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 we ll bores to provide information for correcting the drilling direction to mainta in 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.