Image Number 7 for United States Patent #5857530.
A borehole drilling system has a well tubing actuator with a well tubing connector on a working end of the well tubing actuator, a transducer responsive to longitudinal movement of the working end of the well tubing actuator and a control system for the well tubing actuator to provide controlled longitudinal movement of the well tubing connector using a selected drilling program and feedback from the transducer. Plural lengths of well tubing are connected to the well tubing connector, with a jet drilling apparatus connected to the downhole end of the well tubing. An underreamer apparatus may be attached to the bottom hole end of the well tubing. Coiled tubing may be attached to the bottom hole end of the well tubing and directed through a whipstock. A method of drilling a borehole comprising moving well tubing longitudinally in a borehole with a well tubing actuator mounted on a frame, producing electrical output corresponding to longitudinal movement of a working end of the well tubing actuator; and controlling longitudinal movement of the working end of the well tubing actuator according to a selected drilling program and using the electrical output as feedback. The method may be used for drilling, section milling and underreaming.