A Review on the Influence of CO 2 /Shale Interaction on Shale Properties: Implications of CCS in Shales

• Published in: Energies
• Main Authors: Ahmed Fatah, Ziad Bennour, Hisham Ben Mahmud, Raoof Gholami, Md. Mofazzal Hossain
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2020
• Subjects: shale gas; CO 2 injection; CO 2 sequestration; CO 2 storage capacity; CO 2 /shale interaction; Technology; T; Carbonic acid
• Online Access: https://doi.org/10.3390/en13123200; https://doaj.org/article/69dd3b2f52b840f4bd201389ada73dde

Carbon capture and storage (CCS) is a developed technology to minimize CO 2 emissions and reduce global climate change. Currently, shale gas formations are considered as a suitable target for CO 2 sequestration projects predominantly due to their wide availability. Compared to conventional geological formations including saline aquifers and coal seams, depleted shale formations provide larger storage potential due to the high adsorption capacity of CO 2 compared to methane in the shale formation. However, the injected CO 2 causes possible geochemical interactions with the shale formation during storage applications and CO 2 enhanced shale gas recovery (ESGR) processes. The CO 2 /shale interaction is a key factor for the efficiency of CO 2 storage in shale formations, as it can significantly alter the shale properties. The formation of carbonic acid from CO 2 dissolution is the main cause for the alterations in the physical, chemical and mechanical properties of the shale, which in return affects the storage capacity, pore properties, and fluid transport. Therefore, in this paper, the effect of CO 2 exposure on shale properties is comprehensively reviewed, to gain an in-depth understanding of the impact of CO 2 /shale interaction on shale properties. This paper reviews the current knowledge of the CO 2 /shale interactions and describes the results achieved to date. The pore structure is one of the most affected properties by CO 2 /shale interactions; several scholars indicated that the differences in mineral composition for shales would result in wide variations in pore structure system. A noticeable reduction in specific surface area of shales was observed after CO 2 treatment, which in the long-term could decrease CO 2 adsorption capacity, affecting the CO 2 storage efficiency. Other factors including shale sedimentary, pressure and temperature can also alter the pore system and decrease the shale “caprock” seal efficiency. Similarly, the alteration in shales’ surface chemistry and functional species after CO 2 ...