Drill String Support

Field of the Invention

This invention relates to drill string support and in particular it relates to a clamping means which is capable of engaging a drill string during breakout operations.

Background Art

In drilling operations it is necessary that a drill rig have a clamping means which is capable of engaging the drill string to hold it in place whilst installing a new length of drill pipe to the drill string or removing a length of drill pipe from the drill string (hereinafter referred to as "breakout"). During breakout it is necessary to be able to clampingly engage the drill string to prevent relative rotation of the drill string and to prevent vertical movement of the drill string which can include the drill string falling into the borehole while inserting or removing a length of drill pipe.

A device which is commonly used to retain drill strings comprise hydraulically actuated clamps. These are not fail safe since if there is a hydraulic failure the clamping action is no longer fully applied and the drill string can fall into the hole. In addition the hydraulically operated clamps are not load sensitive and as result the maximum clamping pressure is usually applied to the drill string.

It is an object of the invention to at least partially overcome some of the problems of the prior art devices

Disclosure of the Invention

Throughout the specification and claim, unless the context requires otherwise, the word "comprise" or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated integer or group of integers but not the exclusion of any other integer or group of integers.

Throughout the specification and claim, the context requires otherwise, the term "drill tube" will be understood to include tubes, tubulars, rods and casings which are used in association with drilling operations to provide bore holes and the like.

According to one aspect the invention resides in a drill string support comprising a drill string support comprising a pair of first cam members each rotatably supported for rotation about one of a pair of first axes which are substantially parallel to each other and transverse to the axis of the drill string, each first cam member having an eccentric arcuate cam surface wherein the cam surfaces are in opposed in relation to each other and in use the space between the first cams is to be occupied by the drill string, the first cam members being jointly moveable to cause the cam surfaces clamping engage with the drill string between the cam surfaces, said cam surfaces being eccentric, the first cams being arranged such that when the drill string is engaged between the cam surfaces the weight of the drill string will bias the first cam surfaces into an increased clamping engagement with the drill string.

According to a preferred feature of the invention the cam surfaces have a concave transverse profile.

According to a preferred feature of the invention each cam member comprises a set of laminar elements, the laminar members being fixed in face to face relationship such that an outer edge of the laminar elements jointly defines the respective cam surface.

According to a preferred feature of the invention the first cams are interconnected by a first linkage comprising a link member associated with each first cam and connected at one end to the respective first cam and interconnected at their other ends, a drive member associated with the first linkage to cause longitudinal movement of the interconnected other ends and consequently the joint rotation of the first cams.

According to a preferred feature of the invention the drive comprises an extendible element having one end mounted to a fixed base and the other end mounted to

the interconnected other ends. According to one embodiment the drive member comprises a fluid operated ram.

According to preferred feature of the invention the linkage is associated with a biasing means which is capable of biasing the linkage into a first position at which the cam surfaces are out of clamping engagement with the drill string and a second position at which the cam surfaces are in clamping engagement with the drill string. According to one embodiment the biasing mean comprises a spring having two ends where an end is connected to one or the other the link members intermediate of the one end of the respective link member and the other interconnected end. According to a preferred feature of the invention the one end of each link member is connected to the respective first cam by a radial arm which is fixed to the respective first cam and interconnected with the other end of the link member at apposition spaced from the axis of rotation of the cam and radial arm. According to a preferred feature of the invention the radial arms are positioned relative to each other such that when the cam surfaces are in the first or second positions their interconnections to the link members are at their most remote positions with respect to each other and on movement of the cam surfaces between the first and second positions and between the second and first positions, the interconnections to the link members move through a position at which they are most proximate each other.

According to another aspect the invention resides in a breakout tool comprising a longitudinally extendable member, a jaw element pivotally supported from the extendible member through a pivot, , the jaw member having an engagement face with a concave profile which is to receive the drill string, wherein the pivot is located at one side of the engagement face, the extendable member being arranged to cause movement of jaw member into and out of engagement with the drill string, a clamping element pivotally mounted to the jaw member to the side of the pivot remote from the engagement face, the clamping element having an eccentrically arcuate convex clamping face which is in opposed relation to the engagement face whereby with rotation of the clamping element the spacing between can be varied, the clamping member being biased to a position at which the spacing is at its minimum, the clamping member being arranged and

configured and supported from the jaw element to be caused to rotate on the jaw element on retraction of the jaw element out of engagement with the drill string to increase the spacing between the clamping face and the engagement face, wherein on the jaw member being moved by the drive means towards engagement with the drill string, the drill string becomes engaged between the engagement face and the clamping face to become clampingly engaged therebetween, wherein with continued movement of the jaw member the clamping member, the jaw member, and drill string are caused to rotate about the central axis of the drill string.

According to preferred feature of the invention the breakout tool comprises a pair of said breakout tools supported in spaced axial relationship from each other wherein the torque applied to the of the drill string engaged by the tools is in opposed relation to each other.

According to preferred feature of the invention the clamping face is eccentric.

According to preferred feature of the invention the clamping face and the engagement face are formed to provide a not rotating engagement with the drill string when engaged with the drill string on application of a torque therebetween as a result of extension of the extendible member only.

According to preferred feature of the invention the clamping face and the engagement face are formed with a serrated formation.

According to an alternative preferred feature of the invention the clamping face and the engagement face are coated with a high friction coating

According to another aspect the invention resides in a drill string handling means comprising a drill string support means which is positioned to clampingly engage a drill string below an intended or existing junction between to lengths of drill pipe and a break out tool which is positioned to be able to engage a length of pipe above the drill string support and the junction, said drill string support being pivotally supported to be movable into and out of engagement with the drill string

and the break out tool being pivotally supported to be movable into and out of engagement with the drill string, the drill string support and breakout too each comprising a cam element having a cam surface of eccentric arcuate profile which is co operable with another surface and each supported to be pivotable about an axis wherein in use the drill string is receivable between the respective cam element and the associated other surface to clampingly engage the drill string.

According to a preferred feature of the invention the drill string support and the breakout tool are supported from a common structure which in use is to be pivotally supported alongside the intended position of a drill string.

According to a preferred feature of the invention a pair of break out tools are provided whereby the break out tools are located in spaced axial relationship to each other and are positioned to be able to apply an opposite torque to the drill string, wherein in use the break out tools are to be located one to either side of the junction between lengths of drill tube in the drill string.

According to a preferred feature of the invention the drill string support comprises a drill string support of the form as described above.

According to a preferred feature of the invention the break out tool comprises a break out tool of the form as described above.

The invention will be more fully understand in the light of the following description of several specific embodiments.

Brief Description of the Drawings

The description is made with reference to the accompanying drawings of which:

Figure 1 is an isometric view of the drill string support means according to the first embodiment with the cam members in the clamping position relative to the drill string;

Figure 2 is an isometric view of the drill string support means according to the first embodiment with the cam members in the retracted position relative to the drill string;

Figure 3 is an isometric view of the drill string support means according to the first embodiment with the cam members in an intermediate position relative to the drill string;

Figures 4 to 7 are a series of isometric views of the breakout tool according to the first embodiment of the invention showing the steps of engagement of the breakout tool with the drill string and the rotation of the drill string;

Figure 8 is an isometric view of the breakout tool according to a second embodiment of the invention prior to engagement with a length of drill tube;

Figure 9 is an isometric view of the breakout tool according to a second embodiment of the invention in association with the drill string support of the first embodiment; and

Figure 10 is an isometric view of a cam element of the drill string support shown at Figures 1 and 2 .

Detailed Description of Specific Embodiments

The first embodiment of the invention relates to a drill string handling apparatus which comprises a drill string support 11 as shown at Figures 1 , 2 and 3 and the associated break out tool 13 as shown at Figures 4 to 6 which apparatus is capable of clampingly engaging a drill string and effecting the desired loosening of the threaded junction between a length of drill pipe and the drill string.

The drill string support 11 as shown at Figures 1 , 2 and 3 comprises a housing 15 which is pivotally supported by a support structure 17 located on a drill rig. The support structure has a base plate (not shown) with an aperture through which the drill string is to pass and is provided with an upstanding portion (not shown)

from which the housing is pivotally supported such that the housing 15 can be moved between a position to one side of the drill string and a position at which it can be engaged with the drill string to enable breakout.

The drill string support 11 comprises a pair of first cam members 19 which are located in opposed relation to either side of a central position which is to be occupied by the drill string when the housing is in the engaged position. The first cam members are mounted to rotate about axes which are parallel to each other and which are also transverse to the central axis of the drill string. Each of the first cam members 19 are formed with an eccentrically arcuate cam surface 21 whereby rotation of the first cam members causes the spacing between the opposed cam surfaces to be reduced. In addition as shown more clearly at Figure 9 the cam surface 21 is arcuate in cross-section. In this regard each of the first cam members 19 are formed from plate members whereby the edges of the plate members serve to jointly define the respective cam surface 21. The plate members are fixed to each other to be incapable of independent limited transverse movement with respect to their axis of rotation. Thus the plate members of the first cam members define the eccentric cam surface which is concave in profile which is stepped and the edges of the plate members which define the cam surface are serrated. The stepped nature of the edges together with their serrations serve to enhance the frictional engagement capacity of the cam surfaces. Furthermore the stepped nature of the cam surface ensure that the first cam surfaces are able to engage with drill strings of differing diameter.

According to an alternative embodiment the edges of the plate members which define the cam surface are not serrated but are coated with a suitable material (such as carbide) which increase the frictional characteristics of the cam surface to enable the cam surfaces to frictionally engage the drill string.

The joint rotation of the first cam members 19 is effected by an articulated linkage comprising a pair of link members 23 and one end of each of the link members are pivotally connected to the outer end of a radial arm 25 fixed to the respective first cam member 19 whereby the one end is pivotable with the respective cam member about the respective pivot axis. The other ends of the link members are

pivotally interconnected. The interconnected other ends are supported from the housing to be movable along an activation axis, as defined by a slot 29 in the housing, which is parallel to the drill string. Such movement is effected through a fluid operated ram 27 which is fixed at one end to the housing and at the other end to a bracket 29 to which the other ends of the link members are connected. As a result of the extension and retraction of the ram 27 the interconnection between the other ends is caused to move along the activation axis. The movement of the interconnected one ends causes the first cam members to rotate which results in the spacing between the cam surfaces to vary because of their eccentricity. The radial arms are positioned such that when they are at the end positions (as shown at Figures 1 and 2) the spacing between their free ends is at its greatest and the spacing its most reduced an with the movement of the free ends between the end positions they move through an intermediate position at which the free ends are at their minimal spacing as shown at Figure 3. As a result the link members pivot about their interconnected ends towards and away from each other on movement of the radial arms between the end positions. A coil spring 31 is mounted between the link members such that its ends are fixed to the respective link member intermediate of its length. The coil spring 31 supported such that it applies a biasing force on the arms to cause them to move apart. The spring makes the jaws tend to flip over-centre from their intermediate position to either end position (i.e. move to the fully open or fully closed position).

The first cam members 19 are positioned relative to each other such that the spacing between the cam surfaces 21 reduces with the rotational movement of the cam surfaces jointly in a downwards direction. As result when the drill string is located between the cam surfaces and the first cams are caused to rotate to reduce the spacing between the cam surfaces on engagement of the cam surfaces with the drill sting the gravitational force exerted on the drill string will cause the degree of engagement between the cam surfaces and the drill string to be increased.. This biasing resulting from gravity is supplemented by the coil spring 31

Once engaged on the drill string, the weight of the drill string holds the jaws shut. The only way the jaws can be released is by lifting the drill string. While the ram

27 is able to assist in the disengagement of the cams from the drill string it is desired that the power of the ram is not sufficient to cause such disengagement by itself and as a result the disengagement is only effected once the weight of the drill string is taken up by another means. This serves to prevent the accidental release of the drill string

A pair of the breakout tools 13 which is shown at Figures 4, 5 and 6 are mounted above the housing accommodating the drill string support and are pivotally supported to be movable between a drill sting engaging position and a retracted position. In use it is intended that the uppermost break out tool be used to loosen a length of drill tube from the upper end of the drill string whilst the lower break out tool and the drill string support engages and supports the drill string at a position below the junction between the drill string and the length of drill tube. The breakout tools break the tool joint by having the tools working against each other.

The breakout tool 13 of the first embodiment and as shown at Figures 4 to 7 is supported within a housing 50 ( which is shown i broken lines) and comprises an extendable fluid operated ram 53 which is fixed at one end and pivotally supports a jaw member 51 at its other end. The jaw member is supported from the other end through a pivot 55. The jaw member 51 is formed with a recess 57 which is spaced radially from the pivot 55 and which is configured to be able to partially encompass the drill string. The jaw member is formed by a set of three plate like elements which are of corresponding configuration in the region of the recess. However the central plate like element only defines the region of the recess. The outer plate like elements pivotally support between themselves a clamping element 59 at a position which is in opposed relation to the recess and which is also spaced radially from the pivot at whereby the clamping element is in opposed relation to the recess. The clamping element 59 is formed with an eccentric arcuate clamping edge 61 which in use can be positioned such that it extends across the recess 57 of the jaw member. Both the clamping edge 61 and the surface of the recess define between themselves a space which will in use receive the drill string 10 and they are provided with a surface which will enable them to frictionally engage the drill string 10.

One side face of the clamping element is provided with an upstanding peg 71 which is supported from a disc 73 which is in turn fixed to pivot of the clamping element which is fixed to the clamping element and is pivotally received in the outer plate-like elements and as a result the disc will rotate with the clamping elementas will the upstanding peg. The peg 71 is radially offset from the pivot axis of the clamping member. The clamping element is associated with a guide 77 which is fixed to the housing of the break out tool. The guide is provides with a guide surface 79 which is formed with an inner linear portion 79a and an outer curved portion 79b and which is positioned to be engaged by the peg 71. The guide slidably supports a stop 81 which is associated with a spring (not shown) which biases the stop to its outermost position along the guide. In addition the clamping element is associated with another biasing spring (not shown) which biases the clamping element into a position at which the spacing between the clamping face 61 and the recess 57 is minimised. When the extension member in its retracted position the the peg 71 is biased into engagement with the guide 79 and the stop 81 and is forced into the position of maximum spacing from the recess against the biasing action of the spring associated with the clamping element.

During the initial movement of extension of the cylinder 53 the clamping member 59 is moved outwardly from the housing and as result the peg 71 is caused to move along the guide. Because of its spring biasing the stop 81 will be caused to move along the guide and follow the movement of the peg. As the peg 71 enters the curved portion 79b of the guide the biasing force applied to the clamping element will exceed that applied to the stop and as a result the clamping element will be able to rotate such that the clamping face approaches the recess. The degree of rotation will be controlled by the guide. The clamping element will continue to rotate on continued extendison of the cylinder 53 until the clamping surface 61 is brought into engagement with the drill string to become frictionally engaged therewith to cause the engaging surface 61 of the clamping element 59 to become engaged with the drill string 10. As result the drill string will become clamped between the jaw member 51 and the clamping member. With further extension of the cylinder 53 the jaw member and the clamping element will jointly

rotate about the pivot mounting tho the free end of the cylinder 53 and such rotation will cause the portion of the drill string engaged thereby to rotate.

On retraction of the cylinder 53 the reverse action occurs and the clamping element is moved out of engagement with the drill string 10. When this happens the clamping element will rotate under the influence of its biasing spring whereby the peg will become engaged with the guide. With continued retraction of the cylinder the peg will bear on the stop to move the stop 81 to its innermost position as shown at Figure 4.

In use and as shown in Figures 4, 5, 6 and 7 when it becomes appropriate to use the break out tool. The clamping element 59 is held by the biaising spring in a position as shown at Figure 4 where the clamping element lies clear of the recess to enable the drill string to be received in the recess and the cylinder 53 is retracted. With the extension of the extendable ram 53 the jaw 51 is initially moved from the position as shown at Figure 4 to a position as shown at Figure 5 at which position the recess 57 becomes engaged with the drill string 10. As a result of the movement of the jaw member the peg 71 is moved along the guide due to the biasing applied to the clamping element along with the stop which will follow the peg because of the biasing force applied to the stop. As the peg moves along the outer curved portion 79b of the guide the eccentric clamping edge 61 of the clamping element 59 is moved into a position at which it will engage with the drill string as shown at Figures 5 and 6. On continued extension of the extendable ram 53 the length of drill tube is clamped between the edge of the recess and the clamping edge of the clamping element and with continued extension of the ram the jaw member is caused to pivot on the other end of the ram about the central axis of the length of drill tube and consequently so does the clamping element and the length of drill tube as shown at Figure 7. The resultant rotation of the length of drill tube will serve to break the threaded connection between the length of drill tube and the drill string.

The eccentric nature of the arcuate clamping edge 61 of the clamping element 59 in cooperation with the jaw 51 enables the breakout tool to be able to be engagable with a variety of drill string diameters without further adjustment.

The clamping face and the engagement face can be formed to be serrated and/or may have a high friction coating such as carbides applied thereto

The second embodiment as shown at Figures 8 and 9 comprises a of pair break out tools 13 which are supported within a housing to be in opposed relation to each other and which are intended in use to jointly engage the length of drill tube to effect its rotation. In use the break out tools are located one to either side of the junction between the drill string and the upper length of pipe which is to be removed or inserted into the drill string and they work against each other such that the desired torque is applied to the upper length. As shown at Figure 9 the breakout tools 13 are supported within a second housing which is fixed to the upper face 11 of the drill string support 11 of the first embodiment to be movable relative to the support 17 into and out of engagement with the drill string 10. The housing serves to ensure that even when not clampingly engaged with the drill string the breakout tools remain in position.

The present invention is not to be limited in scope by any of the specific embodiments described herein. These embodiments are intended for the purpose of exemplification only. Functionally equivalent products, elements and methods are clearly within the scope of the invention as described herein.