Microstructural Characterization of Siltstone and Sandstone Pore Space by X-Ray Microtomography

Abstract

Microstructural parameter assessment of reservoir rocks is extremely important for oil companies. In this regard, computerized X-ray microtomography (mu-CT) has proven to be an exceptionally useful methodology for the analysis of these rocks, since it provides significant microstructural parameters, such as porosity, permeability, and pore distribution. X-ray microtomography is a relatively novel non-destructive technique in the petroleum area which, besides enabling the reuse of already measured samples, also provides 2-D and 3-D images, as well as a 3-D mathematical model of the sample. This technique has the great advantage that it does not require sample preparation, allowing the reuse of the sample and also reducing the measurement time. A Skyscan model 1172 microtomograph was used for the acquisition of microtomographic data from the reservoir rocks. This work presents results of porosity and pore size distribution of six sandstones and two siltstones. Most of the analyzed samples from the Tibagi River basin had porosity below 10 %, except for the PG6 and PG8 samples, which presented 12 % and 13 %, respectively. Maximum pore radius ranged from 8 to 59 nm for sandstones and from 5 to 6 mu m for siltstones.