The experimental investigation of effect of supercritical CO2 immersion on mechanical properties and pore structure of shale

• Published in: Energy (Oxford) Vol. 228; p. 120663
• Main Authors: Bai, Bing, Ni, Hong-jian, Shi, Xian, Guo, Xing, Ding, Lu
• Format: Journal Article
• Language: English
• Published: Oxford Elsevier Ltd 01.08.2021; Elsevier BV
• Subjects: Adsorption; Carbon dioxide; compression strength; Compressive strength; energy; Horizontal orientation; Immersion; Layer inclination; Layering; Low pressure; macropores; Mechanical properties; micropores; Microstructure; Modulus of elasticity; nitrogen; Reservoirs; Shale; Shales; Submerging; Supercritical carbon dioxide; X-ray diffraction; Mechanical properties; Supercritical carbon dioxide; Layer inclination; Microstructure; Shale
• ISSN: 0360-5442; 1873-6785
• DOI: 10.1016/j.energy.2021.120663

The interactions between supercritical carbon dioxide (ScCO2) and shale significantly affect shale reservoir exploitation. This study investigates the effect of ScCO2 immersion on the mechanical behavior and microstructure of shale with inclined layering. The orientations α of the bedding plane with respect to the horizontal direction are 0°, 30°, 45°, 60°, and 90°. Mechanical experiment results indicated that the compressive strength of shale decreased, while the elastic moduli increased in ScCO2 immersion. The compressive strength exhibited the same variation tendency, while the elastic modulus exhibited the opposite change trend with increasing α before and in ScCO2 immersion. ScCO2 alters the mechanical properties of shale through pressure, adsorption, and dissolution; the dominant factor enhancing the elastic modulus is adsorption. X-ray diffraction and low-pressure nitrogen adsorption experiments showed that the influence of ScCO2 on the microstructure of the layering was more significant than the influence on the matrix; ScCO2 mainly broadened the micropores in the matrix, while transforming the mesopores and macropores in the bedding plane. This study provides the theoretical basis for the development of shale reservoirs using ScCO2. •Performing mechanical experiments of shale immersed in ScCO2 atmosphere.•The UCS decreases, elastic modulus increases when immersing in ScCO2 for shale.•Adsorption of ScCO2 is the dominant factor enhancing elastic modulus of shale.•The dissolution effect of ScCO2 is stronger in bedding plane than that in matrix.