Simulation Study on the Mechanical Effect of CO2 Geological Storage in Ordos Demonstration Area

In order to understand the long-term process of CO2 storage and demonstrate its safety, multi-field coupled numerical simulation is considered a crucial technology in the field of geological CO2 storage. This study establishes a site-specific homogeneous thermo-hydro-mechanical coupling model based on TOUGH-FLAC3D coupling program using actual stratigraphic data from the Ordos demonstration area. The analysis investigates the transport behavior of CO2 within the formation considering pore permeability homogeneity, incorporates redistribution of effective stress and rock deformation, and provides a mechanical evaluation of the effectiveness of CO2 sequestration at this specific site. The findings indicate that: (1) the sealing effect of the cap rock depends on the difference of permeability between the reservoirs. The greater the permeability difference, the better the sealing effect. (2) High pore fluid pressure can lead to a decrease in the effective stress of rocks, causing deformation. After simulation calculations, the maximum deformation of rocks can reach 7.79 mm within a decade of CO2 injection. (3) Under the condition of continuous CO2 injection, the pore pressure will not be able to dissipate quickly and will continue to rise, and eventually shear failure will occur in the rock layer, but it is mainly concentrated in the lower part of the cap rock.