Correlation of geophysical logs

Claim 1

IN GEOPHYSICAL EXPLORATION WHEREIN A FIRST LOG, OBTAINED FROM A FIRST BOREHOLE AND INDICATIVE OF THE SUBSURFACE LAYERING OF THE EARTH ADJACENT SAID FIRST BOREHOLE, IS CROSS-CORRELATED WITH AT LEAST AN OPERATOR PORTION OF A SECOND LOG, OBTAINED FROM A SECOND BOREHOLE AND INDICATIVE OF THE SUBSURFACE LAYERING OF THE EARTH ADJACENT SAID SECOND BOREHOLE, TO PRODUCE A CROSS-CORRELATION HAVING HAVING A MAXIMUM OCCURRING AT A TIME INDICATIVE OF THE DIP OF THE SUBSURFACE LAYERING BETWEEN SAID FIRST AND SAID SECOND BOREHOLES, AND WHEREIN SAID FIRST AND SAID SECOND LOGS INCLUDE VARIATIONS INDICATIVE OF CHANGES IN SAID SUBSURFACE LAYERING AND A MEAN COMPONENT OF MAGNITUDE WHICH CHANGES SLOWLY WITH RESPECT TO SAID VARIATIONS, THE IMPROVEMENT COMPRISING GENERATING A FIRST ELECTRICAL SIGNAL VARYING AS A FUNCTION OF THE SUBSURFACE LAYERING AS REPRESENTED BY THE FIRST LOG, GENERATING A SECOND ELECTRICAL SIGNAL VARYING AS A FUNCTION OF THE SUBSURFACE LAYERING AS REPRESENTED BY AT LEAST THE OPERATOR PORTION OF THE SECOND LOG, APPLYING SAID FIRST AND SECOND ELECTRICAL SIGNALS TO A HIGH-PASS FILTER TO CANCEL THE SLOWLY CHANGING MEAN COMPONENTS AND THEREBY PRODUCE THIRD AND FOURTH ELECTRICAL SIGNALS WHOSE VARIATION IN AMPLITUDE WITH RESPECT TO AN AVERAGE VALUE IS GREATER REPECIVELY THAN THE VARIATION IN AMPLITUDE WITH RESPECT TO AN AVERAGE VALUE OF SAID FIRST AND SECOND ELECTRICAL SIGNALS, AND APPLYING SAID THIRD AND FOURTH ELECTRICA SIGNALS TO A CORRELATOR TO PRODUCE BY CROSS-CORRELATION A CORRELOGRAM HAVING A MAXIMUM IDENTIFYING THE TIME SEPARATION BETWEEN SAID OPERATOR PORTION AND ITS COUNTERPART IN SAID FIRST LOG TO INDICATE THE DIP OF SUBSURFACE LAYERING BETWEEN SAID FIRST AND SECOND BOREHOLES.