Anisotropy of sandstone permeability
Small-scale probe permeability measurements on differently oriented faces of highly compacted and quartz-cemented Viking Formation sandstones yield detailed permeability distributions that appear to be diagnostic of the grain- and lamina-scale fabric of the samples. Permeability anisotropy of a single 'structureless'-appearing sample is low, reflected by a kV / kH-ratio of 0.7; corresponding k-distributions are homogeneous. Permeability anisotropy of a strongly laminated sample is variable, with kV / kH-ratios of 0.1 and 2.8, thought to be a function of the variability of the pore network connectivity for any given lamina. Significantly, the pore network anisotropy established during deposition has been maintained after several kilometres of burial, and cementation and dissolution processes. Lamina-perpendicular permeability distributions are very homogeneous relative to those of kH, which is taken to imply that fluid-fluid displacement processes are potentially more efficient in that orientation. In comparison to the dataset presented herein, industry-standard core analyses of kMAX, k90, and kV, do not appear to yield relevant kV / kH-ratios that may be linked to the evolution of permeability anisotropy with depth. In future work, quantitative measures of pore network anisotropy will be compared to multi-directional probe permeability data to test causal relationships between permeability and pore network evolution.