GB2249117A

GB2249117A - Steering device

Info

Publication number: GB2249117A
Application number: GB9122532A
Authority: GB
Inventors: James D Base; David Harvey
Original assignee: Fontan Ltd
Current assignee: Fontan Ltd
Priority date: 1990-10-24
Filing date: 1991-10-24
Publication date: 1992-04-29
Also published as: GB9122532D0

Abstract

A directional drilling device includes an expandible stabilizer and a variable angle bent sub, both of which are operated by axial movement of a common mandrel such that, for straight hole drilling, the bent sub has zero angle whilst the stabilizer pads are expanded, and for directional drilling, the mandrel is moved axially to retract the stabilizer pads and create a bend in the bent sub, the mandrel then being releasably locked in its new position.

Description

STEERING TOOL Field of the Invention The invention relates to steering devices to be used, for example, as drilling implements, and in particular as lateral thrusting devices.

Although the invention will be described in relation to a drill string, it will be clear that the invention is applicable to other kinds of toing where an adjustable deflection is rured.

Summary of the Invention In its broadest aspect the invention provides a steering tool comprising a first barrel and a second barrel, both barrels being contained within a freely moveable sleeve having an off-centre machined inner surface; means immobilising the tool; engaging the fist baael with a first part of the tool and engaging the freely moveable sleeve with a second part of the tool, such that movement of the first part of the tool advances both barrels, the second barrel describing an arc such that a bend is created in the toaL Preferably, the tool provides a method of operating a moveable pad, causing stabilisation of the bent tool; the method comprising the steps of: a Disengaging the driving force to the inner cammed mandril and liiting the drill string vertically; b Causing the inner cammed mandril to move downwards to impinge on the cammed pad; c Causing the pad to move radically away from or towards the centre of the drill string; d Causing a packing block, cam med on one side and serrated on the ather, the cammed side abutting the inner cammed mandril at a paint remote from (a), to engage with sensations on an outer manddi corresponding to the serrations on the packing hock;; and e Causing the pad to move in a direction generally opposite to the direction of movement of the tooL The invention may be embodied in apparatus as well as in the method, the apparatus comprising: a A drill string mandrill b A tool; c An inner cam med mandrill d Means driving the inner cammed mandril down the drill string against a cammed pad;; e Means linking the mandril to the pad in such a way that movement of the cammed pad and disengaging the driving means, causes the inner cam med mandril to move downwards to impinge on the cammed pad and causes the pad to move in a direction generally opposite to the direction of movement of the tool; f A packing block above the mandril, said packing hock cammed on one side and serrated on the other, and g Means engaging the packing block serrations with corresponding serrations on an outer mandrill The direction and amount of movement of the pad may be altered using interchangeable pads; alternatively, the siting of the pad around the drill string may be varied, Preferably the outer mandril has a series of serrations, some of which are unoccupied by the packing block serrations, and which provide a range of postions at which the packing bZock serrations can engage.

AdvantageousLy, the packing block is internally sprung such that its cam med side abuts the correspondingly cam med side of the inner cammed mandril The drill string body may move freely when the packing block is engaged with the outer mandril Preferably the position of the cammed pad and the poiaon of the bent tool can be achieved by using a computer controlled package.

Brief Description of the Drawinqs The invention will now be described, by way of example only, and with reference to the accompanying drawings, in which; Figures 1A, 1B, 1C and lD combined, show a sectional view of the drill string embodying the tool; Figures 2A, 2B, 2C, 2D and 2E comhined, show a sectional view of the drill string embodying a pivoting pawl; Figure 3 shows an enlarged sectional view of the sleeve between points X-X'; Figure 4 shows a cross-section of the tool and a perspective view of the outer surface of the second barrel;; Figures 5A, 5B and 5C are a longitudinal section through the drill string and tool, showing the pad in a retracted position; and Figure 6A, 6B and 6C are a plan view of the drill string and toaL showing the pad in an extended pooooon DesQiation of the Preferred Embodiment Referring to Figure 1, a drill string 20' commies an outer casing 10, having a central bore along its length and in which an inner camed mandril 11 is slideably mounted.

A fleRe hydraulic high pressure wash pipe 12 runs the length of the drill string 20' and is fitted at the end of each section of the outer casing 10 with a heavy duty seal 13, one only of which is shown. The wash pipe 12 passes through adjustable deflection attachment tool 18 and is fitted into the seals 13a.

Before the tool 18 is screwed onto the adjustable stabiliser outer casing 10, pins are put into pin holes 16 and 17 to prevent rotation of the mandril 11 at 11a. The tool 18 is screwed onto the mandril of the staLtiser at paint Y, which is shown in Figure 2A. Barrel 14 of the tool 18 engages the mandril 11 and the plus are removed, allowing the slid able outer sleeve 10a to engage the outer casing 10, shown at paint Z-Z' on Figure 1D. A mud motor, not shown, is attached to a pin that is on the bottom of saversub P shown on Figure 1A.

The section, as shown in Figure 4, of the tool which causes a bend in the drill stating, consisting of a second barred 15 which is machined in the form of a round ansn 39 which mates with the matching inner machine surface 21. Linear movement of the mandril 11 within the outer casing 10 causes barrel 15 to describe an arc causing deflection of the mud motor.

The tool is currently machined such that six inches of linear movement of the mandriL 11 results in a 1.625 degrees of detection when the tool is filly extended.

Referring now to Figures 2A, 2B, 2C, 2D and 2E together with Figure 3.

As the sleeve 37 is driven downwards, cam med surface 30 abuts cammed surface 31 on packing tilock 23 forcing serrations 24 to engage with serrations 26 on the inner surface of mandril 11. The distance of outward movement of pad 32 depends on the linear distance moved by upper pat 33 of the mandril 11. By removing block 34, spacers can be added to void 35 to change the amount of linear movement of the pad 32. It will be appreciated that the sleeve 37 will have fewer serrations 26, corresponding with added spacers in the void 35. It is possible to use this procedure when the mandril is in its lower most position and add spacers which abut surface 36 of the block 34.

A pivoting pawl 22 is used to detect the mode of operation of the mandril 11. When the mandril 11 is in its uppermost position, as shown in Figure 2D, sleeve 37 abuts the pivoting pawl 22, graving a maximum precmure difference and thus indicating the mode of operation of the mandril 11. When the mandrill is allowed to move downward the pawls will pivot out of the fluid fow and pressure will be reduced.

The drawings 5A, 5B and 5C, together with Figures 6A, 6B and 6C, shown part of a drill string 20' incorporating the tool which is the subject of the invention. The tool together with the rest of the drill string 20, can be operated by a computer contained package which can be constructed and operated, for examp~e, in the same way as that shown in published United Kingdom patent application No GB 2 223 251A (inventor: BASE - now aligned to FONTAN LIMITED as applicant).The computer controlled package is situated to the left hand side of the region shown in the drawings, whilst, to the right hand side of the region, there are the conventional drill string subs. Alternatively, the tool can be mechanically operated.

Referring to Figures 5A, SB and 5C an inner cammed mandril 11 is driven down an outer casing 10, by a pump (not shown) in the direction shown by the arrow X. The inner camed mandril 10 is shaped as shown, such that it presents a sloped surface 12' to a retractable/extendible pad 32 at surface 14'.

The pad 32 is mounted in the closed position by, for example, a computer controlled package, so that the inner cammed mandril 11 is prevented from moving down the outer drill string mandril 10.

Referring to Figure 5A. The inner cammed mandril 11 is cammed at a second point, remote from that which abuts the pad 32. This second point is cammed along the inner mandril 11 abutting against which is a packing block 23. Within the packing h7ock 23 is a spring 16' shown at section G-G. The spring 16' encourages the packing brock 23 to abut against the inner cammed mandrit 11. The spring 16' is retained by screws 17'.

On a second side of the packing LJock 23 are serrations 24 which engage with some of the serrations 26 located on the inner surface of outer drill string 10.

Referring now to Figure 5B. The pad 32 extends radially from drill string 20' using a computer controlled package (not shown). The pump is disengaged and the drill string 20' is lifted vertically, in a direction generally opposte to X. When the pad 32 is at its greatest paint of extension, a computer contiLed package can be utiLized to control the movement of the mandril 11 in the same way as the adjustable stabilizer (lateral thrusting device).

The outward movement pf the pad 32 allows the inner cammed mandril 11 to pass down the outer casing 10. The maximum distance which the inner cammed mandrel 11 can be moved is reached when inner mandril 11 abuts block 34. The mentions 24 and 26 engage and packing block 23 is held in place by abutting against inner cammed mandrel 11.

Figures 6A, 6B and 6C shown the drill string 20', the pad 32 in an extended position, and the paint Z at which the tool plots, in a dirion generally opposite to the direction of movement of the pad 32. Clearly, the movement of pad 32 relative to the inner cammed mandril 11 allows for intermediate stages of actuating to be achieved.

This embodiment is mainly to be used for medium radius wells.

The particular advantage of this steering tool is that a substantial increase in the number of degrees per 100 of angular bend can be achieved. Other modifications within the scope of the invention will become apparent.

Also relevant to an understanding of the present invention is pending United Kingdom patent application No 91 068 13.0 (filed in the name of FONTAN LIMITED as applicant). This application which is currently unpublished, relates - like the present invention and the invention of published UK patent application No GB 2 223 251A - to an overall concept in which the tool is a muli-padded adjustable staiser.

In prctical embodiments it is currently envisaged that a three-padded arrangement will be used. The tool is screwed into a mud motor that has a set of fixed stabilise pads near the bottom of the moter 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 mandril sXs down for any actuating, the pads are immediately moved 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 statt 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 trilled ahead with a straight drilling assembly using a rotary table to slowly rotate the drill pipe whilst the mud motor does the drilling.

A change in the linear distance moved by mandril 11 corresponds to a change in the size of arc described by barrel 15 and, hence the amount of deflection of the mud motor.

Claims

CLAIMS:

1. A steering tool comprising a first barrel and a second barrel, both barrels being contained within a freely movable sleeve having an off-centre machined inner surface; means immobilising the tool; engaging the first barrel with a first part of the tool and engaging the freely movable sleeve with a second part of the tool, such that movement of the first part of the tool advances both barrels, the second barrel describing an arc such that a bend is created in the tool.

2. A tool according to Claim 1, in which, a method of operating a movable pad, causing stabilisation of the bent tool, comprises the steps of: a) Disengaging the driving force to the inner cammed mandrel and lifting the drill string vertically; b) causing the inner cammed mandrel to move downwards to impinge on the cammed pad; c) causing the pad to move radially away from or towards the centre of the drill string; d) causing a packing block, cammed on one side and serrated on the other, the cammed side abutting the inner cammed mandrel at a point reinote from (a), to engage with serrations on an outer mandrel corresponding to the serrations on the packing block; and e) causing the pad to move in a direction generally opposite to the direction of movement of the tool.

3. Apparatus for operating a movable pad, causing stabilisation of the bent tool, the apparatus comprising: a) A drill string mandrel; b) a tool; c) an inner cammed mandrel; d) means driving the inner cammed mandrel down the drill string against a cammed pad; e) means linking the mandrel to the pad in such a way that movement of the cammed pad and disengaging the driving means, causes the inner cammed mandrel to move downwards to impinge on the cammed pad and causes the pad to move in a direction generally opposite to the direction of movement of the tool; f) a packing block above the mandrel, said packing block cammed on one side and serrated on the other; and g) means engaging the packing block serrations with corresponding serrations on an outer mandrel.

4. A tool according to any of the preceding Claims in which the outer mandrel has a series of serrations, some of which are unoccupied by the packing block serrations, and which provide a range of positions at which the packing block serrations can engage.

5. A tool according to Claim 4 in which the packing block is internally sprung such that its cammed side abuts the correspondingly cammed side of the inner cammed mandrel.

6. A tool according to Claim 5 in which the drill string body moves freely when the packing block is engaged with the outer mandrel.

7. A tool according to Claim 6 in which the direction and amount of movement of the pad can each be altered using interchangeable pads.

8. A tool according to Claim 7 in which the citing of the pad around the drill string is varied.

9. A tool according to Claim 8 in which the position of the cammed pad and the position of the bent tool can be achieved using a computer controlled package.

10. A tool as described herein, with reference to, and as illustrated in, the accompanying drawings.