Boring or penetrating the earth – Means traveling with tool to constrain tool to bore along... – Axially spaced opposed bore wall engaging guides
Patent
1993-07-12
1995-06-06
Britts, Ramon S.
Boring or penetrating the earth
Means traveling with tool to constrain tool to bore along...
Axially spaced opposed bore wall engaging guides
E21B 706
Patent
active
054214211
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
This invention relates to apparatus for directional drilling.
BACKGROUND OF THE INVENTION
Directional drilling tools proposed hitherto have a sleeve member disposed on the drillstring adjacent the drillbit and provided with laterally extendable and retractable steering elements operable selectively by means of pressure of the drilling mud to press on the hole wall or borehole and so steer the drillbit. Typical of such tools are those described in, for example, U.S. Pat. Nos. 2,316,409 (Downing) and 3,595,326 (Claycomb); and French Patent Publication 2622920 (SMF International). One disadvantage of these previously proposed tools is that they have not been immediately responsive to actioning of the steering elements due to a delay while these elements move across the well annulus. An associated disadvantage is that a significant portion of the available range of steering element movement, ie. the cross-annulus movement, is not useful for steering.
An object of the present invention is to provide apparatus for directional drilling whereby the mentioned disadvantages may be obviated or mitigated.
SUMMARY OF THE INVENTION
According to the present invention, there is provided apparatus for directional drilling comprising: axis; forming a borehole co-axial with the mandrel; for carrying drilling fluid to the drill bit means; portions journalled on the mandrel to permit independence of rotation between the mandrel and the sleeve about said mandrel axis; rotationally; response to the action of fluid under pressure; tubular wall having a longitudinal axis which extends parallel with and offset from said mandrel axis; laterally thereof with respect to the mandrel axis to and from pressure contact with the intended borehole in response to action of fluid under pressure for steering said drillbit means when in use; cross-section in that quadrant thereof most distant from the mandrel axis; release means and between said supply duct and said steering means; and diverting drilling fluid from said supply duct to operate the release means and the steering means.
By virtue of the lateral offset of the tubular wall, the steering means can be arranged closer to the hole wall and without seriously obstructing the annulus. Thus, the distance between the hole wall and the steering means can be reduced thereby to obviate or mitigate the aforementioned disadvantages.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a sectional elevation of a downhole tool in accordance with the present invention and showing steering means in an extended condition;
FIG. 2 is a sectional elevation corresponding with part of FIG. 1, but to a larger scale and showing steering means in a retracted condition;
FIG. 3 is a cross-section on the line III--III in FIG. 2;
FIG. 4 is a cross-section similar to FIG. 3, but showing steering means in an extended condition; and
FIG. 5 is a sectional elevation corresponding with another part of FIG. 1 and to a larger scale than FIG. 1.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the drawings, the downhole tool is indicated generally by reference numeral 10 and consists of a hollow mandrel 11 for running in a drillstring (not shown), a sleeve 12 extending over a portion of the mandrel 11 the sleeve and the mandrel being mutually independently rotatable, steering means 13 carried by the sleeve 12 and extendable and retractable laterally thereof, releasable locking means 14 for locking the sleeve 12 to the mandrel 11 rotationally, and fluid control means 15.
More particularly, the mandrel 11 consists of a tubular shaft which defines a supply duct for carrying drilling fluid. A lower end portion of the mandrel 11 is machined to accommodate the fluid control means 15 and also to carry and drive a drillbit (not shown) by means of an adaptor 16 which is provided with standard tapered screw-threaded sockets 17. The mandrel 11 also defines a shoulder 18 for the location of the lowermost of two bearing sets 19A and 19B. Each bearing set 19A, 19B is housed in a respective end portion of the sleeve
REFERENCES:
patent: 3595326 (1971-07-01), Claycomb
patent: 4305474 (1981-12-01), Farris et al.
patent: 4471843 (1984-09-01), Jones, Jr. et al.
patent: 4947944 (1990-08-01), Coltman et al.
patent: 5181576 (1993-01-01), Askew et al.
patent: 5186264 (1993-02-01), du Chaffaut
Britts Ramon S.
Tsay Frank S.
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