Pore geometry and transport properties of Fontainebleau sandstone

Abstract Quantitative characterization of pore geometry using laser scanning confocal microscopy and measurements of permeability, resistivity, and pore volume were performed on four samples of Fontainebleau sandstone with effective porosities ranging from 4% to 20% at confining pressures up to 70 MPa. Observed bench permeabilities and hydraulic radii for samples with porosities of 10%, 16%, and 20% agree well with those predicted using the equivalent channel model of Walsh and Brace [1]; however, there is more than an order of magnitude over estimation for a sample with a porosity of 4%. The relative pressure dependence of permeability and formation factor for this sample differs from that of the three more porous samples. We interpret the behavior to result from fundamental differences in the topology and geometry of pore space at low porosity. Comparison of our data with results in the literature for rocks synthesized by hot isostatic pressing suggests that the mechanism by which porosity reduction occurs strongly affects the pore geometry and transport properties of sedimentary rocks.