3D pore space characterization for classification of flow properties of reservoir rocks

A method of obtaining petrophysical and single- and multi-phase properties of reservoir rocks without the use of Special Core Analysis techniques is presented. The approached involved three-dimensional image reconstruction from 2-D images of reservoir rocks obtained by micro-computer tomography. Two rock samples were used for the study, namely, a Carbonate-28 rock sample and a Castlegate sandstone. The Carbonate-28 sample was studied at two different resolutions of 1.33 microns and 0.133 microns; while the Castlegate sandstone was investigated at a resolution of 5.6 microns. Network models were extracted from the pore architecture models (PAMs) obtained from the 3-D image reconstruction. The geometrical and topological properties of the extracted networks were then studied; this was followed by numerical flow simulation to derive the single- and multi-phase properties of the rocks studied. The geometrical and topological characteristics of the reconstructed pore architecture models were analysed with the aid of a pore analysis software tool (PAT). The main geometry and topological – characteristics studied included the pore size distribution, pore shape factor, and pore connectivity (in terms of coordination number and specific Euler number). Single- and multi-phase flow properties, namely: average porosity, absolute permeability, relative permeability, and capillary pressure, were measured for all three structures. Results obtained showed that pore size connectivity, and pore size distribution had the greatest impact on flow properties. Specifically, it was observed that the larger the interconnected pore sizes, the greater the absolute permeability; whereas observed permeability was low for interconnectedness involving smaller pores, even with high pore connectivity (that is, favorable specific Euler number). These results can be applied in reservoir characterization to generate flow properties for reservoir rocks; which can be utilized in reservoir simulation and reservoir engineering calculations.