Abstract:

 In this paper, we have reviewed the recent progress in the studies of the key problems that how was the mantlederived CO2 degassed from mantle magma and how did it migrate into sedimentary formations forming CO2 gas accumulations, and have pointed out the frontier problems in the related research area. These studies indicate that only alkaline basalt magma and alkaline magma are the medium and channel in which deep fluids and volatile components including CO2 are massively lodged, filtered and discharged. Shallow intrusive rocks, subvolcanic rocks and volcanic conduits are the favorable positions for CO2 degassing and accumulation. Hydrothermal activity in post magmatic and magma declining period are the favorable stages for massive CO2 degassing and accumulation. Mantlederived CO2 migrated into basins with three types of degassing model, including the model of inorganic gas directly overflowing through lithosphere faults, heat flow piercement degassing model, and degassing model of crustal magma chamber combined with basement faults. The intrinsic physicochemical properties of CO2 determine its various migration phases, and the synchronous migration and accumulation process. Only after massive chemical consuming and dissolution by formation water or oil can CO2 form effective accumulation. Pool formation and distribution of mantlederived CO2 are mainly controlled by magma gassource bodies and gassource fault systems. In future, further research and exploration need to be taken on some frontier issues, such as supercritical CO2 and its function on petroleum migration and accumulation, the relationship between CO2 and deeplarge faults and volcanic rocks, CO2 degassing and migration pattern, and the coupled but different poolforming mechanism between CO2 and normal hydrocarbon.

Key words:

deep fluids in mantle; CO2 gas pool; magma chamber; deeplarge fault; degassing model; poolforming mechanism