Damping drill string vibrations

Abstract

A device for damping vibrations of a rotary drill string in motion in a wellbore, a related method, drill string and drill string sub or section, where at least one component of motion of the drill string is communicated to the device, and brake means counter the vibrations, resisting the motion in dependence upon the speed of motion. The device may have an outer sleeve arranged on an inner, tubular body which is rotatably arranged within the outer sleeve. Roller wheels support the sleeve on the wellbore wall and facilitate longitudinal movement of the device and prevent rotational slipping of the outer sleeve relative to the wall upon rotating the tubular body and drill string. One brake part of the brake means on the outer sleeve and another on the tubular body operate to resist rotational vibration components.

Claims

1. A device for damping vibrations of a rotary drill string in motion in a wellbore, the device comprising: brake means to counter the vibrations, by way of resisting the motion in dependence upon the speed of motion, wherein the brake means comprises at least one pair of brake parts; an inner, tubular body extending longitudinally between first and second ends, the first end being configured with a threaded section to screw connect the tubular body to a first adjacent section of a drill string, and the second end being configured with a threaded section to screw connect to a second adjacent section of the drill string, the tubular body thus being configured to rotate with the drill string; an outer sleeve supported on the inner, tubular body, the tubular body being arranged rotatably within the outer sleeve; and at least one roller wheel for supporting the outer sleeve on a wall of the wellbore, the roller wheel being configured to facilitate longitudinal movement of the device along the wall and prevent rotational slipping of the outer sleeve relative to the wall upon rotation of the drill string; wherein the outer sleeve is associated with a first brake part of the pair, and the inner, tubular body is associated with a second brake part of the pair, the second brake part being movable relative to the first brake part upon rotation of the tubular body relative to the outer sleeve; wherein the pair of brake parts are operable, through the movement of the second brake part relative to the first brake part upon rotation of the tubular body relative to the outer sleeve with the drill string, to produce a braking force in dependence upon the speed of rotation of the inner, tubular body relative to the outer sleeve for braking or resisting rotational vibrations; and one of the first brake part or the second brake part comprising at least one magnet to produce a magnetic field, and the other of the first brake part or second brake part comprising non-magnetic, conductive material to be subjected to the magnetic field, so that upon relative movement between the brake parts, eddy currents are obtained in the non-magnetic, conductive material of the other part for resisting the movement.

2. The device as claimed in claim 1, wherein the second brake part associated with the inner, tubular body comprises non-magnetic, conductive material, and the first brake part assoicated with the outer sleeve comprises at least one magnet for producing a magnetic field so that upon relative rotation of the inner, tubular body relative to the outer sleeve, in use, eddy currents are produced in the non-magnetic, conductive material for braking or resisting a rotational component of movement between the inner, tubular body and the outer sleeve.

3. The device as claimed in claim 1, wherein the first brake part associated with the outer sleeve comprises non-magnetic, conductive material, and the second brake part associated with the inner, tubular body comprises at least one magnet for producing a magnetic field so that upon relative rotation of the inner, tubular body relative to the outer sleeve, in use, eddy currents are produced in the non-magnetic, conductive material for braking or resisting a rotational component of movement between the inner, tubular body and the outer sleeve.

4. The device as claimed in claim 1, wherein either or both of the brake parts comprise a ring or sleeve or annular member.

5. The device as claimed in claim 1, wherein the outer sleeve is supported on the inner, tubular body on bearings for facilitating rotation of the inner, tubular body with respect to the outer sleeve upon rotating the drill string in use.

6. The device as claimed in claim 1, further comprising at least one other pair of brake parts for braking or resisting a longitudinal component of movement of the device relative to the wellbore in use, wherein the pair of brake parts are for braking or resisting a rotational component of movement between the inner, tubular body and the outer sleeve.

7. The device as claimed in claim 6, wherein the other pair of brake parts for braking or resisting the longitudinal component and the pair of brake parts for braking or resisting the rotational component are operable to respond independently to longitudinal and rotational components of motion of the rotary drill string with respect to the wellbore.

8. The device as claimed in claim 6, wherein the pair of brake parts for braking or resisting the longitudinal component are disposed on the outer sleeve.

9. The device as claimed in claim 8, wherein the at least one roller wheel is coupled to at least one of the brake parts or the other pair so that the movement of the roller wheel on the wall of the wellbore in use longitudinally is communicated to produce movement between the brake parts of the other pair in dependence upon the movement of the rotary drill string along the wellbore.

10. The device as claimed in claim 9, wherein either or both brake parts of the other pair for braking or resisting the longitudinal movement along the wellbore comprises a ring, a body or a sleeve which is rotatable about an axis and is coupled to the roller wheel through a gear arrangement for converting the rotational movement between the brake parts to longitudinal tracking of the roller wheel along the wellbore or vice versa in dependence upon the longitudinal movement of the drill string with respect to the wall of the wellbore.

11. A rotary drill string including at least one device in accordance with claim 1, disposed on a downhole section of the drill string.

12. The rotary drill string as claimed in claim 11, including a plurality of devices disposed on the drill string for damping vibrations at different downhole positions along the drill string.

13. A method of drilling a borehole using a drill string in accordance with claim 11.

14. The device as claimed in claim 7, wherein the pair of brake parts for braking or resisting the longitudinal component are disposed on the outer sleeve.

15. A device for damping vibrations of a rotary drill string in motion in a wellbore, the device comprising: brake means to counter the vibrations, by way of resisting the motion in dependence upon the speed of motion, wherein the brake means comprises at least one pair of brake parts; an inner, tubular body extending longitudinally between first and second ends, the first end being configured with a threaded section to screw connect the tubular body to a first adjacent section of a drill string, and the second end being configured with a threaded section to screw connect to a second adjacent section of the drill string, the tubular body thus being configured to rotate with the drill string; an outer sleeve supported on the inner, tubular body, the tubular body being arranged rotatably within the outer sleeve; at least one roller wheel for supporting the outer sleeve on a wall of the wellbore, the roller wheel being configured to facilitate longitudinal movement of the device along the wall and prevent rotational slipping of the outer sleeve relative to the wall upon rotation of the drill string; wherein the outer sleeve comprises an outer brake part of the pair, and the inner, tubular body comprises an inner brake part of the pair; wherein the brake parts are operable, through relative movement between the outer brake part and the inner brake part upon rotation of the tubular body relative to the outer sleeve with the drill string, to produce a braking force in dependence upon the speed of rotation of the inner, tubular body relative to the outer sleeve for braking or resisting rotational vibrations; and the inner brake part comprising at least one magnet to produce a magnetic field, and the outer brake part comprising non-magnetic, conductive material to be subjected to the magnetic field, so that upon relative movement between the brake parts, eddy currents are obtained in the non-magnetic, conductive material of the other part for braking or resisting a rotational component of movement between the inner, tubular body and the outer sleeve.

16. The device as claimed in claim 15, wherein either or both of the brake parts comprise a ring or sleeve or annular member.

17. The device as claimed in claim 15, wherein the outer sleeve is supported on the inner, tubular body on bearings for facilitating rotation of the inner, tubular body with respect to the outer sleeve upon rotating the drill string in use.

18. The device as claimed in claim 15, further comprising at least one other pair of brake parts for braking or resisting a longitudinal component of movement of the device relative to the wellbore in use, wherein the pair of brake parts are for braking or resisting a rotational component of movement between the inner, tubular body and the outer sleeve.

19. The device as claimed in claim 18, wherein the other pair of brake parts for braking or resisting the longitudinal component and the pair of brake parts for braking or resisting the rotational component are operable to respond independently to longitudinal and rotational components of motion of the rotary drill string with respect to the wellbore.

20. The device as claimed in claim 18, wherein the pair of brake parts for braking or resisting the longitudinal component are disposed on the outer sleeve.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) There will now be described, by way of example only, embodiments of the invention with reference to the accompanying drawings, in which:

(2) FIG. 1 is a sectional representation of a vibration damping device in accordance with an embodiment of the invention for damping rotational vibrations;

(3) FIG. 2 is a representation of the magnet ring from the section line AA in FIG. 1, indicating the magnetic field generated by the magnet ring; and

(4) FIG. 3 is a representation of the outer sleeve and tubular section of the drill string tubular along the section line AA in FIG. 1 illustrating the movement of the tubular section within the magnetic field of the magnet ring;

(5) FIG. 4 is a perspective representation of a vibration damping device on a drill string tubular;

(6) FIG. 5 is a sectional representation of the vibration damping device of FIG. 4;

(7) FIG. 6 is a perspective sectional representation of a first end portion of the vibration damping device of FIGS. 4 and 5, in larger scale;

(8) FIG. 7 is a side sectional representation of an intermediate portion of the vibration damping device of FIGS. 4 and 5, in larger scale; and

(9) FIG. 8 is a perspective part sectional representation of a second end portion of the vibration damping device of FIGS. 4 and 5, in larger scale; and

(10) FIG. 9 is another sectional representation of a portion of the vibration damping device of FIGS. 4 and 5, near the first end and in larger scale.

DETAILED DESCRIPTION OF THE DRAWINGS

(11) Turning first to FIG. 1, a vibration damping device 200 for coupling to a drill string is depicted. The device 200 has an outer structure comprising an outer sleeve 260 and an inner structure comprising a body in the form of a drill string tubular 110 arranged to be screw connected to adjacent sections of the drill string. The device also comprises brake means operable for resisting motions of the string in the wellbore in dependence upon the speed of motion.

(12) The outer sleeve 260 is supported on the drill string tubular 110. The drill string tubular 110 comprises a tubular section 113 that is surrounded by the sleeve. The sleeve 260 is supported upon thrust bearings 121a, 121b which permit rotation of the drill string tubular 110 relative to the outer sleeve 260. The inner structure comprises a brake part in the form of a surrounding layer of non-magnetic, conductive material 115, which forms part of the tubular section 113 being rotatable as the tubular section of the drill string tubular 110 is rotated about the longitudinal axis of the drill string. The sleeve 260 comprises another brake part in the form of a magnet ring on an inside of the sleeve and which extends circumferentially around tubular section 113 of the drill string. The sleeve 260 is arranged so that a small clearance 108 is present between the layer of conductive material 115 and the magnet ring 265. A magnetic field is generated in the region within the magnet ring 265. By rotational movement of inner structure within the magnetic field upon rotation of the string, eddy currents arise in the non-magnetic, conductive material 115 so that a braking force is produced proportional to the rate of rotation to resist the rotation between inner and outer structures. In the event of rotational vibrations, which in effect produce small variations in rotation speed of the drill string, the eddy current braking force obtained as a result, being proportional to the speed variations of the vibrational movements, suppress or reduce the rotational vibration component in the motion.

(13) The principle can be further understood with reference to FIGS. 2 and 3, where permanent magnets 266a-266h are arranged with poles in various directions as indicated by arrows P combining to produce a uniform magnetic field F in the area enclosed by the ring 265. The tubular section 113 is rotated as indicated by arrow R about the longitudinal axis L of the tubular. The rotation of the conductive layer 115 in the area of the magnetic field produces eddy currents in the conductive material of the layer 115 that resist the rotation and the resistance of the eddy currents varies according to the rate of rotation which in turn varies in response to vibrations, so that when the rate of rotation varies because of vibrations, the eddy currents generated give rise to magnetic braking and attenuation or reduction of the vibrations rotationally in the string. Solely using mechanical components, the vibration damping device conveniently provides damping and restrict vibrations in use, so that significantly improved performance of drilling can be obtained using the drill string with the vibration damping device.

(14) Turning then to FIGS. 4 and 5, another vibration damping device 100 is arranged on a drill string tubular 10. The vibration damping device 100 is configured to damp or restrict, through eddy current braking, both rotational and longitudinal vibration components.

(15) As can be seen, the drill string tubular 10 has a box end 11 and a pin end 12 for connecting the tubular 10 to adjacent tubulars of a drill string (not shown) for incorporating the tubular 10 into the drill string. The drill string tubular 10 is rotatable with the drill string about the longitudinal axis 7 of the string.

(16) The vibration damping device 100 comprises an outer sleeve 60 that extends around the drill string tubular 10. The drill string tubular 10 has a body 13 that extends through the sleeve between the box end 11 and the pin end 12. The sleeve 60 is elongate and extends longitudinally between first and second ends 61a, 61b.

(17) The sleeve 60 is supported rotatably on the body 13 via thrust bearings 21a, 21b arranged near the first and second ends 61a, 61b, as seen in more detail in FIG. 6. The sleeve 60 also has roller wheels 64 which extend radially from an outer surface of the sleeve. The roller wheels 64 are spaced apart around a circumference of the sleeve 60 and arranged to be rotatable about axes tangentially along the circumference. In this way, the rollers 64 may roll to facilitate movement of the string in a longitudinal direction but may resist movement of the sleeve rotationally with respect to the wall of the wellbore when in contact with the wall of the wellbore.

(18) Thus, the sleeve 60 is arranged on the drill string tubular 10 so that the drill string tubular 10 and sleeve 60 are rotatable one relative to the other. Thus, the drill string can be rotated in the wellbore about the longitudinal axis of the string by rotary equipment on a drilling rig at the surface. The sleeve 60 is arranged to be in frictional contact with a surrounding wall of the wellbore through the roller wheels 64. The roller wheels when in contact with the wellbore wall can hinder rotational slippage of the sleeve relative to the wellbore wall. This tends to result in the sleeve being retained rotationally, typically fixedly, in rotational position relative to the wall of the wellbore. The drill string tubular 10 is thus rotatable relative to the sleeve 60 about the longitudinal axis 7, on the bearings 21a, 21b.

(19) To address rotational vibrations, the vibration damping device 100 has an intermediate damping section 97, seen in further detail in FIG. 7, which is generally configured to operate similarly to the device 200 above described with reference to FIGS. 1 to 3. In this intermediate damping section 97, the drill string tubular 10 has a surrounding sheath of non-magnetic, conductive material 15. The conductive material 15 comprises an integrated outer layer of the drill string tubular 10 that extends ring-wise circumferentially around the longitudinal axis 7. The outer sleeve 60 has a magnet ring 65 affixed to the sleeve 60. The portion of the tubular drill string tubular 10 with the conductive layer extends through the area enclosed by the magnet ring 65. Similar to the device of FIGS. 1 to 3 therefore, upon rotation of the drill string, the tubular body 13 with the applied conductive material 15 is rotatable about the longitudinal axis 7 relative to the magnet ring 65 of the surrounding sleeve 60. In the presence of the magnetic field in the area enclosed by the magnet ring 15, eddy currents are produced in the conductive material 15 of the layer, in dependence upon the rotational speed of the tubular body, and thus upon variations in rotational speed due to rotational vibrations, the generated eddy currents produce a braking force which counters the effect of the rotational vibration component.

(20) To address longitudinal vibrations, the vibration damping device 100 of FIGS. 4 and 5 has two further damping sections 96, 98 which are mirror configurations of one another in respective end regions of the device 100. The damping section 96 is described further now with reference additionally to FIG. 8.

(21) The outer sleeve 60 in the damping section 96 carries a magnet sleeve 75 that is located within and is rotatable with respect to the outer sleeve 60. The rotatable magnet sleeve 75 is supported on the outer sleeve 60 upon bearings 51. The bearings 51 facilitate to position and permit rotation of the magnet sleeve 75 with respect to the outer sleeve 60. The magnet sleeve 75 comprises a cylindrical body extending circumferentially around the drill string tubular 10. The magnet sleeve 75 is also therefore rotatable relationship with respect to the drill string tubular 10, such that the drill string tubular 10 is rotatable both with respect to the magnet sleeve 75 and outer sleeve 60 in drilling operations.

(22) The magnet sleeve 75 is further arranged longitudinally spaced apart from the fixed magnet ring 65 of outer sleeve 60 in the intermediate section 97. That is, the fixed magnet ring 65 in this example is in an intermediate location extending axially along the device between the magnet sleeves 75 of the further damping sections 96, 98.

(23) The outer sleeve 60 in the damping section 96 also has a cylindrical collar 68 affixed to the outer sleeve 60. The cylindrical collar 68 is arranged within and has a cylindrical body portion 68p that extends longitudinally along the drill string tubular 10. The magnet sleeve 75 is arranged in an annular region 69 between an outer surface of the tubular body portion 68p and an inner surface of the outer sleeve 60. The cylindrical collar 68, in particular the wall of the cylindrical body portion 68p facing outwardly toward the magnet sleeve 75 comprises non-magnetic, conductive material. The magnet sleeve 75 is configured as the magnet ring to comprise permanent dipole magnets arranged to produce a magnetic field in the area enclosed by the magnet sleeve 75. Upon rotation of the magnet sleeve 75 with respect to the sleeve 60 (and the collar 68), eddy currents are generated in the conductive material of the collar 68.

(24) The roller wheels 64 are coupled to the magnet sleeve 75 through a gear arrangement 80. Longitudinal rolling movement of the roller wheels 64 is transferred through the gear arrangement 80 into rotational movement of the magnet sleeve 75 relative to the outer sleeve 60 and vice versa. Thus, longitudinal vibrations of the drill string produce variations in the longitudinal speed of movement of the roller wheels 64, and this is expressed as variations in the rotational movement of the magnet sleeve 75. Eddy currents consequently produced in the conductive collar 68 generate breaking forces to the magnet sleeve 75 which is translated through the gear arrangement to brake the longitudinal rolling movement of the wheels 64 thereby counteracting the vibration longitudinally.

(25) As can be seen best in FIG. 8, the roller wheels 64 are daisy chained together through universal couplings between adjacent wheels 64. In this way, if only one of the wheels 64 happens to be in contact with the wellbore wall, then the rotation of the contacting wheel along the wellbore will result correspondingly in rotation of the coupled other wheels 64. The wheels 64 are daisy chained via the couplings around the circumference of the sleeve 60, which is facilitated by the universal couplings comprise bent joints between axles of the roller wheel 64 to wheels 64. The gear arrangement 80 in this example includes a worm gear 83 incorporated into the coupling 63 between one pair of the roller wheels 64. The worm gear 83 is generally cylindrical, having an end-to-end central axis about which the worm gear is rotatable. The worm gear 83 rotates with the rotation of the wheels 64.

(26) The worm gear 83 in turn is coupled to the magnet sleeve 75 through first and second pinion gears 84, 85 rotating about a common, fixed axis perpendicular to the axis of the worm gear 83. The first pinion gear 84 intermeshes with the worm gear 83 and the second pinion gear 85, which is mounted on a common pin along coaxially with the first pinion gear 84, intermeshes with a tooth ring 86 along the circumference of one end of the magnet sleeve 75.

(27) The turning of the worm gear 83, produces rotation of the first and second pinion gears 84, 85 and the rotation of the pinion gear 85 in engagement with the magnet sleeve 75 produces rotation of the magnet sleeve 75. Conversely, the gear arrangement 80 can operate in opposite sense so that rotation of the magnet sleeve 75 produces turning of the worm gear and the wheels 64. Rotation of the magnet sleeve 75 in a clockwise direction causes rotation of the wheels 64 in one direction, and rotation of the magnet sleeve 75 in an anticlockwise direction causes rotation of the wheels 64 in an opposite direction.

(28) Thus, in the presence of longitudinal vibrations of the drill string during drilling as the drill string progresses and is advanced along the wellbore, the vibrational movement longitudinally is transmitted through the gear arrangement to the magnet sleeve 75 which produces eddy currents in the collar associated with the vibration which counteracts the vibration. Thus, longitudinal vibrations can be suppressed or reduced by the damping device 100 merely through the arrangement of mechanical components, in particular the sleeve, gear arrangement and magnet rings. Moreover, the longitudinal component of vibration can be suppressed or reduced independently of the rotational component of vibration. By incorporating the vibration damping device into the string, it can automatically act to attenuate the vibrations during the drilling process when the drill string is advanced into the well and rotated.

(29) Although the device of FIGS. 4 to 9 provides for damping both rotational and longitudinal vibrations, the damping device in other variants can provide longitudinal only damping, for example where the intermediate portion for the rotational damping is omitted, and in other variants can provide rotational only damping, for example by omitting the coupling between the roller wheels to the brake parts.

(30) In certain variants which provide rotational only damping, a device is configured as set out in relation to FIGS. 1 to 3 and further includes one or more roller wheels that support the device on the wellbore wall, and that permits rolling the device on the roller longitudinally along the wellbore and prevents rotational slippage of the sleeve and/or wheel relative to the wall when rotating the drill string and the tubular body within the sleeve. In FIG. 1, it can be appreciated that the sleeve is retained in position longitudinally with respect to the tubular body by suitable retainment means, and that the tubular body is rotatable within the outer sleeve with the rotation of the drill string. Other means than the thrust bearings could be used to support the sleeve on the tubular body. Also, the brake parts or brake means in some variants are not necessarily those arranged for eddy current or magnetic braking as described with reference to FIGS. 1 to 3. Such an arrangement using the roller wheel advantageously provides low friction on the string axially and separates rotational friction components from axial friction components whilst preventing slippage rotationally so that the rotational vibration components can be effectively braked or resisted by the brake means to damp the rotational vibration component.

(31) The outer sleeve with roller wheels can extend outward from the drill sting tubular beyond width of the pipe collars so that the sleeve provides stand off for the string from the wall of the wellbore.

(32) The damping device may be advantageous in various ways. For example, by way of the brake means operating in dependence upon the speed of motion of the string, the device may reduce vibrations of different magnitudes and characteristics and may reduce vibrations in different component directions of motion in accordance with the motion taking place at the time. The device may therefore damp a greater range of drill string vibrations than typical prior art solutions. Being a mere mechanical device operating passively, set up may be carried out more easily, requiring for example merely to insert the device into the string, without onerous tuning. The device may operate to damp both torsional i.e. rotational and axial vibrations. The device may cope with vibrations that originate anywhere along the drill-string in contrast to prior art solutions which may only address bit-rock interaction excitations. In various embodiments, the damping device can be completely mechanical in design and therefore may be suitable to be used in very high temperature settings like for geothermal drilling. In contrast, to certain examples of prior art with an electronic-based control may be limited to temperatures that allow use electronic equipment. Energy consumption may be reduced everywhere there a vibration damping sub is provided in the string since the motion can be accommodated on bearings rather than sliding between two surfaces (mechanical friction).

(33) Various modifications and improvements may be made without departing from the scope of the invention herein described.