ausblenden:
Schlagwörter:
4-7 March, 2012
DDC:
550 - Earth sciences
Zusammenfassung:
Rock core samples of Ketzin reservoir sandstone were exposed to pure CO2 and synthetic reservoir brine at simulated in-situ P-T conditions (5 MPa and 40C). Mineralogical and geochemical analyses were performed on rock and fluid samples taken after 15, 21, 24 and 40 months, respectively. Over time, XRD data with Rietveld refinement show decreasing proportions of analcime, chlorite, hematite and illite, and increasing proportions of quartz. On freshly broken rock fragments, CO2-treated samples show corrosion textures on plagio-clase, K-feldspar and anhydrite surfaces. EMPA data display a change in plagioclase composition from intermediate to Na-rich and albite endmember compositions. Compared to the synthetic reservoir brine, Na+, Mg2+ and Cl concentrations increased slightly, while K+, Ca2+ and SO42 concentrations increased significantly. K+ and Ca2+ even exceed reservoir brine concentration levels. Reactive geochemical modeling using Phreeqc-2 code was performed to reproduce experimental observations. The mineralogical and geochemical measurements imply preferred dissolution of Ca2+ out of plagioclase next to dissolution of K-feldspar and anhydrite. Assuming thermodynamic equilibrium preliminary reactive geochemical modeling of the observed CO2-fluid-rock interactions shows that the measured evolution of fluid composition is consistent with precipitation of albite and dissolution of anhydrite and illite, respectively. Based on experimental data, the integrity of the Ketzin reservoir is not significantly affected by CO2.
