Abstract: A method of automatic drilling of a well with coil tubing or drill pipe tubing utilizes AC motors coupled to variable frequency drives controlled by a programmable logic controller. For example, a coil tube injector is supported in a mast for injecting coil tube from a reel and into a wellbore for drilling the wellbore. The AC motors for the injector are driven for controlling a rate of injection of coil tube by the injector for maintaining at least one drilling parameter such as weight-on-bit, differential mud pressure or rate of penetration. The AC motor for the reel is also controlled for driving the reel and maintaining a relative rate of coil tube supplied from the reel to the injector. Drawworks and a top drive supported by the draworks can also be equipped with AC motors and variable frequency drives for controlling a drilling rate for maintaining at least one of the drilling parameters.

Abstract: A method of automatic drilling of a well with coil tubing or drill pipe tubing utilizes AC motors coupled to variable frequency drives controlled by a programmable logic controller. For example, a coil tube injector is supported in a mast for injecting coil tube from a reel and into a wellbore for drilling the wellbore. The AC motors for the injector are driven for controlling a rate of injection of coil tube by the injector for maintaining at least one drilling parameter such as weight-on-bit, differential mud pressure or rate of penetration. The AC motor for the reel is also controlled for driving the reel and maintaining a relative rate of coil tube supplied from the reel to the injector. Drawworks and a top drive supported by the draworks can also be equipped with AC motors and variable frequency drives for controlling a drilling rate for maintaining at least one of the drilling parameters.