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Pore Space Relevant of Gas Transport in Opalinus Clay - Homogeneity, Percolation and Capillary Properties
- Publisher: European Association of Geoscientists & Engineers
- Source: Conference Proceedings, Fourth EAGE Shale Workshop, Apr 2014, Volume 2014, p.1 - 5
Abstract
The application of percolation theory to geomaterials generally includes the study of simplified lattice models in order to derive information on pore connectivity. Here, and possibly applied for the first time to shales, we computed key percolation variables such as the percolation probability distribution from our reconstructed pore microstructures. Then, we used a finite-scaling approach to calculate the critical porosity (i.e. percolation threshold) of pore microstructures from sandy and shaley facies of Opalinus Clay. Both microstructures show anisotropic characteristics with respect to connectivity and percolation threshold. We found percolation thresholds with critical porosities 0.04 – 0.12 parallel to bedding and 0.11 – 0.19 perpendicular to bedding. The resolved porosity of the sandy facies (low clay content) is close to the percolation threshold, whereas the porosity of the shaley facies (high clay content) is below the percolation threshold. The approach yields similar results when compared to an approach that is based on morphological image techniques and involves the modification of the original pore voxel data. Therefore, we used modified pore structures in combination pore network modeling to discuss changes in gas transport properties in case porosity approaches the critical porosity from above.