Neutron Absorption Measurement of Cores

G. Stufflebeme, C. W. Tittle, R. A. Skopec

The first commercial adaptation of a steady-state system for measuring the thermal-neutron-absorption cross section of core samples and liquids uses certain improvements, including smaller (200 cm³), and dry as well as water-saturated samples. The core samples can be solid or crushed. The method is fast and accurate. Data on reproducibility and system performance will be presented.

Measuring the neutron-absorption cross section can be important for two reasons. The first (and more important) reason is to correct log anomalies. The presence of certain elements such as boron or chlorine, which have large absorption cross sections, can lead to faulty log values. Obtaining a correct measurement for the absorption cross section of samples helps determine water saturation from pulsed neutron logs since some uncertainty is removed in its calculation. The presence of elements with large absorption cross sections also leads to poor porosity values from compensated neutron logs.

The ability to measure the neutron-absorption cross section also helps calibrate the compensated neutron logging tool using samples from the tool's test well. Tool measurements can then be compared with laboratory measurements.

AAPG Search and Discovery Article #91037©1987 AAPG Southwest Section, Dallas, Texas, March 22-24, 1987.