Experimental research on carbon storage in a CO2-Based enhanced geothermal system

Abstract Ensuring sustainable energy development and reducing CO2 emissions are two major challenges that need to be overcome to deal with the global economic crisis and to alleviate climate change. Hot dry rock is a renewable energy resource with a huge potential. CO2-based enhanced geothermal systems (CO2-EGS) can achieve both heat extraction and CO2 storage in hot dry rock. To investigate the storage rate, a heat extraction experiment involving the alternating cyclic injection of water and supercritical CO2 was conducted. The ion contents of the fracture solution of the different injection cycles were measured, and the amount of CO2 mineralization storage was calculated. In addition, changes in the mineral composition of the fracture surface were observed and analysed. The results revealed that the mineral dissolution on the fracture surface was mainly feldspars, which possibly accompanied biotite dissolution. The precipitated minerals that stored the carbon were mainly calcite and dolomite, and possibly illite and cancrinite. Many blocky carbonate minerals were distributed on the flat surface of the fracture, while many rod-shaped carbonates were distributed in the concave holes of the microfractures. The research results reveal the CO2 storage mechanism and are significant for the CO2 storage prediction in the CO2-EGS.