Patent ID: 7237624
Filing Date: 2007-07-03
Classification: E21B

Abstract:
1. In a system for forming a borehole including a drill string which is made up of a series of elongated sections that is connected to a leading arrangement having a steering configuration that is responsive to a roll position thereof, which roll position is controlled using the drill string, a method comprising: providing an assembly that is configured for sensing a roll orientation thereof, referenced to a roll indexing orientation that is defined by the assembly, so as to produce a roll output signal and for transmitting said roll output signal in a predetermined way; configuring a housing to support the assembly in relation to the drill string behind said leading arrangement in fixed rotational communication with the leading arrangement such that the roll indexing orientation is in a fixed, but arbitrary angular offset with respect to the roll position of the leading arrangement; with said assembly supported in said housing, orienting the roll position of the steering configuration in a predetermined way; receiving the roll output signal, with the steering configuration of the leading arrangement oriented in said predetermined way, for use in identifying a value of the fixed angular offset; and saving the value of the fixed angular offset.