Method for gamma ray spectral analysis

Claim 1

APPARATUS FOR RADIOACTIVITY WELL LOGGING COMPRISING A SUBSURFACE INSTRUMENT CONTAINING A GAMMA RAY SOURCE COMPOSED OF RADIOACTIVE COBALT, A GAMMA RAY DETECTOR OF THE TYPE WHICH EMITS ELECTRICAL PULSES SYSTEMATICALLY RELATED TO THE ENERGY OF THE RESPECTIVE GAMMA RAYS INCIDENT THEREON, SHIELDING SUBSTANTIALLY OPAQUE TO GAMMA RAYS HAVING ENERGIES LESS THAN 500 KEV., MEANS URGING SAID SUBSURFACE INSTRUMENT AGAINST A WALL OF A WELL TO BE LOGGED, A PAIR OF SPACED RECESSES FORMED IN SAID SHIELDING ADJACENT THAT PORTION OF SAID INSTRUMENT WHICH IS NEAREST THE WALL OF THE WELL, SAID DETECTOR BEING MOUNTED IN ONE OF SAID RECESSES, SAID SOURCE BEING MOUNTED IN THE OTHER OF SAID RECESSES, A PLURALITY OF INDEPENDENT ELECTRONIC PULSE HEIGHT ANALYZER CIRCUITS EACH SUPPLIED WITH THE OUTPUT FROM SAID DETECTOR, ONE OF SAID CIRCUITS EMITTING A SIGNAL CORRESPONDING TO THE NUMBER OF GAMMA RAYS PER UNIT TIME INCIDENT ON SAID DETECTOR HAVING ENERGIES LESS THAN 100 KEV., A SECOND OF SAID CIRCUITS EMITTING A SIGNAL CORRESPONDING TO THE NUMBER OF GAMMA RAYS PER UNIT TIME INCIDENT ON SAID DETECTOR HAVING ENERGIES GREATER THAN 100 KEV. AND LESS THAN 150 KEV., A THIRD OF SAID CIRCUITS EMITTING A SIGNAL CORRESPONDING TO THE NUMBER OF GAMMA RAYS PER UNIT TIME INCIDENT ON SAID DETECTOR HAVING ENERGIES GREATER THAN 100 KEV. AND LESS THAN 500 KEV., A FOURTH OF SAID CIRCUITS EMITTING A SIGNAL CORRESPONDING TO THE NUMBER OF GAMMA RAYS PER UNIT TIME INCIDENT ON SAID DETECTOR HAVING ENERGIES GREATER THAN 500 KEV., AND LESS THAN 1 MEV., A FIFTH OF SAID CIRCUITS EMITTING A SIGNAL CORRESPONDING TO THE NUMBER OF GAMMA RAYS PER UNIT TIME INCIDENT ON SAID DETECTOR HAVING ENERGIES GREATER THAN 1 MEV., MEANS FOR TRANSMITTING SAID SIGNALS TO THE SURFACE OF THE EARTH, AND MEANS FOR INDEPENDENTLY RECORDING EACH OF SAID SIGNALS.