Petrophysical analysis of limestone rocks by nuclear logging and 3D high-resolution X-ray computed microtomography

This study presents the pore-space system analysis of the 2-ITAB-1-RJ well cores, which were drilled in the Sao Jose do Itaborai Basin, in the state of Rio de Janeiro, Brasil. The analysis presented herein has been developed based on two techniques: nuclear logging and 3D high-resolution X-ray computed microtomography. Nuclear logging has been proven to be the technique that provides better quality and more quantitative information about the porosity using radioactive sources. The Density Gamma Probe and the Neutron Sonde used in this work provide qualitative information about bulk density variations and compensated porosity of the geological formation. The samples obtained from the well cores were analyzed by microtomography. The use of this technique in sedimentary rocks allows quantitative evaluation of pore system and generates high-resolution 3D images (∼microns order). The images and data obtained by microtomography were integrated with the response obtained by nuclear logging. The results obtained by these two techniques allow the understanding of the pore-size distribution and connectivity, as well as the porosity values. Both techniques are important and they complement each other.