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Monte Carlo simulation of the neutron lifetime logging tool

Conference · · Trans. Am. Nucl. Soc.; (United States)
OSTI ID:5515958
The decay time of neutron pulses in a medium provides a measure of the macroscopic capture cross section of the medium. This principle has long been exploited in oil well logging to differentiate between hydrocarbon-bearing rock formations and water-bearing formations and to detect changes in the water saturation during the production period. The logging tool typically contains a 14-MeV pulsed neutron generator and two NaI(Tl) scintillation detectors, which detect the neutron capture gamma rays. The interpretation of the measured time constant in terms of the cross section of the formation is not straightforward because of the effect of the borehole environment on neutron transport. To assist in log interpretation and in tool design, we have initiated a program to model the response of such neutron lifetime tools by Monte Carlo techniques. In contrast to prior work using large general-purpose Monte Carlo codes such as MCNP or SAMCE, our effort focuses on the development of an efficient program that can run on relatively small minicomputers. The project is sponsored jointly by several corporations and is based on our prior success with the simulation of neutron capture gamma-ray analyzers.
Research Organization:
North Carolina State Univ., Raleigh
OSTI ID:
5515958
Report Number(s):
CONF-860610-
Conference Information:
Journal Name: Trans. Am. Nucl. Soc.; (United States) Journal Volume: 52
Country of Publication:
United States
Language:
English