engleski

Regional Capacity Estimates for Geological Storage of CO2 in Deep Saline Aquifers – Upper Miocene Sandstones in the Sw Part of the Pannonian Basin

Deep saline aquifers –formations of porous and permeable rocks deeper than 800m, are regarded as the most promising objects for CO2 geological storage, mostly because of their large storage capacities and extensive spatial distribution in most sedimentary basins. The only but important drawback is that these formations have not been as extensively explored compared to the oil and gas fields. That is why present capacity estimations are burdened with the greatest level of uncertainty. The first estimations of storage capacities in deep saline aquifers within the Croatian part of Pannonian basin were made in FP6 projects Castor and EU GeoCapacity. Methodology was simplified, based on a volumetric approach and with the single average value of thickness, temperature, pressure and porosity used for each of the objects. Therefore, the obtained capacities were only theoretical, with no attempt to delineate the most prospective areas within aquifers and to really define the distribution of the cap rock and reservoir rock properties. Significant step from regional towards local capacity estimation is redefinition of regional storage capacities applying modified methodology for integrated studies of hydrocarbon reservoirs. The most important aspects of this novel procedure were investigated by detailed mapping of the West Sava aquifer. First, the caprock was chosen based on its depth, thickness and lateral continuity. The target reservoir was chosen in the second phase – the Upper Miocene Poljana sandstone layers underlying the regional caprock. Their depth and effective thickness, as well the subsurface pressure, temperature and resulting density of CO2 were mapped based on the well data. The aquifer body was then divided into prisms and the storage capacity was calculated for each of these elements. Due to the lack of data concerning the spatial distribution of porosity, the average porosity value from the neighbouring oil fields was used. The resulting map of specific storage capacity shows the areas of greater potential for geological storage, namely parts of the deep saline aquifer that should be further investigated for detailed definition of the potential storage objects.

CO2 geological storage; storage capacity estimates; deep saline aquifers; Upper Miocene sandstones; Sava depression

nije evidentirano