Acoustic well logging method and apparatus

Claim 1

IN A SYSTEM FOR LOGGING A CASED BOREHOLE EXTENDING INTO THE EARTH''S FORMATIONS AND HAVING A CEMENT LAYER BETWEEN THE EXTERIOR OF THE CASING AND THE WALLS OF THE BOREHOLE THE COMBINATION OF A DOWNHOLE TOOL WITHIN THE BOREHOLE; A CABLE EXTENDING FROM THE DOWNHOLE TOOL THROUGH THE BOREHOLE TO THE EARTH''S SURFACE; MEANS AT THE SURFACE COOPERATING WITH THE CABLE TO RAISE AND LOWER THE DOWNHOLE TOOL WITHIN THE BOREHOLE; AND EQUIPMENT AT THE SURFACE CONNECTED TO SAID CABLE; SAID DOWNHOLE TOOL COMPRISING A CASING COLLAR LOCATOR FOR PROVIDING COLLAR LOCATING SIGNALS HAVING AT LEAST ONE CHARACTERISTIC AFFECTED BY THE CASING THICKNESS, A TRANSMITTER FOR REPEATEDLY EMITTING THROUGH THE BOREACOUSTIC PULSES FOR TRANSMISSION THROUGH THE BOREHOLE CASING AND THROUGH THE EARTH FORMATIONS COUPLED TO THE CASING THROUGH THE CEMENT LAYER AND FOR PRODUCING A SYNCHRONIZING PULSE COINCIDENT WITH EACH ACOUSTIC PULSE, AND A RECEIVER SPACED FROM THE TRANSMITTER IN A DIRECTION EXTENDING LONGITUDINALLY OF THE BOREHOLE FOR RECEIVING SAID ACOUSTIC PULSES AND FOR DEVELOPING CORRESPONDING ELECTRICAL SIGNALS; MEANS FOR TRANSMITTING TO SAID SURFACE EQUIPMENT OVER SAID CABLE SAID COLLAR LOCATING SIGNALS, SAID SYNCHRONIZING PULSES AND SAID ELECTRICAL SIGNALS; SAID SURFACE EQUIPMENT INCLUDING RECORDING MEANS CONNECTED TO SAID CABLE FOR DEVELOPING LONGITUDINALLY ALONG A RECORDING MEDIUM AND IN RESPONSE TO SAID SYNCHRONIZING PULSES AND SAID ELECTRICAL SIGNALS A FIRST CURVE PROPORTIONAL TO THE TRAVEL TIME OF THE ACOUSTIC PULSES FROM THE TRANSMITTER TO THE RECEIVER AT THE DIFFERENT BOREHOLE DEPTHS, MEANS RESPONSIVE TO SAID ELECTRICAL SIGNALS FOR DEVELOPING LONGITUDINALLY ALONG SAID RECORDING MEDIUM A SECOND CURVE PROPORTIONAL TO THE AMPLITUDE OF THE ELECTRICAL SIGNALS AT THE DIFFERENT BOREHOLE DEPTHS AND SPACED FROM SAID FIRST CURVE IN A DIRECTION EXTENDING TRANSVERSELY OF SAID MEDIUM, AND MEANS CONNECTED TO SAID CABLE AND RESPONSIVE TO VARIATIONS IN SAID CHARACTERISTIC OF SAID COLLAR LOCATING SIGNALS FOR PROVIDING AN INDICATION ON