Origin, migration and accumulation of CO_2 in East China and offshore shelf basins
HE Jia-xiong 1,2 , XIA Bin 1 , LIU Bao-ming 1 , ZHANG Shu-lin 1 (1. Laboratory of Marginal Sea Geology and Resources, CAS, Guangdong 510640, China; 2. Nanhai West Research Institute, CNOOC, Guangdong 524057, China)
Based on the geological and geochemical data of the CO_ 2 reservoirs and high CO_ 2 content oil/gas reservoirs discovered in east China and offshore shelf basins, CO_ 2 is classified into 3 types as crust origin, crust-mantle origin and volcano-mantle origin. The CO_2 gases from the CO_2 reservoirs and high CO_2 content oil/gas reservoirs in onshere fault basins in east China, East China Sea Basin, East Qiongdongnan Basin and Pearl River Mouth Basin are all of typical volcano-mantle origin, the gas sources are the CO_ 2 produced by mantle volcano activities, and the gas migration and accumulation were controlled by mantle volcano activities and the gas channeling of the large faults connecting deep gas sources. The CO_ 2 gases from the CO_ 2 reservoirs and high CO_ 2 content oil/gas reservoirs in the Yinggehai Basin are of crust origin and crust-mantle origin which were controlled by the local up invasion of the mud diapir hot fluid in multi blocks and zones, and by the physical-chemical mechanism of thick marine calcareous sandstone and mudstone. According to the regularities of the migration and distribution of gases from different origins, the gas sources may be traced, the migration and distribution of natural gas, especial CO_2 , be analyzed and predicted,and the CO_2 resources potential be evaluated, and these provide foundation for decision making in natural gas exploration.