Borehole sensing tool with optical rotation sensor.

摘要

A tool (50) for measuring the direction of a subterranean borehole (200) includes an optical rotation sensing device (52) which accurately measures attitude of the tool housing (51). The optical rotation sensor (52) includes two optical fiber coils (74, 76) configured in the shape of a race track. The optical fiber coils (74, 76) are fixedly disposed on a frame (78) and positioned such that the plane of one coil (74) is rotated a predetermined angle with respect to the plane of the other coil (76). The frame (78) is periodically rotated about an axis which is axial to the borehole (200). An accelerometer (58) measures acceleration with respect to terrestrial gravitational forces. Tool attitude is calculated from the measurements performed by the optical rotation sensor (52) and the measurements produced by the accelerometer (58). A signal indicating the measured attitude is transmitted to the surface for analysis and display.