Drill String Suspension

Abstract

Vertical and/or directional drilling apparatus where compliant support air bag, magnetic or the like) is provided for a vibrational head and drive assembly that carries the drill string. With the vibrational head having a shuttle from which vibration is not directly taken and with the compliant support allowing pull back in the directional mode several advantages arise.

Description

The present invention relates to a drilling apparatus and in particular the drill string suspension of apparatus for in ground drilling. In our PCT/NZ04/000128 patent specification, we disclose a number of options for vibrational apparatus for use in drilling as a vibrational head. The content of that specification is here included by way of reference.

Many vibrational apparatus rely upon the rotation of an eccentric. Others rely on pneumatics and/or hydraulics in order to reciprocate a piston which provides a direct output of the vibrational output. Such structures however, whilst disclosed for many end uses, have a downside in that where the device to which the output piston is attached has itself stalled there is a difficulty in ensuring a recommencement of the vibrational output as a consequence of the piston itself refusing to move relative, to its cylinder or the equivalent. Such would be the case with apparatus of PCT/NZ2003/000158 (published as WO 2004/009298) of Bantry Limited.

The present invention, in some aspects, recognises a significant advantage to be derived from the vibrational commencement point of view and/or tuning point of view irrespective of how the apparatus is mounted. This arises from the fact that we have determined that a shuttle without a direct output to the apparatus to be vibrated can itself be sufficient without impacting solid to solid (whether in conjunction with magnetics, hydraulic and/or pneumatics, or not) to provide the requisite output from the containment structure of a shuttle (e.g. the housing of a shuttle, one end complement of a shuttle or both such end complements of the shuttle). Examples include some of the vibrational head forms disclosed in our PCT/NZ2003/000128 (published as WO 2004/113668), our PCT/NZ2005/000047 (published as WO2005/087393) and our PCT/NZ2005/000329 (published as WO2006/065155).

The present invention, in some aspects, recognises at least one of the following as desirable irrespective of the form of the vibrational head:

an ability to drill to greater depth

an advantage in drill withdrawal

an advantage in drilling restarts

an advantage with vibrational drilling

an advantage in directional drilling.

The present invention also or alternately sees an advantage in a manoeuvrable support of or frame to compliantly support a vibrational head. It is to the vibrational head to which lengths of the drill string are added. The compliant mounting or support advantageously allows the vibrational head degrees of freedom in movement non destructively of the support or frame yet which nonetheless confers (a) a benefit to drilling, an ability to drill to greater depth, a benefit in the situations of commencement, restart and/or withdrawal and/or (b) a benefit in apparatus longevity and/or simplicity over otherwise suspended vibrational heads and any attached or to be attached drill string, and

preferably an ability to orient it for directional drilling.

The invention also recognises another benefit from a floating or compliant support for the vibrational head attached to or attachable to a drill string especially when there is both the floating or compliant bearing of the weight of the vibrational head and/or drill string and a confinement of the vibrational head and/or drill string support to that floating or compliant support by a further compliant means. Whilst such a floating and/or compliant support can rely wholly or impart upon gas or confined gas it can be enhanced or instead be replaced by other such constraints of a floating or compliant matter e.g. magnetic. It is therefore within the scope of the present invention to encompass such other forms.

Frequently drilling is of a kind where the drill bit, or at least connections in the drill string, tighten in one direction and loosen in the other direction. Frequently also there is the use of a bit which has some measure of asymmetry thus allowing a measure of directional control. Such directional control ordinarily relies upon a variation from a full rotational movement of the bit (which provides no steering control) to a back and forth limited rotation thereby to build asymmetry in the resistant rock such that pushing forward of the drill string and the bit causes a controlled deviation. Such directional drilling characteristics are well known and I exemplify it by way of example by our PCT/NZ98/00055 (published as WO98/50667).

We have determined where there is a compliant or floating support that there is the prospect of a relief of pressure into the drill string and its bit (whether vibrational output continues or is discontinued) by pressurising with an appropriate mechanical fluid or other input (mechanical or otherwise) into the floating or compliant support of the weight. When there is no such relief there can be limited rotation and pressure on a rock face (with or without vibrational input) and there can be limited rotation in the other direction once there is the relief of the pressure (by affecting the floating or compliant support) such that there will be less tendency to undo any connection in the drill string. For example, if the normal rotation direction for drilling is clockwise, there can be relief of the pressure during a partial anti-clockwise rotation following a pressured partial clockwise rotation.

It is to those aspects that the present invention is also directed.

In an aspect the invention is drilling apparatus comprising or including

a support frame,

a vibrational head,

a first vibrationally responsive support directly or indirectly from the support frame to directly or indirectly carry the vibrational head,

a second vibrationally responsive support directly or indirectly from the support frame to directly or indirectly hold the vibrational head to said first vibrationally responsive support,

a drill string directly or indirectly carried by the vibrational head, said drill string optionally having a bit, and

a drive or drives directly or indirectly to rotate the drill string and any optional bit.

Preferably said vibrational head is dangle supported on said first vibrationally responsive support from said support frame.

Optionally said first vibrationally responsive support includes a compliant reservoir of a fluid.

Optionally said first vibrationally responsive support includes a repulsive magnetic interaction.

Optionally said second vibrationally responsive support includes a compliant reservoir of a fluid.

Optionally said second vibrationally responsive support includes a repulsive magnetic interaction.

Preferably said support frame includes a structure from which an inverted top hat type connection of the vibrational head is suspended between said first and second vibrationally responsive supports. Optionally the vibrational head hangs from either its substantially horizontal plate or substantially horizontal pair of plates and the support respectively has either a pair of substantially horizontal plates or a substantially horizontal plate respectively such that there can be compliant interaction(s) both above and below the single substantially horizontal plate.

Preferably a bit is present.

Preferably said bit is a bit of a kind that allows directional drilling.

Preferably said drive or drives can rotate the drill string, and thus any bit through 360°.

Preferably said drive or drives can also rotate the drill string and thus the bit through less than 360° prior to its reversal in direction.

Preferably at least said first vibrationally responsive support is able to be modified to lift the vibrational head and thus the drill string and a directional drilling bit.

Optionally when at least the first vibrationally responsive support is or has been modified, the drive or drives is able to rotate, or is synchronised to rotate, the drill string and thus the bit in a direction opposite that in which is rotated when drilling through 360° or when being rotated by less than 360° for directional drilling purposes.

In another aspect the invention is drilling apparatus comprising or including

a support frame,

a vibrational head,

at least one vibrationally responsive support directly or indirectly from the support frame to directly or indirectly carry the vibrational head,

a drill string directly or indirectly carried by the vibrational head, said drill string optionally having a bit,

a drive or drives directly or indirectly to rotate the drill string and any optional bit,

wherein at least said first vibrationally responsive support is able to be modified to lift the vibrational head and thus the drill string and a directional drilling bit,

and wherein, when at least the first vibrationally responsive support is or has been modified, the drive or drives is able to rotate, or is synchronised to rotate, the drill string and thus the bit in a direction opposite that it in which is rotated when drilling through 360° or when being rotated by less than 360° for directional drilling purposes.

Preferably said vibrational head is dangle supported on and/or by said at least one vibrationally responsive support from said support frame.

Optionally said at least one vibrationally responsive support includes a compliant reservoir of a fluid.

Optionally said at least one vibrationally responsive support includes a repulsive magnetic interaction.

Preferably said support frame includes a structure from which an inverted top hat type connection of the vibrational head is suspended between said first and second vibrationally responsive supports. Optionally the vibrational head hangs from either its substantially horizontal plate or substantially horizontal pair of plates and the support respectively has either a pair of substantially horizontal plates or a substantially horizontal plate respectively such that there can be compliant interaction(s) both above and below the single substantially horizontal plate.

Preferably a bit is present and the bit is of a kind that allows directional drilling. Preferably said drive or drives can rotate the drill string, and thus any bit, through 360°.

In another aspect the present invention is the use of drilling apparatus having a floating or compliant support for a vibrational head attached to or attachable to a drill string that the present invention is directed.

The floating or compliant support preferably includes some gaseous and/or magnetic weight support and preferably some gaseous and/or magnetic constraint to such weight support. Preferably also constraint to lateral migration.

Preferably there is a compliant restriction on one (or both) limit(s) of a or the shuttle stroke i.e. no striking.

Preferably there is compliant restriction on movement of the vibrational head relative to its support

Preferably there is compliant bearing of the weight of the vibrational apparatus and any connected drill string.

Preferably there is a drive to rotate the drill string independently of movement of rotation or lack of rotation of part or all of the vibrational apparatus.

Preferably there is a top hat type support assembly to dangle the vibrational head.

In another aspect the invention is a drilling apparatus comprising

a vibrational head attached to or attachable to a drill string,

a support, and

at least one reconfigurable (e.g. compliant) fluid reservoir (e.g. a compliant gas bag) to carry yet constrain the vibrational head to the support,

wherein the interaction of the vibrational head, the support and the at least one reconfigurable fluid reservoir has the effect of carrying the weight of the attached or the to be attached drill string yet allowing some freedom of movement of the vibrational head relative to the support both longitudinally and laterally of the drill string axis.

Preferably there are at least two reservoirs.

Preferably the fluid in at least one reservoir is a gas (e.g. air).

Preferably at least one, and preferably several or all, of the reservoirs is a gas bag.

Preferably the support is a frame.

Preferably most of the vibrational head (when the drill axis is vertical) is below the reservoir(s).

Preferably the longituding support allows a greater freedom of movement than the lateral support but not necessarily so.

Preferably the vibrational head includes a shuttle.

Preferably irrespective of how the shuttle is caused to shuttle there is

• • (a) preferably a vibrational outtake not directly from the shuttle,
  • (b) the shuttle preferably reciprocates
  • (c) the shuttle preferably impinges at each end of its stroke on a compliant structure
  • (d) a or each compliant structure may be a gas bag
  • (e) the compliant structure(s) preferably can be varied in character to affect stroke by a variation of a fluid or gas supply
  • (f) the vibrational outtake is not from a compliant structure but is via a compliant structure
  • (g) the shuttle may or may not rotate on its stroke axis.

Preferably the vibrational outtake from the vibrational head into the drill string is via a transition from a non rotating but vibrating component directly or indirectly into a rotatable and rotating component (e.g. connectable to or forming part of the drill string).

In another aspect the invention is a drilling apparatus comprising

a vibrational head attached to or attachable to a drill string,

a support,

at least one gas bag interposed between part(s) of the vibrational head and the support, as a first interaction, to carry the weight of the vibrational head and the or any attached drill string, and

• • at least one gas bag interposed between the support and part(s) of the vibrational head, as a second interaction, to constrain the vibrational head relative to the support whereby said first interaction is not totally lost during any part of the vibrational cycle of the vibrational head.

Preferably part(s) of the vibrational head is (are) interposed between top and bottom constraints provided by said support and at least one air bag is interposed above the part(s) and below one constraint and at least one air bag is interposed below the part(s) and above the other constraint.

Preferably most of the vibrational head is below said part(s).

The arrangement is such as to provide freedoms of movement of the vibrational head and its carried or to be carried drill string relative to the support yet able, responsive to weight, to bias to a datum condition of the vibrational head relative to the support.

In another aspect the invention is a drilling apparatus comprising

a vibrational head attached to or attachable to a drill string, the vibrational head having laterally of the longitudinal axis defined, or to be defined, by the drill string one or more projection(s) to define at least one upper surface and at least one lower surface,

a support frame for the vibrational head,

at least one gas bag to act between the frame and said at least one upper surface, and

at least one gas bag to act between the frame and said at least one lower surface.

Preferably the vibrational head has provision both for a compliant (e.g. gas bag or the like) limitation at each end of a shuttle stroke and a compliant (e.g. gas bag or the like) mounting of the vibrational head itself from a support or frame.

Preferably both the upper surface(s) and the lower surface(s) are nearer the top than the bottom of the vibrational head.

In another aspect the invention is a drilling apparatus comprising

a vibrational head attached to or attachable to a drill string,

a support, and

wherein (I) the vibrational head has a shuttle compliantly restricted in its stroke at least in part by compliant means, and (II) the vibrational head is compliantly supported by the support,

and wherein the support via the compliantly supported vibrational head is adapted to carry the weight of, or bear the inertia of or momentum of, the attached or the to be attached drill string yet allow some freedom of movement of the vibrational head relative to the support both longitudinally and laterally of the drill string axis.

Preferably there are at least two reservoirs of a fluid to provide a compliant support of the vibrational head.

Preferably the fluid in at least one reservoir is a gas (e.g. air).

Preferably at least one, and preferably several or all, of the reservoirs is a gas bag.

Preferably the support is a frame.

Preferably most of the vibrational head (when the drill axis is vertical) is below the reservoir(s).

Preferably the longituding support allows a greater freedom of movement than the lateral support but not necessarily so.

Preferably the compliant restriction of the shuttle is a reservoir of a fluid at an end of the shuttle when at a limit of a stroke.

In another aspect the invention is a drilling apparatus comprising

a vibrational head attached to or attachable to a drill string,

a support,

compliant means (e.g. preferably at least one gas bag interposed between part(s) of the vibrational head and the support), as a first interaction, to carry the weight of the vibrational head and the or any attached drill string, and

compliant means, as a second interaction, (preferably to constrain the vibrational head relative to the support) whereby said first interaction is (preferably) not totally lost during any part of the vibrational cycle of the vibrational head.

Preferably the vibrational head includes a shuttle compliantly restricted as to stroke.

Preferably part(s) of the vibrational head is (are) interposed between top and bottom constraints provided by said support and at least one air bag is interposed above the part(s) (e.g. as one option of said compliant means) and below one constraint and at least one air bag is interposed below the part(s) and above the other constraint.

Preferably most of the vibrational head is below said part(s).

Other options exist for the compliant means including a spring, a compressible fluid in a variable volume reservoir, an incompressible or compressible fluid, or both, in a bag, bellows, or any such variable geometry containment, resilient or otherwise.

The arrangement is such as to provide freedoms of movement of the vibrational head and its carried or to be carried drill string relative to the support yet able, responsive to weight, to bias to a datum condition of the vibrational head relative to the support.

In another aspect the invention is a drilling apparatus comprising

a vibrational head attached to or attachable to a drill string, the vibrational head having laterally of the longitudinal axis defined or to be defined by the drill string one or more projection(s) to define at least one upper surface and at least one lower surface,

a support frame for the vibrational head,

at least one gas bag to act between the frame and said at least one upper surface, and

at least one gas bag to act between the frame and said at least one lower surface,

and wherein the vibrational head has a drill string rotational drive to or adjacent its connection for a drill string.

In a particularly preferred embodiment of the present invention preferably the apparatus is vibrational drilling apparatus comprising

a vibrational head having a shuttle yet a vibrational outtake not directly from the shuttle,

a manoeuvrable support from which the vibrational head is mounted to compliantly vibrate under the action of the shuttle,

a bearing supported from the vibrational outtake from the vibrational head, and a drill string connector carried by the bearing,

a rotational drive to the drill string connector.

Preferably the rotary drive to the drill string connector is from a flexible transmission from a motor engine or other power source, (e.g. combustive, hydraulic, pneumatic, electric, or the like).

Preferably the flexible drive is of a belt able to provide a rotary transmission having some capability of reducing transmission of shock from the drill string connector to the support yet able to allow vibrational movement of the drill string connector through the bearing from the outtake.

Optionally there is no reliance upon the provision of an externally pressurised fluid as the sole means of empowerment of shuttle movement by being introduced so as to pressurise without further event between a complementary structure and said shuttle.

The present invention also consists in vibrational apparatus capable of providing a vibrational output, said apparatus comprising or including

a shuttle able to shuttle reproducibly on a shuttle axis or locus between first and second complementary structures,

a drive to rotate the shuttle about at least part of the shuttle axis or locus, and

magnetic interacting regions on each of at least one complementary structure and the shuttle whereby rotation of the shuttle has the effect of subjecting the shuttle to shuttle inducing forces being alternately attractive and repulsive forces between the or a complementary structure and the shuttle,

and wherein the output of the vibration is from one or other, or both, of said complementary structures and not directly from the shuttle itself.

Preferably at least one, some or all of the following is included;

• • compliant restriction on one (or both) limits) of a or the shuttle stroke
  • compliant restriction on movement of the vibrational apparatus relative to its support
  • compliant bearing of the weight of the vibrational apparatus and any connected drill string
  • a drive to rotate the drill string independently of movement of rotation or lack of rotation of part or all of the vibrational apparatus
    a top hat type support assembly to dangle the vibrational head. Preferably this involves the vibrational head hangs from either its substantially horizontal plate or substantially horizontal pair of plates and the support respectively has either a pair of substantially horizontal plates or a substantially horizontal plate respectively such that there can be compliant interaction(s) both above and below the single substantially horizontal plate.

The present invention also consists in vibrational apparatus capable of providing a vibrational output, said apparatus comprising or including

a shuttle rotatable about a defined shuttle axis and moveable back and forth on the shuttle axis,

a drive to rotate the shuttle about its shuttle axis,

a first complementary structure towards which and away from which, and vice versa, the shuttle moves,

a second complementary structure away from which and towards which, and vice versa, the shuttle moves, the shuttle being between said complementary structures,

wherein proximal regions of each pairing of first complementary structure/shuttle and shuttle/second complementary structure have magnetic areas operable to provide alternatively for each pairing attractive or repulsive forces as the shuttle rotates,

and wherein the phasing between the pairings is, or can be, such that the shuttle reciprocates on its shuttling axis as a consequence of the magnetic interactions that act on the shuttle by virtue of its rotation,

and wherein the vibrational output is from one or other, or both, of said complementary structures and not directly from the shuttle itself.

Preferably at least one, some or all of the following is included;

• • compliant restriction on one (or both) limit(s) of a or the shuttle stroke
  • compliant restriction on movement of the vibrational apparatus relative to its support
  • compliant bearing of the weight of the vibrational apparatus and any connected drill string
  • a drive to rotate the drill string independently of movement of rotation or lack of rotation of part or all of the vibrational apparatus
    a top hat type support assembly to dangle the vibrational head. Preferably this involves the vibrational head hangs from either its substantially horizontal plate or substantially horizontal pair of plates and the support respectively has either a pair of substantially horizontal plates or a substantially horizontal plate respectively such that there can be compliant interaction(s) both above and below the single substantially horizontal plate.

Preferably said first and second complementary structures are fixed relative to each other insofar as distance is concerned.

Preferably the shuttling is without solid to solid high impact or impact contact.

Optionally said shuttle co-acts at least at one end with its complementary structure so as to provide a cushioning affect, e.g. by squeezing a fluid. Alternatively that can be at both ends. One or both ends of the shuttle (despite any guiding contact it may already have) can be adapted to contact part of the complementary structure only at the end of its shuttling travel or to contact some material interposed between that end of the shuttle and the complementary structure.

Preferably the vibrational output is from one of the complementary structures.

In another aspect the invention is vibrational drilling apparatus comprising

a vibrational head,

a drill string support dependent from the head having a rotational drive to rotate a drill string connected or to be connected thereto,

a vibrational head support, and

a mount for the vibrational head from the vibrational head support which both compliantly interacts with the support and dangles the vibrational head.

Preferably the compliant interaction involves at least one gas bag.

Preferably the drill string support and rotational drive allows the vibrational head not to rotate with the drill string.

In still another aspect the invention consists in vibrational apparatus capable of providing a vibrational output, said apparatus comprising or including an assembly having a shuttle capable of shuttling between complementary structures, at least one of which complementary structures provides the vibrational output, the arrangement being characterised in that there is a drive to rotate the shuttle and there are magnetic interactions between the rotating shuttle and the complementary structures such that interactions with each complementary structure, and the phasing of the complementary structures relative to the shuttle, alternating magnetic results in the shuttling movement of the shuttle.

Preferably at least one, some or all of the following is included;

• • compliant restriction on one (or both) limit(s) of a or the shuttle stroke
  • compliant restriction on movement of the vibrational apparatus relative to its support
  • compliant bearing of the weight or inertia or thrust of the vibrational apparatus and any connected drill string
  • a drive to rotate the drill string independently of movement of rotation or lack of rotation of part or all of the vibrational apparatus
  • a top hat type support assembly to dangle the vibrational head.

Preferably the magnetic interactions are as a result of permanent magnets.

Preferably the drive of the shuttle is a belt or other peripheral drive of the shuttle or a drive to an axial extension of or connecting to the shuttle not deleterious to the shuttling movement of the shuttle between shuttling limits (preferably magnetically defined).

Optionally there is no reliance upon the provision of an externally pressurised fluid as a means of empowerment of shuttle movement by being introduced so as to pressurise without further event between a complementary structure and said shuttle.

In another aspect the invention is the use of the state of a compliant dangled support for a direction drill bit carrying drill string as a means to relieve pressure from or allow the application of weight to the bit via the drill string.

As used herein “shuttle” has the broadest meanings with respect to what moves and what does not, etc. Preferably it is a shuttle to move rectilinearly. It can be subject to any drive one or both ways.

As used herein the term “and/or” means “and” or “or”, or, where the context allows, both.

As used herein the term “comprises” or “comprising” can mean “includes” or “including”.

As used herein the term “(s)” following a noun can mean both the singular and plural versions of that noun.

As used herein the terms “stroke” or “stroke limit” can refer to limits of a rectilinear stroke or any curved stroke (e.g. can swing about a pivot axis or other support, whether fixed or moving).

As used herein “compliant” and variations thereof refer to the character of any structure, whether a gas bag, gas spring or the like, or not, able to achieve a desired stated outcome (e.g. stroke limitation, shock reduction, damping, impact avoidance, etc.) or, in the case of the vibration head support (i.e. of its weight or inertia or thrust and that of the drill string/bit etc) and its being held to that support, any such arrangement (e.g. fluid bag, fluid [liquid and/or gas] reservoir, etc and/or any magnetic or other floating or clear support).

As used herein “floating” for non-directional drilling usually but not solely includes at least near vertical disposition of the shuttle axis but not necessarily so. It can mean “floating” with respect to the drill string axis even if horizontal.

A preferred form of the present invention will now be described by reference to the accompanying drawing in which

FIG. 1 is an elevational diagram of a preferred form of an embodiment of the present invention, the vibrational head dangling down from a top hat support on air bags,

FIG. 2 is a similar diagram to that of FIG. 1 but showing disposed within the airbags or gas bags or the like reservoirs of FIG. 1 some spaced magnetic arrangements adapted to assist in a repulsive force but which repulsive force can in part be overcome as desired to allow the vibrational output from the vibrational head into the drill string and, in addition, can be overcome in part when wanting to relieve the pressure on the downhole drill string reliant upon some mechanical input i.e. squeezing up or inflation and/or deflation,

FIG. 3 is a similar diagram to FIG. 2 showing no air bags but simply the magnetic interactions, there being other magnetic or the like compliant restraints to hold the horizontal position of the support against migration, it being appreciated (e.g. by showing air bags in broken lines) how hybrids of the arrangement shown in FIGS. 1, 2 and 3 can be utilised,

FIG. 4 is a variation of the arrangement shown in Figure showing how under the action of inflation/deflation, or mechanical prodding, the lower most bag(s) of the FIG. 1 arrangement can be caused to be partly uplift the vibrational head and thus relieve pressure on the downhole bit,

FIG. 5 is a broken open perspective view of a vibrational head operable under fluid pressure (e.g. hydraulics and/or pneumatics) where each end of the shuttle is alternately driven by the ingress of a rotary valve controlled injection of the fluid whilst the other end allows egress (also preferably via a rotary valve), (this Figure equating to FIG. 11 of our PCT specification PCT/NZ2005/000047 published 22 Sep. 2005 as WO2005/087393),

FIG. 6 is also the apparatus of FIG. 5 but showing it from a different broken open condition to better demonstrate the shuttle, the shuttle including a rotary shaft as a guide or a carried shaft, but preferably the vibrational output coming from the fixed piston-like members of the casing rather than from any direct connection to the shuttle itself,

FIGS. 7A and 7B show the principle of magnetic shuttling interactions as described in FIGS. 2 and 4 of our PCT/NZ2005/000329 published 22 Jun. 2006 as WO2006/065155 showing rotation relativities for (A) attraction of the shuttle and (R) repulsion of the shuttle,

FIG. 8 is, in a similar view to FIGS. 1 to 4 hereof, an embodiment of such a magnetic interaction shuttling head as disclosed in FIG. 8 of our WO2006/065155,

FIG. 9 is our proprietary directional drill bit attachable to the end of a drill string so as to be able to be rotated through more than 360° to achieve straight drilling and to be partially rotated through less than 360° to allow some directional drilling,

FIG. 10 is a side elevational view showing the asymmetry of the bit of FIG. 9,

FIG. 11 is a view towards the business end of the bit,

FIG. 12 shows a bit as shown in FIGS. 9 through 11 with an approximately 12.5° steering face but being operated in a straight drill mode i.e. with rotation about greater than 360° thereby to provide the downhole profile shown,

FIG. 13 is a similar view to that of FIG. 12 but this time showing its having being moved forward after some rotation through less than 360° i.e. in a steering mode thereby building up some asymmetry in the downhole profile, the bit having made forward progress a distance as little as 8-10 mm,

FIG. 14 is a similar view to that of FIG. 13 but with the bit still in the steering mode but this time after approximately 50 mm of forward travel in a steering mode,

FIG. 15 is a similar view to that of FIG. 14 but showing advancement to about 110 mm from the 50 mm position of FIG. 14,

FIG. 16 is a similar view to that of FIG. 15 but showing advancement by a further 25 mm e.g. to about 135 mm in the steering mode,

FIG. 17 shows a similar view of that of FIG. 16 but with still a further 25 mm of progress in a steering mode i.e. to a total distance of about 160 mm,

FIG. 18 shows the result of commencement of full rotation of our proprietary bit subsequent to its assuming a condition as shown in FIG. 17,

FIG. 19 shows related plots showing, as a progressively deeper drilling plot, the partial clockwise rotation to cut rock, the relief from the drilling pressure, anti-clockwise partial rotation, etc (“clockwise” being shown in the lower plot by an ascending line, “anti-clockwise” partial rotation being shown by a descending line, the “pull back” condition without rotation being shown by the horizontal lines at the top and the “push forward” without rotation being shown by the horizontal lines at the bottom),

FIG. 20 shows the 10 to 12 o'clock limited rotation shown in the plots of FIG. 19,

FIG. 21 is a pressure line feed to and from the inflatable reservoirs of an arrangement as shown in FIG. 1, such pressure lines allowing variation by inflation and deflation so as to effect an outcome prior to and during reverse partial rotation (in the steering mode) by the rig assuming the condition as shown in FIG. 4,

FIG. 22 shows a preferred tie rodded two plate embodiment working on a thrust plate with which the tie rods constrain the front and back plates to align, and

FIG. 23 shows a flow diagram for both a hydraulic drive to each of the shuttle and the drill string and a flow diagram of the pneumatic circuit to inflate/deflate the air bags of, say, FIGS. 1 and 4.

Preferably, as at the publication date of out aforementioned patent specifications, all of our said specifications are herein included by way of reference. Likewise that of WO2004/009298. The present invention in its preferred form is directed preferably to a dangle supported vibrational head and its drive (including any clutching or other mechanism included therein) and including any controls which allows rotation in a drilling sense through greater than 360° and, for directional drilling purposes, preferably about an arc in the drilling direction less than 360° and in the retreating or return condition a similar arc in the other direction (e.g. nominally clockwise and anti-clockwise respectively).

In a preferred form of the present invention the support comprises a supported pressure plate on either side of which is located (preferably by tie bars or the like) other plates notionally the “front” and “rear” plates or the “lower” and “upper” plates. Between these plates and the pressure plate is to be the interaction of a compliant type kind (preferably both top and bottom).

It is made to lower and upper plates and whilst reference is made herein to suspension or dangling it should be appreciated that for directional drilling purposes the disposition of the vibrational head may very well be other than at the near vertical. for example, horizontal disposition of the vibrational head in its support is also contemplated within the scope of the present invention and therefore terms such as dangle, lower, upper, etc should take appropriate meanings when such apparatus is to be used in such a disposition. In such horizontal usage preferably guides, e.g. the tie bolts etc hereinafter described preferably assume greater importance to ensure that the compliant means remains available in order to protect the support from the vibrations or largely from the vibrations of the shuttle.

Preferably interposed between such plates are the compliant means or the means to provide the compliant interaction.

As herein follows reference to “air or fluid (gas) bag” includes any containment structure or applicable gas containing form capable of being responsive to an infill of a fluid and/or an egressing of a fluid under some control or responsive, without any movement to fluid inwardly and outwardly, of complying to changes as maybe appropriate in the circumstances.

Any suitable natural or synthetic rubber type material can form such a container. Any suitable woven or non-woven pliable material (irrespective of whether resilient or not) can also be used and, if desired, can that itself be impregnated with an appropriate sealing of a rubber nature or not. Suitable woven material include synthetic fibres such as those of TEFLON™, glass, nylon or the like.

Other materials can also be used.

FIG. 1 shows a main air or fluid (gas) bag group (4) co-acting between vibration apparatus part (“vibrational head” with a shuttle, the vibration output being from its casing) 11 and fixed or manoeuvrable drill head frame assembly (6) is shown. This assembly provides the drill string (7) with the ability to “float” in the drill hole while operating regardless of the weight of the drill string as it can be, if desired, be adjusted by air valves to provide equal pressure on the drill string fixture held between the air bags (4) as shown. Of course that capability also allows unequal pressure to be used, as will be hereafter described, for pressure relief when directional drilling.

This assembly also provides the insulation between the moving mass of the drill string (7) and shuttle assembly and the drill rig structure or support/frame (6).

Those two functions are preferred and can prove to be critical in the operation of the head.

The moving mass (shuttle) shown as (5) can have air bags or compliant means at each end within end plates. End plate 12 is that to provide output to the drill string. The air bags shown as (8) are used to position the shuttle in the centre of its operational shuttle movement. This is preferred and can prove critical as the shuttle could bottom out against the end plates 12 and 13 (of 11) while it is operating. The pressure in these air bags 8 can be varied symmetrically or asymmetrically to change the operating parameter of the shuttle i.e. to restrict or increase the movement of the shuttle. This assembly allows the shuttle assembly to be completely suspended while attached to the drill string.

A rotation bearing assembly as a transition allows rotation to the drill string (7). Above the bearing the vibrational outtake does not rotate i.e. is fixed or independent of drill string rotation, but does vibrate. The rotary input is preferably provided by a wide tooth belt assembly (2) driven by a fixed motor (1). The distance between the drives is such the movement of the drill string and the associated vibration is dissipated by the belt drive and therefore is not transmitted to the drill structure. The belt drive is also such as not to fail owing to the vibration.

FIGS. 1, 2, 3 and 4 show a thrust plate 10 interposed between (in the case of FIGS. 1, 2 and 4) plates 14.

So that each gas bag 4 is located as in FIG. 1 and able to accommodate movements under vibrational inputs upwardly (as shown in FIG. 4) or downwardly in a vice versa situation to the distortions shown in FIG. 4 from those shown in FIG. 1. If desired such movements can be induced by appropriate inflation deflation of the bags 4 as will be described hereafter.

FIG. 2 shows a hybrid where magnets 15 are disclosed inwardly or outwardly of the bags 4 so as to provide a repulsive effect one to the other i.e. magnets aligned from one of the plates 14 with respect to one of the plates of the thrust plate 10 is of the same thereby preventing contact. This is a system by the air bags themselves. The provision of such a mix of magnetic interactions and air bag interactions makes it possible by appropriate means to induce vibrational movement or to cause a dislocation upwardly or downwardly but still without contact of magnet 15.

The purpose of the shuttle is to transfer energy onto the adjacent members and in a reciprocal motion. This transfer of energy can be achieved, as in the past, by the injection of oil between the shuttle and its adjacent members with the appropriate timing to cause the shuttle to move in a reciprocal motion, thus to cause the drill string to move in a linear motion in parallel with the shuttle motion thus transferring the energy down the drill string to the bit in the most efficient manner. We also favour the magnetic interaction approach to be described hereafter.

The shuttle mass is the key to the transfer of the energy to the adjacent members. The change in direction of travel imparts the energy to the adjacent members. The more mass the shuttle has the greater the energy required to achieve this change in direction and is directly linked to the horse power required. The relationship between the mass of the shuttle and the total mass of the drill string being vibrated has to be considered and sized appropriately.

The shuttle action (the shuttle being independent of the take off of the vibration) has the advantage of never having the vibrational head being in a situation of being stalled by locking or binding of the drill string in the drill hole. The shuttle can deliver full power to the drill string or attachments that may be fitted.

FIGS. 5 and 6 equate to FIGS. 11 and 10 respectively of our WO2005/087393. Shown is a shuttle 17 able to reciprocate backwardly and forwardly on the shaft (preferably provided with a bearing at each end) 18. The shuttling motion as described in the aforementioned specification occurs by the introduction and removal from each chamber 18 and 20 respectively of a fluid which can act against fixed pistons 21 and 22 respectively. The closed a chamber 19 or 20 at each end of the shuttle 17. Rotary valve arrangements 23 and 24 are adapted to provide the ingress and egress respectively of fluid from a chamber 19 or 20 thereby providing a vibrational output through for example the fixed piston 21 and not the shaft 18. If the shaft is fixed to the shuttle 19. If the shaft is not fixed to the shuttle 19 it can be power output from that shaft irrespective of whether or not it has any rotational role or simply sealed in the fixed pistons.

The appropriate pneumatic controls to and from the arrangement of a vibrational head as shown in FIGS. 5 and 6 is fully described in our patent specification referred to.

In respect of a magnetic interaction head as in our WO2006/065155 FIG. 7A is a diagrammatic view showing rotation of the shuttle in a clockwise sense between the fixed complementary members and showing with “R” and “A” a circumstance of repulsion and attraction respectively between a complementary component and the shuttle and between the shuttle and the other complementary member such that there is a net shuttling thrust on the shuttle in the arrowed direction. FIG. 7B shows the arrangement as in FIG. 3 at a moment in time later when there is a reversal of the attractive “A” and repulsive “R” forces between the pairings of the fixed complementary component and the shuttle, the shuttle having shuttled in the arrowed direction.

FIGS. 7A and 7B by reference to regions of different polarity of permanent or other magnets shows the effect. The broken zigzagging arrow is indicative of power take off from a first complementary structure. In the arrangement shown however there is a second complementary structure shown out of phase so far as the “plus” and “minus” polarities depicted are concerned. The shuttle preferably has the same polarity at each end such that, in a condition as shown in FIG. 3, there is a net repulsive force arising from alignment of “plus” and “plus” polarities between the shuttle and the first complementary structure whilst, at the same time, there is a “plus” and “minus” attractive force “A” between the shuttle and the second complementary structure. A short moment in time later the opposite situation, as depicted in FIG. 7B, exists and it is this rapid alternating of “R” and “A” to “A” and “R” that leads to the reversal in shuttle direction as the shuttle rotates.

In some forms of the present invention, provision is made whereby the 180° out of phase situation shown for the complementary structures and can be varied.

The outtake of vibration is preferably as shown in FIGS. 7A and 7B via the first complementary structure.

The shuttle is preferably reciprocated by magnetic means. Ends of the shuttle have electromagnets or (preferably) rare earth magnets fitted in such an arrangement that when the shuttle is rotated it will pulse responsive to adjacent members also fitted with magnets in such a way that would cause the shuttle to reciprocate.

Hybrids of the foregoing and/or other drives can be used.

The examples above all have a common theme.

The shuttle preferably never needs to touch the adjacent members in a physical sense as this could damage the magnets and the drill string joints together with the together with the associated down hole equipment.

The movement of the shuttle preferably is never dependent on the drill string or attached equipment, being free to move in relation to the movement of the shuttle.

The shuttle action preferably drives the drill string in both directions i.e. in and out and in doing so allows drill bit rotation to move with very little drag on the drill bit carbides. This action allows for back reaming of holes.

Preferably used are permanent magnets (particularly Rare Earth type magnets of high magnetic density, e.g. Neodymium magnets, such as those of NdFeB, can be stable to 180° C. and Samarium Cobalt magnetic (FmCo) which can be used up to 400° C.).

Other forms of magnet can be utilised including those magnets that may be developed in the future. Generally speaking however, electro magnets are contra-indicated purely from the point of view of size and the need to provide adequate electrical inputs in a structure that does vibrate and is subject to adverse environments.

It is envisaged that rotational speeds for the shuttle can vary significantly. A mere example of one such rotation is 1600 RPM which is sufficient, with magnets as depicted, to provide a sufficient throw of the shuttle backwards and forwards to provide a worthwhile vibrational output. Usual ranges can be from 1000 to 2000 RPM but can be higher or lower. 2000 RPM equates to approximately 130 Hz.

FIG. 8 shows a drilling head in accordance with the invention of our WO2006/065155 suspended so as to dangle carry a vibrating head in accordance with the present invention, the vibrating apparatus itself being shown in partial section. The full content of the specification is here included by way of reference but on the basis it was not published prior to 22 Jun. 2006.

With the arrangement of FIG. 8, for example, the shuttle if 1.5 m long can have an amplitude of shuttle movement of from 0.1 mm to 15 mm (depending on shuttle rotation speeds, shuttle mass, magnetic arrays, magnetic strengths, geometry and clearances).

Preferably a cycling frequency of from (preferably) above 20 cycle/sec to say, 200 cycles/sec are contemplated in steady state conditions. A frequency 200 cycles/sec can easily be generated using 4/8 magnetic interactions reliant on shuttle rotation of about 3000 RPM.

The end plates and tie rods are the link between the adjacent members and these transfer the reciprocating energy to the drill string.

In FIG. 8 a main air or fluid (gas) bag group co-acting between vibration apparatus part being a fixed or maneuverable preferably dangled drill head frame assembly is shown. This assembly provides the drill string 25 with the ability to float in the drill hole while operating regardless of the weight of the drill string as it is capable of being adjusted by air valves (not shown) to provide equal pressure on the drill string fixture held between the air bags or can be left to itself. This assembly also provides the insulation between the moving mass of the drill string 25 and shuttle assembly 26 and the drill rig structure or support/frame 27.

Those two functions are preferred and can prove to be critical in the operation of the head. It also allows advantages for directional drilling to be discussed in more detail later.

End plates 28 and 29 react to the shuttle. End plate 28 provides output to the drill string via a shaft 30 and its extension 31. A rotation bearing assembly 32 as a transition allows rotation to the drill string. Above the bearing assembly 32, the vibrational outtake is independent of drill string rotation i.e. need not rotate. The rotary input to the drill string spindle below is preferably provided by a wide tooth belt assembly 33 driven by a fixed motor 34. The distance from motor 34 is such the movement of the drill string and the associated vibration is dissipated by the belt drive 33 and therefore is not transmitted from the drill structure to the motor 34. The belt drive is also such as not to fail owing to the vibration.

The shuttle 25 carries (in the manner as in FIGS. 7A and 7B) arrays of magnets 36 and 37 to interact as described with the arrays of magnets 38 and 39 respectively.

Preferably the drive of the shuttle rotation is an electric, pneumatic or hydraulic motor 40 drive flexible drives e.g. belts 41. Preferably several drive belts are used. Such belts 41 preferably can accommodate the amplitudes of movement required.

In other drive forms the shuttle can be impelled to rotate reliant on vanes being struck by a fluid (e.g. air, water or the like). Other options for a drive also exist or can be used e.g. some drive to an axial extension of the shuttle (not necessarily a peripheral transmission).

As far as the vibrational apparatus is concerned, it can be seen that an end plate carries 42 and 43 of the shuttle (e.g. bolted appropriately to the shuttle or lapping and being fixed radially into the sides of the shuttle) each holds to the shuttle an array of magnets 36 and 37, each array co-act (as in FIGS. 7A and 7B) with an array of magnets 38 and 39 of plates 28 and 29.

As can be seen, at least on the shuttle, each of the magnets are frustoconical or shaped forms capable of being held by retention plates 42 and 43 and to the main body of the shuttle. The same can be used, if desired, for plates 28 and 29 and their arrays 38 and 39.

That main shuttle body preferably is lined with permanent magnets of a first pole 44 which are to be magnetically levitated about the magnetic lining of a second pole 45 of the shaft.

Whilst preferably the magnets are exposed at the end of each shuttle, in some instances, there can be a protective covering provided that it does not interfere with the effectiveness of the magnetic interaction. Likewise for the fixed magnets of the end plates respectively. These can be retained similarly to the shuttle or simple adhesion may suffice.

It is envisaged that each or one end plate is able to be rotated (e.g. by)45° so that when desired the shuttle can be kept at a stable condition between the end plates and irrespective of whether being rotated or not.

The magnetic support of the shuttle on a guiding axis is preferred but in other alternative forms some air or other support can be provided. This is to avoid any unnecessary heat build up which may degrade the performance of the permanent magnets.

There is the prospect of a fluid pathway 46 that extends through the apparatus into the drill string thus providing a flushing capability as well as a prospect of a cooling function. Such a fluid can be air, a liquid (e.g. water) or can include a lubricant fluid typically (e.g. a slurry) used in drilling.

FIG. 9 is a directional drill bit attachable to the end of a drill string so as to be able to be rotated through more than 360° to achieve straight drilling and to be partially rotated through less than 360° to allow some directional drilling reliant on the asymmetry provided by its flat face 47. FIG. 10 is a side elevational view showing the asymmetry of the bit of FIG. 9. FIG. 11 is a view towards the business end of the bit showing the cutters.

FIG. 12 shows a bit as shown in FIGS. 9 through 11 with an approximately 12.5° steering face 47 but being operated in a straight drill mode i.e. with rotation about greater than 360° thereby to provide the symmetric downhole profile 48 shown e.g. with a 95 mm diameter Sonde housing body in a directional bit created 145 mm diameter hole. FIG. 13 is a similar view to that of FIG. 12 but this time showing its having being moved forward after some rotation through less than 360° i.e. in a steering mode thereby building up some asymmetry in the downhole profile, the bit having made still further forward progress a distance as little as 8-10 mm. FIG. 14 is a similar view to that of FIG. 13 but with the bit still in the steering mode but this time after approximately 50 mm of forward travel in a steering mode. FIG. 15 is a similar view to that of FIG. 14 but showing advancement to about 110 mm from the 50 mm position of FIG. 14. FIG. 16 is a similar view to that of FIG. 15 but showing advancement by a further 25 mm e.g. to about 135 mm in the steering mode. FIG. 17 shows a similar view of that of FIG. 16 but with still a further 25 mm of progress in a steering mode i.e. to a total distance of about 160 mm. This shows the material 49 from the asymmetric profile region 50 to be removed upon full rotation/new direction drilling through more than 360°.

FIG. 18 shows the result of commencement of full rotation subsequent to its first assuming a condition as shown in FIG. 17.

FIG. 19 shows related plots [Action vs. Time (at the bottom) and Depth vs. Time (at the top)] showing, as a progressively deeper drilling plot, the partial clockwise rotation to cut rock, the relief from the drilling pressure, anti-clockwise partial rotation, etc (“clockwise” being shown in the lower plot by an ascending line, “anti-clockwise” partial rotation being shown by a descending line, the “pull back” (“PB”) condition without rotation being shown by the horizontal lines at the top and the “push forward” (“PF”) without rotation being shown by the horizontal lines at the bottom).

In FIG. 19 the more adjacent pairings of vertical broken lines corresponds alternately to a 200 millisecond (“PF”) thrust pressure (i.e. when the plot on the lower graph is horizontal and lower most) and a corresponding 200 millisecond thrust pressure release (“PB”) when the plot on the same graph is horizontal at an upper condition. These positions correspond alternately to push forward with zero rotation and pull back with zero rotation respectively.

The cutting is shown on the bottom plot by the upwardly inclined lines where there is approximately 10 rpm drill rod rotation but only between the time the plot at the bottom of the inclined line when it is at the 10 o'clock position shown in FIG. 20 through to the top of the upwardly inclined line when it is at the 2 o'clock position shown in FIG. 20. The 12 o'clock position is the central line of the plot passing horizontally midway through both the ascending and descending plotted lines.

Conversely to the upwardly inclined lines of the lower plot of FIG. 19, the descending lines show counter-clockwise rotation prior to the push forward.

There is of course to be understood the cutting rotation of a clockwise nature shown with the ascending lines of the lower plot and the counter-clockwise non-cutting rotation shown by the descending lines.

The upper plot corresponds exactly in time to the lower most plot. It shows the graph linked of the lower graph at a starting point for a rock face (the horizontal plotted line) and shows the sequential movement downwardly of the bit with respect to the various conditions described in respect to the lower plot.

FIG. 20 shows the 10 to 12 o'clock limited rotation shown in the plots of FIG. 19.

FIG. 21 is a pressure line feed to and from the inflatable reservoirs of an arrangement as shown in FIG. 1, such pressure lines allowing variation by inflation and deflation so as to effect an outcome prior to and during reverse partial rotation (in the steering mode) by the rig assuming the condition as shown in FIG. 4. Shown is rig that can be as shown or inverted.

What is important is that the bladders, bellows or bags 51 and 52 can be separately inflated/deflated reliant on hydraulic input and/or pneumatic input to cylinders 53 and 54 respectively to pressurise/depressurise with air/gas the respective bag(s) 51/52.

FIG. 22 shows a preferred tie rodded two plate embodiment working on a thrust plate with which the tie rods constrain the front and back plates to align. Here bladders, bellows or like 57 and 58 are each able to move the tie rods 59 upwardly and downwardly through plate 60 by acting on plates 60 and 61, in one instance, and plates 60 and 62, in the other instance. The fixed or crane or like supported frame can be that of or linked fixedly to plate 60.

FIG. 23 shows a flow diagram for both a hydraulic drive to each of the shuttle and the drill string and a flow diagram of the pneumatic circuit to inflate/deflate the air bags of, say, FIGS. 1 and 4.

This figure shows the plates 60, 61 and 62, the tie rods 59 and the bellows, bags or the like 57 and 58 of FIG. 22. Shown feeding bags 57 and 58 respectively are cylinders 66 and 67 which equate to those of 53 and 54 respectively of FIG. 21. Here the control to the cylinders 66 and 67 is under the action of a valving mechanism receiving a pressurised fluid intake (hydraulic and/or pneumatic) and able to pass it to the lower side of the rams in the cylinders 66 and 67 as shown as and when needed thereby to either inflate or deflate a respective gas type connected bladder, bellows, bag or the like 57 or 58.

Shown is the housing 63 in which the shuttle (not shown) is to move, as previously described, preferably under the input from belt 65 from an electric or hydraulic motor 64 which has the effect of rotating the preferred form of shuttle to derive the shuttling magnetic interactions with end plate positioned magnets.

Shown is a CPU 69 which controls both the valving mechanism 68 and a valving mechanism 70 to receive or release fluid but which has the action of powering rotational hydraulic motors 71 thereby to impart the appropriate rotation to the spindle 74 of the drill string. These belts 72 and 73 to their respective hydraulic motor 71 allows, under the control of the CPU 69 and its valving arrangement 70, at least either the greater than 360° rotation referred to for straight forward drilling or the selective less than 360° rotational drilling back and forth as mentioned previously.

In this specification where reference has been made to patent specifications, other external documents, or other sources of information, this is generally for the purpose of providing a context for discussing the features of the invention. Unless specifically stated otherwise, reference to such external documents is not to be construed as an admission that such documents, or such sources of information, in any jurisdiction, are prior art, or form part of the common general knowledge in the art.

Claims

1. A vibrational apparatus comprising or including

a support,

a vibrational head selectively operable to provide a vibrational output, and

apparatus or an assembly (hereafter “assembly”) to receive the vibrational output directly or indirectly from said vibrational head,

wherein said vibrational head and the directly or indirectly connected assembly to receive the vibrational output is flotably located relative to, yet is carriable or carried by, said support.

2. The vibrational apparatus of claim 1 wherein the flotable location is reliant on at least one compliant gas reservoir interposed between the support and said vibrational head.

3. The vibrational apparatus as claimed in claim 1 wherein (a) there is at least one compliant gas reservoir interposed between the support and said vibrational head so as to resist movement in a first direction parallel to the vibrational output from the vibrational head and (b) there is at least one compliant gas reservoir interposed between said support and said vibrational head to resist movement in a second direction opposite said first direction.

4. The vibrational apparatus as claimed in claim 1 wherein said vibrational head includes a shuttle and the vibrational output of the vibrational head is not directly from the shuttle itself.

5. The vibrational apparatus as claimed in claim 4 wherein the shuttle acts through a fluid to provide said vibrational output to said assembly.

6. The vibrational apparatus as claimed in claim 4 wherein said shuttle is able to shuttle reproducibly on a shuttle axis relative to at least one complementary structure of the vibrational head from which complementary structure(s) there is to be the vibrational output, and wherein there is a drive to rotate the shuttle about a rotational axis which is the shuttle axis, or is parallel to the shuttle axis, thereby to cause magnetic interactions which has the effect of driving the shuttle back and forth.

7. The apparatus of claim 1 wherein the or each said compliant gas reservoir is a gas bag.

8. The apparatus of claim 1 wherein said assembly is a drill string assembly.

9. The apparatus of claim 8 which includes, at or adjacent the vibrational head, a drive to rotate said drill string assembly.

10. The vibrational apparatus as claimed in claim 8 wherein the drill string assembly can rotate in either direction.

11. A drilling apparatus comprising or including

a support, and

a vibrational head adapted to be connected directly or indirectly to a drill string so as to both carry the drill string as a dangling assembly and to provide axial vibration thereinto;

and optionally a drive to rotate such a drill string when connected;

and optionally, a said drill string directly or indirectly connected to or connectable to said vibrational head so as selectively to be vibrated thereby and, when so connected, selectively adapted to be rotated by said drive,

wherein said vibrational head and any directly or indirectly connected drill string is flotably located relative to, yet is carriable or carried by, said support.

12. The drilling apparatus of claim 11 wherein the flotable location is reliant on at least one compliant gas reservoir interposed between the support and said vibrational head.

13. The drilling apparatus of claim 11 wherein the drill string is connected.

14. The drilling apparatus as claimed in claim 11 wherein there is a drive to rotate said or a drill string.

15. The drilling apparatus as claimed in claim 14 wherein said drive is at or adjacent the vibrational head.

16. The drilling apparatus of claim 11 wherein the flotable relativity is so as to facilitate vibrational axial input into any such connected drill string irrespective of whether or not the drill string is under pressure.

17. The drilling apparatus of claim 11 wherein the flotable relativity is so as to facilitate vibrational input irrespective of the downhole status of the drill string relative to the drill face.

18. The drilling apparatus of claim 11 wherein (a) there is at least one compliant gas reservoir interposed between the support and said vibrational head so as to resist movement in a first direction parallel to the vibrational output from the vibrational head and (b) there is at least one compliant gas reservoir interposed between said support and said vibrational head to resist movement in a second direction opposite said first direction.

19. The drilling apparatus of claim 11 wherein said vibrational head includes a shuttle and the vibrational output of the vibrational head to any connected drill string is not directly from the shuttle itself.

20. The drilling apparatus as claimed in claim 19 wherein the shuttle acts through a fluid to provide said vibrational output to the or a said drill string.

21. The drilling apparatus of claim 18 wherein said shuttle is able to shuttle reproducibly on a shuttle axis relative to at least one complementary structure of the vibrational head from which complementary structure(s) there is to be the vibrational output, and wherein there is a drive to rotate the shuttle about an axis which is the shuttle axis, or is parallel to the shuttle axis, thereby to cause magnetic interactions which has the effect of driving the shuttle back and forth.

22. The drilling apparatus of claim 11 wherein the or each said compliant gas reservoir is a gas bag.

23. (canceled)

24. (canceled)