Effects of supercritical carbon dioxide on rocks having carbon dioxide storage potential

Abstract

One of the most important problems of our society is the rising CO2 concentration of the atmosphere supposed to be a reason of the climate change. The Carbon Capture and Sequestration (CCS) may be a temporary solution for this problem. CCS is the technology when the CO2is separated from the local CO2 sources, and is injected at least 800–1000 m deep where, because of the high pressure and higher than ambient temperature, it will be supercritical (scCO2). We need to study what are the geochemical changes induced by scCO2 to use safely this technology. This was the main motive why we started to make experimental and analytical methods on real core samples from exploration drilling. We added scCO2 to sandstone core samples in brine and very high purity calcite samples in 5 w/w% NaClsolution in 70–220 bar pressure interval and in 55–65 °C temperature interval in a high pressure resistant bomb and autoclave. After experiments the brine and solution samples were analyzed by ICP-MS and the core samples by XRF and SEM. The results indicated significant alteration in the concentration of Na, Ca, Mg, K, Fe and Srions concentration before and after the addition of scCO2. After adding scCO2the concentration of Ca grew in the brine and was reduced on the surface of the sandstone. The XRF results indicated a very high dispersion of the elements on the surface of the samples. The SEM images show Ca soluble-cuts and solution of the surface.