GB2245623A

GB2245623A - Directional drilling tool

Info

Publication number: GB2245623A
Application number: GB9106813A
Authority: GB
Inventors: James D Base; David Harvey
Original assignee: Fontan Ltd
Current assignee: Fontan Ltd
Priority date: 1990-04-04
Filing date: 1991-04-02
Publication date: 1992-01-08
Also published as: GB9106813D0

Abstract

A directional drilling tool includes the combination of a lateral thrusting stabiliser and a bent sub. The tool is operated by (a) driving a mandrel 11 assembly down against a return spring 12; (b) causing pads 12A to move laterally in the direction of arrows B, C; and (c) causing the top end of a lever 16 to pivot about axis 17 in a direction generally opposite to the direction of a movement of the pads; the mandrel, pads, the lever and that portion of the drillstring moved by the lever, all being appropriately linked. <IMAGE>

Description

COMBINATION TOOL Field of the Invention The invention relates to drilling implements, for example, the control of a lateral thrusting stabilizer and an angular bend in the drillstring, and more particularly to activating and instructing a combination of these mechanisms. Although the invention will be described in relation to a drillstring, it will be clear that the invention is applicable to other kinds of drilling implements.

Summary of the Invention In one broad aspect, the invention provides a method of operating a - lateral thrusting stabilizer, so that the drillstring is forced laterally away from the well bore and then, following this, an operation to cause an angular bend to occur in the drillstring; the method comprising the steps of: (a) driving a mandrel assembly down against a return spring; (b) causing a retracting pad to move in a direction generally towards the centre of the drillstring, thus forcing a thrusting pad in a direction generally away from the centre of the drillstring; (c) causing the top end of a lever to pivot in a direction opposite to that of the impinging force from the bore of a cam driven by the mandrel; and (d) causing the lever movement to create a bend in the drillstring in a direction generally opposite to the direction of movement of the retracting pad; the mandrel, the retracting and thrusting pads, the lever and that portion of the drillstring moved by the lever, all being appropriately linked.

The invention may be embodied in apparatus as well as in a method, the apparatus comprising: (a) a drillstring mandrel; (b) means driving the mandrel assembly down the drillstring against the action of a return spring; (c) means linking the mandrel to a retracting pad and to a thrusting pad in such a way that downward movement of the mandrel, against the return spring action, causes the retracting pad to move in a direction generally towards the axis of the drillstring and forces the thrust ing pad in a direction generally away from the axis of the drillstring; (d) a lever below the mandrel; (e) means pivoting the lever for movement in a direction generally across the drillstring axis; (f) a cam; (g) means linking the top end of the cam operatively to the mandrel for movement up and down the drillstring axis as the mandrel is driven up and down;; (h) means linking the bottom end of the cam to the top end of the lever in such a way that movement of the cam down the drillstring by the mandrel causes the cam to impinge on the lever-end and pivot the lever about its pivot; and (i) means linking the thus-pivoted bottom end of the lever in use to the rest of the drillstring in such a way that said pivotal movement of the lever creates a bend in the drillstring.

Preferably the amount of thrust by the pad to impinge on the side of the well bore and thus the severity of the bend of the drillstring is determined by the position of the mandrel assembly against the return spring.

The direction and amount of lateral force, preferably may be altered using interchangeable pads or, alternatively, an interchangeable mandrel.

Preferably the amount of total bend of the drillstring may be varied by using different combinations of the cam and lever.

The position of the mandrel assembly and thus the various stages of actuation of the tool, preferably can be achieved by using a computer controlled package.

The combination of the lateral thrusting stabilisers, the angular bend in the drillstring and method for using the same, each of which individually and in combination is believed to embody the invention.

Brief Description of the Drawings The drawings show,by way of example only, a computer controlled adjustable bent sub/lateral thrusting stabiliser combination tool embodying the invention. The drawings consist of several successive Figures which show the tool, and the portion of the drillstring containing it, illustratively in succession from top end to bottom end.

Description of the Preferred Embodiment The drawings show part of a drillstring incorporating a computer controlled package. The combination tool which is the subject of the invention extends between the markers A-A in the drawings.

To the left hand side of this region there is a computer-controlled package which (for example) can be constructed and operated in the same way as that shown in pending United Kingdom Patent Application number 88 16130.2 (inventor BASE, now assigned to Fontan Limited as Applicant). Whilst to the right hand side of this A-A region there are the conventional drillstring subs.

A mandrel 11, shaped as shown, is driven down the drillstring axis against the action of a coiled compression return spring 12 as required. This left-to-right (axial) movement of the mandrel 11 causes three equi-angularly spaced pads 12A (only two of which are shown) to move in the direction of arrows B and C according to whether the pads are thrusting pads or retracting pad respectively.

This same movement of mandrel 11 drives a cam 13 down the drillstring axis. The top end of cam 13 is operatively linked to mandrel 11. The bottom end is so internally machined that it presents a sloped surface 14 to the top end 15 of a lever 16; the end 15 of the lever being effectively cammed inside the thus-machined sloped surface 14 of the cam 13.

Lever 16 is pivoted at 17 to the tool body 18. The axis of pivot 17 runs across the axis of the tool body which is coincident with the axis of the drill string as a whole in this region.

Axial movement of cam-end 14 will cause the cam end to impinge on the lever end 15 and move the lever as a whole about the pivot 17. The bottom end 19 of the lever will thus describe a limited arc about pivot 17 and, if connected (as shown) to a bottom sub 21, will move the sub in such a way as to effec tively create a bend in the drillstring.

Details of the construction illustrated can be supplied by the skilled reader. For example, pivot 17 may be spherical rather than circular-cylindrical. And pads 22 may be set into diame trally opposite surfaces of that region of lever 16 which surrounds pivot 17, as illustrated, the pads moving between the extremities of housings 23 machined into the bottom end region of tool body 18, to delimit the extremes of movement of lever end 19 about pivot 17. Other modifications within the scope of the invention will become apparent.

In practical embodiments it is currently envisaged that a three-padded arrangement will be used. The combination tool is screwed into a mud motor that has a set of fixed stabiliser pads near the bottom of the motor and with a tool bit screwed into the bottom of the motor.

When the bent sub is in "zero" size, the pads are in their largest diameter mode. When the mandrel starts down for any actuation, the pads immediately move inward to their smallest size and stay there until the tool is instructed to go back to size "zero". Using this method, the well can be drilled to kick-off point with a straight stabilised assembly. At the point where the well is to start its deviation, the pads are retracted, and the decided amount of bend is put in the bent sub; and the deviation begins.

After the proper angle and direction has been achieved, the tool is placed in size "zero" again, and the hole can be drilled ahead with a straight drilling assembly using a rotary table to slowly rotate the drill pipe whilst the mud motor does the drilling.

In this way there has been established and disclosed, overall, a method of directional drilling which is believed to be both novel and inventive, as well as similarly novel and inventive apparatus.

Claims

CLAIMS:

1. A method of operating a lateral thrusting stabiliser, so that the drillstring is forced laterally away from the well bore and then, following this, an operation to cause an angular bend to occur in the drillstring; the method comprising the steps of: (a) driving a mandrel assembly down against a return spring; (b) causing a retracting pad to move in a direction generally towards the centre of the drillstring, thus forcing a thrusting pad in a direction generally away from the centre of the drillstring; (c) causing the top end of a lever to pivot in a direction opposite to that of the impinging force from the bore of a cam driven by the mandrel; and (d) causing the lever movement to create a bend in the drillstring in a direction generally opposite to the direction of movement of the retracting pad; the mandrel, the retracting and thrusting pads, the lever and that portion of the drillstring moved by the lever, all being appropriately linked.

2. Apparatus comprising: (a) a drillstring mandrel; (b) means driving the mandrel assembly down the drillstring against the action of a return spring; (c) means linking the mandrel to a retracting pad and to a thrusting pad in such a way that downward movement of the mandrel, against the return spring action, causes the retracting pad to move in a direction generally towards the axis of the drillstring and forces the thrusting pad in a direction generally away from the axis of the drillstring; (d) a lever below the mandrel; (e) means pivoting the lever for movement in a direction generally across the drillstring axis; (f) a cam; (g) means linking the top end of the cam operatively to the mandrel for movement up and down the drillstring axis as the mandrel is driven up and down;; (h) means linking the bottom end of the cam to the top end of the lever in such a way that movement of the cam down the drillstring by the mandrel causes the cam to impinge on the lever-end and pivot the lever about its pivot; and (i) means linking the thus-pivoted bottom end of the lever in use to the rest of the drillstring in such a way that said pivotal movement of the lever creates a bend in the drillstring.

3. A method according to claim 1 in which the amount of thrust by the pad to impinge on the side of the well bore and thus the severity of the bend of the drillstring is determined by the position of the mandrel assembly against the return spring.

4. Apparatus according to claim 2 in which the direction and amount of lateral force, are altered using interchangeable pads and/or an interchangeable mandrel.

5. Apparatus according to claim 4 in which the amount of total bend of the drillstring may be varied by using different combinations of the cam and lever.

6. A method of or apparatus for operating a lateral thrusting stabiliser according to claim 1 or claim 2 in which the position of the mandrel assembly and thus the various stages of actuation of the tool, are achieved by using a computer controlled package.

7. A method of operating a lateral thrusting stabiliser according to and as illustrated in the accompanying drawings.

8. Apparatus according to and as described herein with reference to the accompanying drawings.