Basement structure of the Hontomín CO₂ storage site (Spain) determined by integration of microgravity and 3-D seismic data

Abstract. A multidisciplinary study has been carried out in Hontomín (Spain) to determine the basement structural setting, its geometry and the geometry of the sedimentary succession of an area aimed to be the first Spanish pilot plant for CO₂ storage. An integration of coincident 3-D seismic results, borehole data and unpublished microgravity data were used to reproduce the deep structure and topography of the basement and to quantify the thickness of the Triassic Keuper evaporites. The subsurface structure is characterized by a half-graben setting filled with Keuper evaporites (up to 2000 m thick), forming an extensional forced fold. All data sets clearly identify two main fault systems, compartmentalizing the main structural domain into three differentiated blocks. These faults have been interpreted to be reactivated normal faults that have led to the formation of the Hontomín dome.