X-Ray microscopy imaging of reactive transport and drying of salt solutions in fractured porous media from core-to pore-scale

摘要

During the sequestration of CO2 into down-hole rock formations,salt precipitation may occur due to drying of the brine associated with the CO2 injection process. Previous work [1,2] showed that the location of the precipitate depends on the competition of advective and capillary forces on the aqueous fluid phase transporting brine to the drying front. Here we consider the drying process of reservoir brine in fractured porous media by the injection of sub-saturated CO2. In the case of a heavily fractured reservoir,the injected CO2 will start drying the fracture-matrix interface,which may result in capillary driven transport of brine and salt to the fracture-matrix interface,where it potentially will precipitate. The morphology and the exact location of the precipitate at the interface are the crucial issues to solve. In certain circumstances,the precipitate forms a low permeability layer in the fracture space,reducing the fracture permeability(injectivity)leading to an increase of the injection pressure. Precipitation in fractures is a multi-scale problem which requires imaging on different length scales: the propagation of the dry zone and the location of the precipitate on the fracture or core scale,and the location of precipitation at the fracture-matrix interface on the pore scale.