Patent ID: 7243719
Filing Date: 2007-07-17
Classification: E21B

Abstract:
1. A method for determining a rate of change of longitudinal direction of a subterranean borehole, the method comprising: (a) providing a downhole tool including first and second surveying devices including corresponding first and second gravity measurement devices disposed at corresponding first and second longitudinal positions in the borehole, the first and second surveying devices being free to rotate relative to one another about a longitudinal axis of the downhole tool, the downhole tool further including a steering tool, the steering tool including a plurality of radially actuatable force application members each configured to displace radially from a longitudinal axis of the borehole within a range of radial positions; (b) causing the first and second surveying devices to measure a longitudinal direction of the borehole at the corresponding first and second positions; and (c) processing the longitudinal directions of the borehole at the first and second positions and the radial position of at least one of the plurality of force application members to determine the rate of change of longitudinal direction of the borehole between the first and second positions.