RELATIVE DRILL BIT DIRECTION MEASUREMENT

摘要

Apparatus and Methods are disclosed for determining the direction between a rotating magnetic field and alternating magnetic field sensors at a remote location. The curvature of a borehole drilling assembly between a rotating drill bit (10) carrying a permanent magnet (50) and sensors (46) behind a drilling motor (16) is measured to provide early indication of changes in drilling direction. A second application concerns measurement of the convergence and divergence and the skewness of two approximately parallel well bores to provide information for correcting the drilling direction to maintain parallelism. A third application measures the direction and distance to a point target to provide data for guiding drilling toward that target. The primary apparatus are an oriented, rotating permanent magnet (50) and an oriented, three component alternating magnetic field sensor.