Effect of CO2-H2O-Smectite Interactions on Permeability of Clay-Rich Rocks Under CO2 Storage Conditions.
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| Title: | Effect of CO |
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| Authors: | Zhang, M.1,2 (AUTHOR) zmcumtb@qq.com, Spiers, C. J.2 (AUTHOR), Hangx, S. J. T.2 (AUTHOR) |
| Source: | Rock Mechanics & Rock Engineering. May2023, Vol. 56 Issue 5, p3451-3474. 24p. |
| Subjects: | Cap rock, Rock permeability, Fault gouge, Fluid-film bearings, Fluid pressure, Smectite |
| Abstract: | CO2 uptake by smectites can cause swelling and self-stressing in shallow clay-rich caprocks under CO2 storage P–T and constrained conditions. However, little data exist to constrain the magnitude of the effects of CO2-H2O-smectite interactions on the sealing properties of clay-rich caprocks and faults. We performed permeability experiments on intact and fractured Opalinus Claystone (OPA) cores (~ 5% smectite), as well as on a simulated gouge-filled faults consisting of Na-SWy-1 montmorillonite, under radially constrained conditions simulating "open" transport pathways (dry and variably wet He or CO2; 10 MPa fluid pressure; 40 °C). Overall, the flow of dry CO2 through intact OPA samples and simulated smectite fault gouge caused a decrease in permeability by a factor of 4–9 or even by > 1 order, compared to dry He permeability. Subsequent to flow of dry and partially wet fluid, both fractured OPA and simulated gouge showed a permeability reduction of up to 3 orders of magnitude once flow-through with wet CO2 was performed. This permeability change appeared reversible upon re-establishing dry CO2 flow, suggesting fracture permeability was dominated by water uptake or loss from the smectite clay, with CO2-water-smectite interactions play a minor effect. Our results show that whether an increases or decreases in permeability of clayey caprock is expected with continuous flow of CO2-rich fluid depends on the initial water activity in the clay material versus the water activity in the CO2 bearing fluid. This has important implications for assessing the self-sealing potential of fractured and faulted clay-rich caprocks. Highlights: Permeability of potential clay-rich caprock (Opalinus Claystone) was systematically measured using variably wet CO2 versus He. Through-flow of dry CO2 caused a decrease in permeability of intact Opalinus Claystone and simulated smectite fault gouge by up to > 1 order, as composed to dry He. Fractured Opalinus Claystone and simulated gouge showed a permeability reduction of up to 3 orders of magnitude with through-flow of wet CO2. Permeability decrease by through-flow of variably wet CO2 appeared reversible upon re-establishing dry CO2 flow. The initial water activity in the clay material versus the water activity in the CO2 bearing fluid determines change in permeability upon CO2 flushing. [ABSTRACT FROM AUTHOR] |
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| Database: | Engineering Source |
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| Abstract: | CO2 uptake by smectites can cause swelling and self-stressing in shallow clay-rich caprocks under CO2 storage P–T and constrained conditions. However, little data exist to constrain the magnitude of the effects of CO2-H2O-smectite interactions on the sealing properties of clay-rich caprocks and faults. We performed permeability experiments on intact and fractured Opalinus Claystone (OPA) cores (~ 5% smectite), as well as on a simulated gouge-filled faults consisting of Na-SWy-1 montmorillonite, under radially constrained conditions simulating "open" transport pathways (dry and variably wet He or CO2; 10 MPa fluid pressure; 40 °C). Overall, the flow of dry CO2 through intact OPA samples and simulated smectite fault gouge caused a decrease in permeability by a factor of 4–9 or even by > 1 order, compared to dry He permeability. Subsequent to flow of dry and partially wet fluid, both fractured OPA and simulated gouge showed a permeability reduction of up to 3 orders of magnitude once flow-through with wet CO2 was performed. This permeability change appeared reversible upon re-establishing dry CO2 flow, suggesting fracture permeability was dominated by water uptake or loss from the smectite clay, with CO2-water-smectite interactions play a minor effect. Our results show that whether an increases or decreases in permeability of clayey caprock is expected with continuous flow of CO2-rich fluid depends on the initial water activity in the clay material versus the water activity in the CO2 bearing fluid. This has important implications for assessing the self-sealing potential of fractured and faulted clay-rich caprocks. Highlights: Permeability of potential clay-rich caprock (Opalinus Claystone) was systematically measured using variably wet CO2 versus He. Through-flow of dry CO2 caused a decrease in permeability of intact Opalinus Claystone and simulated smectite fault gouge by up to > 1 order, as composed to dry He. Fractured Opalinus Claystone and simulated gouge showed a permeability reduction of up to 3 orders of magnitude with through-flow of wet CO2. Permeability decrease by through-flow of variably wet CO2 appeared reversible upon re-establishing dry CO2 flow. The initial water activity in the clay material versus the water activity in the CO2 bearing fluid determines change in permeability upon CO2 flushing. [ABSTRACT FROM AUTHOR] |
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| ISSN: | 07232632 |
| DOI: | 10.1007/s00603-023-03259-6 |
