Basement structure of the Hontomín CO<sub>2</sub> storage site (Spain) determined by integration of microgravity and 3-D seismic data

Abstract

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 CO 2 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 An integration of coincident 3-D seismic results, borehole data and unpublished microgravity data were used to reproduce the deep structure and topography of the basement and to quantify the thickness of the Triassic Keuper evaporites.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.

A review of structural inheritance in rift basin formation

“…The examples we discuss here suggest that there is scope for applying our knowledge of lithospheric and crustal-scale controls of inheritance to geothermal and mineral systems, which can contribute to successful exploration and development of geothermal energy, base metals, and critical metals. Basement structure characterisation and quantification of the reactivation potential of pre-existing fractures (including faults) under in-situ stresses must also be implemented in geothermal drilling projects (Deichmann and Giardini, 2009;Diehl et al, 2017), in addition to exploring the feasibility of geological storage of CO2 (e.g., Andrés et al, 2016) and nuclear waste (e.g., Barton and Zoback, 1994) to support the current energy transition.…”

“…A more complete picture of different inheritance mechanisms can help us clarify the mechanical controls on rift and basin evolution and open up opportunities to: (i) "uncover" the characteristics of buried basement rocks that are commonly poorly imaged in geophysical surveys; (ii) better understand the structural evolution of rifted margins; and (iii) provide additional constraints on plate reconstructions. Understanding the potential impact of preexisting basement structures on younger fault networks also has implications for seismic hazards assessment (e.g., Fonseca, 1988;Wedmore et al, 2020b;Hecker et al, 2021), geothermal energy (e.g., Schumacher, 2002;Bertrand et al, 2018), mineral exploration (e.g., Rowland and Sibson, 2004), and CO2 and nuclear waste storage (e.g., Barton and Zoback, 1994;Andrés et al, 2016).…”

3-D seismic travel-time tomography validation of a detailed subsurface model: a case study of the Záncara river basin (Cuenca, Spain)

“…Geophysical techniques provide a great variety of approaches to accurately describe the structure and the distribution of different physical properties in the subsurface. Depending on the target depth and the required spatial resolu-D. Marti et al: A case study of the Záncara river basin (Cuenca, Spain) tion, different methodologies can be applied (e.g., Bryś et al, 2018;Novitsky et al, 2018;Malehmir et al, 2009 andCarbonell et al, 2010;Ogaya et al, 2016;Andrés et al, 2016;Alcalde et al, 2013b). Since the late 90s, sophisticated geophysical techniques have been developed to estimate near-surface velocity models as a proxy for subsurface stiffness in seismic applications with different targets (Bergman et al, 2004 andHeincke et al, 2010).…”