Single conductor acoustic well logging system

Claim 1

IN A SYSTEM FOR LOGGING A CASED BOREHOLE EXTENDING INTO THE EARTH''S FORMATIONS AND HAVING CEMENT INTERPOSED BETWEEN THE EXTERIOR OF THE CASING AND THE WALLS OF THE BOREHOLE THE COMBINATION OF A DOWNHOLE TOOL WITHIN THE BOREHOLE; A CABLE HAVING A SINGE INNER CONDUCTOR WITHIN AN OUTER SHEATH AND 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 TH 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 LEST ONE CHARACTERISTIC AFFECTED BY THE CASING COLLARS, A TRANSMITTER FOR REPEATEDLY EMITTING SPACED APART ACOUSTIC PULSE FOR TRANSMISSON THROUGH THE CASING AND THROUGH THE EARTH FORMATIONS COUPLED TO THE CASING VIA SAID CEMENT AND FOR PRODUCING A SYNCHRONIZING PULSE COINCIDENT WITH EACH ACOUSTIC PULSE, 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 SURFACE EQUIPMENT OVER SAID SINGLE CONDUCTOR SAID COLLAR LOCATING SIGNALS, SAID SYNCHRONZING PULSES AND SAID ELECTRICAL SIGNALS; SAID SURFACE EQUIPMENT INCLUDING MEANS CONNECTED TO SAID INNER CONDUCTOR FOR SEPARATING SAID COLLAR LOCATING SIGNAL, SAID SYNCHRONIZING PULSES AND SAID ELECTRICAL SIGNALS, RECORDING MEANS INCLUDING SAID SEPARATING MEANS FOR DEVELOPING LONGITUDINALLY ALONG A RECORDING MEDIUM AND IN RESPONE 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, ADDITIONAL RECORDING MEANS CONNECTED TO SAID INNER CONDUCTOR AND RESPONSIVE TO SAID SYNCHRONIZING PULSES AND SAID ELECTRICAL SIGNALS FOR DEVELOPING LONGITUDINALLY ALONG SAID MEDIUM A SECOND CURVE PROPORTIONAL TO THE AMPLITUDE OF THE ELECTRICAL SIGNALS AT THE DIFFERENT BOREHOE DEPTHS, SAID FIRST AND SECOND CURVES BEING DISPLACED TRANSVERSELY OF SAID RECORDING MEDIUM AND HAVING A COMMON TIME BASE SO THAT TRANSVERSELY ALIGNED POINTS ON SAID CURVES REPRESENT A COMMON BOREHOLE DEPTH, WHEREBY THE ACOUSTIC PULSES ARRIVING AT SAID RECEIVER AFTER PASSING THROUGH THE CASING AND HAVING AN AMPLITUDE REPRESENTED BY SAID SECOND CURVE CAN BE READILY DISTINGUISHED ON SAID SECOND CURVE FROM THE ACOUSTIC PULSES ARRIVING AT SAID RECEIVER AFTER PASSING THROUGH THE CEMENT AND THE EARTH FORMATIONS BY THE DIFFERENCES IN TRAVEL TIME INDICATED ON SAID FIRST CURVE, THE DIFFERENCES IN AMPLITUDE OF THE SIGNALS RECORDED ON SAID SECOND CURVE BEING INDICATIVE OF THE RELATIVE AMOUNTS OF ENERGY OF SAID ACOUSTIC PULSES PASSING THROUGH SAID CASING AND THROUGH THE CEMENT AND THE EARTH FORMATIONS SO THAT HIGH AMPLITUDE RECORDINGS ON SID SECOND CURVE REPRESENT BOREHOLE DEPTHS WHERE A LARGE PROPORTION OF THE ENERGY OF SAID ACOUSTIC PULSES REACHES SAID RECEIVER AFTER PASSING THROUGH SAID CASING WHILE RELATIVELY LOWER AMPLITUDE RECORDINGS ON SAID SECOND CURVE REPRESENT BOREHOLE DEPTHS WHERE A SUBSTANTIAL PORTION OF THE ENERGY OF SAID ACOUSTIC PULSES IS COUPLED FROM THE CASING THROUGH THE CEMENT INTO THE EARTH FORMATIONS, SAID RECORDING MEANS ALSO INCLUDING MEANS FOR PROVIDING ON SAID MEDIUM AN INDICATION FROM WHICH THE DEPTHS OF THE CASING COLLARS MAY BE DETERMINED.