A numerical study of the coupled evolutions of microgeometry and transport properties of simple 3D porous media

Simulating, understanding and predicting the evolution during mineral diagenesis of porous rocks physical properties is a very complex problem. When properties like effective diffusivity, formation factor or permeability are considered interest can be mainly focussed on the coupled evolutions of micro-geometry and transport properties. This approach is theoretically justified using the volume averaging method: This now classical method yields differential problems at the microscopic scale. Their resolution permits the computation of the macroscopic transport properties. For the properties listed above, the results are completely determined by the microscopic geometry. The principles and the main properties of the numerical programs used to solve those 3D closure problems are presented. For well-sorted granular porous media, random closed packings (RCP) of spheres with realistic porosity are good first approximations of an initial micro-geometry. After a short presentation of the algorithm used to generate RCP of spheres for any granulometry, the different methods used to modify the micro-geometry are exposed. The differences observed between the effects of a purely geometrical evolution and geochemically governed evolutions suggested that both the history and the depositional conditions influence the properties of natural porous media.