Controllable stabilizer

Details Controllable stabilizer Controllable stabilizer

2000-01-28

2001-09-18

Tsay, Frank S. (Department: 3672)

Boring or penetrating the earth

Means traveling with tool to constrain tool to bore along...

C175S325100

Reexamination Certificate

active

06290003

ABSTRACT:

BACKGROUND OF THE INVENTION
This invention relates to a controllable stabilizer, and relates more particularly but not exclusively to a controllable direction deviator for use in steering the direction in which a well is drilled, e.g. to produce a deviated oil well.
Modern drilling techniques for the creation of wells between a surface drilling station and oil-bearing geological strata horizontally remote from the surface drilling station require close control of the drilled well to a pre-planned trajectory. Known directional drilling techniques typically involve the use of a downhole drilling motor and a bent sub, with the drill pipe being non-rotating and the rotational position of the bent sub being used to determine the direction of deviation (i.e the direction and angular extent to which the currently projected drilling direction deviates from a straight-ahead projection of the most recently drilled section of the well; directional drilling may thus be considered as downhole steering of the drill).
Prior to the use of downhole motors with bent subs for directional drilling, whipstocks were used to deviate rotating drilling assemblies. The disadvantages of whipstocks were that they required orientation by drillstring movements initiated from the surface station, and that the whipstocks had to be reset (re-orientated) after the drilling of relatively short distances.
It is an object of the invention to provide a substitute for known directional drilling techniques, in the form of a controllable stabilizer for producing a radial load in a rotatable drillstring or drill shaft such as to control the deviation of a well being drilled. It is a further object of the invention to provide a directionally-controlled eccentric which is also applicable to producing directionally controlled eccentricity In circumstances which may not involve drilling.
BRIEF SUMMARY OF THE INVENTION
According to a first aspect of the present invention there is provided a controllable stabilizer in the form of a directionally-controlled eccentric comprising a first sub-assembly and a second sub-assembly, the first sub-assembly being adapted to be rotated in use by rotation of a rotatable shaft, the second sub-assembly being rotatably mounted with respect to the first sub-assembly, the second sub-assembly comprising eccentric thrust means controllably radially extensible in a predetermined direction to exert an eccentric sidethrust, the second sub-assembly being rotatably mounted with respect to the rotatable shaft such that eccentric sidethrust exerted by the eccentric thrust means is reacted in use by the rotatable shaft to tend to deviate the shaft in a direction opposite to the direction of the eccentric sidethrust, the directionally-controlled eccentric further comprising directionally-sensitive control means for sensing direction and for controllably radially extending the eccentric thrust means in a direction which tends to deviate the rotatable shaft in a requisite direction.
Preferably, mutually cooperating ports of the first and second sub-assemblies constitute hydraulic pump means functioning upon relative rotation of the first and second sub-assemblies to generate hydraulic power for use by the controllable stabilizer. Further mutually cooperating parts of the first and second sub-assemblies preferably constitute alternator means or other dynamo-electric generating means for generating electric power for use by the controllable stabilizer.
Preferably also, the eccentric thrust means are radially extensible by hydraulic linear motor means.
Preferably also, said control means controls hydraulic power from the hydraulic pump means to the hydraulic means in a manner which controllably radially extends the eccentric thrust means in a direction which tends to deviate the rotatable shaft in a requisite direction.
Said second sub-assembly is preferably rotatably mounted on said first sub-assembly.
Said hydraulic pump means is preferably a positive-displacement hydraulic pump. The hydraulic power output of the hydraulic pump means is preferably comprised in said second subassembly. Said control means is preferably comprised in said first sub-assembly. Said control means may comprise a controllable drain valve hydraulically coupled to said hydraulic means, said drain valve being controllably openable to drain hydraulic power from said hydraulic means and thereby cause or allow said eccentric thrust means to retract radially, said drain valve being controllably closable to prevent hydraulic power being drained from said hydraulic means and thereby tend to cause said eccentric thrust means to be radially extended.
Said eccentric thrust means and said hydraulic means preferably comprise a circumferentially distributed plurality of radially displaceable pistons each slidably mounted in and slidably sealed to a respective cylinder formed in the periphery of said second sub-assembly. The hydraulic power output of said hydraulic pump means is preferably commutated to successive individual ones of said cylinders in synchronism with rotation of said second sub-assembly with respect to said first sub-assembly, and said controllable drain valve is controlled to be closed only when said hydraulic power output is commutated to a given cylinder whose piston is intended to be extended. The radially outer ends of the radially displaceable pistons comprised in said eccentric thrust means and hydraulic means are preferably circumscribed by a unitary ring or tyre which is preferably substantially rigid and serves in use to transfer the eccentric sidethrust to the wall of drilled hole in which the stabilizer is operating.
The first and second sub-assemblies are preferably mutually coupled by a coupling mechanism which constrains relative longitudinal movement between the two sub-assemblies while permitting a range of relative radial movements between the two sub-assemblies sufficient to encompass requisite deviation of the shaft, the coupling mechanism preferably also limiting relative rotational movement between the two sub-assemblies. The coupling mechanism may comprise a plurality of part-annular segments secured to or integral with the second sub-assembly and further comprise a circumferentially extending slot in the first sub-assembly, the segments radially depending into the slot to permit relative radial movement of the second sub-assembly with respect to the first sub-assembly while preventing substantial relative longitudinal movement between the two sub-assemblies. The slot is preferably circumferentially interrupted by radially extending key means secured to or integral with the first sub-assembly, the key means being disposed in inter-segment gaps to prevent substantial rotational movement of the second sub-assembly with respect to the first sub-assembly.
According to a second aspect of the present invention there is provided a directional drilling assembly for controllable deviation of a well or other hole being drilled by said drilling assembly, said drilling assembly comprising a rotatable drillstring and a controllable stabilizer according to the first aspect of the present invention, said first sub-assembly being mounted around and secured to said drillstring, said second sub-assembly being rotatably mounted around said drillstring and/or said first sub-assembly.
The directionally-sensitive control means of the controllable stabilizer is preferably responsive to resolved vectors of the geomagnetic field.


REFERENCES:
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patent: 5000272 (1991-03-01), Wiebe et al.
patent: 5220963 (1993-06-01), Patton
patent: 5311953 (1994-05-01), Walker
patent: 5318138 (1994-06-01), Dewey et al.
patent: 5603386 (1997-02-01), Webster
patent: 6092610 (2000-07-01), Kosmala et al.
patent: 0 209 318 A2 (1987-01-01), None
patent: 0 497 422 A1 (1992-08-01), None
patent: 0 685 623 A3 (1995-12-01), None

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