Analysis of the genesis and migration and accumulation of CO2 and controlling factors in the onland and offshore areas of eastern China

Abstract：According to a wealth of geological and geochemical data，this paper focuses on the genesis and characteristics of migration and accumulation of CO2 and thｅｉｒ key controlling factors in eastern China and its sea areas and on that basis a preliminary evaluation of the favorable CO2 distribution areas ｉｓ ｍａｄｅ.The study shows that in various continental downfaulted basins in eastern China，the China East Sea basin of the southeast sea region and the continental shelf—Qiongdongnan basin and Zhujiangkou basin—of the northern South China Sea，CO2 in CO2 reservoirs and CO2-rich oil/gas reservoirs is of typical volcanic mantle-derived type and that its migration and concentration is mainly controlled by mantle-derived volcanism and gas-conducting distribution of deep basement faults connected with the gas source at depth. CO2 is mainly sourced from substantial amount of CO2 associated with mantle-derived volcanism at the deep level of the crust. CO2 in the CO2 reservoirs and CO2-rich oil/gas reservoirs in the Yinggehai basin on the continental shelf of the northern South China Sea is of crust origin and crust-mantle mixing origin and mainly controlled by local，layer-by-layer and zone-by-zone，multiple intrusion of late hydrothermal fluids in mud diapir areas and physico-chemical processes of very thick Pliocene-Miocene marine calcareous sandstone and mudstone. Therefore according to the characteristics of migration and accumulation of different genetic types of CO2，we can trace the CO2 source，analyze and predict the migration，accumulation and distribution of gas and especially CO2 so as to provide a basis for make the plan and decision of gas exploration and reduce the risk of exploration.