Prospects for CO2 carbonation and storage in Upper Miocene sandstone of Sava Depression, Croatia

Upper Miocene sandstones in the Sava Depression (Northern Croatia) are potential targets for carbon dioxide (CO2)-based enhanced oil recovery (EOR) processes or mineral carbonation with reservoir brine. In general, sandstone lithology, even rich with aluminosilicate minerals, is not the most favourable rock medium for efficient sequestration of CO2 in minerals. However, CO2 is naturally sequestered in minerals when CO2 is injected into sandstone reservoirs and subdued to carbonation. The timescale of such sequestration is on the order of 104–105 years. Upper Miocene sandstones in the Sava Depression could incorporate up to 25% of aluminosilicate minerals (10% K-feldspars) and up to 20% dolomites and often laterally transition between pelitic and psammitic lithofacies, rich in clay minerals (15% micas). Total volumes are approximately 107 and 62 million m3 (approximately 268 and 155 million t of rocks), respectively for the potential injection reservoirs in the Ivanić Field. Oil saturation in the injection intervals is estimated to be approximately 14.8 and 4.1 million m3 respectively. Geochemical analogies and mineralogy can be used to support predictions for the low percentages of injected CO2 that may be stored during carbonation and form secondary minerals