Boring or penetrating the earth – With below-ground tool drive prime mover
Patent
1987-08-24
1989-07-04
Dang, Hoang C.
Boring or penetrating the earth
With below-ground tool drive prime mover
175325, E21B 400, E21B 1710
Patent
active
048441791
DESCRIPTION:
BRIEF SUMMARY
This invention relates to drill string stabilisers incorporating rig interchangeable sleeves and is particularly, but not exclusively, useful in connection with down-hole motors and/or at the bottom hole assembly of a drill string to assist in directional drilling
It is known to provide integral stabilisers and clamp-on type stabilisers. Currently known sleeve type stabilisers are not suitable for attaching to down hole motors or like devices. Integral stabilisers are normally workshop fitted and cannot be removed from a drilling motor whilst at the rig site. Clamp-on stabilisers are designed for removal at the rig site and several prior proposals have met with varying levels of success without having been completely satisfactory.
A clamp-on stabiliser for location at any position in a drill string is disclosed in U.S.-A-No. 4,384,626 and comprises a stabiliser body, an internal gripper sleeve and a lock nut acting to lock the gripper sleeve within the stabiliser body and about the drill string.
Conventional sleeve type string stabilisers are used in a drill string to support the string in the previously drilled hole to prevent contact between the drill string and the bore hole and one embodiment comprises a stabiliser sleeve mounted about the upper end of a drill string tube, complimentary threads of right hand at the upper ends of the sleeve and the drill tube engaging to secure the sleeve to the drill tube against loosening during drilling.
It is an object to provide an improved stabiliser of the sleeve type suitable for use with down hole motors and/or at the bottom hole assembly of a drill string, and elsewhere in the drill string.
According to the invention a stabiliser sleeve for a drill string comprises a sleeve adapted to fit about a down hole motor or the like device or drill string member and formed externally with stabiliser means extending radially outwards for engaging a bore hole wall, the sleeve being formed at a lower end with coupling means adapted for releasable coupling to complimentary coupling means at the lower end of the down hole motor or like device or member.
The down hole motor or like device will generally be formed at its lower end with a bottom nut for releasable coupling to the down-hole motor casing, and the releasable coupling between the stabiliser sleeve and motor or device is suitably formed above the bottom nut and between the sleeve and a bottom nut-forming member. The nut-forming member is suitably formed at its upper end with an external upward right-hand threaded taper engaging a complimentary threaded taper within the lower end of the down hole motor body or other body, and between the uppermost threaded portion and the bottom nut with an intermediate portion, of intermediate diameter and upwardly tapered form having an external left-hand screw thread engageable with a complimentary thread within the lower end of the sleeve to form the releasable coupling.
The above stabiliser is laterally supported by the bottom nut and the down hole motor body and suitably engages the outer wall of the motor body in this regard.
An abutment shoulder flange is suitably formed at the lower end of the intermediate threaded portion of the bottom nut-forming member to engage a complimentary shoulder at the lower end of the stabiliser sleeve.
If a slick assembly is required, i.e. one in which no bottom hole stabilisation is necessary then the stabiliser sleeve may readily be removed and replaced by a reduced diameter protective sleeve matching the outer diameter of the shoulder flange.
A stabiliser sleeve according to the invention may be used with other down hole devices, or sub-assemblies provided at their lower ends with an external shoulder flange and threaded portion for engaging the internal thread portion and shoulder at the lower end of the stabiliser sleeve. This has the advantage that the same motor or down hole device may be used in both directional and slick modes.
The stabiliser sleeve is suitably formed with stabilising means comprising radially outwardly projecting fins
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Forrest John
Stewart William
Tulloch Rory
Dang Hoang C.
Drilex UK Limited
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