Patent ID: 7677331
Filing Date: 2010-03-16
Classification: E21B

Abstract:
1. A method of automatic drilling a well comprising: supporting a coil tube injector in a mast for injecting a string of coil tube with a drill bit from a reel and into a wellbore for drilling the wellbore; placing the drill bit at a bottom of the wellbore; determining a tare mud pressure; setting a differential pressure; measuring a drilling mud pressure while drilling; establishing a differential pressure between the tare mud pressure and the measured drilling mud pressure for controlling a first variable frequency drive for controlling a first alternating current motor driving the injector for controlling a rate of injection of coil tube by the injector for maintaining the differential pressure; and controlling a second variable frequency drive for controlling a second alternating current motor driving the reel for maintaining a relative rate of coil tube supplied from the reel to the injector.