Impact of CO2 injection on the hydro-mechanical behaviour of a clay-rich caprock

摘要

The safe storage of CO2 in deep reservoir units requires an efficient sealing of the overlaying caprock. The acidic environment caused by the dissolution of CO2 into the pore fluid can induce changes in the microstructure of the material over the long term and might consequently impact its retention capabilities through changes in the pore size and pore connectivity. In the first part of this paper, the impact of a low pH environment on some of the physical properties, such as grain density, void ratio and dominant entrance pore size, and on the retention capacity of a shaly caprock representative material, i.e., Opalinus Clay shale, is investigated by using an HCl solution inducing a pH=3. The results show that grain density, dominant entrance pore size and void ratio are not significantly affected by the contact with a low pH environment in the considered period. Similar conclusions can be drawn for the retention capacity because the air entry value appears to be the same for treated and non-treated material.