CO_2 Sequestration and Utilization in Deep Saline Aquifers

CO2 sequestration in deep saline aquifers is one of the most effective and promising choices to mitigate anthropogenic CO2 emissions.Commercial scale CO2 injection projects and pilot scale field tests have demonstrated that it is technologically feasible.The state of the art and future challenges including CO2 trapping mechanism,capacity assessment technology,monitoring technology,safety assessment technology,and utilization technology are discussed based on the review of existing literatures.Hydrothermal experiment and numerical simulation in particular have proven to be very important methods to study the water-rock-CO2 interaction process and mechanism supported by field tests.Geophysical methods,seismic monitoring methods,in particular 4D,cross well and vertical seismic,could effectively detect the CO2 plume in reservoirs.However,they are unable to be widely applied due to the high cost,meanwhile geochemical methods(e.g.water chemistry and isotopes) could reflect reservoir responses in time after CO2 injection which is simple with low cost,and numerical simulation could provide the basis for CO2 plume migration.It is suggested that a set of multi-methods monitoring technology with easy operations should be established.Safe assessment technology includes numerical simulation,mechanical parameters testing,and establishment of various models;and further consideration of public acceptance and practical experience from large-scale CO2 storage projects need to be integrated for the improvement.Considering the high cost of CCS implementation,CO2 utilization should be encouraged and in particular,the CO2-EATER technology needs to be further discussed in order to improve waste geothermal water injectivity and sustainable development of geothermal resources.Technologies and methods of CO2 sequestration in marine saline formations develop very fast abroad,in the meantime most of the sedimentary basins in China that are suitable for CO2 sequestration are continental deposition with great differences in formation water and reservoir rock compositions and in this way,it is important and necessary to emphasis our specialty and focus when learning from experiences abroad.