Resistance of cementing systems under the conditions of permanent geological storage of CO₂ (CCS technology)

1 CCS diagram

2 Timon Echt closes the 4 l autoclave for the precuring of the cement samples under N₂

3 Experimental setup for the long-term storage of cement samples in scCO₂; left and centre: 2 L autoclaves; right: stainless steel rack for positioning the test samples in the autoclaves

4 Appearance of the cement samples after 6 months storage in CO₂ at 90 °C and a pressure of 400 bar

5 Cracking in in the test specimens of cementing systems C and D after 6 months’ storage in scCO₂ at 90 °C and 400 bar

6 Optical appearance (colouring by means of phenolphthalein) of cement specimens after storage in water-saturated CO₂ for 1 and 6 months at 90 °C and 400 bar pressure

7 Total porosity and pore size distribution of the cement samples after storage at 400 bar CO₂ pressure and 90 °C in synthetic reservoir fluid (liquid phase) or water-saturated CO₂; storage times: 1 and 6 months

Long-term stability of CCS systems

Permanent sealing of underground disposal sites for CO₂using CCS technology is only possible if suitable cementing systems are used.

In order to test their stability agains CO₂, four cementing systems prepared from different Portland cement and additive combinations were exposed to supercritical CO₂ at 90 °C and 400 bar. All cementing systems were attacked by the CO₂, but the rates of carbonation of the cement matrix were negligibly small. It was of greater significance that two of the tested systems suffered massive cracking due to the crystallization pressure of the CaCO₃formed. This process allows a relatively fast ascension of the CO₂. Cracking is therefore a key parameter concerning the long-term sealing of a CCS...

TEXT Prof. Dr. Johann Plank, Dipl.-Ing. Matthias Lesti, Dipl.-Chem. Constantin Tiemeyer, M. Sc. Timon Echt
Chair for Construction Chemicals, Technische Universität München, Garching/Germany