GB2252578A - Stabilising tool - Google Patents

Abstract

A stabilising tool for connection in a drill string comprising a central shank (10) and a fluted stabilising portion (14). The stabilising portion is formed in two parts: an upper portion (16) formed integrally with the shank and a removable lower portion (18) in abutment with the upper portion, which can be removed for refurbishment or replacement when necessary. Movement of the lower portion about or along the shank is restrained, so as to maintain the upper and lower portions in 22 abutment and their flutes in proper alignment, by means of one or more (preferably three) lock pins (24) located in one or more bores (26) extending through the cap and intersecting the central bore through the cap 18. The lock pins engage corresponding grooves formed in the shank and so prevent the removable portion sliding along or rotating about the shank. <IMAGE>

Description

Stabilising Tool This invention relates to rock drilling and more particularly, to a stabilising tool for connection in a drill string behind a drilling collar carrying a drill bit.

Such stabilising tools generally comprise a fluted stabiliser portion on a central shank, are typically 6 to 8 feet in length, and are expensive both to manufacture and refurbish, refurbishment often being necessary since a worn drill bit tends to leave debris which cannot be broken down and transported past the stabiliser with the result that the stabiliser tends to wear badly.

US 3,642,079, US 3,933,395 and GB-A-2,133,059 all disclose stabilisers in which the entire fluted stabiliser portion is removably secured to the shank of the tool. Such stabilisers are not however, widely used in practice. In the case of US 3,933,395, the stabiliser portion is formed in two parts which are secured on the shank by threads of opposite hand, so as to enable a worn tool to be repaired by simply removing and replacing the worn half of the stabiliser portion.

One disadvantage of such an arrangement is the tendency for the upper part to work loose and 'back-off'. If the drill string jams, so necessitating the use of a power jar to reverse the string, too much torque is applied to the lower part resulting in stripping of the mounting threads.

EP-A-0,188,343 discloses a stabilising tool for connection in a drill string, having a shank adapted for connection by its ends in the drill string, which overcomes the above problem by providing a fluted stabilising portion having a body part integral with the shank and a leading end part or cap which is removably secured to the shank, again by means of a screw thread. In this case it is possible for the flutes of the integral body portion and of the cap to become misaligned, so inhibiting or obstructing the free passage of debris past the stabiliser in use.

It is an object. of the present invention to obviate or mitigate the abovementioned disadvantages.

Accordingly, the invention provides a stabilising tool for connection in a drill string, comprising a shank adapted for connection by its ends in the drill string and a fluted stabilising portion comprising a body part integral with the shank and a leading end part or cap having an axial through bore and adapted to be removably secured to the shank adjacent said body part such that the flutes of the body part are aligned with the flutes of the cap, wherein means are provided for securing said cap to said shank in proper alignment with said body part comprising at least one bore formed in said cap extending through a radial plane extending from the axis of the cap, said at least one bore intersecting the axial bore of the cap, at least one groove formed in the shank of the tool adjacent said body part such that said groove is aligned with the intersection of said at least one bore and said axial bore of the cap when the cap is located on the shank, and at least one lock pin for insertion into said at least one bore so as to engage said groove and prevent movement of the cap about and along the axis of the shank.

Preferably, there are three bores, grooves and pins spaced equiangularly about the axis of the shank.

Preferably also, the at least one lock pin is generally cylindrical and has a tongue formed along one side thereof for engaging said groove.

Preferably also, said at least one bore is increased in diameter at either end thereof to define first and second shoulders, and said pin is provided with a projecting flange at one end to engage said first shoulder and is secured within the bore by means of bolt means adapted to engage a threaded bore formed in the other end of the pin, the bolt means having a projecting flange to engage said second shoulder.

Since the leading edge of the stabiliser constituted by the cap suffers most of the wear, it will be understood that the cap can readily be replaced when necessary, so avoiding the need to maintaining on the rig a stock of bulky or expensive stabilising tools. Further, only the worn caps need to be sent ashore for refurbishment.

The arrangement of bores, grooves and lock pins in accordance with the arrangement serves to ensure positive alignment of the flutes of the cap with those of the integral body part of the stabiliser portion of the tool.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which: Fig. 1 is a schematic side view of a stabilising tool embodying the invention; Fig. 2 is a schematic side view of a main body portion of the tool of Fig. 1; Fig. 3 is a schematic side view of a removable end cap of the tool of Fig. 1; Fig. 4 is a section on line IV-IV of Fig. 3; Fig. 5 is a section on line V-V of Fig. 2; Fig. 6 is a section on line VI-VI of Fig. 1; Fig. 7 is a fragmentary sectional view on line --VII-VII of-Fig. 6; Figs. 8(a), 8(b) and 9(c) are, respectively, side, bottom and end elevations of a lock pin of the tool of Fig. 1; Fig. 9 is a section on line IX-IX of Fig. 8(a); and Figs. 10(a) and 10(b) are, respectively, side and end elevations of a retaining bolt for use with the lock pin of Figs. 8 and 9.

Referring now to the drawings, the stabiliser tool has a shank or body 10 adapted at each end by conventional means (not shown) for connection in a drill string, the leading end 12 being connected in use to a drill collar (not shown) which carries the drill bit. A stabilising portion 14 has a nominal diameter slightly smaller than the diameter of the drill bit and is formed with flutes through which debris is transported upwardly past the stabiliser. The stabilising portion is in two parts; a body part 16 integral with the shank 10 and a removable sleeve or cap 18 having an axial through-bore 19, which may be removably located on the shank 10 in abutment with a shoulder 20 at the leading end of the body part 16.

The body part 16 has spiral flutes 22 typically forming three cutting blades, and the cap 18 has corresponding spiral flutes 23, of the same size and shape such that the flutes in the two parts of the stabilising portion are aligned at the interface when the cap 18 is secured in position.

The cap 18 constitutes the leading end of the stabilising portion 14 with the result that cutting edges on the cap, which are dressed with diamonds or cutting carbides, will wear first. When the cap wears away it can be removed and replaced from a stock of caps on the rig. Only the cap needs to be sent away for refurbishing.

The cap 18 is retained in position on the shank 10 with its flutes 23 in alignment with the flutes 22 of the body portion 16 by means of lock pins 24 located in bores 26 formed in the cap 18, which engage grooves 28 formed on a thickened portion 30 of the shank 10 below the shoulder- 20.

As is best seen in Fig. 4, there are three bores 26 each extending between two adjacent flutes 23 at right angles to equiangularly spaced radial planes extending from the central axis of the cap 18. The bores 26 each intersect the central bore 19, and increase in diameter at either end to provide shoulders 32 and 34.

The grooves 28, as may be seen in Fig. 5, also extend at right angles to equiangularly spaced radial planes, such that when the collar 18 is located on the shank 10 and its flutes 23 aligned with the flutes 22 of the body portion 16, the grooves 28 are aligned with the apertures formed by the intersection of the bores 26 and the axial bore 19.

The lock pins 24 each comprise a cylindrical shank 36 machined to form a rectangular tongue 38 along one side thereof, and each have a projecting flange 40 at one end and an internally threaded bore 42 at the other.

When the lock pins 24 are inserted into the apertures 26 the tongues 38 engage the grooves 28 (Fig. 7), so preventing any movement of the collar 18 along or about the shank 10. The pins are secured in place by retaining bolts 44, each comprising a hexagonal head 46 (or similar means engageable by a tool for tightening the bolt), a projecting flange 48 and an externally threaded shank 50. The shank 50 is inserted into the threaded bore 42 of the pin 24 and the bolt 44 tightened so that the flanges 40 and 48 engage the shoulders 32 and 34 of the bores 26.

It will be appreciated that the number and configuration of the flutes 22 and 23 of the stabiliser may be varied for different purposes, as is well known in the art, as may the number of pins 24, bores 26 and grooves 28 of the present invention in accordance with the configuration of the flutes.

Modifications and improvements may be incorporated without departing from the scope of the invention.

Claims (5)

1. A stabilising tool for connection in a drill string, comprising a shank adapted for connection by its ends in the drill string and a fluted stabilising portion comprising a body part integral with the shank and a leading end part or cap having an axial through bore and adapted to be removably secured to the shank adjacent said body part such that the flutes of the body part are aligned with the flutes of the cap, wherein means are provided for securing said cap to said shank in proper alignment with said body part comprising at least one bore formed in said cap extending through a radial plane extending from the axis of the cap, said at least one bore intersecting the axial bore of the cap, at least one groove formed in the shank of the tool adjacent said body part such that said groove is aligned with the intersection of said at least one bore and said axial bore of the cap when the cap is located on the shank, and at least one lock pin for insertion into said at least one bore so as to engage said groove and prevent movement of the cap about and along the axis of the shank.

2. A stabilising tool as claimed in Claim 1, wherein there are three bores, grooves and pins spaced equiangularly about the axis of the shank.

3. A stabilising tool as claimed in Claim 1 or Claim 2, wherein at the least one lock pin is generally cylindrical and has a tongue formed along one side thereof for engaging said groove.

4. A stabilising tool as claimed in any one of Claims 1 to 3, wherein said at least one bore is increased in diameter at either end thereof to define first and second shoulders, and said pin is provided with a projecting flange at one end to engage said first shoulder and is secured within the bore by means of bolt means adapted to engage a threaded bore formed in the other end of the pin, the bolt means having a projecting flange to engage said second shoulder.

5. A stabilising tool substantially as hereinbefore described with reference to the accompanying drawings.