Induced gamma ray logging at a plurality of levels in a well bore

Claim 1

A METHOD OF LOGGING EARTH FORMATIONS TRAVERSED BY A BORE, THE FORMATIONS INCLUDING AT LEAST A FIRST ELEMENT THAT IS SUSCEPTIBLE OF INDUCED RADIOACTIVITY IN RESPONSE TO INTERACTION WITH RELATIVELY LOW ENERGY NEUTRONS TO PRODUCE RADIOACTIVE PRODUCTS AND A SECOND ELEMENT THAT IS SUSCEPTIBLE OF INDUCED RADIOACTIVITY IN RESPONSE TO INTERACTION WITH RELATIVELY HIGH ENERGY NEUTRONS TO PRODUCE RADIOACTIVE PRODUCTS, SAID RADIOACTIVE PRODUCTS OF EACH OF SAID FIRST AND SECOND ELEMENTS HAIVNG SUBSTANTIALLY THE SAME HALF-LIVES, SAID METHOD COMPRISING THE STEPS OF BOMBARDING FOR A PREDETERMINED INTERVAL THE FORMATIONS ADJACENT A FIRST LEVEL IN THE BORE WITH NEUTRONS OF RELATIVELY HIGH ENERGIES; DURING A SEOCND PREDETERMINED INTERVAL SUBSEQUENT TO SAID INTERVAL OF BOMBARDMENT, CONTINUOUSLY MEASURING, SIMULTANEOUSLY AT A PLURALITY OF LEVELS IN SAID BORE SPACE LONGITUDINALLY WITH RESPECT TO THE AXIS OF SAID BORE FROM SAID FIRST LEVEL OF BOMBARDMENT, THE GAMMA-RAY ACTIVITY RESULTING FROM THE DECAY OF HTE RADIOACTIVE PRODUCTS OF SAID FIRST AND SECOND ELEMENTS PRODUCED AS A RESULT OF SAID BOMBARDMENT; AND RECORDING SUCCESSIVE INDICATIONS REPRESENTATIVE OF SAID GAMMA-RAY ACTIVITY AS A FUNCTION OF TIME MEASURED AT EACH OF SAID PLURALITY OF LEVELS AFTER TERMINATION OF SAID BOMBARDMENT TO ENABLE A DETERMINATION OF THE RELATIVE QUANTITIES OF SAID FIRST AND SECOND ELEMENTS IN SAID FORMATIONS.

Claim 2

A METHOD OF LOGGING EARTH FORMATIONS TRAVERSED BY A BORE, THE FORMATIONS INCLUDING AT LEAST A FIRST ELEMENT THAT IS SUSCEPTIBLE OF INDUCED RADIOACTIVITY IN RESPONSE TO INTERACTION WITH RELATIVELY LOW ENERGY NEUTRONS TO PRODUCE RADIOACTIVE PRODUCTS AND A SECOND ELEMENT THAT IS SUSCEPTIBLE OF INDUCED RADIOACTIVITY IN RESPONSE TO INTERACTION WITH RELATIVELY HIGH ENERGY NEUTRONS TO PRODUCE RADIOACTIVE PRODUCTS, SAID RADIOACTIVE PRODUCTS OF EACH OF SAID FIRST AND SECOND ELEMENTS HAIVNG SUBSTANTIALLY THE SAME HALF-LIVES, SAID METHOD COMPRISING THE STEPS OF BOMBARDING FOR A PREDETERMINED INTERVAL THE FORMATIONS ADJACENT A FIRST LEVEL IN THE BORE WITH NEUTRONS OF RELATIVELY HIGH ENERGIES; DURING A SEOCND PREDETERMINED INTERVAL SUBSEQUENT TO SAID INTERVAL OF BOMBARDMENT, CONTINUOUSLY MEASURING, SIMULTANEOUSLY AT A PLURALITY OF LEVELS IN SAID BORE SPACE LONGITUDINALLY WITH RESPECT TO THE AXIS OF SAID BORE FROM SAID FIRST LEVEL OF BOMBARDMENT, THE GAMMA-RAY ACTIVITY RESULTING FROM THE DECAY OF HTE RADIOACTIVE PRODUCTS OF SAID FIRST AND SECOND ELEMENTS PRODUCED AS A RESULT OF SAID BOMBARDMENT; AND RECORDING SUCCESSIVE INDICATIONS REPRESENTATIVE OF SAID GAMMA-RAY ACTIVITY AS A FUNCTION OF TIME MEASURED AT EACH OF SAID PLURALITY OF LEVELS AFTER TERMINATION OF SAID BOMBARDMENT TO ENABLE A DETERMINATION OF THE RELATIVE QUANTITIES OF SAID FIRST AND SECOND ELEMENTS IN SAID FORMATIONS.