Synthesis of the exploration of formations with a potential of CO_2 storage: Intermediate Depression and Madrid Basin

摘要

As a part and continuation of the work that is being done under the GeoCapacity Project,Spanish Geological Survey (IGME) has developed a selection of CO_2 storages in the great sedimentary basins of Spain. This presentation is a result of these studies in the Tagus River Basin,including the two zones in which this basin is traditionally divided in geological publications: Intermediate Depression and Madrid Basin. Using information from hydrocarbon exploration campaigns,mostly seismic and borehole logging,as a starting point,storage-seal pairs have been identified,attending to different criteria,such as depth,height,porosity or salinity of the formation water. Through the analysis of these parameters two geological formations have been selected as the most promising: Buntsandstein sandstone Formation,with a primary seal in R?t clays and a secondary seal in Keuper clays,and Utrillas sandstone Formation (Lower Cretaceous) with a seal in the Superior Evaporitical Formation (Upper Cretaceous). On the other hand,as a special case study of the GeoCapacity Project,a detailed study of a selected structure is being carried out in the Tagus River Basin,about 70 Km to the South East from Madrid. This structure is a long double-domed anticline detected under a thick Tertiary deposit that is not folded. Two different formations have been selected as potential storages: -Utrillas sandstone (L-M Cretaceous): It completely covers the extension of the structure,and it is sealed by Tertiary marls and gypsum. Average porosity varies from 7 to 18% and height is about 120 m at a depth of 1550 m. -Buntsandstein sandstone (L Triassic): It is only deposited in the Eastern dome of the structure,sealed by R?t clays of the Middle Triassic. Average porosity is 14% and height is about 50 m at a depth of 1700 m. Total capacity of the structure has been evaluated at a first stage in 812 Mt in the case both formations can be used as storage.