GB2363811A

GB2363811A - Steerable drilling tool

Info

Publication number: GB2363811A
Application number: GB0114585A
Authority: GB
Inventors: Philip Head; Michael Andrew Yuratich
Original assignee: TSL Technology Ltd; XL Technology Ltd
Current assignee: TSL Technology Ltd; XL Technology Ltd
Priority date: 2000-06-16
Filing date: 2001-06-15
Publication date: 2002-01-09
Anticipated expiration: 2021-06-15
Also published as: GB2363811B; GB0114585D0; GB0014802D0

Abstract

A downhole tool comprises a first part 7 to be fixed to the end of a downhole tube and a second part 8 that can be adjusted with respect to the first part in any two of the three possible component angular directions. The second part may be a drill bit which pivots about ball joint 14. Relative rotation of the bit about the axis of the tool is prevented by splines 13 that transmit torque from the drive shaft to the bit. Material such as drilling mud may be passed through both first and second parts via a conduit and the tool may comprise a third part that is adjustable with respect to the second part in one angular direction. Also disclosed is a downhole tool that is oriented by movement of at least one cammed surface 18 inclined with respect to the tool axis and operating in conjunction with a follower 20. The forming of a window in a borehole by use of a directional tool is also disclosed.

Description

2363811 DIRECTIONAL DRILLING TOOL This invention relates to directional

drilling tools In particular, the invention relates to directional drilling tools which are used to control the direction of drilling of bore holes.

Changes in the direction of drilling of bore holes are required for a number of reasons The most frequent reason is to change from vertical drilling to horizontal drilling or drilling at any particular angle other than vertical.

Horizontal drilling has been known for many years and there are a number of established methods of changing the direction from vertical drilling to horizontal drilling For example long radius drilling which is used for accessing oil reservoirs in remote locations, under cities, offshore or to avoid geological isolation.

Medium radius drilling is used for pinnacle relief, fractured formations and gas and water coning Short radius drilling can be used for all these applications The particular method used is chosen based on the economic considerations of the particular well.

The most common existing method to change the direction of drilling is to use a bent support for the drill bit or a "bent sub" as it is often referred to.

Typically a drill bit is used which is powered by a motor and the bent sub is positioned behind the motor It is also possible for the bent sub to be positioned in front of the motor The bent sub effectively causes the axis of rotation of the drill to be at a different angle to that of the drill pipe.

Continuous drilling with the bent sub causes continuous changes of direction which results in a curved well hole in the direction of the bend of the bent sub.

When the required curvature has been achieved drilling can be stopped and the bent sub changed for a straight sub to resume straight drilling.

Alternatively, the entire drill pipe can be rotated at the surface resulting in a io small rotation of the bent sub, motor and drill bit assembly The bend of the bent sub is now positioned in a different direction and drilling can be resumed in this different direction.

Directional sensors such as gyroscopic sensors are used to check the progress and direction of the drilling to establish what adjustments to the drilling angle are required.

A disadvantage of this existing method of directional drilling is that the drilling tool has to be removed from the bore hole and changed before drilling in the straight direction can be recommnenced This results in an expensive operation and increases the time to complete the required drilling.

A further disadvantage is that when drilling is restarted in a new direction it is often the case that the drill bit kicks in an unpredictable direction due to unevenness in the hardness of the formation at the point of stoppage of the drill head.

A further disadvantage with this known method is that control of the direction of the drill bit is inaccurate because it relies on rotation of the whole of the drill pipe which can result in unpredictable degrees of rotation of the drill bit.

Furthermore in some applications such as with the use of continuous drill pipe or coiled tubing it is not practical to rotate the drill pipe.

It is an object of the present invention to provide a directional drilling tool which can be controlled remotely and accurately.

It is a further object of the invention to provide a directional actuator for purposes other than drilling which can be controlled remotely and accurately.

According to the present invention, there is provided a variable orientation downhole actuation tool comprising a first part which is adapted to be fixed with respect to the end of a down hole tube and a second part which is adjustable with respect to the first part, characterised in that the first and second parts are adjustable with respect to each other in any two of the three possible angles; said three possible angles being the so-called Euler angles, namely the included angle or bend of a respective reference axis, the plane of included angle, or direction, and the rotation of the first body about its reference axis.

Preferably the the tool further comprises a third part such that the said third part is adjusted by at least one of the possible angles with respect to the second part which second part is adjusted by a further of the possible angles with respect to the first part.

Preferably a passageway is provided between the first and second parts for the conveyance of material, gas, liquid, solid or a combination thereof.

According to antoher aspect of the present invention, there is provided a variable orientation downhole actuation tool comprising a first part which is adapted to be fixed with respect to the end of a down hole tube and a second part whose orientation is adjustable with respect to the characterised in that the first part and the second part includes at least one cammed surface and at least one corresponding cam follower respectively, the cammed surface being at an inclination to the second part's axis, such that movement of the cam follower relative to the cammed surface causes a change of inclination of the second part relative to the first part.

1 o Preferably the first part and the second part includes a first and a second cammed surface and a first and a second corresponding cam follower respectively, relative movement of the first cammed surface and first cam follower causing a change of inclination of the second part relative to the first part in a first plane, relative movement of the second cammed surface and second cam follower causing a change of inclination of the second part relative to the first part in a second plane different to the first plane.

According to a further aspect of the present invention, there is provided a method of forming windows in borehole casings by means of a variable orientation downhole window forming tool comprising a first part which is fixed with respect to the end of a down hole tube and a second part which is adjustable with respect to the first part, characterised in that the forming tool is run in hole with a closely fitting straight orientation and then a bend is set to bring the window forming tool into contact with the casing upon further advancement of the window forming tool.

An embodiment of an orientation tool, will now be described, by way of example only, with reference to the accompanying figures, in which:Figure 1 shows a longitudinal cross-section of a drilling assembly according to the invention in a first orientation, Figure 2 shows a longitudinal cross-section of an orientation tool according to the invention in a straight position, Figure 3 shows a longitudinal cross-section of an orientation tool according to the invention in a first orientation, Figure 4 shows an internal cross section of an orientation tool according to the invention in a first orientation, and Figure 5 shows an internal cross section of an orientation tool according to the invention in a second orientation.

Referring firstly to Figure 1, the representative directional drilling tool 1 in accordance with the invention comprises a bottom hole assembly connected to the drill pipe 2 The bottom hole assembly comprises an instrumentation sub 6 and drill bit 3 that is powered by motor 4 via an internal shaft S Onot shown running through the orientation sub 5 The drill pipe 2 referred to throughout this specification can either be conventional drill pipe comprising sections connected together or alternatively, and preferably to achieve the full advantages of the present invention, a continuous coiled tubing type drill pipe.

Further details of the bottom hole assembly well-known in the art such as weak-point connector are not shown Power for the orientation sub 5 may be supplied by batteries in instrumentation sub, by direct cable connection to surface or by downhole generation means such as turbine alternators known in the art Instrument sub 6 may also carry sensors to provide feedback information to control the orientation sub 5 It will be understood that the invention does not depend on the precise location of said instrumentation,

which might be also be placed close to the point of drilling between drill bit 3 and orientation sub 5, or made integral with orientation sub 5 Preferably the orientation sub 5 will be placed below the motor 4 in order to maximise its influence on steering, but it is also possible to position it between drill pipe 2 and motor 4.

Figure 1 depicts the orientation sub 5 with a bend in the plane of the paper.

1 o When the bend is reduced to zero the drilling assembly becomes straight and drilling will be in line with the drill pipe.

It will be appreciated that it is desirable to adjust in the plane of the paper of figure 1 being the vertical plane to achieve changes in the build or drop angle and it is also desirable to adjust in the plane orthogonal to the plane of the paper in figure 1 being the horizontal plane to achieve changes in the azimuth angle Vertical and horizontal adjustments may be combined as will become apparent from the following description Vertical and horizontal reference planes are being used for convenience of description but any preferably orthogonal planes can be used During drilling, twisting in the bottom hole assembly and drill pipe will cause these planes to vary, necessitating the use of downhole angular sensors such as accelerometers and magnetometers well known in the art to measure orientation The severity of steering may be controlled by the amount of bend.

The directional drilling tool of the invention is shown in more detail in figure 2 It comprises a first end 7 and a second end 8 said first end 7 being fixed with respect to motor 4 and said second end 8 being fixed in direction with respect to a drill bit 3 Protrusion 9 is fixed to second end 8, and retainer 10 is fixed to first end 7.

Protrusion 9 carries a spherical bearing surface 11, and retainer 10 holds mating rings 12, such that the first end 7 and second end 8 are held together and transmit axial compressional and tensional loads to each other while permitting free angular deflection between them Protrusion 9 also carries crown spline teeth at 13 which engage in a straight spline at 14 These splines transmit torque between first end 7 and second end 8, so that the two may not rotate axially with respect to each other Seal 15 provides a barrier between 1 o internal fluid in the invention and drilling fluid returning past its outer surface.

This seal allows lateral movement of protrusion 9 and retainer 10 This description shows how a sealed coupling may be made between first end 7 and second end 8 that allows tilting in any direction but not relative axial rotation Other methods may be used.

Protrusion 9 extends inside first end 7 so as to provide a lever arm pivoted on the centre 16 of the spherical bearing surface 11 By deflecting the lever end 17 transverse to the axis of the first end 7, the second end 8 may be made to point in any direction about the axis of first end 7 and with a bend angle limited only by the mechanical proportions of the components.

Figure 2 shows the tool in a straight position Figure 3 and Figure 4 shows the tool in a position whereby the second end has been deflected in the plane of the paper by moving the lever end 17 in the plane of the paper If the lever end is moved back through and past its centre position then the same deflection will be achieved, but 180 degrees rotated about the axis of first end 7 It will be appreciated that by deflecting the lever end 17 in and out of the plane of the paper similar results may be obtained in an orthogonal plane, and that by combining different amounts of orthogonal deflection, the lever end 17 and hence the second end 8 may be tilted in any direction relative to first end 7 Figure 5 shows such a combined deflection in cross-section.

A first pair of parallel cammed surfaces 18 and 19 are provided on the protrusion 9 at the lever end 17 A corresponding first pair of cylindrical rollers 20 and 22 are carried on first link 23 Roller 20 bears on surface 18 and roller 22 bears on surface 19 As first link 23 moves axially within first end 7, the rollers and cams remain proximate This ensures that there is a 1 o close correspondence between first link 23 position and the deflection of lever end 17 in the plane of the paper Reaction forces will be such that only one at a time of rollers 18 and 20 bears a heavy load as the forces shift.

Figure 2 shows first link 23 near its mid point of travel, where rollers 18 and 20 hold the lever end 17 centrally, and hence the second end 6 is straight in the plane of the paper Figure 3 shows first link 23 near one end of its travel, where rollers 18 and 20 hold the lever end 17 offset from the centre line of first end 7, and hence the second end 6 is tilted in the plane of the paper.

Figure 2 also shows a first electric motor 24 whose rotor 25 is extended by tube 26 to an externally threaded ring 27 First link 23 is internally threaded to engage with ring 27 When the first motor 24 is powered, it turns ring 27, thereby causing first link 23 to move axially back and forth according to the sense of motor rotation Using linear position or rotation sensors such as potentiometers to monitor movement, the motor 24 may be controlled by well-known techniques to precisely position first link 23 and hence to precisely control deflection of second end 6 in the plane of the paper.

It will be appreciated that by forming second parallel cams on the lever end 17, rotated a quarter turn about the axis of the protrusion, a second link 28, externally threaded ring 29, motor 30 and rotor 31 may be used to effect deflection of second end 6 in the orthogonal to the plane of the paper Rotor 31 and ring 29 rotate freely over extension tube 26.

It will further be appreciated that by co-ordinating operation of first motor 24 and second motor 25, second end 8 may be tilted incrementally in any direction and with any bend within the mechanical limits of the assembly.

1 o Electrical control of the motors may be effected from annular enclosure 32.

This enclosure may be made self-contained by incorporating batteries and a communications sensor, such as a gauge to sense drilling fluid pressure or a magnetic pickup to sense drilling shaft rotation speed As is well known in the art of drilling surveys, gravity-reading accelerometers may be used to measure the rotation from the vertical plane of a reference mark on first end 7.

The direction of the second end 8 relative to the first end 7 may be measured using position sensors as aforementioned, and in conjunction with the accelerometer measurements may be used to set the second end 8 at any rotation from the vertical plane This so-called toolface control is sufficient for many purposes and does not require azimuth input Azimuth measurement using magnetometers requires extensive use of non-magnetic materials which may not be practical in the vicinity of the orientation sub and electric motors It will be appreciated that this description of control is given for completeness but that there are many ways of controlling the motors to achieve the desired orientation, such as direct electrical connection to separate instrumentation 6 which may also contain azimuth sensors.

As is well known, the thread pitch on a screw may be chosen so that axial force on its mating nut will not cause unscrewing Thus the thread on rings 27 and 29 can be chosen so that back-driving forces transmitted to links 23 and 28 cannot cause the rings 27 and 29 to rotate Thus it can be arranged without further mechanisms and without constant motor correction that the orientation of second end 6 will remain unchanged when the motors are powered off.

This is preferred for battery operated systems, but has the slight disadvantage that in the event of tool failure, the bend will remain set at its last position throughout retrieval to surface Where natural closing is required, the thread pitch and cam angles will be chosen to allow back driving, so that when pulling out the assembly will have a tendency to straighten It will be 1 o appreciated that back driving can then be resisted by continued use of electrical power to servo the motors or by other dieans.

While the foregoing description has used electrical motors and screws to effect cam movement, it will be appreciated that hydraulic force could be s 5 used, such as via hydraulic power fed through pipes from surface or using a downhole hydraulic pump The cams may alternatively be replaced by radially pointing pegs running in short approximately helical slots cut in the wall of the lever end 17.

Claims

1 A variable orientation downhole actuation tool comprising a first part which is adapted to be fixed with respect to the end of a down hole tube and a second part which is adjustable with respect to the first part, characterised 1 o in that the first and second parts are adjustable with respect to each other in any two of the three possible angles; said three possible angles being the so- called Euler angles, namely the included angle or bend of a respective reference axis, the plane of included angle, or direction, and the rotation of the first body about its reference axis.

2 A variable orientation downhole actuation tool according to any previous claim, comprising a third part such that the said third part is adjusted by at least one of the possible angles with respect to the second part which second part is adjusted by a further of the possible angles with respect to the first part.

3 An actuation tool according to any previous claim, characterised in that a passageway is provided between the first and second parts for the conveyance of material, gas, liquid, solid or a combination thereof.

4 An actuation tool according to any previous claim, characterised in that a joint is provided for coupling the first part to the second part, said joint permitting the said adjustment of the first part with respect to the second part.

An actuation tool according to any previous claim, characterised in that coupling means are provided between the first and second parts to the other member to resist reaction forces.

6 An actuation tool according to any previous claim, characterised in that the tool is a steerable drilling tool.

7 An actuation tool according to any previous claim, characterised in that 1 o the too, comprises a means of manipulating a cutting or cleaning a drilling head or other implement.

8 An actuation tool according to any previous claim, characterised in that a rotary power means is provided for of supplying mechanical rotary power to the actuation tool.

9 A variable orientation downhole actuation tool comprising a first part which is adapted to be fixed with respect to the end of a down hole tube and a second part whose orientation is adjustable with respect to the characterised in that the first part and the second part includes at least one cammed surface and at least one corresponding cam follower respectively, the cammed surface being at an inclination to the second part's axis, such that movement of the cam follower relative to the cammed surface causes a change of inclination of the second part relative to the first part.

A tool according to claim 9 wherein the first part and the second part includes a first and a second cammed surface and a first and a second corresponding cam follower respectively, relative movement of the first cammed surface and first cam follower causing a change of inclination of the second part relative to the first part in a first plane, relative movement of the second cammed surface and second cam follower causing a change of inclination of the second part relative to the first part in a second plane different to the first plane.

11 A tool according to either claim 9 or claim 10, wherein the second part includes a substantially spherical joint and bearing surface, the joint and bearing surface featuring corresponding splines and grooves such that torque may be transmitted from the first part to the second part.

12 A tool substantially as herein described and illustrated.

13 A method of forming windows in borehole casings by means of a variable orientation downhole window forming tool comprising a first part which is fixed with respect to the end of a down hole tube and a second part which is adjustable with respect to the first part, characterised in that the forming tool is run in hole with a closely fitting straight orientation and then a bend is set to bring the window forming tool into contact with the casing upon further advancement of the window forming tool.

14 Any novel and inventive feature or combination of features specifically disclosed herein within the meaning of Article 4 H of the International Convention (Paris Convention).