Steering device for downhole tools
An exemplary device carried on a rotating drill string includes an actuator that moves force application members and an associated controller. The force application members are actuated by an eccentricity between a force application members housing and the actuator. The controller synchronizes the extension of the force application members with the rotation of the drill string such that a steering force applied by the force application members is applied in the same azimuthal direction. The controller may also control magnitude of the steering force by adjusting the eccentricity. Another exemplary device maintains a wellbore device, such as a sensor, in a substantially non-rotating condition relative to a reference frame. The device includes a sensor conveyed by a rotating wellbore tubular, a drive configured to rotate the sensor; and a processor that controls the drive to maintain the sensor in a substantially non-rotating condition relative to the reference frame.
1. An apparatus for forming a wellbore in an earthen formation, comprising:
a drill string configured to form the wellbore;
a force application member positioned on the drill string, the force application member being configured to apply a steering force to a wellbore wall;
an actuator configured to extend and retract the force application member, the actuator including a first cam positioned within a second cam; and
a controller configured to control the actuator to synchronize the extending and retracting with a rotation of the drill string.
2. The apparatus according to claim 1 , wherein the actuator extends and retracts the force application member once per revolution of the drill string.
3. The apparatus according to claim 1 , wherein the first cam and the second cam each having enlarged sections.
4. The apparatus according to claim 3 , wherein the actuator is configured to control a magnitude of the steering force applied by the force application member by rotating the first cam relative to the second cam.
5. The apparatus according to claim 3 , further comprising a ring in which the first cam and the second cam are positioned, the ring being connected to the force application member.
6. The apparatus according to claim 5 , further comprising a housing in which the force application member is positioned, the housing having a first axis, and wherein the ring has a second axis, and wherein the actuator is configured to control an eccentricity between the first axis and the second axis to extend and retract the force application member.
7. The apparatus according to claim 3 , wherein the controller includes a motor rotating the second cam.
8. The apparatus according to claim 3 , wherein (i) the actuator extends and retracts the force application member once per revolution of the drill string, (ii) the controller rotates the actuator in a direction opposite to the direction of rotation of the drill string.
9. The apparatus according to claim 1 , wherein the controller is configured to rotate the actuator to control one of (i) an azimuthal direction and (ii) an inclination for the steering force applied by the force application member.
10. The apparatus according to claim 1 , wherein the controller includes a motor rotating the first cam.
11. A method for forming a wellbore in an earthen formation, comprising:
rotating a drill string to form the wellbore;
applying a steering force to a wellbore wall using a force application member positioned on the drill string;
moving the force application member using an actuator; and
controlling the actuator to synchronize the movement of the force application member with the rotation of the drill string, wherein the actuator includes a first cam positioned within a second cam.
12. The method according to claim 11 , wherein, the first cam and the second cam each having enlarged sections.
13. The method according to claim 12 , further comprising controlling a magnitude of the steering force applied by the force application member by rotating the first cam relative to the second cam.
14. The method according to claim 12 , further comprising rotating the actuator to control an azimuthal direction for the steering force applied by the force application member.