MULTISCALE CHARACTERIZATION OF RESERVOIR ROCK MICROSTRUCTURE: COMBINING SMALLANGLE NEUTRON SCATTERING AND IMAGE ANALYSIS

摘要

The correlation function and the absolute neutron scattering cross section are obtained for a sample of reservoir sandstone in the linear scale range 10 A to 1 mm by combining small-angle neutron scattering data(SANS/USANS)with statistical analysis of backscatter scanning electron micrographs(BSEM)of the pore space.The pore-rock fabric interface is a surface fractal(D = 2.47)over 4 orders of magnitude of the length scale and 15 orders of magnitude in scattering intensity,with an upper limit cut-off of about 40 μm.The specific surface area,pore size distribution and total porosity,calculated along the lines of a polydisperse spherical pore(PDSP)model,are consistent with mercury porosimetry data.The PDSP analysis quantifies the fraction of pore volume in the fractal regime and illustrates the possibility of characterizing the microgeometry in terms of a continuous pore size distribution,covering length scales from few nanometers to hundreds of microns.Such information is useful in the interpretation of special core analysis data,as illustrated for the case of the NMR-T2 distributions for the sample studied.