Long-term impact of CO2 on the stability of mineral assemblages in porous reservoir sandstones - Analogue study in natural CO2 reservoirs form Central Europe
Final Report Abstract
Predictions on the fate and impact of industrial injected CO2 on the mineralogical stability of clastic reservoir rocks are essential for the realization of planned carbon capture and storage (CCS) projects. Therefore we performed an analogue study on rocks, assumed to be affected by natural CO2-bearing fluids during geological time, to substantiate potential mineralogical/ geochemical variations in rock composition caused by (CO2-bearing) fluid-rock interactions. Applying mainly (sub-) microscopic and geochemical methods Buntsandstein and Palaeozoic rocks from 5 areas of western and central Germany were investigated. In most of these areas the occurrence of recent natural CO2-bearing fluids is established. Based on the assumption that the alteration of red bed facies rocks by (CO2-bearing) fluidrock interaction led to specific mineral dissolution and precipitation processes and thus to variations in element content, red bed sandstones and their altered/bleached modifications were analyzed. Our investigations sustain that: (1) Sandstone bleaching of originally red bed sediments is associated with Fe-depletion and Ca-enrichment, implying the involvement of CO2-bearing fluids during such alteration processes. Accepting this assumption, CO2-bearing fluids were involved far beyond the reaches of the present CO2 provinces. Significant mass transfer was associated with the bleaching process as the most apparent process with CO2 involvement. (2) Bleaching cannot be related to pure CO2-H2O-fluids alone, instead the impact of reducing volatiles, like HCs and/or sulfides has to be assumed. (3) CO2 impact on red bed sandstones is case specific. There appear to be no general mineralogical differences between sandstones from present CO2 provinces and those from areas without present CO2 activity. Obviously the observed/inferred reactions involved CO2, but only as one of several components in solution. (4) At low (to intermediate) rock porosities and permeabilities, CO2-induced bleaching processes have little effect on porosity and permeability. (5) Despite the increased content of clay minerals (illite, chlorite) in bleached rocks, red bed sediments have higher specific surface areas and therefore increased potential reactivity with fluids; this feature is strongly related to the absence/presence of hematite cutans. (6) Mature sandstones, like the Buntsandstein exhibit only minor mineralogical alteration and element transfer during fluid-rock interaction, thus favoring capillary and solubility CO2 trapping. In contrast Palaeozoic sediments reveal major mineralogical and geochemical differences, reflecting pronounced element transfer, induced by bleaching alteration reactions. Thus in Rotliegend sandstones mineral CO2 trapping will be much more effective, than in Buntsandstein deposits. (7) Mineral alteration, respectively element transfer associated with bleaching processes is site specific and varies within same geological formations as well as individual well sites. Therefore detailed geological-sedimentological-mineralogical studies are essential in the realization of future CCS-projects.
Publications
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(2006): Long-term impact of CO2 on the stability of mineral assemblages in porous reservoir sandstones – Analogue study in natural CO2 reservoirs from Central Europe. DGMK spring conf., Celle/Germany, 20.04.-21.04.2006. Abstract vol., p. 165-172
Adelmann, D. and Gaupp, R.
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(2007): Mineralogical and geochemical investigations on red and bleached Buntsandstein deposits from CO2 accumulation sites in the Thuringian Basin, a southern extension of the CEBS. PTG-DGG conference, Szcecin/Poland, 24.09.-26.09.2007. Schriftenreihe Deut. Ges. Geowissensch., 53, p. 226
Pudlo, D., Gaupp, R. and Nover, G.
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(2009). Chlorite precipitation and dissolution in Palaeozoic wells sites in central and western Germany – reactions induced by CO2- bearing fluids?. GeoDresden 2009, Dresden, 30.09.-02.10.2009. Schriftenreihe Deut. Ges. Geowissensch., 63, p. 198
Pudlo, D., Gaupp, R. and May, F.
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(2009): Alteration phenomena in feldspar, sheet silicates, and carbonate minerals – clues to mineral-CO2-rich fluid interaction?. European Science Foundation conference (ESF-FWF), CO2 Geological Storage: Latest Progress. Obergurgl/Austria, 22.-27.11.2009
Pudlo, D., Eusterhues, K., Totsche, K.U. and Gaupp, R.
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(2009): Fault-related bleaching of Buntsandstein (Central Germany): Mineral reactions associated with fluids containing CO2. GeoDresden 2009, Dresden, 30.09.-02.10.2009. Schriftenreihe Deut. Ges. Geowissensch., 63, p. 206
Wendler, J., Köster, J., Kasch, N., Zisser, N., von der Gönna, J., Kley, J., Pudlo, D., Nover, G. and Gaupp, R.
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(2009): Fault-related bleaching phenomena in the Buntsandstein of central Germany – caused by CO2 release from volcanic sources? Int. conf. Deep Saline Aquifers for Geological Storage of CO2 and Energy. Paris/France, 27.05-29.05.2009. Abstract vol., p. 103
Köster, J., Wendler, J., Pudlo, D. and Gaupp, R.
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(2009): Genesis and alteration of volcanic lithoclasts in Rotliegend deposits in central Germany. GeoDresden 2009, Dresden, 30.09.-02.10.2009. Schriftenreihe Deut. Ges. Geowissensch., 63, p. 199
Pudlo, D., Hilse, U., Gaupp, R. and Gernert, U.
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(2010): Geochemical variations in German Buntsandstein and Rotliegend sandstones – the main CO2 reservoir rocks in Germany. Goldschmidt 2010 conf., Knoxville/USA, 13.06.-18.06.2010
Hilse, U., Pudlo, D. and Gaupp, R.
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(2010): Mineralalterationsphänomene im mittleren und oberen Buntsandstein des Thüringer Beckens. Thüringischer Geologischer Verein, 20. Jahreshauptversammlung, Jena/Germany, 04.06.-06.06.2010
Pudlo, D. and Gaupp, R.
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(2010): Mineralogische und geochemische Unterschiede von red bed Sedimenten (Buntsandstein, Rotliegend) in der Bohrung Metzels 1/64 (Thüringische Vorderrhön). Thüringischer Geologischer Verein, 20. Jahreshauptversammlung, Jena/Germany, 04.06.-06.06.2010
Hilse, U., Pudlo, D. and Gaupp, R.
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(2010): Petrographische, geochemische und Thermo-Gasuntersuchungen an red bed Sandsteinen der Thüringischen Vorderrhön. Thüringischer Geologischer Verein, 20. Jahreshauptversammlung, Jena/Germany, 04.06.-06.06.2010
Goepel, A., Hilse, U., Pudlo, D., Heide, K. and Gaupp, R.
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(2010): The relevance of chlorite-/biotite alteration on porosity/permeability attributes of CO2 reservoir rocks. AAPG conf., New Orleans/USA, 11.04.-14.04.2010
Pudlo, D. and Gaupp, R.
