VERFAHREN ZUR SIMULTANEN BESTIMMUNG DES SAUERSTOFF- UND SILIZIUMANTEILES VON ERDFORMATIONEN IM BEREICH EINES BOHRLOCHES

Disclosed is a well logging system for performing a continuous log of the oxygen and silicon content of earth formations in the vicinity of a well bore. A downhole sonde housing a pulsed source of 14 mev neutrons is used to irradiate earth formations in the vicinity of the well bore. A NaI (T1) detector spaced approximately 253/8 inches from the source detects gamma rays caused by neutron activation of elemental oxygen and silicon in the formations and produces voltage pulses representative of the elemental oxygen and silicon. The voltage pulses are transmitted to the surface where they are separated, corrected for background radiation and plotted continuously as a function of bore hole depth. The resultant well log traces may be interpreted in terms of lithology or formation water saturation by the use of disclosed techniques.