A thick composite coal seam at Dartbrook Mine has been characterised by stress and permeability testing over several years. Most recently, a four well injection interference test was conducted to measure the overall seam permeability anisotropy, and core samples from various sites near the interference test array have been tested in the laboratory. The magnitudes of horizontal permeability components as measured by the well test and by core tests were found to be similar, but the principal permeability directions were reversed. The interference test measured the permeability anisotropy of the entire composite seam while the core samples came from only one of the four seams making up the composite seam. Structural features and hydraulic fracture results suggest that different seams and even parts of single seams in the composite seam are very likely to have significantly different permeability tensors.

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