In–situ quantification of mechanical and permeability properties on outcrop analogues of offshore fractured and weathered crystalline basement: Examples from the Rolvsnes granodiorite, Bømlo, Norway

Multiscale lineament analysis and permeability heterogeneity of fractured crystalline basement blocks

“…The in situ analysis and characterization of the structural elements forming this fracture and fault zone network, e.g., the Goddo Fault Zone (GFZ, Fig. 1), have previously allowed us to reconstruct the absolute and relative timing of the various brittle deformation phases that affected the area and to quantify the geometry and petrophysical properties of the fractures (Ceccato et al, 2021b, a;Scheiber and Viola, 2018;Viola et al, 2016), although the larger-scale geometry and organization of the fracture and fault network on Bømlo remained poorly constrained and thus needed further constraining and quantification. To this end, fracture network maps of the study area were obtained from the manual picking of lineaments on lidar digital terrain model, aerial, and unmanned aerial vehicle (UAV, drone) orthophotos of the exposure area of the Rolvsnes granodiorite (Fig.…”

“…In this work, rather than trying to accurately quantify the scaling parameters, we focused on highlighting and analyzing the weaknesses and uncertainties that invariably accompany this sort of lineament analysis even when very robust statistical approaches and analytical methods are applied (Dichiarante et al, 2020). By integrating this information with existing field structural analyses and modeling of lineament petrophysical properties (Ceccato et al, 2021b, a;Scheiber and Viola, 2018), we provide further constraints on the multi-scale heterogeneity in magnitude, orientation, and spatial distribution of the permeability structure of the studied fractured crystalline basement.…”

“…A key structure for the detailed analysis of the timing of deformation, the geometry of the deformation structures, and the effects of deformation on the petrophysical properties of the crystalline basement of Bømlo is the Goddo Fault Zone (GFZ, Fig. 1), (Ceccato et al, 2021b, a;Scheiber and Viola, 2018;Viola et al, 2016). The GFZ is an east-dipping normal fault that accommodated multiple slip increments during the prolonged Permian-to-Cretaceous rifting of the North Sea, recording several stages of reactivation, during which a complex network of brittle structural facies developed in the fault core (sensu Tartaglia et al, 2020).…”

“…The GFZ is an east-dipping normal fault that accommodated multiple slip increments during the prolonged Permian-to-Cretaceous rifting of the North Sea, recording several stages of reactivation, during which a complex network of brittle structural facies developed in the fault core (sensu Tartaglia et al, 2020). Structures like the GFZ actually controlled the permeability and fluid flow evolution from rifting to current times of the crystalline basement (Ceccato et al, 2021b, a;Viola et al, 2016).…”

“…Crystalline rocks are characterized by very low intrinsic permeability, usually on the order of 10 −18 m 2 (Achtziger- Zupančič et al, 2017;Brace, 1984), so that their capability to transmit and/or store fluids is mainly related to the structural permeability associated with fracture and fault networks created by brittle deformation and the associated fluid-rock interaction (Caine et al, 1996;Caine and Tomusiak, 2003;Ceccato et al, 2021b, a;Evans et al, 1997;Pennacchioni et al, 2016;Schneeberger et al, 2018;Stober and Bucher, 2015). When studied at different scales, fracture and fault networks commonly exhibit variable geometrical and spatial characteristics, which may significantly affect the overall permeability structure (spatial heterogeneity and anisotropy of permeable zones) of the fractured crystalline rock (Le Garzic et al, 2011;Hardebol et al, 2015;Holdsworth et al, 2019;Torabi et al, 2018).…”