Radioactivity well logging for determining the presence of hydrogen and chlorine

Claim 1

APPARATUS FOR CONDUCTING A RADIOACTIVITY WELL LOG COMPRISING AN INSTRUMENT HOUSING ADAPTED TO BE PASSED THROUGH A BORE HOLE TRAVERSING A PLURALITY OF EARTH FORMATIONS, SAID HOUSING CONTAINING A SOURCE OF FAST NEUTRONS, A FIRST DETECTING UNIT QUANTITATIVELY SENSITIVE TO GAMA RADIATION RETURNING TO THE BORE HOLE AS A RESULT OF IRRADIATION OF THE FORMATION BY NEUTRONS FROM THE NEUTRON SOURCE AND WHICH IS ADAPTED AND ARRANGED TO PROVIDE AN OUTPUT SIGNAL PRIMARILY INDICATIVE OF THE PRESENCE OF HYDROGEN IN SAID FORMATION AND SUBSTANTIALLY INSENSITIVE TO THE PRESENCE OF CHLORINE, SAID FIRST DETECTING UNIT COMPRISING A GAMMA RADIATION DETECTRO AND A PREDETERMINED QUANTITY OF NEUTRON ABSORBING MATERIAL POSITIONED IN THE VICINITY OF SAID DETECTOR AND CHARACTERIZED BY THE EMISSION OF RADIATION TO WHICH THE DETECTOR IS SENSITIVE, SAID DETECTOR BEING SUBSTANTIALLY UNSHIELDED WITH RESPECT TO SAID RADIATION EMITTED FROM SAID NEUTRON ABSORBING MATERIAL SUCH THAT SAID DETECTOR IS EXPOSED TO AT LEAST A MAJOR PORTION OF SAID RADIATION EMITTED FROM SAID NEUTRON ABSORBING MATERIAL AND TRAVELING TOWAR SAID DETECTOR, WHEREBY SAID DETECTOR IS RENDERED SENSITIVE TO BOTH NEUTRON-GAMMA RADIATION AND THERMAL NEUTRON RADIATION IN THE BORE HOLE RESULTING FROM SAID IRRADIATION OF THE FORMATION BY NEUTRONS, A SECOND RADIABEING ADAPTED TO PROVIDE A QUANTITATIVE SIGNAL OF THE GAMMA RADIATION RETURNING TO THE BORE HOLE AS A RESULT OF IRRADIATION BY NEUTRONS FROM THE NEUTRONS SOURCE AND