Abstract
CO2 reservoirs are widely distributed within the Yingcheng Formation in the Songliao Basin, but the extreme horizontal heterogeneity of CO2 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 CO2 content, but few are reported about migration and accumulation of CO2. Using the East Changde Gas Field as an example, we studied the accumulation mechanisms of CO2 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 CO2 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 CO2 contents. This conclusion provides useful theories for prediction of CO2 distribution in similar basins and reservoirs.
Highlights
The Songliao Basin is a Mesozoic–Cenozoic basin located in northeastern China that contains abundant oil and gas resources
The fault-controlled accumulation model refers to gas accumulation in the reservoir body that is cut by a basement 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 CO2 content
Gas reservoirs in East Changde are mostly located in the Lower Cretaceous volcanic strata, which is why this study focuses on the Lower Cretaceous strata (Fig. 3)
Summary
The Songliao Basin is a Mesozoic–Cenozoic basin located in northeastern China that contains abundant oil and gas resources. Edited by Jie Hao been accidentally discovered during natural gas exploration over the past two decades (Xu et al 1995; Sun et al 2009; Guo et al 2017a, b) These CO2 reservoirs are located within a narrow strip within the Xujiaweizi Depression, the Changling Depression, and the Wanjinta Depression. In wells Fs7 and Fs6, located less than 3 km away, the CO2 content is 15%–40% This phenomenon has resulted in a great deal of interest in the genesis of CO2 and the reservoir formation process in the Songliao Basin (Yang et al 2011; Fu and Song 2005; Shao et al 2000; Qu et al 2016; Xu et al 1999; Dai 1996; Du 2005; Guan 1990; Zhang et al 2009; Li et al 2006; Guo et al 2000; Yu et al 2010; Cao 1996; Rui et al 2018a, b). Most scholars agree that the CO2 in the Songliao Basin is inorganic and mantle-derived
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