Jarring apparatus

Abstract

A jarring apparatus includes first and second jarring assemblies which are axially moveable relative to each other between first and second axial configurations, and a thrust assembly interposed between the first and second jarring assemblies to limit relative axial movement therebetween at the second axial configuration and permit axial loading in one axial direction to be transferred between the first and second jarring assemblies via the thrust assembly. The apparatus further includes a jarring mass axially moveable within the jarring apparatus in reverse first and second directions upon relative rotation between the first and second jarring assemblies.

Claims

1. A jarring apparatus, comprising: first and second jarring assemblies configured to be axially moveable relative to each other between first and second axial configurations; a thrust assembly interposed between the first and second jarring assemblies configured to limit relative axial movement therebetween at the second axial configuration and permit axial loading in one axial direction to be transferred between the first and second jarring assemblies via the thrust assembly; and a jarring mass configured to be axially moveable within the jarring apparatus in a first axial direction and a second axial direction in response to relative rotation between the first and second jarring assemblies, the first axial direction being opposite the second axial direction, wherein respective loading faces on the first and second jarring assemblies define at least a portion of the thrust assembly, wherein the respective loading faces are axially engaged when the first and second jarring assemblies reach the second axial configuration.

2. The jarring apparatus according to claim 1, further comprising: a force mechanism configured to bias the jarring mass in the first axial direction and bias the first and second jarring assemblies in a direction towards the first axial configuration; and a lifting assembly configured to be operable by relative rotation between the first and second jarring assemblies to cyclically lift the jarring mass in the second axial direction against the bias of the force mechanism and release the lifted jarring mass to permit the jarring mass to be driven by the force mechanism in the first axial direction.

3. The jarring apparatus according to claim 2, wherein the force mechanism is of a displacement type such that the force generated within the force mechanism is a function of the relative axial movement of the first and second jarring assemblies towards the second axial configuration.

4. The jarring apparatus according to claim 2, wherein initial relative axial movement of the first and second jarring assemblies from the first configuration towards the second axial configuration is permitted without corresponding operation of the force mechanism.

5. The jarring apparatus according to claim 2, wherein the force mechanism is interposed between one of the first and second jarring assemblies and the jarring mass, and is configured to be operated on opposing sides thereof by one of the first and second jarring assembles and the jarring mass.

6. The jarring apparatus according to claim 2, further comprising a bearing structure which is interposed between the force mechanism and the jarring mass.

7. The jarring apparatus according to claim 2, comprising an arresting mechanism configured to arrest movement of the jarring mass based on moving in the first axial direction under the action of the force mechanism.

8. The jarring apparatus according to claim 7, wherein a first impact surface provided on the jarring mass and a second impact surface provided on at least one of the first and second jarring assemblies defines at least a portion of the arresting mechanism, and the first and second impact surfaces are configured to be impacted together based on the jarring mass being driven in the first axial direction under the action of the force mechanism.

9. The jarring apparatus according to claim 8, wherein the first and second impact surfaces are provided separately from the lifting assembly.

10. The jarring apparatus according to claim 2, wherein the lifting assembly comprises: a first lifting structure rotatably and axially fixed relative to one of the first and second jarring assemblies and a second lifting structure rotatably fixed and configured to be axially moveable relative to the other of the first and second jarring assemblies, wherein the second lifting structure acts axially on the jarring mass, wherein the first and second lifting structures are configured to cooperate during relative rotation therebetween to cause the second lifting structure to be axially moved in cyclical lifting and dropping phases, wherein during the lifting phase the second lifting structure is configured to cause the jarring mass to be lifted in the second axial direction.

11. The jarring apparatus according to claim 10, wherein the second lifting structure is separately formed from the jarring mass, and the apparatus further comprises a bearing structure which is interposed between the second lifting structure and the jarring mass.

12. The jarring apparatus according to claim 10, wherein the first lifting structure is releasably axially connected to one of the first and second associated jarring assemblies such that axial release of the first lifting structure permits axial release of the jarring mass to be driven in the first axial direction by the force mechanism.

13. The jarring apparatus according to claim 12, wherein the first lifting structure is axially releasable from one of the first and second jarring assemblies prior to initiation of the dropping phase.

14. The jarring apparatus according to claim 12, wherein the first lifting structure is axially releasable from one of the first and second jarring assemblies prior to completion of the lifting phase.

15. The jarring apparatus according to claim 10, wherein the first and second lifting structures comprise inter-engaging profiles which are configured to cooperate during relative rotation of the lifting structures to cause the cyclical lifting and dropping phases.

16. The jarring apparatus according to claim 10, further comprising a locking system configured to selectively axially fix and release the first lifting structure relative to one of the first and second jarring assemblies.

17. The jarring apparatus according to claim 16, wherein the locking system is configured to be operated by relative rotational movement between the first and second jarring assemblies.

18. The jarring apparatus according to claim 16, wherein the locking system comprises a hydraulic locking system configured to hydraulically lock and release the first lifting structure relative to one of the first and second associated jarring assemblies.

19. The jarring apparatus according to claim 18, wherein the hydraulic locking system is configured to hydraulically lock a volume of hydraulic fluid axially against the first lifting structure to provide locking, and release the hydraulic fluid to provide unlocking.

20. The jarring apparatus according to claim 18, wherein the hydraulic locking system comprises a first hydraulic chamber, wherein hydraulic fluid is configured to be hydraulically locked within said first hydraulic chamber to hydraulically lock the first lifting structure relative to one of the first and second jarring assemblies.

21. The jarring apparatus according to claim 20, wherein the hydraulic locking system comprises a valve assembly which, based on the valve assembly being closed, is configured to hydraulically lock the fluid within the first hydraulic chamber, and, based on the valve assembly being open, is configured to release the hydraulically locked fluid.

22. The jarring apparatus according to claim 21, wherein the valve assembly is configurable between open and closed configurations in response to relative rotation between the first and second jarring assemblies.

23. The jarring apparatus according to claim 1, wherein the thrust assembly is configured to permit the first and second jarring assemblies to be rotatable relative to each other based on being in the second axial configuration.

24. The jarring apparatus according to claim 1, comprising a releasable rotary connection which is configurable between a connected configuration in which the first and second jarring assemblies are rotatably fixed relative to each other, and a released configuration in which the first and second jarring assemblies are rotatable relative to each other.

25. The jarring apparatus according to claim 1, comprising a releasable axial locking mechanism arranged between the first and second jarring assemblies.

26. A method for providing jarring, comprising: establishing relative axial movement between first and second jarring assemblies of a jarring apparatus from a first axial configuration towards a second axial configuration; limiting relative axial movement between the first and second jarring assemblies at the second axial configuration by a thrust assembly; establishing relative rotational movement between the first and second jarring assemblies to move a jarring mass in a first axial direction and a second axial direction, wherein the first axial direction is opposite the second axial direction; and axially engaging respective loading faces on the first and second jarring assemblies based on the first and second jarring assemblies reaching the second axial configuration.

27. The method according to claim 26, wherein the establishing relative axial movement between the first and second jarring assemblies from the first axial configuration towards the second axial configuration energises a force mechanism configured to bias a jarring mass in a first axial direction.

28. The method according to claim 27, wherein establishing relative rotational movement between the first and second jarring assemblies operates a lifting assembly within the jarring apparatus which cyclically lifts the jarring mass in the second axial direction against the bias of the force mechanism and releases the lifted jarring mass to permit the jarring mass to be driven by the force mechanism in the first direction to generate a jarring force within the apparatus.

29. A method for providing jarring, comprising: establishing relative axial movement between first and second jarring assemblies of a jarring apparatus from a first axial configuration towards a second axial configuration; limiting relative axial movement between the first and second jarring assemblies at the second axial configuration by a thrust assembly; and establishing relative rotational movement between the first and second jarring assemblies to move a jarring mass in reverse first and second directions; wherein the establishing relative axial movement between the first and second jarring assemblies from the first axial configuration towards the second axial configuration energises a force mechanism which functions to bias a jarring mass in a first axial direction.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) These and other aspects of the present disclosure will now be described, by way of example only, with reference to the accompanying drawings, in which:

(2) FIGS. 1 and 2 illustrate a prior art jarring tool;

(3) FIGS. 3A and 3B diagrammatically illustrate a jarring apparatus in accordance with the present disclosure in different operational configurations;

(4) FIGS. 4 to 6 provide graphical illustrations of different parameters associated with the jarring apparatus of FIG. 3 when in use;

(5) FIG. 7A is a cross-sectional view of a jarring apparatus according to the present disclosure;

(6) FIG. 7B is an enlarged split view of the portion of the apparatus of FIG. 7A contained within the broken outline;

(7) FIG. 8 is an exploded view of a rotary connection between a jarring mass of the apparatus of FIG. 7A and an outer housing;

(8) FIGS. 9 and 10 illustrate separate lifting structures of a lifting assembly of the apparatus of FIG. 7A;

(9) FIGS. 11A to 11D illustrate a rotary sequence of cooperation between the separate lifting structures of the lifting assembly;

(10) FIG. 12 is an exploded view of a rotary valve of the jarring apparatus of FIG. 7A;

(11) FIGS. 13A to 13D are sectional views through line 13-13 of FIG. 7B, and illustrate sequential stages of operation of the rotary valve;

(12) FIGS. 14A to 14B illustrate a releasable axial connection of the apparatus of FIG. 7A, shown in different configurations;

(13) FIGS. 15A to 21C illustrate the jarring apparatus of FIG. 7A in sequential stages of operation;

(14) FIG. 22 illustrates the jarring apparatus of FIG. 7A in use without engagement of a thrust assembly;

(15) FIG. 23 illustrates the jarring apparatus of FIG. 7A performing a linear down-jar operation;

(16) FIGS. 24 and 25 illustrate an alternative form of lifting structures of a lifting assembly which may be used in the apparatus of FIG. 7A;

(17) FIG. 26 is a cross-sectional view of a rotary valve which may be used in combination with the lifting structures of FIGS. 24 and 25;

(18) FIG. 27 is a split sectional view of a jarring apparatus according to the present disclosure;

(19) FIG. 28 illustrates the jarring apparatus of FIG. 27 in use without engagement of a thrust assembly;

(20) FIG. 29 illustrates the jarring apparatus of FIG. 27 in use with engagement of a thrust assembly;

(21) FIG. 30 illustrates the jarring apparatus of FIG. 27 performing a linear up-jar operation;

(22) FIGS. 31A to 31D illustrate an alternative form of rotary valve which may be used in a jarring apparatus, such as any jarring apparatus disclosed herein;

(23) FIGS. 32 to 34 illustrate exemplary uses of a jarring apparatus according to the present disclosure; and

(24) FIGS. 35 and 36 provide diagrammatic illustrations of alternative examples of a jarring apparatus.

DETAILED DESCRIPTION OF THE DRAWINGS

(25) Aspects of the present disclosure relate to a jarring apparatus. Such a jarring apparatus may be used in any application which requires the application of a jarring force, extending from downhole applications, subsea applications, topside applications and the like. For the purposes of the present exemplary description a jarring apparatus for use within a wellbore is described. However, this is not limiting, and the principles of the present disclosure may be applied in any jarring application, which may or may not be utilised in a wellbore.

(26) A jarring apparatus, generally identified by reference numeral 10, is diagrammatically illustrated in cross-section in FIG. 3A. The jarring apparatus 10, which is only partially shown in FIG. 3A, is illustrated in a non-jarring configuration and is sized and arranged to be deployed into a wellbore. Although not shown, the jarring apparatus 10 may be deployed into a wellbore on wireline, tubing, such as coiled tubing, jointed pipe or the like.

(27) The jarring apparatus 10 comprises a first jarring assembly in the form of a mandrel 12, and a second jarring assembly in the form of an outer housing assembly 14. The jarring apparatus 10 is configured such that relative rotation established between the mandrel 12 and outer housing assembly 14 causes reciprocating motion of a jarring mass 24 to generate repeated linear jarring forces. In this regard, as jarring is achieved through relative rotation, the apparatus 10 may be defined as a rotary jarring apparatus. In use, the outer housing assembly 14 may be engaged with an object (not shown), such as a stuck object within a wellbore, with the mandrel 12 rotated via a suitable rotary drive, such as a motor, rotatable work string or the like, thus applying the generated jarring forces to the object.

(28) In the present example the jarring apparatus 10 is arranged to provide axial jarring forces in the direction of arrow 16, which may be defined as an uphole direction. In use, an axial pulling force may be applied to the mandrel 12 in the direction of arrow 16 during the jarring operation, and a load/resistance applied to the housing in the direction of arrow 17, such as from a stuck object, suspended load etc. Such loading through the apparatus 10 may contribute to the generation of a jarring force. However, in the present example the jarring apparatus 10 incorporates features to provide a degree of protection from excessive loading or overloading.

(29) The mandrel 12 includes a tubular structure which extends into the outer housing assembly 14. A first or upper end of the mandrel 12 may include a suitable connector (not shown) for facilitating connection with a suitable deployment or drive structure, such as a work string (e.g., drill pipe). The mandrel 12 may be provided as a unitary component, or may be composed of multiple connected components. Similarly, the housing assembly 14 may be provided as a unitary component, or may be composed of multiple connected components.

(30) The apparatus 10 further comprises a thrust assembly 18 interposed between the mandrel 12 and housing 14. In the illustrated example the thrust assembly 18 includes a first thrust shoulder 20 provided on the mandrel 12, and a second thrust shoulder 22 provided on the housing 14. In the configuration shown in FIG. 3A the first and second thrust shoulders 20, 22 are axially separated and thus disengaged. However, as will be described in more detail below, relative axial movement between the mandrel 12 and housing 14 (in the relative direction of arrows 16, 17) will eventually bring the first and second thrust shoulders 20, 22 into engagement, such that axial loading (in the relative direction of arrows 16, 17) may be transmitted between the mandrel and 12 and housing 14 via the thrust assembly 18, thus diverting such loading from other components within the apparatus 10. In this respect the thrust assembly may function or define a load limiter. The thrust assembly 18 permits rotation between the first and second thrust shoulders 20, 22 when engaged, such that the thrust assembly 18 may function as a thrust bearing.

(31) The jarring mass 24 is radially positioned between the mandrel 12 and housing 14, and is axially moveable in reverse directions (directions 16, 17) relative to both the mandrel 12 and housing 14. The jarring mass 24 is rotatably fixed relative to the mandrel 12 via a rotary connection 26, such as a keyed or splined connection. However, in other examples the jarring mass may alternatively be rotatably fixed relative to the housing 14.

(32) The jarring mass 24 includes a first impact surface 28, and the housing 14 includes a second impact surface 30, wherein, in use, reciprocating axial movement of the jarring mass 24 causes the first and second impact surfaces 28, 30 to axially impact together, thus generating repeated axial jarring forces within the apparatus 10. In an alternative example the mandrel 12 may comprise an axial impact surface, alternative or in addition to the impact surface provided on the housing 14. As the jarring mass 24 is responsible for generating impact within the apparatus 10, the jarring mass may thus also be defined as a hammer.

(33) A force mechanism 32 in the form of a power spring (e.g., a Bellville spring stack) is provided within the apparatus 10, and is configured, in use, to bias the jarring mass 24 to move axially in the direction of arrow 16, and thus to bias the first and second impact surfaces 28, 30 into engagement. As will be described in more detail below, relative movement between the mandrel 12 and housing 14 in the direction of arrows 16, 17, will cause the spring 32 to be engaged and compressed by an annular shoulder 34 on the mandrel 12. In this respect, the force generated by the spring 32 against the jarring mass 24 is a function of the compression or displacement of the spring 32. In some examples the spring 32 may be uncompressed until engaged by the mandrel. However, in other examples the spring may carry a degree of pre-compression.

(34) The jarring apparatus 10 further includes a lifting assembly 36 which is operable by relative rotation between the mandrel 12 and housing 14 to cyclically lift the jarring mass 24 in the direction of arrow 17 against the bias of the spring 32, and release the lifted jarring mass 24 to permit the jarring mass to be driven by the spring 32 in the direction of arrow 16, causing the impact surfaces 28, 30 to rapidly engage to establish a jarring force. Any suitable form of lifting assembly 36 may be provided to function to cyclically lift and release the jarring mass 24 in the manner described.

(35) In the present example the lifting assembly 36 includes a first lifting structure 38 rotatably and axially fixed relative to the housing 14, and a second lifting structure 40 rotatably fixed, but axially moveable, relative to the mandrel 12. In the present example the second lifting structure 40 is integrally formed with the jarring mass 24, and is thus rotatably connected to the mandrel 12 via rotatable connection 26. In other examples the second lifting structure 40 may be separately formed and rotatably coupled to the jarring mass 26. In further examples the second lifting structure 40 may be separately rotatably coupled to the mandrel 12. In such examples the jarring mass 24 may not necessarily be rotatably coupled to the mandrel 12.

(36) The lifting structures 38, 40 include cooperating cam structures which cooperate during relative rotation therebetween to cause the second lifting structure 40 to be axially moved in cyclical lifting and dropping phases, thus effecting axial reciprocating movement of the jarring mass 24. The cam structures may be provided as in the example of FIG. 2, or may be provided in accordance with later described examples.

(37) Loading may be applied between the first and second lifting structures 38, 40 which is a function of the biasing force provided by the spring 32. In this respect such loading may be controlled by appropriate selection of the spring 32, by the extent of compression of the spring 32 caused by relative movement between the mandrel 12 and housing 14, and by virtue of the load limiting effect of the thrust assembly 18, which will be described in more detail below. This may assist to increase the longevity of the first and second lifting structures, and thus of the lifting assembly.

(38) The jarring apparatus 10 further includes an optional releasable rotary connection 42 between the mandrel 12 and housing 14. In the present example the releasable rotary connection 42 includes a splined connection. When the apparatus 10 is configured as shown in FIG. 3A, the releasable rotary connection 42 is engaged, and the mandrel 12 and housing 14 are rotatably coupled. Such a configuration may thus prevent any jarring to occur, to the extent that this configuration may be defined as a non-jarring configuration. Further, the rotary connection may allow torque to be transmitted between the mandrel 12 and housing 14, which may be useful or required in many applications, such as in drilling applications and the like.

(39) When jarring is to be performed, the mandrel 12 and housing 14 are axially moved relative to each other (in the relative direction of arrows 16, 17) to disengage the rotary connection 42, as illustrated in FIG. 3B, thus permitting relative rotational movement to be achieved to operate the lifting assembly 36 and lift/drop the jarring mass 24 to generate jarring. In some applications the housing 14 may be held stationary, such that the relative movement is achieved by moving, for example pulling, and rotating the mandrel 12. Such axial movement, in addition to releasing the rotary connection 42, causes the annular shoulder 34 of the mandrel 12 to pick up and energise the spring 32, thus establishing the bias force acting against the jarring mass 24 in the direction of arrow 16.

(40) Although not shown, the apparatus may further comprise a releasable axial connection between the mandrel 12 and housing 14 which first needs to be disengaged to allow the relative axial movement. Such a releasable axial connection may be releasable upon application of a threshold release force applied between the mandrel 12 and housing 14.

(41) In the configuration of FIG. 3B the mandrel 12 has been moved until the thrust assembly 18 is engaged, such that further axial loading applied between the mandrel 12 and housing (e.g., by increasing an overpull on the mandrel 12) will be transmitted via the thrust assembly 18 and thus diverted from the spring 32 and the lifting assembly 36. In this configuration the spring 32 may be considered to provide its maximum bias force, subject to any minor variation caused by the cyclical lifting of the jarring mass 24 by the lifting assembly 36, which will be described further below.

(42) While FIG. 3B illustrates the thrust assembly 18 fully engaged, it should be understood that jarring may be effected at any stage following release of the rotary connection 42 and energising of the spring 32. In this respect, the extent of axial loading applied between the mandrel 12 and housing 14, prior to engagement of the thrust assembly 18, will dictate the level of bias force developed by the spring 32 and thus the level of jarring forces created within the apparatus 10. In this respect, a user may control the jarring force output by controlling the overpull on the mandrel 12, up until the load limit has been reached via engagement of the thrust assembly 18. This can provide a significant degree of operational flexibility within the apparatus 10, while minimising risk of overloading.

(43) The effect of the load protection within the apparatus 10 is graphically shown in FIG. 4, which illustrates the forces experienced within components of the apparatus 10 during increasing load applied therethrough. In this example line 44 represents the total loading applied through the apparatus 10, while line 46 illustrates the loading generated between the first and second lifting structures 38, 40 of the lifting assembly 36. During initial stages of loading, and assuming the spring 32 has been energised, loading within the lifting assembly 38 increases in accordance with the total loading applied through the apparatus 10, until point 48 when the thrust assembly 18 is engaged. Once the thrust assembly 18 is engaged, the loading within the lifting assembly 36 will remain constant at the illustrated maximum value, with the thrust assembly 18 picking up any increasing load applied, illustrated by line 50.

(44) FIG. 5 graphically illustrates the effect of the compression of the spring 32 by axial movement of the mandrel 12 in the direction of arrow 16. In this case, the spring 32 remains in its initial uncompressed state (or initial pre-compressed state) until engaged by the mandrel 12, illustrated by point 52 in FIG. 5. Further axial displacement of the mandrel 12 causes the spring to be compressed up until point 54 is reached, which coincides with the engagement of the thrust assembly 18.

(45) FIG. 6 graphically illustrates the effect of the operation of the lifting assembly 36 on compression of the spring 32. The initial compression of the spring 32 is represented at point 56, which will be the compression caused by the displacement of the mandrel 12 at any point in time. That is, the graphical representation of FIG. 6 is intended to illustrate operation at an initial spring compression at any stage up to engagement of the thrust assembly 18. As such, the scale in FIGS. 5 and 6 may be different. During relative rotation within the lifting assembly 36 the spring 32 is further compressed during lifting of the jarring mass 24, illustrated by line 58, and then rapidly relieved, illustrated by line 60, which drives the jarring mass 24 to impact. In some examples the extent of additional compression caused by the lifting assembly 36 may be considered negligible in terms of increasing the bias force of the spring 32.

(46) Another example of a jarring apparatus, in this case represented by reference numeral 100, is illustrated in FIG. 7A in cross-section, which is similar in many respects to apparatus 10 first shown in FIG. 3A. The apparatus 100 is sized and arranged to be deployed in a wellbore, for example on wireline, tubing etc. However, the jarring apparatus 100 may be used in any application requiring application of jarring, including operations outside of a wellbore.

(47) The apparatus 100 comprises a first jarring assembly in the form of a mandrel 102, and a second jarring assembly in the form of a housing assembly 104. The mandrel 102 and housing assembly 104 in the present example are each composed of multiple connected components. As in the previous example, the apparatus 100 is configured such that relative rotation established between the mandrel 102 and housing 104 causes repeated jarring forces to be generated, and as such the apparatus 100 may also be defined as a rotary jarring apparatus. In use, the outer housing assembly 104 may be engaged with an object (not shown), such as a stuck object, suspended object etc., with the mandrel rotated via a suitable rotary drive, such as a motor, rotatable work string or the like, thus applying the generated jarring forces to the object.

(48) In the present example the jarring apparatus 100 is arranged to provide axial jarring forces in the direction of arrow 16, which may be defined as an uphole direction. As such, the jarring may be defined as upjarring. An axial pulling force may be applied to the mandrel 102 in the direction of arrow 16 during the jarring operation. As in the previously described example, such loading through the apparatus 100 may contribute to the generation of a jarring force, and the jarring apparatus 100 incorporates features to provide a degree of protection from excessive loading or overloading.

(49) As will be described below in more detail, axial jarring in an opposite (e.g., downhole) direction, illustrated by arrow 17, may also be possible, with an optional axial pushing force applied to the mandrel in the direction of arrow 17.

(50) The mandrel 102 includes a tubular structure which extends into the outer housing assembly 104. A first or upper end of the mandrel 102 includes a suitable connector 106 for facilitating connection with a suitable deployment or drive structure, such as a work string (not shown). A releasable rotary connection 107 is provided between the mandrel 102 and housing 104. In the present example the releasable rotary connection 107 includes a splined connection, and when the apparatus 100 is configured as shown in FIG. 7A, the releasable rotary connection 107 is engaged, and the mandrel 102 and housing 104 are rotatably coupled. Such a configuration may thus prevent any jarring to occur, to the extent that this configuration may be defined as a non-jarring configuration. Further, the rotary connection may allow torque to be transmitted between the mandrel 102 and housing 104, which may be useful or required in many applications, such as in drilling applications and the like. When jarring is required, axial movement between the mandrel 102 and housing 104 in the relative direction of arrows 16, 17 will cause the rotary connection 107 to be disengaged.

(51) To aid the current description an enlarged split view of the jarring apparatus 100 in region 7B of FIG. 7A is illustrated in FIG. 7B, reference to which is now made.

(52) As in the previously described example, the apparatus 100 includes a thrust assembly (or thrust bearing) 108 interposed between the mandrel 102 and housing 104. In the illustrated example the thrust assembly 108 includes a first thrust shoulder 110 provided on the mandrel 102, and a second thrust shoulder 112 provided on the housing 104. The first thrust shoulder 110 is provided on a coupling 111 which provides a connection between separate mandrel components. As will be described in further detail below, the coupling 111 also includes an impact surface 214 which is configured to impact against a matching impact surface 216 on the housing 104 to provide a secondary linear impact function within the apparatus 100.

(53) In the configuration shown in FIG. 7B the first and second thrust shoulders 110, 112 are axially separated and thus disengaged. However, as will be described in more detail below, relative axial movement between the mandrel 102 and housing 104 (in the relative direction of arrows 16, 17) will eventually bring the first and second thrust shoulders 110, 112 into engagement, such that axial loading (in the relative direction of arrows 16, 17) may be transmitted between the mandrel 102 and housing 104 via the thrust assembly 108, thus diverting such loading from other components within the apparatus 100. In this respect the thrust assembly may function as or define a load limiter.

(54) The apparatus 100 further comprises a jarring mass 114 radially positioned between the mandrel 102 and housing 104, and being axially moveable in reverse directions (directions 16, 17) relative to both the mandrel 12 and housing 14. The jarring mass 114 may be of any required length, for example in accordance with a desired weight to be provided, and in the present example the apparatus 100 is illustrated axially split over the length of the jarring mass 114 to reflect the non-specific length requirement of the mass 114.

(55) The jarring mass 114 includes a first impact surface 116 (provided on an impact insert), and the housing 104 includes a second impact surface 118 (also provided on an impact insert), wherein, in use, reciprocating axial movement of the jarring mass 114 causes the first and second impact surfaces 116, 118 to axially impact together, thus generating repeated axial jarring forces within the apparatus 100. In an alternative example the mandrel 102 may comprise an axial impact surface, alternative to or in addition to the impact surface provided on the housing 104. As the jarring mass 114 is responsible for generating the impact within the apparatus 100, the jarring mass may thus also be defined as a hammer.

(56) A force mechanism in the form of a power spring 120 (e.g., a Bellville spring stack) is provided within the apparatus 100, and is configured, in use, to bias the jarring mass 114 to move axially in the direction of arrow 16, and thus to bias the first and second impact surfaces 116, 118 into engagement. A mass pusher sleeve 122 extends between the spring 120 and the jarring mass 114, such that the spring 120 may act indirectly on the jarring mass 114, and vice versa. In the present example the mass pusher sleeve 122 extends past a coupling 124 of the housing 104, and as also shown in the exploded view of FIG. 8, the mass pusher sleeve 122 is rotatably connected to the coupling 124 via a first castellated connection 126, and also to the hammer via a second castellated coupling 128.

(57) The mandrel 102 carries a spring pick-up ring 130 which defines an annular shoulder 132. In the initial configuration of FIG. 7B the mandrel 102 is positioned within the housing 104 such that the annular shoulder 132 is separated from the spring 120. As will be described in more detail below, relative movement between the mandrel 102 and housing 104 in the direction of arrows 16, 17, will cause the annular shoulder 132 to engage and compress the spring 120. In the present example a thrust bearing 134 is interposed between the spring 120 and spring pick-up ring 130, which transmits axial loading while accommodating relative rotation between the spring 120 and the spring pick-up ring 130. The force generated by the spring 120 against the jarring mass 114 (via the pusher sleeve 122) is thus a function of the compression or displacement of the spring 120 caused by movement of the mandrel 102 in the direction of arrow 16. In some examples the spring 120 may be uncompressed until engaged by the mandrel. However, in other examples the spring may carry a degree of pre-compression.

(58) The spring pick-up ring 130 may be adjustably mounted on the mandrel 102, which may allow a user to set the spring pick-up point within the apparatus 100. Furthermore, in some examples the spring pick-up ring 130 may be releasably secured to the mandrel 102, for example via a shear pin connection. Such a releasable connection may permit the spring pick-up ring 130 to be released upon exposure to an over-load condition within the apparatus, thus providing a degree of load protection.

(59) The apparatus 100 further comprises a lifting assembly or mechanism 136 which includes a first lifting cam structure 138 rotatably fixed to the outer housing 104 (in a manner described later), and a second lifting cam structure 140 rotatably fixed relative to the mandrel 102 via keys 142. The keys 142 are engaged within axial key-ways 144 within the mandrel 102 such that relative axial movement is permitted between the second lifting cam structure 140 and the mandrel 102. A cam pusher sleeve 146 extends axially between the second lifting cam structure 140 and the jarring mass 114. As will be described in detail below, relative rotation between the mandrel 102 and housing 104 causes the first and second lifting cam structures 138, 140 to cooperate to cause cyclical lifting and dropping of the second lifting cam structure 140, thus facilitating lifting and dropping of the jarring mass 114 to generate impact between the impact surfaces 116, 118.

(60) Reference is additionally made to FIG. 9 which is a perspective view of the first lifting cam structure 138, and FIG. 10 which is a perspective view of the second lifting cam structure 140. The first lifting cam 138 includes a first rotary cam profile 148 which in the present example includes two circumferentially distributed cam lobes 150 each having a gradual ramp or rising portion 152, and a drop-off or falling portion 154, with a base portion 156 circumferentially positioned between each cam lobe 150. The second lifting cam 140 includes a complimentary second rotary cam profile 158, and thus includes two circumferentially distributed cam lobes 160 each having a gradual ramp or rising portion 162, and a drop-off or falling portion 164, with a base portion 166 circumferentially positioned between each cam lobe 160.

(61) The complementary rotary cam profiles 148, 158 inter-engage and cooperate upon relative rotation therebetween to cyclically cause the cam structures 138, 140 to be displaced in one axial direction in a lifting phase, and to be displaced in a reverse axial direction in a dropping phase, as illustrated in FIGS. 11A to 11D. In this respect, FIG. 11A illustrates initial engagement of the respective ramp portions 152, 162 at the start of a lifting phase, with relative rotation therebetween permitting the cooperating ramp portions 152, 162 to circumferentially slide relative to each other and axially drive the cam structures 138, 140 apart towards a peak separation, as shown in FIG. 11B. As the cam structures 138, 140 progress towards the illustrated peak position in FIG. 11B the area of contact therebetween reduces, thus causing the stresses induced in the cam structures 138, 140 to increase. As will be described herein, the jarring apparatus 100 provides measures to minimise such stresses within the cam structures 138, 140 thus prolonging their operational life span.

(62) Following completion of this lifting phase the drop-off portions 154, 164 become aligned, allowing the cam structures 138, 140 to “drop” and cause reverse axial displacement in a dropping phase, as illustrated in FIG. 11C. The cam structures 138, 140 are arranged within the jarring apparatus 100 such that at this dropping phase the first and second cam profiles 148, 158 are prevented from axial engagement or impact therebetween. That is, immediately following the dropping phase an axial separation gap 168 is provided between the first and second cam profiles 148, 158. This is achieved, at least in part, in the present example by the provision of a no-go profile in the form of an annular lip 170 provided on the first cam structure 138 which engages a corresponding axial shoulder 172 on the housing 104 (see FIG. 7B). Alternatively, or additionally, a no-go profile may be provided on the second cam structure 140 to provide this function.

(63) Following this dropping phase the cam lobes 150, 160 become aligned with the opposing base portions 156, 166, as illustrated in FIG. 11D, without contact therebetween, as noted above (i.e., the axial separation gap 168 is maintained). Further relative rotation may provide a transition from the completed dropping phase to initiation of a subsequent lifting phase, with the cycle of FIGS. 11A to 11D being repeated, causing cyclically lifting and dropping of the cam structures 138, 140. In the present example, with each cam structure 138, 140 comprising two cam lobes 150, 160, the cams structures 138, 140 will undergo two cycles of lifting and dropping for each full 360 degrees of relative rotation therebetween. The provision of more or less cam lobes 150, 160 on each cam 138, 140 may facilitate more or less cycles for each full 360 degrees of relative rotation.

(64) Loading may be applied between the first and second cam structures 138, 140 which is a function of the biasing force provided by the spring 120. In this respect such loading may be controlled by appropriate selection of the spring 120, by the extent of compression of the spring 120 caused by relative movement between the mandrel 102 and housing 104, and by virtue of the load limiting effect of the thrust assembly 108, which will be described in more detail below. This may assist to increase the longevity of the first and second cam structures 138, 140, and thus of the lifting assembly 136.

(65) Referring again to FIG. 7B, the first cam structure 138 is positioned radially between the mandrel 102 and the housing 104, and is sealed relative to the mandrel 102 via inner seals 174, and sealed relative to the housing 104 via outer seals 176. The first cam structure 138 is rotatably fixed relative to the housing 104, specifically to a coupling portion 180 of the housing 104, which will be described in more detail below. A spring 182 biases the first cam structure 138 towards the second cam structure 140.

(66) The first cam structure 138 is configured to be selectively axially fixed and released relative to the housing 104 via a hydraulic locking system. The hydraulic locking system functions to fix the first cam structure 138 relative to the housing 104 during the lifting phase between the first and second cam structures 138, 140, which thus permits the cooperation of the first and second cam profiles 148, 158 to cause the jarring mass 114 to be lifted in the direction of arrow 17 by the second cam structure 140, against the bias of the spring 120, and thus axially separate the first and second impact surfaces 116, 118. The hydraulic locking system also functions to release the first cam structure 138 relative to the housing 104 prior to completion of the lifting phase between the cam structures 138, 140, with such axial release permitting the spring 120 to drive the jarring mass 114 in the direction of arrow 16 and cause the impact surfaces 116, 118 to be rapidly impacted together, to generate a jarring force.

(67) In the present example, the hydraulic locking system 186 includes a hydraulic chamber 184 which is defined radially between the mandrel 102 and housing 104, and axially between the first cam structure 138 and the coupling portion 180. A valve assembly 186 is provided between the hydraulic chamber 184 and a flow path 188 extending through the mandrel 104, wherein the valve assembly 186 is configurable between open and closed positions by relative rotation between the mandrel 102 and housing 104. When the valve assembly 186 is in its closed position fluid communication between the hydraulic chamber 184 and flow path 188 is prevented, thus hydraulically locking the hydraulic fluid in the hydraulic chamber 184, effectively axially fixing the first cam structure 138 relative to the housing 104. When the valve assembly 186 is in its open position fluid communication between the hydraulic chamber 184 and flow path 188 is permitted, allowing fluid to be displaced from the hydraulic chamber 184, and effectively axially releasing the first cam structure 138 from the housing 104.

(68) Reference is additionally made to FIG. 12 which is a perspective exploded view of the valve assembly 186 and the first cam structure 138. The valve assembly 186 in the present example is provided in the form of a rotary plug valve and comprises a valve sleeve 190 which is rotatably fixed to the coupling portion 180, and thus to the housing 104, via a castellated coupling 192. In this example the valve sleeve 190 is coupled with the first cam structure 138, and thus provides a rotary connection between the housing 104 and the first cam structure 138. The valve sleeve 190 includes two circumferentially arranged (in this case diametrically opposed) ports 194 extending radially therethrough.

(69) The valve assembly 186 further comprises a valve selector portion 196, which is formed by the mandrel 102, and includes a single port 198 extending radially through the valve selector portion 196 (two diametrically opposed ports could be provided in the selector portion 196). When the mandrel 102 and housing 104 are in the illustrated relative axial configuration of FIG. 7B, the port 198 in the valve selector portion 196 is axially misaligned from the ports 194 in the valve sleeve 190, which is also illustrated in the cross-sectional view of FIG. 13A, with the spring 182 removed for clarity. However, when the mandrel 102 is moved in the direction of arrow 16 to prepare for jarring, the ports 194, 198 will become axially aligned and thus allow the valve assembly 186 to become operational. In this respect, and with additional reference to the sequence of FIGS. 13B-D (also taken along line 13-13 assuming the ports 194, 196 have become axially aligned), relative rotation between the valve sleeve 190 and valve selector portion 196 in accordance with relative rotation between the mandrel 102 and the housing 104 will cause cyclical alignment and misalignment of the ports 194, 198 to effectively open and close the valve assembly 186. By appropriate timing between the lifting and dropping phases of the first and second cam structures 138, 140 within the lifting assembly 136, and of the opening and closing of the valve assembly 186, suitable operation of the jarring apparatus 100 may be achieved. In this respect, such timing may be readily facilitated by virtue of both the lifting assembly 136 and valve assembly 186 being commonly operated by relative rotation between the mandrel 102 and housing 104.

(70) Referring again to FIG. 7B the jarring apparatus 100 further comprises a releasable axial connection 200 between the mandrel 102 and housing 104 which first needs to be disengaged to allow relative axial movement therebetween. The axial connection 200 includes a circumferential array of dogs 202 which are positioned radially between the mandrel 102 and housing 104. In the connected configuration shown in FIG. 7B the dogs 202 are received within a circumferential groove 204 in an outer surface of the mandrel, and held in place by the radial constraint of the housing 104. Upper and lower springs 206, 208 are positioned on either side of the dogs 202, and function to bias the dogs 202 towards the illustrated central position, such that the springs 206, 208 function to retain the mandrel 102 in position relative to the housing 104. In this position the mandrel 102 may be permitted to move in reverse axial directions relative to the housing 104, albeit resisted by the springs. As such, the connection may be considered to be a compliant connection. The housing 104 further includes upper and lower circumferential grooves 210, 212 which are positioned on either side of the dogs 202 when in the illustrated initial connected configuration.

(71) The process of releasing the axial connection, in reverse directions, is illustrated in FIGS. 14A and 14B. Referring first to FIG. 14A, a release of the mandrel 102 in the direction of arrow 16 is illustrated, which corresponds to the direction to release the rotary connection 107 (FIG. 7A) between the mandrel 102 and housing 104, and permit the spring 120 to be compressed in preparation for rotary jarring. The housing 104 is held stationary (e.g., by engagement with an object, suspended load etc.) and an axial pulling force is applied on the mandrel 102 in the direction of arrow 16, which causes the mandrel 102 and dogs 202 to move in the same direction, compressing upper spring 206. Such movement of the mandrel 102 will eventually cause the dogs 202 to become aligned with upper circumferential groove 210 in the housing 104, permitting the dogs to be released from the groove 204 in the mandrel 102, thus achieving disconnection. At this point the pulling force on the mandrel 102 will rapidly cause the mandrel 102 to move in the direction of arrow 16, radially constraining the dogs 202 in place within the upper groove 210, effectively deactivating the connection 200. In the example presented, the upper spring 206 primarily dictates the required threshold pulling force which must be exceeded to achieve disconnection.

(72) The connection 200 may be subsequently reset, but relieving any pulling force on the mandrel 102, and/or by setting a pushing force on the mandrel 102, to re-align the groove 204 on the mandrel 102, along the dogs 202 to be released and return to the initial position.

(73) The connection 200 may also permit axial release in a reverse direction, which is illustrated in FIG. 14B. The housing 104 is held stationary (e.g., by engagement with an object, suspended load etc.) and an axial pushing force is applied on the mandrel 102 in the direction of arrow 17, which causes the mandrel 102 and dogs 202 to move in the same direction, compressing lower spring 208. Such movement of the mandrel 102 will eventually cause the dogs 202 to become aligned with lower circumferential groove 212 in the housing 104, permitting the dogs 202 to be released from the groove 204 in the mandrel 102, thus achieving disconnection. At this point the pushing force on the mandrel 102 will rapidly cause the mandrel 102 to move in the direction of arrow 17, radially constraining the dogs 202 in place within the lower groove 212, effectively deactivating the connection 200. In the example presented, the lower spring 206 primarily dictates the required threshold pushing force which must be exceeded to achieve disconnection.

(74) In the present example the ability to permit the described reverse axial release of the mandrel 102 in the direction of arrow 17 may function to provide a linear jar within the apparatus 100. In this respect, and again with reference to FIG. 7B, the apparatus 100 includes the pair of secondary impact surfaces 214, 216 which are caused to impact together upon axial release of the mandrel 102 in the direction of arrow 17.

(75) Referring again to FIG. 7B the apparatus 100 incorporates various features which permits cooling of the various components during use, for example the impact surfaces 116, 118, lifting assembly 136 and spring 120. For example, the mandrel 102 includes a number of cooling ports 220 which permit fluid flowing through the apparatus 100 when in use to also function as a cooling medium. Furthermore, the mandrel 102 may also include ports (which may or may not be commonly used as cooling ports 220) to prevent hydraulic locking between the mandrel 102 and housing 104.

(76) A full cycle of operation of the apparatus 100 will now be described with reference to FIGS. 15A to 21C.

(77) Referring initially to FIG. 15A an overpull is applied on the mandrel 102 in the direction of arrow 16 (for example via a rotary drive string, such as drill pipe—not shown), which causes the axial connection 200 to be released (as described above with reference to FIG. 14A), and the rotary connection 107 between the mandrel 102 and housing 104 to be disengaged. In the illustrated configuration of FIG. 15A a very high overpull has been imparted, such that in addition to the spring 120 being compressed, the thrust assembly 108 has been engaged. As such, the apparatus 100 is shown operated in its load limit configuration.

(78) When in the configuration of FIG. 15A the valve assembly 186 is also operationally aligned, which is also shown in the cross-sectional view of FIG. 15B, taken along line 15B-15B of FIG. 15A (with the spring 182 removed in FIG. 15B for clarity). In this regard the valve assembly 186 is in an open configuration, with the port 198 in the valve selector portion 196 aligned with one of the ports 194 of the valve sleeve 190. As such, the first lifting structure 138 of the lifting assembly 136 is axially released relative to the housing 104. Although the first lifting structure 138 may be considered to be axially released from the housing 104 when the valve assembly 186 is open, the first lifting structure 138 is nevertheless biased axially towards the second lifting structure 140 by virtue of the action of the spring 182.

(79) The corresponding configuration of the lifting assembly 136 is illustrated in FIG. 15C, wherein the first and second cam profiles 148, 158 of the lifting structures 138, 140 respectively are not engaged (separation gap 168).

(80) Rotation of the mandrel 102 relative to the housing 104 eventually causes the valve assembly 186 to close by misalignment of the ports 194, 198, as illustrated in FIGS. 16A and 16B, wherein FIG. 16B is a sectional view taken through line 16B-16B of FIG. 16A. The first lifting structure 138 thus becomes hydraulically locked relative to the housing 104. When in this configuration the second lifting structure 140 has rotatably progressed as shown in FIG. 16C, but the first and second cam profiles 148, 158 remain separated and non-engaged (separation gap 168). As an example, the mandrel 102 may have been rotated by around 40 degrees relative to the initial position of FIG. 15A to reach this stage in which the valve assembly 186 becomes closed.

(81) Continued rotation of the mandrel 102, illustrated in FIG. 17A, maintains the valve assembly 186 in its closed configuration, as illustrated in FIG. 17B, which is a sectional view taken through line 17B-17B of FIG. 17A, and eventually brings the cam profiles 148, 158 of the lifting assembly 136 into engagement, as illustrated in FIG. 17C. Specifically, opposing ramp portions 152, 162 become engaged in preparation to initiate the lifting phase. When in the configuration illustrated in FIG. 17A, the jarring mass 114 is positioned such that the impact surfaces 116, 118 remain engaged. As an example, the mandrel 102 may have been rotated by around 77 degrees relative to the initial position of FIG. 15A to reach this stage.

(82) Further rotation of the mandrel 102, illustrated in FIG. 18A, maintains the valve assembly 186 in its closed configuration, as illustrated in FIG. 18B, which is a sectional view taken through line 18B-18B, and causes the ramp portions 152, 162 of the first and second lifting structures 138, 140 to slide over each other and cause relative axial displacement of said lifting structures 138, 140 to provide the lifting phase, as illustrated in FIG. 18C. By virtue of the first lifting structure 138 being hydraulically locked and axially fixed to the housing 104 the axial separation between the lifting structures 138, 140 causes the jarring mass to be moved axially in the direction of arrow 17 against the bias of the spring 120, causing the first and second impact surfaces 116, 118 to become axially separated. As an example, the mandrel 102 may have been rotated by 128 degrees relative to the initial position of FIG. 15A to reach this stage.

(83) Further rotation of the mandrel 102, illustrated in FIG. 19A, causes the ports 194, 198 of the valve assembly 186 to start to become aligned, as illustrated in FIG. 19B, which is a sectional view taken through line 19B-19B, thus reconfiguring the valve assembly 186 into its open configuration. This establishes communication between the hydraulic chamber 184 and the flow path 188, axially releasing the first lifting structure 138 from the housing 104. This axial release of the first lifting structure 138 permits the loading and potential energy stored within the spring 120 to rapidly drive the jarring mass 114 in the direction of arrow 17 and cause the impact surfaces 116, 118 to be rapidly impacted together, generating a jarring force. As an example, the mandrel 102 may have been rotated by 129 degrees relative to the initial position of FIG. 15A to reach this stage of generating a jarring force within the apparatus 100.

(84) As illustrated in FIG. 19C, the ramp profiles 152, 162 of the first and second lifting structures 138, 140 remain engaged. However, the axial release of the first lifting structure 138 from the housing 104 relieves or reduces, for example significantly reduces, loading applied between the lifting structures 138, 140, thus minimising stress therein. The timing of axial release of the first lifting structure 138 may be selected to be such that a relatively large surface area of contact between the ramp profiles 152, 162 exists during the initial lifting and loading phase, again assisting to control levels of stresses applied in the lifting assembly 136.

(85) The configuration of the apparatus 100 upon further rotation of the mandrel 102 is illustrated in FIG. 20A. As shown in FIG. 20B, which is a sectional view taken through lines 20B-20B in FIG. 20A, the valve assembly 186 remains opened, with the ports 194, 198 still aligned during this further rotation. The further rotation also causes the second lifting structure 140 to further rotate relative to the first lifting structure 138, causing the ramp profiles 152, 162 to reach the peak position, as illustrated in FIG. 20C, reflecting the maximum axial displacement between the lifting structures 138, 140. As the valve assembly 186 remains open during this phase of rotation loading applied between the reducing contact area between the ramp profiles 152, 162 is minimised, thus minimising stresses within the lifting assembly 136. As an example, the mandrel 102 may have been rotated by 168 degrees relative to the initial position of FIG. 15A to reach this stage of the ramp profiles 152, 162 peaking.

(86) Further rotation of the mandrel 102, for example now 180 degrees relative to the initial position of FIG. 15A, will cause the first and second lifting structures 138, 140 to effectively drop (i.e., the first lifting structure 138 “drops” relative to the second lifting structure 140 under the bias of spring 182), returning the apparatus 100 to the initial configuration. Continuous rotation of the mandrel 102 will cause continuous cycles of jarring, as described above. In this respect the jarring frequency will be a function of the number of cam profiles provides on the lifting structures 138, 140, and the rotational speed of the mandrel 102. The jarring frequency may also be influenced by the number of ports provided in the valve assembly 186. In use, the jarring frequency may be readily adjusted by adjusting the rotational speed of the mandrel 102.

(87) The timing of the lifting and dropping phases of the lifting structures 138, 140 and the opening and closing of the valve assembly 186 may be readily adjusted to achieve the desired operation of the apparatus 100. For example, delaying the opening of the valve assembly 186 may permit a greater separation between impact surfaces 114, 116 to be achieved, and thus more energy to be generated by the spring 120.

(88) The common operation of the valve assembly 186 and the lifting assembly 136 by the relative rotation between the mandrel 102 and the housing 104 may facilitate the appropriate timing of operation to be readily achieved and adjusted, for example by simple relative alignment of the different components on the mandrel 102 and/or housing 104.

(89) In the operational example described above the overpull applied on the mandrel 102 is such that the thrust assembly 108 is engaged. In this case the force applied for each impact event will be the same as developed by the spring 120, irrespective of any increasing pulling force applied on the mandrel 102 (or alternatively increased loading applied on the housing 104). However, rotary jarring can still be achieved even before the load limit has been reached (i.e., with the thrust assembly 108 not engaged). Such an example configuration is shown in FIG. 22. In this respect the overpull applied on the mandrel 102 in the direction of arrow 16 is sufficient to release the axial connection 200 and compress the spring 120, but has not yet reached the load limit, such that the thrust surfaces 110, 112 of the thrust assembly 108 remain disengaged. The mandrel 102 may then be rotated to provide rotary jarring in the same manner described above. In this case the level of overpull applied on the mandrel 102, up to the load limit, will have a direct effect on the level of jarring forces generated, thus providing a significant degree of user flexibility.

(90) As described above, the apparatus 100 is also configured such that a linear jar can be generated in a reverse or downward direction. Such a downward linear jar operation is illustrated in FIG. 23. In this example a pushing force (e.g., weight) may be applied on the mandrel 102 in the direction of arrow 17, which will manifest through the axial connector 200. Once sufficient force is applied the connector 200 will release, in the manner described above with reference to FIG. 14B, with the energy within the mandrel (and any connected string, such as drill pipe) causing the mandrel 102 to rapidly move in the direction of arrow 17, causing impact between the secondary impact surfaces 214, 216. As the connection 200 is resettable, such a liner downjar may be repeated as required by cyclically triggering and resetting the apparatus 100.

(91) As described above, the frequency of jarring may be dictated by the form of the lifting structures 138, 140, specifically by the number of cam lobes 150, 160 present. In the example described above each lifting structure 138, 140 includes two cam lobes 150, 160, such that two jarring events may be generated for a single full 360 degrees of rotation. As such, increasing or decreasing the number of cam lobes present may alter the jarring frequency for a given rotational speed. An alternative example of a first lifting structure, in this case represented by reference numeral 338 is provided in FIG. 24, wherein four cam lobes 350 are provided. FIG. 25 illustrates a corresponding second lifting structure 340, which thus also includes four cam lobes 360.

(92) With such a modified cam construction a modified valve assembly will be required to accommodate this. Such an example modified valve construction 386 is illustrated in FIG. 26, which also comprises a valve sleeve 390 and a valve selector portion 396 (forming part of a mandrel). In this example the valve sleeve 390 again includes a single port 394, however the valve selector portion 396 includes four ports to permit four cycles of locking and unlocking for each single rotation of the valve selector portion 396.

(93) In the example provided above the apparatus 100 is configured for rotary jarring in an uphole direction. In other examples, however, a jarring apparatus may be provided which permits rotary jarring in a downhole direction. An example of such a jarring apparatus, which is generally identified by reference numeral 400, is illustrated in FIG. 27. The apparatus 400 is similar in many respects to apparatus 100 described above, and as such like features share like reference numerals, incremented by 300. In fact, many of the features provided in the apparatus 100 are also present in apparatus 400, albeit in inverted or reverse form. As such, while the present of such features will be confirmed in the following, a detail description of these will not be repeated for brevity.

(94) The apparatus 400 includes a mandrel 402 which extends into a housing assembly 404, wherein a releasable rotary connection 407 and a releasable axial connection 500 are provided between the mandrel 402 and housing 404, and the apparatus 400 further includes a thrust assembly 408 which includes thrust shoulders 410, 412. An axially moveable jarring mass 414 is provided radially between the mandrel 402 and housing 404, and includes a first impact surface 416 which is configured to engage a second impact surface 418 mounted on the housing 404. A force generator in the form of a spring 420 is provided within the apparatus 400 and is configured to bias the jarring mass 412, via pusher sleeve 422, in the direction of arrow 17, to engage the impact surfaces 416, 418. The mandrel 402 includes a spring pick-up ring 430 which engages and compresses the spring 420 upon movement of the mandrel 402 in the direction of arrow 17.

(95) The apparatus 400 further comprises a lifting assembly 436 and associated valve assembly 486, which function upon relative rotation between the mandrel 402 and housing 404 to cyclically lift and drop the jarring mass 414, thus generating repeated impact between impact surfaces 416, 418.

(96) When rotary jarring is required, as illustrated in FIG. 28, a force is applied on the mandrel 402 in the direction of arrow 17, which releases the axial connection 500 and subsequently the rotary connection 407, allowing the mandrel 402 to be rotated, and thus the jarring mass 414 to be reciprocated and generate repeated jarring in the same manner described above. In the illustrated example the load applied on the mandrel 402 is not yet sufficient to reach a load limit, such that the thrust shoulders 410, 412 of the thrust assembly remain disengaged. However, should the loading applied on the mandrel 402 exceed the load limit of the apparatus 400, the thrust shoulders 410, 412 of the thrust assembly 408 will engage, as shown in FIG. 29.

(97) The apparatus 400 is also configured to permit linear jarring in an uphole direction, as illustrated in FIG. 30. In this respect a pulling force is applied on the mandrel 402 in the direction of arrow 16 which will cause the axial connection 500 to be released (in the manner described with reference to FIG. 14A), with the sudden release of energy causing impact between secondary impact surfaces 514, 516. As the connection 500 is resettable multiple upward linear jarring may be performed.

(98) In the example apparatuses 100, 400 described above a hydraulic locking system is provided which cyclically hydraulically locks and releases the first lifting structure relative to the housing. Specifically, an example described above (apparatus 100) includes a valve assembly 186 incorporating radially arranged ports 194, 198 and operable to selectively isolate and communicate a hydraulic chamber 184 with a flow path 188 through the apparatus 100. However, other examples may use a different form of valve assembly, for example one which includes axial ports. Further, the function of the flow path 188 to supply and receive fluid from the hydraulic chamber 184 may be instead provided by a further hydraulic chamber. Such alternative examples will now be described with reference to FIGS. 31A to 31D.

(99) Referring initially to FIG. 31A, a portion of a jarring apparatus 500 is shown in cross-section. The apparatus 500 is similar in many respects to apparatus 100 first shown in FIG. 7A, and as such like features share like reference numerals, incremented by 400. As such, not all of the apparatus 500 is illustrated and described for brevity, on the basis that the unillustrated features may be provided in accordance with earlier described examples.

(100) The apparatus 500 includes a mandrel 502 and housing 504, and a lifting assembly 536 which includes cooperating first and second lifting structures 538, 540. The lifting assembly 536 is operated by relative rotation between the mandrel 502 and the housing 504 to cause the second lifting structure 540 to act on, directly or indirectly, a jarring mass (not shown), to permit the jarring mass to reciprocate within the apparatus and generate jarring forces. The first lifting structure 538, as in previous examples, is configured to be hydraulically locked and released relative to the housing 504 using a hydraulic locking system. In the present example, the hydraulic locking system includes a first hydraulic chamber 584 which is defined between the mandrel 502, housing 504 and the first lifting structure 538. In the present example the first hydraulic chamber 584 includes a space immediately behind the first lifting structure 538, an annular gap 222 defined between the mandrel 502 and the housing 504, and a valve chamber 224. In the present example the hydraulic locking system further includes a second hydraulic chamber 588 defined between the mandrel 502, housing 504 and a floating piston 226, wherein the floating piston 226 is sealed relative to the mandrel 502 and housing 504. The floating piston 226 is axially moveable in a radial space 228 and is spring biased by spring 230 in a direction to reduce the volume of the second hydraulic chamber 588. In the present example the second hydraulic chamber 588 includes the space immediately behind the floating piston 226 and gun drilled holes 232 through a body portion 234 of the housing 504. A volume of an incompressible hydraulic fluid, such as hydraulic oil is contained within the first and second hydraulic chambers 584, 588. In some examples, the hydraulic fluid may be pre-pressurised. This may allow or accommodate for any fluid compression, and gas compression and small leakage.

(101) Although not illustrated, a pressure relief arrangement (e.g., a pressure relief valve) may be provided within the hydraulic locking system to prevent or minimise risk of overpressure causing damage.

(102) A valve assembly 586 is interposed between the mandrel 502 and housing 504, and also between the first and second hydraulic chambers 584, 588, and is configurable between open and closed positions by relative rotation between the mandrel 502 and housing 504. When the valve assembly 586 is in its closed position fluid communication between the first and second hydraulic chambers 584, 588 is prevented, thus hydraulically locking the hydraulic fluid in the first hydraulic chamber 584, effectively axially fixing the first lifting structure 538 relative to the housing 504.

(103) When the valve assembly 586 is in its open position fluid communication between the first and second hydraulic chambers 584, 588 is permitted, allowing fluid to be displaced from the first hydraulic chamber 584 to the second hydraulic chamber 588, with such fluid displacement accommodated by an increase in the volume of the second hydraulic chamber 588 by virtue of movement of the floating piston 226. Such displacement of fluid from the first hydraulic chamber 584 may effectively axially release the first lifting structure 538 from the housing 504.

(104) The floating piston 226 may also function to accommodate thermal expansion/contraction of the fluid within the hydraulic locking system.

(105) Reference is additionally made to FIG. 31B which is an exploded view of the valve assembly 586 and the body portion 234 of the housing 504, removed from the apparatus 500. The valve assembly 586 in the present example is provided in the form of a rotary gate valve assembly and comprises a gate valve nose 590 which is rotatably fixed to the piston body portion 234, and thus to the housing 504, via a pair of diametrically opposed key tabs 236 received in complimentary slots 238 in the body portion 234. In an alternative example the valve nose 590 may be integrally formed with the body portion 234/housing 502. The valve nose 590 includes two circumferentially arranged (in this case diametrically opposed) ports 594 extending axially therethrough and aligned with the gun drilled bores 232 in the body portion 234.

(106) The valve assembly 586 further comprises a gate valve selector 596 which is rotatably fixed relative to the mandrel 502 via keys (not shown) which extend through key slots 240 in the valve selector 596. The valve selector 596 includes two circumferentially arranged ports 598 which are arranged at the same circumferential spacing as the corresponding ports 594 in the valve nose 590 (i.e., also diametrically opposed).

(107) The valve selector 596 is axially engaged against the valve nose 590, with a gate spring 242 applying a biasing force therebetween. Relative rotation between the mandrel 502 and housing 504 causes corresponding relative rotation and sliding engagement between the valve nose 590 and the valve selector 596, thus cyclically aligning and misaligning the ports 594, 598, as illustrated in FIGS. 31C and 31D, to cyclically open and close the valve assembly 586.

(108) In the various examples described above jarring is provided by an impact between two surfaces, specifically impact between a jarring mass and one or both of a mandrel and housing. However, a jarring or vibratory effect may be achieved without necessarily requiring impact. For example, the reciprocating action of the jarring mass, with the repeated deceleration to provide the direction change, may permit vibration or jarring to be generated. As such, while the examples above include impact surfaces, these are not essential.

(109) As mentioned previously, a jarring apparatus according to the present disclosure may be used in multiple different applications, whether within or outside of a wellbore environment. An example use of a jarring apparatus 600 is illustrated in FIG. 32, wherein the apparatus 600 is coupled within a drill string 602 and is used to provide jarring, when required, during the process of drilling a wellbore 604 using a drilling BHA 606. In the illustration presented a region 608 of the formed bore 604 has collapsed, generating significant friction drag against further advancement, or indeed retrieval of the drilling BHA through the restricted region. In this respect the jarring apparatus 600 may be operated to assist in overcoming the restriction 608.

(110) In an alternative exemplary use, illustrated in FIG. 33, a jarring apparatus 700 may be used to assist in retrieving a section of casing 702 from a wellbore 704. In this respect the jarring apparatus 700 is coupled to a casing spear 706 which is used to grip the casing portion 704. The jarring apparatus 700 may be operable to assist in freeing the casing portion 702 from cement sheath 708, or any other material, within the annulus 710 between the casing portion 702 and wellbore 704. In this example a very significant load may be carried by the jarring apparatus 700, from the weight of the casing portion 702 and the pulling force required to retrieve this from the wellbore. In some examples loads up to and beyond 4.5 MN may be necessary. In such circumstances the load limiting feature, as described in the examples above, may provide significant protection to the jarring apparatus 700.

(111) In a further alternative exemplary use, illustrated in FIG. 34, a jarring apparatus 800 may be used in a fishing operation to assist in retrieving a tool 82 or other equipment from a wellbore 804.

(112) Multiple other exemplary uses are possible, such as in running in equipment, in cementing operations to provide a vibration effect to encourage better cement placement, piling operations and the like.

(113) In the examples provided above jarring is achieved by providing impact between impact surfaces. However, jarring may also be achieved without necessarily requiring such impact. Examples of jarring apparatuses which function to provide jarring without impact are illustrated in FIGS. 35 and 36.

(114) Referring first to FIG. 35, a rotary jarring apparatus 910 is illustrated which is similar in most respects to apparatus 10 first show in FIG. 3A, and as such like features share like reference numerals, incremented by 900. Thus, the apparatus 910 includes a mandrel 912 located within a housing 914, a thrust assembly 918, a jarring mass 924, force mechanism 932 and lifting mechanism 936. However, in the present example the lifting assembly 936 includes a first lifting structure rotatably and axially fixed relative to the mandrel 912 (but alternatively could be connected to the housing 914), and a second lifting structure rotatably fixed, but axially moveable, relative to the housing 914 (but alternatively could be rotatably fixed to the mandrel 912). Further, the jarring mass 924 is rotatably connected to the housing 914 (but alternatively could be rotatably connected to the mandrel 912).

(115) Furthermore, instead of impact surfaces, the apparatus 910 includes an arresting mechanism in the form of a gas spring 8 provided between the jarring mass 924 and the housing 914. A similar gas spring may also or alternatively be provided between the jarring mass 924 and the mandrel 912. In use, relative rotation between the mandrel 912 and housing 914 operates the lifting mechanism 936 to “lift” the jarring mass 924 against the bias of force mechanism 932, and subsequently allow the jarring mass to “drop” and be driven by action of the force mechanism 932. Such movement of the jarring mass 924 under the drive of the force mechanism 932 may be arrested by the gas spring 8, thus generating a jarring effect. Continuous operation may thus generate repeated jarring effects.

(116) FIG. 36 illustrates a similar jarring apparatus 1010 to that shown in FIG. 34. However, in this example an arresting mechanism is provided in the form of a mechanical spring 9, such as a Belleville spring stack.

(117) It should be recognised that the examples provided herein are indeed only exemplary, and that various modifications may be made thereto.