Apparatus for locating a zone of lost circulation

Claim 1

AN APPARATUS FOR LOCATING A PERMEABLE FORMATION TRAVERSED BY A WELL BORE HOLE CONTAINING FLUID AND INTO WHICH FORMATION FLUID FROM THE BORE HOLE IS PASSING, COMPRISING A RADIATION DETECTOR ADAPTED TO BE PASSED THROUGH THE BORE HOLE SUSPENDED FROM A CONDUCTOR CABLE, MEANS FOR INDICATING THE DEPTH OF SAID DETECTOR IN THE BORE HOLE, MEANS FOR INDICATING THE OUTPUT OF THE DETECTOR, AND AT LEAST ONE FLEXIBLE, RADIOACTIVE STREAMER NORMALLY DISPOSED CLOSED TO SAID DETECTOR IN MOVABLE RELATION THEREWITH, THE ARRANGEMENT BEING SUCH THAT AS THE DETECTOR PASSES THROUGH THE BORE HOLE SAID STREAMER WILL REMAIN CLOSE TO THE DETECTOR UNTIL THE DETECTOR REACHES THE PROXIMITY OF SAID FORMATION WHEN THE FLOW OF FLUID INTO THE FORMATION WILL CAUSE THE STREAMER TO MOVE AWAY FROM THE DETECTOR, THUS PROVIDING A SUDDEN DECREASE IN THE OUTPUT OF THE DETECTOR AND THEREBY AN INDICATION OF THE DEPTH OF SAID FORMATION.