Electromagnetic well surveying method and apparatus for obtaining both a dip and conductivity anisotropy of a formation

Claim 1

AN ELECTROMAGNETIC SURVEYING INSTRUMENT FOR USE IN DETERMINING THE CHARACTERISTICS OF EARTH FORMATIONS TRAVERSED BY A BOREHOLE, SAID SURVEYING INSTRUMENT COMPRISING; TWO SOLENOIDS, THE AXIS OF ONE SOLENOID BEING SUBSTANTIALLY ALIGNED WITH THE AXIS OF THE BOREHOLE AND THE AXIS OF SAID OTHER SOLENOID BEING SUBSTANTIALLY NORMAL TO THE AXIS OF SAID ONE SOLENOID; CIRCUIT MEANS FOR COUPLING A SOURCE OF ALTERNATING CURRENT TO SAID SOLENOIDS; A FIRST DETECTOR COIL SPACED FROM SAID SOLENOIDS AND HAVING ITS AXIS SUBSTANTIALLY PERPENDICULAR TO THE AXIS OF THE BORE HOLE AND THE AXIS OF SAID OTHER SOLENOID; A PAIR OF DETECTOR COILS SPACED FROM BOTH SAID SOLENOIDS AND SAID FIRST DETECTOR COIL, THE AXES OF SAID PAIR OF DETECTORS BEING ALIGNED SUBSTANTIALLY PARALLEL TO THE AXIS OF THE BOREHOLE; A FOURTH DETECTION COIL SPACED FROM BOTH SAID SOLENOIDS AND SAID FIRST AND SAID PAIR OF DETECTOR COILS AND HAVING ITS AXIS ALIGNED WITH THE AXIS OF SAID SOLENOID; A SUPPORT MEMBER, SAID SOLENOIDS AND DETECTOR COILS BEING MOUNTED ON SAID SUPPORT MEMBER IN A SPACED POSITION; ROTATION MEANS COUPLED TO SAID SUPPORT MEMBER FOR ROTATING SAID SOLENOIDS AND SAID SUPPORT MEMBER FOR ROTATING SAID AXIS SUBSTANTIALLY PARALLEL WITH THE AXIS OF THE BOREHOLE, CIRCUIT MEANS COUPLING SAID DETECTOR COILS TOGETHER TO FORM DETECTOR COIL SYSTEMS AND RECORDING MEANS COUPLED TO SAID DETECTOR COIL SYSTEMS TO RECORD SIGNALS RELATED TO THE SIGNALS INDUCED IN SAID DETECTOR COILS WHEN SAID SOLENOIDS ARE ENERGIZED FROM SAID ALTERNATING CURRENT SOURCE.