Caracterización conjunta del basamento en Hontomín (España) empleando datos sísmicos y microgravimétricos

Abstract

Hontomín hosts the first Spanish CO2 storage research plant. The geophysical characterisation of the site included the acquisition of a 36 km2 3D seismic and a 16 km2 3D microgravimetric datasets. The integration of these data is here used to: (1) reproduce the deep structure and topography of the basement; (2) quantify the thickness of the Triassic Keuper evaporites, located between the sedimentary succession and the metamorphic basement; and (3) establish relationships between the faults interpreted in the seismic data and those inferred from the gravimetric data in the basement. The geometry of the sedimentary succession and structures interpreted from the seismic volume were used to constrain the inversion of the microgravity data: i.e. their gravimetric signature was calculated and then removed it from the Bouguer Anomaly. The top of the basement geometry was used, along that of the top of the Triassic Keuper, to calculate the salt thickness. The basement structure is characterized by a half-graben, thick-skinned setting filled with thick Keuper evaporites (up to 2000 m thick) forming an extensional forced fold. The two datasets identified two main fault systems compartmentalizing the structural domain into three differentiated blocks: the Central, South and East blocks. Furthermore, another inferred basement fault has been proposed to accommodate the thickening of the Triassic Keuper salts towards the NW of the area. These faults have been interpreted to be reactivated normal faults that led to the development of the Hontomín dome