Carbonates Pore System Characterization Using Multi-Scale Digital Rock Analysis

Detailed understanding of the pore scale rock properties at micron resolution is essential for proper formation evaluation, which includes borehole log interpretation. Micro computed tomography (mCT) imaging becomes the standard tool to generate the framework, on which petrophysical models are applied. The advantage of petrophysical simulation is that the results are obtained with quick turnaround and at a lower cost compared to traditional experimental laboratory work.

This study presents a new multiscale approach to tackle the characterization of heterogeneous multimodal carbonate rocks using digital rock analysis based on mCT scanning. Multimodal carbonates are difficult to investigate because of a wide range of pore sizes, which runs the gamut from vugs (mm scale) down to micro-pores (sub-micron scale). We acquired mCT scans employing variable volumes of rock and at multiple resolutions for several carbonate samples. This resulted in a coarse- and a fine-scale 3D representations of the pores for each sample, on which the petrophysical modelling was conducted. The modelling results, particularly, the pore throat size distribution is a special feature that is used for petrophysical rock typing. Covering all pore sizes in a single mCT scan is not possible for the majority of carbonate formations.