A system, method and apparatus for a clutch for a well string can include a tubular member, a mandrel, a top sub and a bottom sub. A sleeve can be located between the tubular member and the mandrel. The sleeve has an engaged position wherein an inner sleeve spline is coupled to the mandrel spline, and a disengaged position wherein the inner sleeve spline is uncoupled from the mandrel spline. The sleeve has an outer sleeve spline that is coupled to the tubular spline in the engaged position and the disengaged position. A spring in the tubular member can bias the sleeve from one position to another position. The sleeve can be configured to be moved between the positions to overcome the spring bias.

A system, method and apparatus for a clutch for a well string can include a tubular member, a mandrel, a top sub and a bottom sub. A sleeve can be located between the tubular member and the mandrel. The sleeve has an engaged position wherein an inner sleeve spline is coupled to the mandrel spline, and a disengaged position wherein the inner sleeve spline is uncoupled from the mandrel spline. The sleeve has an outer sleeve spline that is coupled to the tubular spline in the engaged position and the disengaged position. A spring in the tubular member can bias the sleeve from one position to another position. The sleeve can be configured to be moved between the positions to overcome the spring bias.

Methods and apparatus for controlling drill string rotation. The apparatus may be a control system for controlling a driver operable to rotate a drill string to form a wellbore extending into a subterranean formation. The control system may include a first controller operable to control rotation of the driver and a second controller communicatively connected with the first controller. During the drilling operations the first and/or second controller may be operable to generate a rotational speed command based on status information indicative of operational status of the drill string, and thereby cause the driver to rotate the drill string based on the rotational speed command

A method for drilling a well. The method may include detecting stick-slip vibrations at a frequency via a downhole sensor. The method may further include determining a reflection coefficient of a drill bit for the frequency based on at least one of a rotational speed of the drill bit or a torque of the drill bit. The method may also include determining a reflection coefficient of a top drive for the frequency based on at least one of a rotational speed of the top drive or a torque produced by the top drive. The method may further include adjusting a control system in electronic communication with the top drive based on the reflection coefficient of the drill bit for the frequency and the reflection coefficient of the top drive for the frequency.

A method for drilling a well. The method may include detecting stick-slip vibrations at a frequency via a downhole sensor. The method may further include determining a reflection coefficient of a drill bit for the frequency based on at least one of a rotational speed of the drill bit or a torque of the drill bit. The method may also include determining a reflection coefficient of a top drive for the frequency based on at least one of a rotational speed of the top drive or a torque produced by the top drive. The method may further include adjusting a control system in electronic communication with the top drive based on the reflection coefficient of the drill bit for the frequency and the reflection coefficient of the top drive for the frequency.

Methods and apparatus for controlling drill string rotation. The apparatus may be a control system for controlling a driver operable to rotate a drill string to form a wellbore extending into a subterranean formation. The control system may include a first controller operable to control rotation of the driver and a second controller communicatively connected with the first controller. During the drilling operations the first and/or second controller may be operable to generate a rotational speed command based on status information indicative of operational status of the drill string, and thereby cause the driver to rotate the drill string based on the rotational speed command.

Methods and apparatus for controlling drill string rotation. The apparatus may be a control system for controlling a driver operable to rotate a drill string to form a wellbore extending into a subterranean formation. The control system may include a first controller operable to control rotation of the driver and a second controller communicatively connected with the first controller. During the drilling operations the first and/or second controller may be operable to generate a rotational speed command based on status information indicative of operational status of the drill string, and thereby cause the driver to rotate the drill string based on the rotational speed command.

Methods and apparatus for controlling drill string rotation. The apparatus may be a control system for controlling a driver operable to rotate a drill string to form a wellbore extending into a subterranean formation. The control system may include a first controller operable to control rotation of the driver and a second controller communicatively connected with the first controller. During the drilling operations the first and/or second controller may be operable to generate a rotational speed command based on status information indicative of operational status of the drill string, and thereby cause the driver to rotate the drill string based on the rotational speed command.

Methods and apparatus for controlling drill string rotation. The apparatus may be a control system for controlling a driver operable to rotate a drill string to form a wellbore extending into a subterranean formation. The control system may include a first controller operable to control rotation of the driver and a second controller communicatively connected with the first controller. During the drilling operations the first and/or second controller may be operable to generate a rotational speed command based on status information indicative of operational status of the drill string, and thereby cause the driver to rotate the drill string based on the rotational speed command.

Design parameters for PDC drill bit are correlated to instances of backward whirl, where backward whirl is detected along a lateral axis in the frequency domain during downhole drilling. Two regimes of backward whirl are described and detectedcutting-induced backward whirl and friction-induced backward whirlwhere each regime has different characteristic frequencies, detection methods, and mitigation guidelines. Design parameters are quantified by gauge fullness, drilling efficiency (DE), and whirl index (WI). Design guidelines to mitigate backward whirl are generated by correlating design parameter quantifiers and instances of backward whirl, including both cutting-induced backward whirl and friction-induced backward whirl. Potential drill bit designs are then validated against the generated guidelines in order to mitigate backward whirl in future drilling runs.