Experimental CO2 injection: Study of physical changes in sandstone porous media using Hg porosimetry and 3D pore network models

Variations in the pore system of sandstones from the so-called Utrillas Formation (Lower Cretaceous, Iberian Peninsula) after CO2 injection have been investigated in a laboratory on a micro scale. In this study, we present results regarding variations in the pore spaces of sandstones caused by the injection of CO2 and its permanence in supercritical conditions in contact with a rock sample for two months. The modifications produced in the porosity and pore size distribution have been evaluated on two geological samples, using a 3D modelling of the results obtained by Hg intrusion porosimetry. Reconstructions of the pore structure of the rock before and after CO2 injection from mercury intrusion–extrusion curves, generating virtual models of pores that reproduce the experimental porosity. By analysing the results, a drastic modification in the mesoporosity of the rock is confirmed, which may have a paramount influence not only on the total storage capacity but also on the percolation of fluid through the rock.