Regional capacity estimates for CO2 geological storage in deep saline aquifers – Upper Miocene sandstones in the SW part of the Pannonian basin

• CCS represents an important option for the reduction of emissions in Croatia.
• A step is missing between storage capacity estimates on a regional and a local level.
• Tailored method for estimation of storage capacity is suggested.
• Suggested method should enable delineation of areas with higher storage potential.

Deep saline aquifers are regarded as the most suitable sites or options for CO2 geological storage, mainly due to their large storage capacity and extensive spatial distribution in most sedimentary basins. The estimation of the storage capacity in this type of sinks presents a problem due to the lack of subsurface data. A significant step from regional towards local capacity estimation is redefinition of regional storage capacity by applying modified methodology for integrated studies of hydrocarbon reservoirs. The suggested procedure was investigated by detailed mapping of the Sava West aquifer in the Croatian part of the Pannonian basin. First, the cap rock was chosen based on its depth, thickness and lateral continuity, and then the target reservoir – Upper Miocene Poljana sandstone layers underlying the regional cap rock. Their depth and effective thickness, as well as the subsurface pressure, temperature and resulting density of CO2 were mapped based on the well data. The aquifer body was then divided into square elements and the storage capacity was calculated for each of them.Mapping of specific storage capacity in this way enables identification of the areas of greater potential for geological storage that should be further investigated for detailed definition of the potential storage objects.