The fractal microstructure of ancient sedimentary rocks

Small-angle neutron scattering (SANS), ultra-small-angle neutron scattering and scanning electron microscopy (SEM) were used to analyze the pore-fabric interface in a 1400 million years old shale. The pore-rock fabric interface is a surface fractal (of fractal dimension 2.82) over three orders of magnitude of the length scale and ten orders of magnitude in intensity (macroscopic differential cross section range 10^-1 - 10⁹ cm^-1). Both SANS and SEM indicate similar fractal dimension for scales less than 4 µm and a breakdown of fractal properties for scales larger than 4 µm.