| Popis: |
Fluid flow properties in porous media are largely determined by the geometry and topology of the pore system, and so are the thermal, electrical and acoustic transport processes. To understand the relationship between these processes and pore geometry and topology, the pore system must be quantified, mapped, and evaluated. The most common approach to model the complex pore system of natural porous media is to represent the pore space by (most frequently overlapping) spheres, usually corresponding to pore bodies. The aim of this work is to develop an efficient and accurate tool to determine pore geometry and topology of the porous media system. Instead of overlapping pore-fitting spheres, we use independent spheres to fit individual pores and record the corresponding pore contact areas, which give unique pore size and connectivity relations. We use the resulting detailed information of pore size distribution and connectivity as a direct input to an invasion percolation simulator. Reservoir rock reconstructions, based on our Markov Chain Monte Carlo approach (Wu et al., Transport in Porous Media, 2005, accepted), are investigated to evaluate our pore analysis tools. The calculated pressure versus invaded volume curve reproduces the lab-measured curve very closely, indicating that the proposed pore space characterisation is a faithful representation of the medium. Additionally, we investigate the relationship of the so-called topological number and the Euler number and propose an efficient algorithm to compute the Euler number. Analysis of this topological descriptor reveals that the specific Euler number as a function of pore size may serve as a simple predictor of the threshold pressure associated with the critical flow path in porous media. |
