Characterization of the pore structure of reservoir rocks with the aid of serial sectioning analysis, mercury porosimetry and network simulation

Processes of fluid transport through underground reservoirs are closely related with microscopic properties of the pore structure. In the present work, a relatively simple method is developed for the determination of the topological and geometrical parameters of the pore space of sedimentary rocks, in terms of chamber-and-throat networks. Several parameters, such as the chamber-diameter distribution and the mean specific genus of the pore network are obtained from the serial sectioning analysis of double porecasts. This information is used in the computer-aided construction of a chamber-and-throat network which is to be used for further analysis. Mercury porosimetry curves are fitted to either 2-parameter or 5-parameter non-linear analytic functions which are identified by the median pressures, mean slopes and breakthrough pressures. A simulator of mercury intrusion/retraction, incorporating the results of serial tomography, in conjuction with the experimental mercury porosimetry curves of the porous solid are used iteratively to estimate the throat-diameter distribution, spatial correlation coefficients of pore sizes and parameters characterizing the pore-wall roughness. Estimation of the parameter values is performed by fitting the simulated mercury porosimetry curves to the experimental ones in terms of the macroscopic parameters of the analytic functions. The validity of the pore space characterization is evaluated through the correct prediction of the absolute permeability. The method is demonstrated with its application to an outcrop Grey-Vosgues sandstone.