A 3D geological model for a potential CO2 reservoir in the El Bierzo Basin (Carboniferous, NW Spain)

• Published in: Near surface geophysics (Online) 2020-04, Vol.18 (2), p.189-201
• Main Authors: Rey‐Moral, Carmen, Motis, Kilian, Fernández‐Viejo, Gabriela, García‐Lobón, Jose Luis
• Format: Article
• Language: English
• Subjects: 3D modelling; CO2 reservoir; intramontane Bierzo Basin; NW Iberia
• ISSN: 1569-4445; 1873-0604
• DOI: 10.1002/nsg.12089

ABSTRACT A 3D geological model of the Torre‐Bembibre Carboniferous sub‐basin, a potential CO2 storage reservoir, is proposed here. The Torre‐Bembibre sub‐basin is part of the El Bierzo coal‐bearing Carboniferous basin located in the westernmost part of León province (NW Spain). It covers an area of about 150 km2. Carboniferous deposits (up to 1500 m of continental siliciclastics) are divided into nine intervals, defined by earlier coal exploration work. They were deposited as intramontane basin infill within a transpressional regime during the last stages of the Variscan Orogeny and are partially covered by Neogene and Quaternary continental siliciclastic sediments, formed by alluvial plains, fans and terraces. To resolve a 3D geological model of the Torre‐Bembibre sub‐basin, including outcropping layers and their prolongation at depth, a 3D dip‐domain method was applied, where data from all stratigraphic positions were used to compose a coherent geological reconstruction of the stratigraphic surfaces. Subsurface information was available from previous and newly acquired seismic reflection profiles and boreholes. The 3D model helped resolving some uncertainties, specifically: (i) the western termination of the Carboniferous basin under the Tertiary sediments, corresponding to an NNE–SSW normal fault, (ii) the depth and morphology of the base of the Carboniferous strata and (iii) the morphology of the intra‐Carboniferous layers. The syncline/anticline shape of the Torre‐Bembibre sub‐basin suggests a reservoir which may be capable of storing CO2 under the Tertiary cover. The total estimated volume is 6.4 km3, while the total capacity for CO2 storage could be as much as 7 Mt. The reservoir is most likely located within the major massive sandstone bodies in the Chuchu interval, in the syncline–anticline structure north of the town of Bembibre. The potential capacity of the reservoir calls for undertaking further studies using the proposed 3D geological model in order to determine more precisely the petrophysics and geometry near Bembibre.