The relationship between pore structure and permeability under confining pressure

The permeability for two types of sandstone, Berea sandstone and sandstone from Otway Paaratte formation, under different confining pressure are measured and porosity is investigated 3D micro-focus X-ray CT and 3D medial axis analysis. The permeability is determined using flow pump test and the porosity is determined by mercury intrusion porosimetry. The total porosity of Berea sandstone and Otway sandstone are around 17.4% and 25.0%, respectively. The permeability of both sandstones with 18 MPa of an effective confining pressure were approximately 70% of that with 10 MPa effective confining pressure. However, the permeability of Berea sandstone is higher than that of Otway sandstone by one order. In order to investigate this curious result, we performed 3D medial axis analysis and conclude that the larger porosity does not mean the higher permeability and the lower of throat/pore ratio has lower permeability.