A natural analogue study of CO2-cement interaction : carbonate alteration of calcium silicate hydrate-bearing rocks from Northern Ireland

摘要

The underground sequestration of anthropogenic carbon dioxide (CO2) is one potential methodology for reducing our emissions of this greenhouse gas into the atmosphere, and hence reducing a driver for climate change. For this technique to be effective, the CO2 must remain underground for timescales measurable in thousands of years or more. A key factor in such long-term containment is the efficacy of the seals overlying the stored CO2. Boreholes penetrating potential CO2 storage aquifer/reservoir formations provide potential pathways for CO2 leakage that may cross formations and breach overlying seals strata. In this respect, understanding the long-term stability of cement and steel casing used in borehole completion and sealing, and their interaction with CO2 are of paramount importance.udThe focus of this report is to provide an insight into the long-term stability of borehole cement and its potential interactions with CO2 from studying the alteration, through carbonation, of naturally-occurring cementitious calcium silicate and calcium silicate hydrate (CSH) materials in natural systems (i.e. “natural analogues”). These natural analogues observations may provide information on processes and reactions that may affect the long-term stability of borehole cements over greater timescales than can be studied in laboratory experiments (which are limited by reaction kinetics and may be influenced by the formation of metastable phases).