Acoustic logging apparatus with selectable transmitters and receivers

Claim 1

IN APPARATUS FOR ACOUSTIC LOGGING OF EARTH FORMATIONS SURROUNDING A WELL BORE INCLUDING A LOGGING TOOL HAVING A PLURALITY OF ACOUSTIC TRANSMITTERS AND RECEIVERS AND SUSPENDED IN SAID WELL BORE BY CONDUCTIVE CABLE MEANS EXTENDING FROM THE SURFACE OF THE EARTH, SURFACE EQUIPMENT COMPRISING, A MASTER PULSE SOURCE FOR GENERATING PERIODIC PULSES HAVING A SPACING BETWEEN SUCCESSIVE PULSES DEFINING A MEASUREMENT INTERVAL, SIGNAL GENERATOR MEANS FOR SELECTIVELY GENERATING DURING AN INITIAL PORTION OF EACH MEASUREMENT INTERVAL A CONTROL SIGNAL REPRESENTATIVE OF ONE OF A PLURALITY OF POSSIBLE PAIRS OF TRANSMITTERS AND RECEIVERS IN SAID TOOL, DETECTING MEANS RENDERED OPERATIVE DURING EACH MEASUREMENT INTERVAL AFTER GENERATION OF SAID CONTROL SIGNAL TO RECEIVE ELECTRICAL SIGNALS FROM SAID TOOL, AND MEANS RESPONSIVE TO THE OUTPUT OF SAID DETECTOR MEANS FOR RECORDING SIGNALS REPRESENTATIVE OF A CHARACTERISTIC OF SAID FORMATIONS AS A FUNCTION OF DEPTH IN THE WELL BORE.