Analysis of induced polarization and radiometric logs from a test borehole in Hawkesbury Sandstone

Abstract

Distinctive resistivity and induced polarization (IP) logs, together with long spaced density, gamma ray and neutron- neutron logs' are presented from a test borehole a in sedimentary environment typical of that encountered in the Sydney region. The high-resolution continuous IP logs are the initial results from a more extensive study aimed at investigating the application of resistivity and IP logging to non-metalliferous environments in Australia. The electrical logging arrays include the dipole-dipole array and the Schlumberger array various electrode spacings. The resistivity log for the small spacing dipole-dipole array (0.25 m) shows a close correlation with the neutron-neutron log and identifies sandstone porosity variations along with the presence of conductive argillaceous horizons. Continuous logs of chargeability windows provide a pictorial display of variations in the rate of polarization decay along the hole. Computer aided interpretation of the resistivity and IP logs for a key interval has resulted in a model of 28 layers. The theoretical logs show an excellent match with field logs. These results confirm that the dipole-dipole array Provides better resolution of thin conductive layers than conventional logging configurations.