of the drill pipe string, and are detectable on correct deployment of the downhole tool 12 by one or more sensors 57 that generate signals to signify such deployment.

[0154] As noted the sensor(s) preferably is/are Hall-effect devices supported as part of the downhole tool 12 when the sensor elements as is preferred are embodied as magnets 55. The Hall-effect sensors 57 are secured close to or on the exterior of the downhole tool 12 such that they efficiently couple the magnetic fields of the magnets 55 and generate signals on deployment of the downhole tool 12 with part of it protruding from the open end of the drill pipe string ready for use. The signals generated by the sensors 57 give rise to commands causing movement of the piston 19 on the shaft 21 and thereby generate an uplink signal indicating the deployment status of the downhole tool 12.

[0155] Additionally or alternatively a similar arrangement may be provided to signal when incorrect deployment of the downhole tool has occurred.

[0156] At its end lying downhole of the magnets 55 the external circumference of the swage member 59 is formed as a downwardly extending taper 61 that is received inside a swage element in the form of a deformable, hollow tube 62. The taper 61 may be hardened or may be formed of an alloy that is otherwise resistant to deformation. The deformable tube 62 is formed of a rigid material that nonetheless is of lesser hardness than the taper 61.

[0157] An uphole end 63 of the deformable tube 62 is of larger internal and external diameter than the remainder 64 of the length of the deformable tube 62. A steady taper 66 interconnects the large-diameter, uphole end and the reduced diameter remainder of the deformable tube 62. The angle of the taper 66 is the same as or similar to that of taper 61. The exterior of taper 61 abuts the interior surface of taper 66 when the drill pipe 13 of FIG. 7 is assembled.

[0158] Near its downhole end the interior of drill pipe 13 is formed to include an inwardly projecting shoulder 67 that in the illustrated embodiment is annular, although in other embodiments need not extend all the way around the interior of the drill pipe 13. The downhole, open end of the deformable tube 62 bears against the shoulder 67. An optional bearing ring 68 is shown in FIG. 7 interposed between the deformable tube 62 and the shoulder 67.

[0159] A short distance uphole from the taper 61 the interior surface of the deformable tube 62 includes an inwardly projecting landing ring 69. The dimensions of this are such as to be engageable by an outwardly projecting landing ring 71 formed on or secured to the exterior of the downhole tool 12 part-way along its length. The landing ring 71 and the length of the swage member 59 are such that the landing ring 71 engages the landing ring 69 when the downhole tool is deployed protruding partly from the open end of the drill string and the Hall-effect sensor(s) is/are in register with the magnets 55.

[0160] On deployment of the downhole tool 12 from a position entirely retracted within the drill pipe 13 to a position partly protruding therefrom as illustrated the landing ring 71 engages the landing ring 69 in a manner limiting movement of the downhole tool 12 out of the drill string. This occurs simultaneously with alignment in register with one another of the magnets 55 and the Hall effect sensor(s) 57 causing generation of one or more signals indicating deployment of the downhole tool 12. As noted such signals in turn initiate a signalling regime as further described herein.

[0161] If the downhole tool 12 on landing in this manner possesses kinetic energy in excess of a threshold determined by the hardness of the metal of the deformable tube 62 the taper 61 causes the taper 66 to travel along the deformable tube. This swaging of the deformable tube dissipates the excess kinetic energy of the downhole tool 12.

[0162] The length of the deformable tube 62 is chosen to accommodate plural landings of the downhole tool 12 as described, with the taper 66 moving along a proportion of the length of the deformable tube 62 each time. The deformable tube 62 therefore is useable multiple times. FIG. 7 shows the position of the taper 66 after for example one or two prior landings of the downhole tool 12.

[0163] In use of the apparatus disclosed herein a downhole tool 12, such as a logging tool, is assembled as illustrated in FIG. 1 with all of the downhole tool 12 recessed within drill pipe. Depending on the length of the downhole tool 12 it may be the case that a relatively short length of it lies within the modified drill pipe section 36 with most of the downhole tool length received within one or more further, conventional drill pipe stands 58 that are secured downhole of the modified drill pipe section 36. Equally, depending on the length of the downhole tool 12, it may not be necessary to provide the further drill pipe stands 58.

[0164] The downhole tool 12 is fixed in position inside the drill pipe through deployment of the latch arms 27, 28 when these are aligned with the recesses 29, 31 formed in the latch sleeve 32. In this regard more or fewer than the two visible latch arms 27, 28 and the two recesses 29, 31 may be provided.

[0165] When the downhole tool 12 is so fixed the sealing member 22 defines a fluid-tight, slideable seal between the exterior of the downhole tool and the interior of the drill pipe 58. At this time if the downhole tool is e.g. a wireline-compatible logging tool, wireline is connected to the wireline neck 15 that defines a releasable connection via which power, commands and data may pass at a high data rate between uphole and downhole locations and vice versa. The wireline reaches the inside of the drill pipe string via a side entry sub in a conventional manner. The side entry sub is omitted from the drawings for simplicity.

[0166] The downhole tool 12 then is conveyed in a downhole direction recessed within the drill pipe 36, 58 through a process of adding stands of drill pipe at the surface end of the drill pipe string. The wireline is paid out from its storage drum as this process takes place.

[0167] Depending on the precise requirement the drill string typically will be circulated with fluid 17 during the progress in a downhole direction. As explained during such circulation the fluid 17 usually is pumped, using one or more surface-located pumps, in a downhole direction inside the drill pipe.

[0168] As signified by the arrows 17 in the vicinity of the downhole tool 12 the fluid flows in the space between the latch sleeve 32 and the inner surface of the modified drill pipe section 36. It then flows along the drill pipe 58 between its inner surface and the downhole tool 12 until the sealing member 22 prevents further downhole progress of the fluid along the exterior of the downhole tool 12.

[0169] At this time the piston 19 occupies a position corresponding to an open state of the first fluid flow path. In consequence the fluid 17 flows via the fluid inlets 16 into and along the hollow interior 14 of the downhole tool 12 before exiting to the exterior of the downhole tool 12 once again via the fluid outlets 18, downhole of the sealing member 22. The fluid 17 then is free to flow out of the downhole end of the drill pipe 58 for recirculation to the surface pumping equipment via the gap defined between the drill pipe and the borehole 11.

[0170] At the end of the described conveyance process the downhole tool 12 is in the vicinity of the total depth of the borehole, the term “total depth” being familiar in the downhole engineering art and not requiring explanation herein; or another location in the borehole at which it is required for the downhole tool 12 to operate.

[0171] At this point a command may be sent using the connected wireline to cause deployment of the downhole tool 12 to an operative position. Such a command causes an actuator mechanism, that may be as described above, to effect retraction of the latch arms 27, 28 from the latch recesses 29, 31. This frees to the downhole tool 12 to move as needed along the inside of the drill pipe.

[0172] The pressure of pumped fluid 17 acting inside the drill pipe pumps the downhole tool 12 in a downhole direction such that part of the downhole tool 12 extends out of the open end of the drill pipe 58 as illustrated in FIG. 7. If as explained the retraction of the latch arms 27, 28 is such as to coincide with movement of the piston 19 the force with which pumping of the downhole tool 12 occurs increases during retraction of the latch arms 37, 38, as the piston 19 closes off the fluid inlets 16.

[0173] Protrusion of the downhole tool is limited when a no-go defined in part by the projection section 23 of the downhole tool 12 and in particular the landing ring 71 engages a further projection, that is exemplified in a non-limiting manner by landing ring 69, or another landing ring of a kind familiar in the art, protruding inwardly from the interior surface of a section of drill pipe downhole of that illustrated in FIG. 1.

[0174] As necessary during such landing excess kinetic energy of the downhole tool 12 resulting from its movement is dissipated, without causing damage, through the described action of the swage element 64 and in particular travel of the taper 66 in a downhole direction as a result of pressing by the taper 61.

[0175] At the end of this process the sensor elements (that as explained are magnets 55 in a typical apparatus) will be aligned with the one or more sensors 57 that generate a signal indicative of correct deployment of the downhole tool 12 to its operative position partly protruding from the lowermost stand of drill pipe 58.

[0176] This signal may be transmitted via connections in the drill pipe and/or the downhole tool 12 for transmission via the wireline. Surface-located processing equipment, a human operator or, conceivably, one or more processors at the downhole location, may then generate a command sequence that: [0177] a) as needed, activates a mechanism (if provided) for locking the downhole tool in position; [0178] b) disconnects the wireline from the wireline neck; and [0179] c) causes winding of the wireline back on to its storage drum, with the wireline exiting the drill pipe via the side entry sub and being completely withdrawn from the borehole in order to avoid fouling with operative equipment such as rotating drill pipe.

[0180] At this point there is no longer any prospect of electrical or electronic communication between the downhole tool 12 and any surface-located equipment or vice-versa. It is necessary however to signify to the surface equipment that correct deployment of the downhole tool 12 has occurred.

[0181] This is achieved by closing of the first fluid flow path. In turn this results from movement of the piston 19 in a downhole direction to close off or at least constrict the fluid inlets 16. This movement may be initiated by e.g. a wireline command as described above, a downlink drill pipe rotation command or a downlink pressure pulse signal.

[0182] Such closing or constriction of the first fluid flow path causes pressure of the fluid 17 uphole of the fluid inlets 16 to rise rapidly, and generate signals in the drill pipe that are exemplified in FIGS. 7 and 8 and are explained below.

[0183] This pressure acts via the apertures 44 and in turn causes pressure in the annular chamber 43 to rise to a level exceeding the bias effected by the spring 47 forming part of the biasing arrangement 39. The tubular valve member 34 is then driven in a downhole direction, opening the openable valve by uncovering the apertures 37, 38 and any other apertures as may form part of the openable valve.

[0184] This causes the fluid pressure within the modified drill pipe section 36 to vent via the second fluid flow path defined by the apertures 37, 38 and generate a high-amplitude, and highly characteristic, increase in the pressure of fluid inside the drill pipe. The venting of fluid pressure via the apertures 37, 38 prevents damage from occurring to the components of the apparatus while allowing the pressure increase to be an unambiguous indicator of correct deployment even in a losing or gaining well as described above.

[0185] The resulting pressure pulse propagates rapidly in an uphole direction to surface-located pressure detecting equipment where it readily is decoded as an indication of correct deployment of the downhole tool.

[0186] Operation of the downhole tool 12, e.g. to commence logging operations (or other operations if appropriate) may then be commanded using available downlink communications methods such as but not limited to drill pipe rotation, downlink pressure pulse generation or in some cases the pumping of a messenger sub that interacts with the downhole tool 12 to initiate its activity.

[0187] Examples of downhole pressure and sensor voltage signals are illustrated in FIG. 8 and examples of the uplink communications pressure pulse described above in FIG. 9. These are exemplary, non-limiting signal plots that have been annotated in order to explain the various artefacts that are apparent. The annotations are self-explanatory. FIGS. 7 and 8 in addition to showing examples of pressure signals generated and detected in order to signify correct tool deployment in the downhole location also show in a non-limiting manner the generation and detection of signals indicative of diagnostic information transmission, as labelled. Such signal generation may be effected in a similar manner to that described above and may readily be envisaged.

[0188] The apparatus and method of the invention amount to significant improvements in the nature, bandwidth and reliability of uplink communications from a downhole tool to uphole equipment.

[0189] Modifications of the apparatuses and methods described herein as would occur to the person of skill in the art are within the scope of the disclosure hereof.

[0190] 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.

[0191] 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.