Quantitative analysis of reservoir rocks by microfocus X-ray computerised tomography M. Van Geet a, * , R. Swennen a , M. Wevers b a Fysico-chemische geologie, Katholieke Universiteit Leuven, Celestijnenlaan 200C, B-3001 Heverlee, Belgium b Department of MTM, Katholieke Universiteit Leuven, de Croylaan 2, B-3001 Heverlee, Belgium Received 7 April 1999; accepted 12 November 1999 Abstract Microfocus Computer Tomography (mCT) is a non-destructive imaging technique that allows visualisation of internal features within non-transparent objects such as sedimentary rocks. With resolution as good as 10 mm in three dimensions, this technique is highly superior to medical CT widely used in geology and material sciences. Superior resolution is achieved by decreasing the X-ray spot size, which allows a decrease in the penumbra effect and an increase in primary magnification by placing the sample close to the X-ray source. Since polychromatic X-ray sources are used, the technique is not free of artefacts. Application of filtering techniques is recommended to circumvent these artefacts and to achieve good quality images for quantitative analysis. Application of a dual energy approach allows quantification of density as well as effective atomic number distribution of internal features. As the technique acquires data in 3D, mCT provides an ideal tool to link 2D thin-section petrography to 3D petrophysical measurements or to be used within an upscaling approach. A number of applications and the use of dual energy density and effective atomic number characterisations are presented. Attention is also paid to some of the limitations of this technique.  2000 Elsevier Science B.V. All rights reserved. Keywords: X-rays; petrography; X-ray tomography; porosity 1. Introduction Computerised tomography (CT), originally devel- oped by the medical field, allows 2D or 3D recon- structions of internal features of an object. Because of its widespread use and application, geologists have implemented this technique in their studies (Welling- ton and Vinegar, 1987; Fabre et al., 1989; Raynaud et al., 1989; Swennen et al., 1990; Orsi et al., 1994; Boespflug et al., 1995; Verhelst et al., 1996). These studies have clearly demonstrated the power of CT with respect to classical petrography in geological research. However, one disadvantage of classical medical CT is that resolution is too low (lowest order of magnitude: 60 mm × 60 mm × 1 mm for detailed geological research, such as reservoir apprai- sal. Recent developments in the field of microfocus computer tomography (mCT) overcome much of this problem. These instruments are based on the same principle as medical CT scanners, but obtain much better resolution (presently as low as 10 mm × 10 mm × 10 mm: This contribution introduces the technique and discusses the usefulness of mCT in geological sciences especially in sedimentary geology. We believe that the technique should be used not only Sedimentary Geology 132 (2000) 25–36 0037-0738/00/$ - see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S0037-0738(99)00127-X www.elsevier.nl/locate/sedgeo * Corresponding author. E-mail address: Maarten.Vangeet@geo.kuleuven.ac.be (M. Van Geet).