Origin, migration, and accumulation of carbon dioxide in the East Changde Gas Field, Songliao Basin, northeastern China

CO 2 reservoirs are widely distributed within the Yingcheng Formation in the Songliao Basin, but the extreme horizontal heterogeneity of CO 2 content causes difficulties in the exploration and exploitation of methane. Former studies have fully covered the lithology, structure, and distribution of the reservoirs high in CO 2 content, but few are reported about migration and accumulation of CO 2 . Using the East Changde Gas Field as an example, we studied the accumulation mechanisms of CO 2 gas. Two original types of accumulation model are proposed in this study. The fault-controlled accumulation model refers to gas accumulation in the reservoir body that is cut by a basement fault (the West Xu Fault), allowing the hydrocarbon gas generated in the lower formation to migrate into the reservoir body through the fault, which results in a relatively lower CO 2 content. The volcanic conduit-controlled accumulation model refers to a reservoir body that is not cut by the basement fault, which prevents the hydrocarbon gas from being mixed in and leads to higher CO 2 contents. This conclusion provides useful theories for prediction of CO 2 distribution in similar basins and reservoirs.