Directional drilling control

A method for oscillating a drillstring with a top drive system, the drillstring extending into the earth, the drillstring having a bit on a tower end thereof, the bit for drilling into the earth, the method comprising

• determining a first amount of energy and a second amount of energy, said determining including calculating the first amount of energy and the second amount of energy based on actual movement of the drillstring by a motive apparatus, the first amount of energy based on a measured amount of energy applied to the drillstring to move the drillstring to a first position, and the second amount of energy based on a measured amount of energy applied to the drillstring to move the drillstring to a second position, the second position subsequent to the first position, said calculating not based on an actual physical position of the drillstring and not based on an actual physical position of the bit,
• applying the first amount of energy to the drillstring in a first rotational direction to move the drillstring to the first position,
• stopping the drillstring at the first position without regard to location of the bit,
• after applying the first amount of energy to the drillstring applying the second amount of energy to the drilling in a second rotational direction, the second rotational direction opposite to the first rotational direction, and
• stopping the drillstring at the second position without regard to location of the bit,
• said oscillating accomplished without rotating the drillstring a predetermined angle,
• continuously oscillating the drillstring cyclically in the first rotational direction then in the second rotational direction by applying additional amounts of energy to the drillstring, said applications of additional amounts of energy to the drillstring not moving the bit,
• wherein the top drive system has a top drive shaft and is driven by a variable frequency drive, and a control system in communication with the top drive system and the variable frequency drive controls the variable frequency drive, the variable frequency drive providing feedback to the control system regarding angular velocity of the top drive shaft and torque applied to the top drive shaft by the top drive system, the method further comprising
• the control system calculating amounts of energy imparted to the drillstring by the top drive system based on the feedback from the variable frequency drive, and
• wherein the control system includes control apparatus containing programmable media, the control apparatus from the group consisting of computer, programmable logic controller, single board computer, central processing unit, microcontroller, and finite state machine.