Correlation between Measurements and Monte-Carlo Calculations for the NNTE Logging-Tool

Abstract

A correlation between Monte-Carlo simulations of the NNTE geophysical neutron logging-tool response and measurements made on the rock blocks at the calibration facility in Zielona Góra (Poland) has been examined. The NNTE tool is a recent achievement of Polish geophysicists. It is equipped with a neutron source and three detectors. The tool is designed to measure the thermal neutron absorption cross-section of geological formations in situ. The computer modelling is intended to complete the calibration measurements with simulated experiments in complicated borehole situations. A good correspondence between the simulated and real experiments is obvious demand. The simulations have been performed using the MCNP4C computer code. In the first approach elemental compositions of block rock matrices have been taken directly from the results of a chemical analysis. In the second approach boron B-10 has been added to the elemental compositions of rocks to compensate the difference between their absorption cross-section calculated from the elemental compositions and those known from the laboratory measurements. The very good agreement has been obtained between results of calculations and measurements. The high correlation creates the basis for further research on the influence of absorption cross-section of geological formation on the NNTE tool response.