Study and review on geochemical effect of coal and rock injected with super－critical CO 2

Based on the comprehensive experiment study and the theoretical analysis on the super－critical CO2 injection in the seam at home and abroad，it was found that the super－critical CO2 injection in the seam would be affected to the material composition and the physical structure and could reconstruct the pore cracking system．The major causes could be that the super－critical CO2 injection individually would have the geochemical reaction with the minerals in the coal and the coal matrix．In the reaction system of the super－critical CO2 injection－H2O－coal and rock，the minerals in the coal would have erosion dissolution sediment．Among them，the most sensitivity would bethe carbonate minerals and then would be the feldspar and clay mineral．The sulfide mineral( pyrites) and quartz would be stable relatively．The super－critical CO2 injection would have a certain extraction role to the small molecule in the coal matrix and thus could change the molecular structure of the coal．The major factors affected to the super－critical CO2 injection－H2O－coal and rock reaction would be the coalmineral composition，macerals and coal grade，coal reservoir pressure and ground temperature condition as well as the formation water salin-ity and others．Due to the limitation of the test simulation and numerical simulation，the response mechanism of the super－critical CO2 in-jection－H2O－coal and rock geochemistry would be needed to be discussed in detail and meanwhile a real time observation and position study on the pore cracking network variation of the coal and rock would be more important．