Damping drill string vibrations
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.
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.