Dawsonite fixation of mantle CO2 in the cretaceous Songliao Basin, Northeast China: a natural analogue for CO2 mineral trapping in oilfields

• Published in: International geology review Vol. 56; no. 14; pp. 1792 - 1812
• Main Authors: Yu, Miao, Liu, Li, Yu, Zhichao, Liu, Na, Yang, Huidong, Qu, Xiyu
• Format: Journal Article
• Language: English
• Published: Philadelphia Taylor & Francis 26.10.2014; Taylor & Francis Ltd
• Subjects: Crude oil; dawsonite; Enhanced oil recovery; fluid inclusions; Fluids; mantle CO; mineral trapping; Minerals; oil pool; Petroleum industry; Songliao Basin; Trapping
• ISSN: 0020-6814; 1938-2839
• DOI: 10.1080/00206814.2014.958765

Abundant crude oil and CO 2 gas coexist in the fourth member of the Upper Cretaceous Quantou reservoir in the Huazijing Step of the southern Songliao Basin, China. Here, we present results of a petrographic characterization of this reservoir based on polarizing microscope, X-ray diffraction, fluid inclusion, and carbon-oxygen isotopic data. These data were used to identify whether CO 2 might be trapped in minerals after the termination of a CO 2 -enhanced oil recovery (EOR) project, and to determine what effects might the presence of CO 2 have on the properties of crude oil in the reservoir. The crude oil reservoir in the study area, which coexists with mantle-derived CO 2 , is hosted by dawsonite-bearing lithic arkoses and feldspathic litharenites. These sediments are characterized by a paragenetic sequence of clay, quartz overgrowth, first-generation calcite, dawsonite, second-generation calcite, and ankerite. The dawsonite analysed during this study exhibits δ 13  C (Peedee Belemnite, PDB) values of −4.97‰ to 0.67‰, which is indicative for the formation of magmatic-mantle CO 2 . The paragenesis and compositions of fluid inclusions in the dawsonite-bearing sandstones record a sequence of two separate filling events, the first involving crude oil and the second involving magmatic-mantle CO 2 . The presence of prolate primary hydrocarbon inclusions within the dawsonite indicates that these minerals precipitated from oil-bearing pore fluids at temperatures of 94-97°C, in turn suggesting that CO 2 could be stored as carbonate minerals after the termination of a CO 2 -EOR project. In addition, the crude oil in the basin would become less dense after deposition of bitumen by deasphalting the injection of CO 2 gas into the oil pool.