Patent ID: 8157023
Filing Date: 2012-04-17
Classification: E21B,G01V

Abstract:
1. In a system for tracking a boring tool which is moved in an underground region using a drill string having a length that extends to the boring tool and said boring tool having an overall orientation that is characterized by a pitch orientation, a yaw orientation and a roll orientation and which is steerable underground in the region using said roll orientation, said boring tool being configured for advancing in a straight ahead mode during a continuous roll and further being configured for advancing in a steering mode by moving the boring tool at a fixed roll orientation, a method comprising: establishing a maximum drill string curvature available in said steering mode within said region; selecting a path segment length for advancing the boring tool along a path segment; advancing the boring tool along said path segment length of the path segment in said region using at least one of the straight ahead mode and the steering mode; establishing an averaged roll characteristic for movement of the boring tool along said path segment; determining a path segment pitch orientation based on one or more measured pitch orientations of said boring tool along said path segment; and using the maximum drill string curvature in combination with the averaged roll characteristic and the path segment pitch orientation, determining said yaw orientation of the boring tool.