Weathering and creep in rocks modelled at the microscale

Many natural processes and energy-related project in the subsurface involve the interactions between the porous rock and the fluids inside the pores. In particular, the fluid can interact with the solid matter by various dissolution-precipitation reactions that can modify the microstructure geometry and thus change the mechanical behavior of the rock and its failure potential or directly induce a creep of the rock. These chemo-mechanical couplings can have important implications for storage applications and induced seismicity. In this contribution, we will show discrete element simulations performed at the microstructural scale of porous matter. First, we will show that the dissolution of the cement in sedimentary rocks strongly influence the lateral earth pressure coefficient. The value of this coefficient tends to an attractor by increasing the degree of dissolution, which can lead to stress redistribution at the reservoir scale and promote faulting or induced seismicity. Secondly, we will show a numerical framework coupling discrete element with a phase field model allowing to capture grains shape changes due to local precipitation or dissolution. This model is applied to study the phenomenon of intergranular pressure-solution and allows to reproduce the creep behavior of the material in compaction. It enables also to study the competition between grain rearrangement and pressure solution in fault gouges to induce a rate dependency of the fault mechanical behavior.