Logging tool with magnetic source and electric dipole sensor for forward and lateral imaging

Abstract

A logging method and system for imaging a subterranean formation intersected by a borehole. A magnetic dipole generates an electromagnetic field in the formation, and an electric field induced by the magnetic dipole is sensed. The electromagnetic field is sensitive to bed boundaries and other changes of formation characteristics, and becomes induced when encountering the changes. Monitoring the time and magnitude of field inducement yields information about the presence and location of the bed boundaries and target formations. The magnetic dipole is oriented transverse to the borehole axis, and measurements of the electric field take place in directions that include transverse to the orientation of the magnetic dipole and transverse to the borehole axis, parallel with the borehole axis, or both.