Borehole direction measuring device - having single-degree-of-freedom gyro and gravity sensors to give inclination and azimuth

摘要

A bore-hole direction measuring instrument has a gyro rotor mounted in a pair of gimbals to form a single degree of freedom gyro, a pick-up and torquer sensing and cancelling relative movement between the gimbals. A resolver measures the rotation of the torquer relative to the instrument casing and a gravity sensor unit measures gravity components along the axes. To survey a borehole, the pick-up and torquer continually operate to eliminate the relative rotation of the two gimbals and at a series of stations gravity components are sensed in three orthogonal directions relative to the outer gimbal. From these measurements the borehole inclination and azimuth are calculated for each station. The use of a single-degree of freedom gyro simplifies instrument design and makes gimbal bearing friction less critical.