title: Rock porosity quantification by dual-energy X-ray computed microtomography.
abstract: Porous media investigation by X-ray microtomography allows obtaining valuable quantitative and qualitative information, while preserving sample integrity. Modern X-ray nanotomography or Synchrotron radiation systems may distinguish structures sized only hundreds of nanometers. However, pores sized less than a few microns (microporosity) may be undetectable due to the system's spatial resolution and noise in microfocus sources, compromising the quality of the measurement. In this study a dual-energy methodology was developed to generate density-based images from two scans made at two different voltages (80kV and 130KV) with a microfocus bench-top microtomography system. The images obtained were quantized in 256 gray levels, where the lowest value (zero) corresponded to voids and the highest value (255) corresponded to the densest regions mapped. From density images and single energy images, porosity was evaluated and compared. Results indicate that density images present better results than single energy images when both are compared with porosity obtained by the helium injection method. In addition, images acquired in dual-energy show good agreement with the sample's real density values.
authors.affiliation: Nuclear Engineering Program, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil. Electronic address: ateles@con.ufrj.br.
authors.forename: A P
authors.initials: AP
authors.lastname: Teles
authors.affiliation: Nuclear Engineering Program, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: I
authors.initials: I
authors.lastname: Lima
authors.affiliation: Nuclear Engineering Program, Federal University of Rio de Janeiro, Rio de Janeiro, Brazil.
authors.forename: R T
authors.initials: RT
authors.lastname: Lopes
keywords: Density; Dual-energy; Porosity; Rocks; X-ray microtomography