Shale Microstructure Characteristics under the Action of Supercritical Carbon Dioxide (Sc-CO 2 )

Chunsheng Yu (), Xiao Zhao, Qi Jiang (), Xiaosha Lin, Hengyuan Gong and Xuanqing Chen
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Chunsheng Yu: State Key Laboratory of Shale Oil and Gas Enrichment Mechanisms and Effective Development, Beijing 100089, China
Xiao Zhao: Petroleum Engineering School, Southwest Petroleum University, Chengdu 610500, China
Qi Jiang: Petroleum Engineering School, Southwest Petroleum University, Chengdu 610500, China
Xiaosha Lin: School of Resources and Safety Engineering, Chongqing University, Chongqing 400044, China
Hengyuan Gong: Petroleum Engineering School, Southwest Petroleum University, Chengdu 610500, China
Xuanqing Chen: Petroleum Engineering School, Southwest Petroleum University, Chengdu 610500, China

Energies, 2022, vol. 15, issue 22, 1-9

Abstract: Supercritical carbon dioxide (SC-CO 2 ) is suitable to extract low-polar organics and to assist in the dissolution of pores and fractures in shale. In this work, we investigate the effect of temperature on the structure of five shale samples via high pressure reaction assisted with SC-CO 2 . Shale samples were analyzed using X-ray diffraction, field emission scanning electron microscopy, and ImageJ software. Due to the extraction of CO 2 , after Sc-CO 2 treatment, carbonate and clay content decreased, while quartz and plagioclase increased slightly, which improved gas and oil flow in microscopic pores and shale cracks. Shale samples showed an increase in surface fracture area as experimental temperature increased. Since Sc-CO 2 fluid density and solubility increase with temperature, more organics can be extracted from shale pores and fractures, resulting in newly formed pores and fractures. As a result, the threshold temperature for shale high-temperature Sc-CO 2 cracking was confirmed to be 400 °C, and the fracture area increased by more than 45% at this temperature. Based on the findings of this study, Sc-CO 2 technology can be used to potentially recover low-maturity shale oil efficiently.

Keywords: shale; exploitation; Sc-CO 2; microscopic features; mineral composition (search for similar items in EconPapers)
JEL-codes: Q Q0 Q4 Q40 Q41 Q42 Q43 Q47 Q48 Q49 (search for similar items in EconPapers)
Date: 2022
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