Dynamic friction drill string oscillation systems and methods

A method of oscillating a drill string while slide drilling, which comprises:

• calculating, by a controller, a resonant frequency of the drill string using an effective torsional spring constant (Kf) of the drill string and moment of inertia (I) of a top drive;
• generating, by the controller, a rotational acceleration profile having the calculated resonant frequency;
• imposing, by the controller, the generated rotational acceleration profile over a first acceleration profile to generate a modified acceleration profile, wherein the first acceleration profile rocks the drill string back and forth so as to maintain a desired toolface orientation;
• and
• instructing the top drive, by the controller, to oscillate the drill string according to the modified acceleration profile so that the drill string oscillates at about the calculated resonant frequency while slide drilling.

A non-transitory machine-readable medium having stored thereon machine-readable instructions executable to cause a machine to perform operations that, when executed, comprise:

• determining a resonant frequency of a drill string;
• generating a rotational acceleration profile comprising a sine wave having a frequency at least substantially similar to the determined resonant frequency;
• imposing the generated rotational acceleration profile over a first acceleration profile to generate a modified acceleration profile, wherein the first acceleration profile rocks the drill string back and forth so as to maintain a desired toolface orientation;
• instructing a top drive to oscillate the drill string according to the modified acceleration profile so that the drill string oscillates at a frequency substantially similar to the calculated resonant frequency while slide drilling;
• and
• maintaining the desired toolface orientation while slide drilling.

A method of oscillating a drill string while slide drilling, which comprises:

• calculating, by a controller, a resonant frequency of the drill string using a torsional stiffness of a drill pipe and a moment of inertia of a bottom hole assembly;
• generating, by the controller, a rotational acceleration profile having the calculated resonant frequency;
• imposing, by the controller, the generated rotational acceleration profile over a first acceleration profile to generate a modified acceleration profile, wherein the first acceleration profile rocks the drill string back and forth so as to maintain a desired toolface orientation;
• and
• instructing a top drive, by the controller, to oscillate the drill string according to the modified acceleration profile so that the drill string oscillates at a frequency substantially similar to the calculated resonant frequency while slide drilling.