Method and apparatus for acoustical logging wherein the amplitude and frequency of the impulse are determined

Claim 1

APPARATUS FOR LOGGING A FORMATION PIERCED BY A BOREHOLE CONTAINING A WELL CASING AND A CEMENT SHEATH BETWEEN THE CASING AND FORMATION TO DETERMINE THE EFFECTIVENESS OF THE BOND BETWEEN THE CASING AND CEMENT SHEATH AND BETWEEN THE CEMENT SHEATH AND THE FORMATION, SAID APPARATUS COMPRISING: A SUBSURFACE INSTRUMENT; SURFACE EQUIPMENT AND A CABLE, SAID CABLE SUPPORTING SAID INSTRUMENT AND ELECTRICALLY CONNECTING SAID INSTRUMENT AND SAID SURFACE EQUIPMENT; SAID INSTRUMENT INCLUDING: TRANSMITTER MEANS FOR GENERATING AN ACOUSTIC SHOCK WAVE, RECEIVER MEANS FOR DETECTING AN ACOUSTIC ECHO PULSE TRAIN RESULTING FROM SAID SHOCK WAVE AND CONVERTING SAID ACOUSTIC ECHO TRAIN INTO CORRESPONDING ELECTRICAL SIGNALS; AND MEANS FOR APPLYING SAID SIGNALS TO SAID CABLE FOR TRANSMISSION TO SAID SURFACE EQUIPMENT; SAID SURFACE EQUIPMENT INCLUDING: MEANS CONNECTED TO RECEIVE SAID SIGNALS FROM SAID CABLE FOR DETERMINING THE AMPLITUDE OF THE FIRST ARRIVAL OF SAID SIGNALS AND PROVIDING AN INDICATION OF SAID AMPLITUDE, MEANS CONNECTED TO RECEIVE SAID SIGNALS FROM SAID CABLE FOR COUNTING THE NUMBER OF PULSES PER UNIT TIME OCCURRING IN SAID ECHO TRAIN AND PROVIDING AN INDICATION OF SAID NUMBER, AND MEANS FOR RECORDING SAID INDICATIONS IN CORRELATION AS A FUNCTION OF DEPTH WHEREBY IRREGULARITIES IN BONDING OF THE CEMENT SHEATH MAY BE DETERMINED.