Method of compensating for the iron casing effect in radioactive well logging

Claim 1

A METHOD OF RADIOACTIVE LOGGING OF FORMATIONS TRANSVERSED BY AN IRON-CASED BOREHOLD WHEREIN THERE IS REDUCED THE EFFECT OF IRON BACKGROUND SECONDARY RADIATION PRODUCED BY THE IRON OF THE BOREHOLE CASING WHEN IRRADIATED WITH PRIMARY RADIATION, COMPRISING THE STEPS OF: PRIOR TO LOGGING, IRRADIATING WITH SAID PRIMARY RADIATION AN IRON ENVIRONMENT FREE OF CHLORINE AND PRODUCTIVE OF SECONDARY RADIATION REPRESENTATIVE OF SAID IRON BACKGROUND RADIATION, DETECTING THE SECONDARY RADIATION PRODUCED FROM SAID IRON ENVIRONMENT, OBTAINING A FIRST INDICATION REPRESENTATIVE OF THE COUNT RATE OF SAID DETECTED SECONDARY RADIATION, IRRADIATING SAID FORMATIONS THROUGH SAID IRON CASING WITH SAID PRIMARY RADIATION, DETECTING WITHIN SAID BOREHOLE THE SECONDARY RADIATION RESULTING FROM THE IRRADIATION OF SAID FORMATIONS, PRODUCING AS A FUNCTION OF DEPTH A SECOND INDICATION REPRESENTATIVE OF THE COUNT RATE OF THE SECONDARY RADIATION RESULTING FROM THE IRRADIATION OF SAID FORMATIONS, AND COMBINING SAID TWO INDICATIONS TO OBTAIN A RESULTANT INDICATION OF THE COUNT RATE OF SECONDARY RADIATION FREE FROM IRON BACKGROUND RADIATION.

Claim 2

A METHOD OF RADIOACTIVE LOGGING OF FORMATIONS TRANSVERSED BY AN IRON-CASED BOREHOLD WHEREIN THERE IS REDUCED THE EFFECT OF IRON BACKGROUND SECONDARY RADIATION PRODUCED BY THE IRON OF THE BOREHOLE CASING WHEN IRRADIATED WITH PRIMARY RADIATION, COMPRISING THE STEPS OF: PRIOR TO LOGGING, IRRADIATING WITH SAID PRIMARY RADIATION AN IRON ENVIRONMENT FREE OF CHLORINE AND PRODUCTIVE OF SECONDARY RADIATION REPRESENTATIVE OF SAID IRON BACKGROUND RADIATION, DETECTING THE SECONDARY RADIATION PRODUCED FROM SAID IRON ENVIRONMENT, OBTAINING A FIRST INDICATION REPRESENTATIVE OF THE COUNT RATE OF SAID DETECTED SECONDARY RADIATION, IRRADIATING SAID FORMATIONS THROUGH SAID IRON CASING WITH SAID PRIMARY RADIATION, DETECTING WITHIN SAID BOREHOLE THE SECONDARY RADIATION RESULTING FROM THE IRRADIATION OF SAID FORMATIONS, PRODUCING AS A FUNCTION OF DEPTH A SECOND INDICATION REPRESENTATIVE OF THE COUNT RATE OF THE SECONDARY RADIATION RESULTING FROM THE IRRADIATION OF SAID FORMATIONS, AND COMBINING SAID TWO INDICATIONS TO OBTAIN A RESULTANT INDICATION OF THE COUNT RATE OF SECONDARY RADIATION FREE FROM IRON BACKGROUND RADIATION.