Factors affecting Thermal Neutron Lifetime Measurements

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D. W. Hilchie, W. R. Mills, C. L. Dennis
and W. W. Givens, Mobil Research & Development Corporation

Abstract

FACTORS AFFECTING THERMAL NEUTRON LIFETIME MEASUREMENTS By By D. W. Hilchie, W. R. Mills, C. L. Dennis D. W. Hilchie, W. R. Mills, C. L. Dennis and W. W. Givens and W. W. Givens Mobil Research & Development Corporation Mobil Research & Development Corporation Field Research Laboratory Field Research Laboratory Dallas, Texas Dallas, Texas FACTORS AFFECTING THERMAL NEUTRON LIFETIME MEASUREMENTS FACTORS AFFECTING THERMAL NEUTRON LIFETIME MEASUREMENTS By By D. W. Hilchie, W. R. Mills, C. L. Dennis D. W. Hilchie, W. R. Mills, C. L. Dennis and W. W. Givens and W. W. Givens I. INTRODUCTION I. INTRODUCTION Thermal neutron lifetime logging is a technique which measures Thermal neutron lifetime logging is a technique which measures the rate of die away of thermal neutrons or the resulting capture the rate of die away of thermal neutrons or the resulting capture gamma rays. This relatively new logging method has been very success gamma rays. This relatively new logging method has been very success ful in the detection of gas and oil bearing reservoirs. This tech- ful in the detection of gas and oil bearing reservoirs. This tech nique is more sensitive to fluid saturations than the older chlorine nique is more sensitive to fluid saturations than the older chlorine logging devices but is relatively insensitive to cement variations logging devices but is relatively insensitive to cement variations behind the casing and to borehole fluids. The older chlorine logs were behind the casing and to borehole fluids. The older chlorine logs were not only sensitive to these ”borehole” influences but also the chlorine not only sensitive to these ”borehole” influences but also the chlorine partially masked by the capture gamma rays from iron partially masked by the capture gamma rays from iron gamma rays were gamma rays were in the casing.