US20020185312A1

US20020185312A1 - Impact tool

Info

Publication number: US20020185312A1
Application number: US10/137,010
Authority: US
Inventors: Richard Armell; Russell Jordan
Original assignee: Individual
Current assignee: Hamdeen UK Ltd
Priority date: 2001-05-03
Filing date: 2002-05-02
Publication date: 2002-12-12
Also published as: GB2375123A; CA2384549A1; GB0110872D0; GB0210101D0; GB2375123B

Abstract

An impact tool for use in a well bore. The impact tool provides a hammer action through reciprocal movement of a cam within a spring mechanism. In an embodiment a drill bit is included to provide an impact drilling tool which requires minimum weight on bit to operate. The impact tool can therefore be run on coiled tubing and wireline.

Description

The present invention relates to impact tools used within oil and gas wells and in particular, though not exclusively, to an impact drilling tool which requires little or no weighting or preloading to operate within a bore hole.

Typical impact tools such as hammer or percussion tools require to be weighted to ensure that the working surface, for instance, a drill bit is held against a rock formation at the bottom of a bore hole and the tool is maintained in a closed working position. This combination ensures that impact from a hammer piston within the tool onto the drill bit is transferred into the rock formation to cause it to fracture and the depth of the bore hole to be increased. Thus the hammering action is directly proportional to the pressure applied with the drill against the rock formation.

Applying weight to the drill bit however has the disadvantage that on impact a significant reactive force and torque is exerted back up the tool and also the drill string on which the tool is mounted. Extreme vibration can also be experienced. This combination of effects can cause mechanical failure of a component on the drill string resulting in overall operational failure of the entire downhole assembly.

It is therefore an object of the present invention to provide an impact tool for use in a bore hole which does not require to be weighted or preloaded to operate.

It is a further object of at least one embodiment of the present invention to provide an impact drilling tool for use in a bore hole which does not require to be weighted or preloaded to operate.

Thus if minimal weight is applied to the drill bit the reactive force, torsional force and resultant vibration are minimised to the extent that they become insignificant. It is then possible to use composite coiled tubing or wire, which cannot be used with standard impact drilling tools due to lack of mechanical ability in torsion, as the drill string.

Thus, it is a further object of at least one embodiment of the present invention to provide an impact drilling tool which can be operated downhole via lightweight tubing/composite pipe such as composite coiled tubing.

It is a still further object of at least one embodiment of the present invention to provide an impact drilling tool which can be operated downhole via an electric line or wireline.

According to a first aspect of the present invention there is provided an impact tool for use in a bore hole from a surface, the impact drilling tool comprising:

a substantially cylindrical body having a longitudinal axis, the axis being aligned co-axially with the bore hole;

a first end, perpendicular to the longitudinal axis, having attachment means to attach the tool to a string for connection to the surface;

a second end including a working sub, the working sub including a surface for contacting a portion of the bore hole; and

a hammer unit located between the first and second ends, the hammer unit providing a hammer action to the working sub via reciprocal movement of a cam within a spring mechanism.

Preferably the working sub is a drill bit wherein the surface contacts with a formation to increase depth of the bore hole. Alternatively the working sub may be a cylindrical body, the hammer action on the body thereby causing a vibratory action to the sub such that the tool may be used to assist in moving a string through a well bore. This arrangement is advantageous in high step/high inclination wells.

Preferably the spring mechanism comprises at least one first spring to bias the working unit towards the cam. The use of a cam in conjunction with a spring, the spring keeping the tool ‘cocked’, to provide the reciprocating or hammer motion of the working sub provides the tool with a self hammer action, and thus no weight is required upon the drill bit to operate the tool as in the prior art.

Preferably the spring mechanism comprises at least one second spring located adjacent the cam to act with the cam in reciprocal motion. Preferably the at least one second spring comprises a spring cage, the spring cage being attached to the cam. The spring cage including one or more springs which compress when the cam moves towards the first end of the tool.

Preferably the tool includes a drive shaft. More preferably the drive shaft is located on the longitudinal axis. The drive shaft may provide rotational drive means to the cam and the working sub. More preferably the tool includes one or more drive keys. Preferably first drive keys are located between the cam and the drive shaft to prevent the cam rotating independently of the drive shaft while permitting the cam to move longitudinally with respect to the drive shaft. Preferably second drive keys are located between the working sub and the drive shaft to prevent the working sub rotating independently of the drive shaft while permitting the working sub to move longitudinally with respect to the drive shaft. Advantageously the each drive key comprises a ball bearing located in a complimentary slot, the slot arranged longitudinally on the tool.

The working sub is disconnected from the hammer unit; that is it is keyed to prevent rotational movement. However, the working sub is free to move longitudinally against the force of the one or more springs. When the working sub is a drill bit, this arrangement facilitates the bit to drill and cut effectively in the bore hole by virtue of the minimum weight on bit. This is due to the fact that the bit will have room to cut the formation more effectively because in effect the impacting surface or cutting face will be intermittently in contact with the formation thereby breaking the formation in a pulverising fashion and then clearing it of cuttings and debris. This would not be possible if the bit was an integral part of the hammer unit, as in the prior art impact drilling tools, because a more significant reactive force would be required to lift a section of the tool which in turn would require more weight on the bit.

Preferably the impact tool may further include drive means, the drive means being used to rotate the drive shaft. By including a drive means on the tool, the tool can be operated on a work string which comprises coiled tubing or electric line/wireline. If there are no drive means within the tool, drive is provided via the surface by rotation of the work string.

Preferably the drive means is a positive displacement motor (PDM). The drive means may be operated by a change of fluid pressure in the string. Additionally, the drive means may be steerable to direct the surface of the working sub. When the working sub is a drill bit, directional drilling from wireline or coiled tubing is achievable with the tool.

A PDM is most appropriate for operating the tool on coiled tubing. Advantageously the drive means is a downhole electric motor for operating the tool on an electric line. Advantageously also the drive means is a downhole battery for operating the tool on a wireline.

Preferably the cam includes a cam groove extending continuously around the circumference of the cam. The cam groove may provide a cam profile which includes one or more ‘V’ grooves. The cam profile thus provides a number of strokes per revolution of the cam. Each stroke will refer to each downward motion of the cam and provide one impacting or hammer action of the drill bit against the formation. Preferably the ‘V’ grooves have rounded peaks and troughs providing an undulating profile on the cam surface. The cycle time/stroke may be adjusted by varying the speed of rotation of the cam, which is in turn controlled by the drive means. The speed of rotation is not dependent on whether the string itself is rotating.

Preferably one or more cam follower pins are located within the cam groove. The cam follower pins are preferably located on the inner surface of an outer housing of the tool. Thus as the cam rotates it is urged into a reciprocal motion as the pins follow the profile of the cam groove. Preferably the outer housing does not rotate. The outer housing may be isolated from the drive shaft by bearings. Preferably the bearings are mounted in a bearing housing located between the cam and the drive means.

Preferably also the tool includes lubrication means. More preferably the lubrication means comprises at least one channel located on the longitudinal axis, adjoining the first end of the tool to the second end of the tool.

Preferably fluid in the form of drilling mud is pumped through the channel and exits at ports on the impacting surface, to both lubricate the impacting surface and push cuttings away from the impacting surface and aid their return to the surface.

Additionally, the tool may include a bumper sub or slip joint. The bumper sub or slip joint comprises a telescopic joint mounted on the longitudinal axis, The bumper sub/slip joint is used to ensure slack in the string is maintained, so that no weight from the string may be applied to the working sub. More preferably, the bumper sub/slip joint includes a weight sensor. The weight sensor may provide a signal to the surface to indicate the weight being applied to the working sub. This will allow an operator to adjust the string accordingly to remove weight on the working sub. The bumper sub/slip joint may also absorb any reciprocal forces after an impact.

Preferably the tool includes a shear disc sub. The shear disc sub is mounted between the attachment means and the drive means. The shear disc sub provides a safety release if an unsuitable pressure differential is established within the tool.

Advantageously, the tool further comprises a release joint. The release joint is preferably ball operated, as is known in the art. The release joint is preferably mounted adjacent to the attachment means. Thus, in the event of the working sub or tool sticking downhole, release of the release joint will disconnect the string from the tool and allow other means to be used to retrieve the tool.

According to a second aspect of the present invention, there is provided a method of drilling a bore hole from a surface, the method comprising the steps:

(a) attaching an impact tool including a drill bit to a work string;

(b) running the string into a bore hole;

(c) operating the impact tool to provide a hammer action to the drill bit via a reciprocating cam within a spring mechanism; and

(d) impacting a surface of the drill bit upon a formation at a base of the bore hole.

Preferably the string is a lightweight type, such as a composite pipe. Alternatively; the string is a coiled tubing. Advantageously, the string is an electric line or a wireline.

Preferably the impact tool is according to the first aspect.

The method may further include the step of pumping fluid through the impact tool, in order to lubricate the drill bit and assist in removing drill cuttings.

Preferably also a number of impact strokes per minute of the drill bit is set by the speed of rotation of the cam.

Preferably also the method includes the step of steering the drill bit by drive means.

These and other aspects of the present invention will now be described by way of example, with reference to the accompanying drawings in which: [0039]
FIG. 1 is a schematic view of a impact tool in accordance with the present invention; [0040]
FIG. 2 is an exploded cross-sectional view of a part of the tool of FIG. 1 illustrating the hammer unit; and [0041]
FIG. 3 is a side view of the cam of FIG. 1.[0042]
Reference is first made to FIG. 1 of the drawings, which illustrates an impact tool, generally indicated by reference numeral [0043] 10, in accordance with the present invention The impact tool 10 has a cylindrical body 12 which includes a first end 14 and a second end 16. The ends 14 and 16 are at opposite positions on a longitudinal axis of the body 12.
Starting to the right of FIG. 1, at the first end [0044] 14 of the impact 10, there is located a tubing connector 18. The tubing connector 18 provides connection between the impact 10 and a work string 19. Adjacent to the tubing connector 18 is a ball operated release joint 20. The ball operated release joint 20 is as known in the art. The ball operated release joint 20 provides for release of the impact tool 10 from the work string 19 in the event that the drill bit 22 or the tool 10 itself has become stuck in the bore hole. Adjacent to the ball operated release joint 20 is a shear disc sub 24. The shear disc sub 24 provides a safety release if an unsuitable pressure differential is established within the tool. The shear disc sub 24 is as is known in the art.
Next in line to the shear disc sub [0045] 24 is located a slip joint 26. The slip joint 26 comprises a telescopic section 28 through which a first part 30 and a second part 32 of the slip joint 26 can move longitudinally in relation to each other. The telescopic joint 28 may also include a weight sensor (not shown). The weight sensor can transmit a signal to the surface to indicate the weight of the impact tool 10 below the telescopic joint 28.
Below the slip joint [0046] 26 is a positive displacement motor 34. Although a positive displacement motor will be described here, it will be understood by those skilled in the art that any downhole drive means such as an electric motor or a battery could be used to provide downhole power to the tool.
The positive displacement motor [0047] 34 is driven by fluid pumped from the surface through the aforementioned components of the impact tool 10. Mounted below the positive displacement motor are the remaining sections of the impact tool 10, which will be described hereinafter with particular reference to FIG. 2. The impact tool 10 terminates at a second end 16, with a drill bit 22. The drill bit 22 could be replaced by a sub, however in the preferred embodiment the tool 10 includes a drill bit 22 to act as an impact drilling tool. The drill bit 22 includes an impacting surface 36 which is used to strike or impact upon the formation at the base of the bore hole being drilled. The impacting surface 36 is made of a hard cutting material.
Reference is now made to FIG. 2 of the drawings, which illustrates the [0048] hammer unit 33 and a bit mandrel 52 providing the hammer to the drill bit 22 of the impact tool 10 towards the second end 16 of the tool 10. Located on the longitudinal axis is a drive shaft 35. The drive shaft 35 is rotated by the motor 34. The hammer unit 33 has an outer housing 37 which is a tubular member providing an outer surface 39 of the body 12 and an inner surface 41. A bearing house 38 isolates the housing 37 from the drive shaft 35. The bearing housing 38 is as is known in the art. Additionally roto-glyd rings 68A,B are mounted between the shaft 35 and housings 37,38 to allow the shaft 35 to rotate freely within the housings.
Below the bearing [0049] housing 38 is located a cam 40. The cam 40 is also illustrated in FIG. 3. The cam 40 is a cylindrical element having upon its surface a continuous cam groove 42. The cam groove 42 has an elliptical profile which can be considered as a ‘V’ groove with two sloping edges. Sloping edge 46 is the down stroke and the sloping edge on the reverse of the cam 40 (not shown) is the reverse stroke. It will be appreciated that any number of strokes may be incorporated in the tool by increasing the number of ‘V’ grooves in the profile.
Into the [0050] cam groove 42 is located a cam follower pin 43. This embodiment only provides one pin, but it will be appreciated by those in the art that more than one pin may provide greater stability to the tool 10. The pin 43 is a protrusion on the inner surface 41 of the housing 39. The pin 43 locates within the cam groove 42 to provide a smooth sliding action continuously around the cam profile, as the cam 40 is rotated. Additionally as the cam 40 is rotated and the pin 43 is stationary the cam 40 will be forced to move in a longitudinal pattern, or reciprocating action, in relation to the pin 43 as the pin 43 travels in the groove 42.
Adjoining the [0051] cam 40 is a spring cage 56. The spring cage 56 provides cage springs 58 mounted longitudinally to provide a bias against which the cam 40 compresses when the cam 40 is forced upwards by the action of the pin 43 in the groove 42. The impact stroke of the tool is aided by the extension of the cage springs 58 under the downward motion of the cam 40 by the action of the pin 43 in the groove 42.
On the [0052] inner surface 54 of the cam 40 are located two slots 48. The slots 48 are positioned longitudinally and have rounded edges. Complimentary slots 44 are located on the drive shaft 35. Positioned within the slots 44,48 is a ball bearing 50 providing a drive key between the cam 40 and the drive shaft 35. This arrangement locks the cam 40 to the drive shaft 35 so that the cam 40 rotates with the drive shaft 35 while allowing the cam 40 to move longitudinally.
This arrangement of drive keys also keys the [0053] bit mandrel 52 to the drive shaft 35 to provide rotational movement to the drill bit 32 while allowing the drill bit 32 to reciprocate in response to action from the cam 40 and springs 58.
A [0054] shock spring 60 is located towards the second end 16 of the tool 10. The shock spring 60 is mounted between the shaft 35 and the bit mandrel 52. A nut 62 retains the spring 60 in an enclosure between the shaft 35 and bit mandrel 52. The shock spring 60 ‘cocks’ the tool and in conjunction with the cam ensures that the drill bit 22 reciprocates even though no weight from the drill string has been slacked down onto the drill bit 22.
A [0055] central bore 62 through the body 12 of the tool 10 provides a channel for the flow of fluid from the surface to the impacting surface 36 of drill bit 22. Returning to FIG. 1, it is seen that the bore 62 may splay within the drill bit 22 to provide a multitude of radial ports 64 on the impacting surface 36.
In use, impact tool [0056] 10 is mounted on a string 19 using a connector 18. The string 19 as shown in FIG. 1 is coiled tubing. It will be appreciated by those in the art that string 19 could equally be a standard drill string, composite pipe, electric line or a wireline. In the embodiment using a electric line or wireline, fluid flow will not be provided from the surface.
Impact tool [0057] 10 is then lowered into a bore hole, the string may be rotated or reciprocated as it enters the bore hole. When the impacting surface 36 reaches the base of the bore hole or any removable obstruction (for example, scale precipitate) the drive mechanism 34 is activated in order to rotate the drive shaft 35. The cam 40 rotates with the drive shaft 35 by virtue of the drive keys 50. As cam 40 rotates it will be urged into a reciprocal motion as the pin 43 on the housing 39 follows the groove 42 in the cam 40. Cam 40 moving upwards against the spring cage 56 provides the upstroke of the tool 10, conversely the impact stroke is created by a downward motion of the cam 40, aided by the springs 58. The impact stroke is not created by a vertical drop alone, there is also a radial component because the springs 58 movement back is not instantaneous. Drill bit 32 is biased against cam 40 via the bit mandrel 52 by shock spring 60. Shock spring 60 ‘cocks’ the tool 10 and consequently the drill bit 32 follows the impact stroke of the hammer unit 33. Each stroke causes the surface 36 of the drill bit 22 to strike the formation and break it up in a pulverising action. The speed of the strokes is dictated by the speed of revolution of the cam 40, which in turn is controlled by the motor 34.
In a further embodiment of the present invention the [0058] drill bit 22 is replaced by a cylindrical sub, as shown in FIG. 2. When the tool 10 is inserted in the well bore on a string, the hammer action is used to vibrate the tool in the well bore and therefore aid the passage of the string through the well bore. This embodiment is particularly useful in highly stepped or highly inclined wells where gravity cannot be used to move the string through the well bore. It will be appreciated that this embodiment could be used within tubulars mounted in a well bore such as casing and liner.
The principal advantage of the present invention is that by disconnecting the working unit from the hammer unit an impact tool is provided with minimum weight on it. By the use of a cam and spring mechanism to provide the reciprocating or hammer motion, the tool provides a self hammer action, i.e., the tool powers both the down stroke and the upstroke. In particular when a drill bit is used as the working unit, no weight is required upon the drill bit to operate the tool, as in the prior art. [0059]
A further advantage of the present invention is that the drive means may be contained within the tool itself. In this way the standard drill pipe sections used to form the string can be dispensed with and an alternative lightweight composite pipe, such as composite coil tubing or in fact a simple electric line/wireline can be used. Thus, the tool of the present invention is more versatile downhole than current impact tools. Additionally, as little or no weight is required upon to operate the tool, reactive forces and torque are minimised, thereby facilitating the use of composite pipe or coiled tubing. [0060]
A further advantage of the present invention is that it provides an impact drilling tool which can drill and cut more effectively in the bore hole than standard tools by virtue of the minimum weight on bit. This is due to the fact that the bit will have room to cut the formation more effectively because in effect the impacting surface or cutting face will be intermittently in contact with the formation thereby breaking the formation and then clearing it of cuttings and debris. This would not be possible if the bit was an integral part of the hammer unit, as in the prior art impact drilling tools, because a more significant reactive force would be required to lift a section of the tool which in turn would require more weight on the bit. [0061]
A yet further advantage of the present invention is that it provides an impact tool which does not require a return fluid flow path to operate. Typically prior art hammer tools are hydraulically operated, thus requiring fluid to be pumped from the surface and the pressure differential created is used to generate the percussion action/force. The present invention is purely mechanical, is not affected by hydraulic or differential pressure and consequently a return flow path is not required. [0062]
Various modifications may be made to the present invention, without departing from the scope thereof. For example the cam surfaces could be reversed such that the rotation of the cam could be provided by an outer rotating body while the cam follower pin could be located at a stationary position on the longitudinal axis. [0063]

Claims

We claim

1. An impact tool for use in a bore hole from a surface, the impact drilling tool comprising:

a second end including a working sub, the working sub including a first surface for contacting a portion of the bore hole; and

2. An impact tool as claimed in claim 1 wherein the working sub is a drill bit and wherein the first surface contacts with a formation to increase depth of the bore hole.

3. An impact tool as claimed in claim 1 wherein the spring mechanism comprises at least one first spring to bias the working unit towards the cam.

4. An impact tool as claimed in claim 1 wherein the spring mechanism comprises at least one second spring located adjacent the cam to act with the cam in reciprocal motion.

5. An impact tool as claimed in claim 1 wherein the tool further comprises a drive shaft located on the longitudinal axis.

6. An impact tool as claimed in claim 5 wherein the tool further includes at least one drive key located between the cam and the drive shaft to prevent the cam rotating independently of the drive shaft while permitting the cam to move longitudinally with respect to the drive shaft.

7. An impact tool as claimed in claim 6 wherein the tool includes a second drive key located between the working sub and the drive shaft to prevent the working sub rotating independently of the drive shaft while permitting the working sub to move longitudinally with respect to the drive shaft.

8. An impact tool as claimed in claim 5 wherein the tool includes drive means, the drive means being used to rotate the drive shaft.

9. An impact tool as claimed in claim 1 wherein the cam includes a cam profile which determines number of strokes per revolution of the cam and thereby the cycle/stroke rate of the hammer unit.

10. An impact tool as claimed claim 1 wherein the tool includes a telescopic joint mounted on the longitudinal axis.

11. An impact tool as claimed in claim 1 wherein the tool includes a shear disc sub.

12. An impact tool as claimed claim 1 wherein the tool includes a release joint.

13. A method of drilling a bore hole from a surface, the method comprising the steps:

(a) attaching an impact tool including a drill bit to a work string;

(b) running the string into a bore hole;

14. A method as claimed in claim 13 wherein the work string is coiled tubing.

15. A method as claimed in claim 13 wherein the work string is a wireline.

16. A method as claimed in claim 13 wherein the method further includes the step of pumping fluid through the impact tool.

17. A method as claimed in claim 13 wherein a number of impact strokes per minute of the drill bit is set by the speed of rotation of the cam.

18. A method as claimed in claim 13 wherein the method further includes the step of steering the drill bit.