Geochemical processes such as mineral dissolution and precipitation alter the microstructure of rocks, and thereby affect their hydraulic and mechanical behaviour. Quantifying and considering these property changes in reservoir simulations substantially supports risk assessments related to geological subsurface utilization.
In our virtual laboratory, 3D pore-scale models of typical reservoir sandstones are applied to determine the effective hydraulic and elastic properties of sandstones. In order to adequately depict characteristic distributions of secondary minerals, the virtual samples are systematically altered, and the resulting changes in geometric, hydraulic, and mechanical rock properties are quantified. Characteristic pore space alterations for a reaction- and a transport-limited precipitation regime are approximated by correlating precipitation with fluid flow velocity magnitudes. A purely surface reaction-limited regime is represented by a uniform modification of the pore space, whereas transport-limited precipitation is characterised by the successive clogging of pore throats and a drastic decrease in permeability. It is demonstrated that the location of mineral growth within the pore space strongly affects the magnitude of permeability reduction. The presented digital pore-scale simulations enable to quantify changes in permeability and stiffness resulting from geochemical processes, and thus are relevant for a wide range of natural and engineered subsurface applications.
Maria Wetzel1, Thomas Kempka1,2, Michael Kühn1,2
1GFZ German Research Centre for Geosciences, Fluid Systems Modelling; 2University of Potsdam, Institute of Geosciences