Permeability Evolution of Fractures in Shale in the Presence of Supercritical CO2. Issue 8 (8th August 2021)

• Record Type: Journal Article
• Authors: Hashemi, Sam S.; Zoback, Mark D.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 8(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-08-08
• Subjects: Shale rocks -- supercritical CO2 -- fracture permeability -- aperture -- fracture roughness; Geomagnetism -- Periodicals; Geochemistry -- Periodicals; Geophysics -- Periodicals; Earth sciences -- Periodicals; 551.1
• DOI: 10.1029/2021JB022266
• Languages: English
• ISSNs: 2169-9313

Abstract

Abstract: We experimentally examined the impact of supercritical carbon dioxide (scCO2 ) on fracture permeability and fracture surface characteristics in shales of various compositions. We measured permeability and fracture normal displacement at different effective stresses using both argon and scCO2 as pore fluids. Both natural fractures and saw cuts in intact samples were used in our study. The permeability and fracture normal displacement decrease after multiple loading/unloading cycles, apparently as the result of inelastic compaction. In samples with high carbonate content, we observe an increase in permeability and fracture surface degradation after more than 3.5 days of exposure to scCO2, apparently due to carbonate dissolution. We demonstrate that the sensitivity of permeability to effective normal stress correlates well with the fracture normal displacement. The dependence of permeability on effective normal stress increases after exposure to scCO2 as the fracture surface became more compliant. Plain Language Summary: In this study, laboratory experiments were used to investigate the effect of supercritical carbon dioxide (scCO2 ) on the fracture permeability and fracture surface characteristics of shales. Supercritical state is characterized by the inability to distinguish whether CO2 is a liquid or a gas. For samples with a wide range of compositions, we measured permeability and fracture normal displacement at different stresses using both argon and scCO2 as pore fluids. Both natural fractures and saw cuts in intact samples were used. The fracture normal displacement and permeability decrease after multiple loading/unloading cycles, apparently as the result of irreversible compaction. In samples with high carbonate contents, we observe an increase in permeability and fracture surface degradation after more than 3.5 days of exposure to scCO2, apparently due to carbonate dissolution. We demonstrate that the sensitivity of permeability to net pressure normal to the fracture surface correlates well with the fracture normal displacement. The sensitivity of permeability on net pressure normal to the fracture surface increases after exposure to scCO2 as the fracture surface became more compliant. Key Points: We studied the effect of scCO2 on fracture permeability evolution and fracture surface characteristics in shales Carbonate dissolution and inelastic compaction appear to mitigate each other's impact in controlling permeability Time‐dependency of the carbonate dissolution and fracture surface degradation process was confirmed in carbonate‐rich samples