Patent ID: 9085938
Filing Date: 2015-07-21
Classification: E21B

Abstract:
1. A method for controlling drilling of a subterranean wellbore through a target waypoint at a prescribed attitude, the method comprising: (a) processing (i) a demand inclination and a demand azimuth received from an outer loop controller and (ii) a measured attitude of the wellbore at an inner loop controller to recursively compute steering tool settings; (b) applying the steering tool settings to a steering tool to control drilling of the wellbore; (c) measuring an attitude of the wellbore while drilling in (b) and feeding back the measured attitude to (a); (d) transforming the attitude measured in (c) to Cartesian coordinates to obtain a measured trajectory including a measured attitude and a measured position in Cartesian coordinates; (e) feeding back the measured trajectory obtained in (d) to the outer loop controller; (f) processing a reference trajectory including a reference attitude and a reference position in combination with the measured trajectory obtained in (d) at the outer loop controller to recursively compute an optimized geometric hermite curve path from the measured trajectory to the reference trajectory to generate the demand inclination and the demand azimuth processed in (a); wherein an inner control loop including (a), (b), and (c) and an outer control loop including (d), (e), and (f) run concurrently while drilling.