Faults and fractures in basement rocks, their architecture, petrophysical and mechanical properties

Torabi, Anita; Alaei, Behzad; Ellingsen, Tor Saltnes Skram

doi:10.1016/j.jsg.2018.07.001

Cited by 28 publications

(13 citation statements)

References 18 publications

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“…Fluid flow is promoted parallel to the main fault plane, especially parallel to the (sub-horizontal) intersection directions of the dominant fracture sets within the fault damage zone, whereas the anisotropic permeability of the fault core brittle structural facies buffers cross-fault fluid flow (Ceccato et al, 2021b, a;Tartaglia et al, 2020). Conversely, fracture clusters, comparable to our Set 1(a) lineaments, may represent effective fluid pathways at the outcrop scale, acting as preferential conduits for vertical fluid flow within the basement (Ceccato et al, 2021b, a;Torabi et al, 2018;Place et al, 2016;Souque et al, 2019). In summary, by integrating field and remote sensing data, we can improve the conceptual models and their dimen-sioning in an attempt to describe the anisotropic permeability structure of a fractured crystalline basement at different scales (e.g., Fig.…”

Section: Constraints On the Multiscale Permeability Structure Of Crys...mentioning

confidence: 84%

“…9d and e) needs to be accounted for when evaluating the upper limit of applicability of the general scaling laws defined here. The outcrop-scale spatial heterogeneity and the overestimation-underestimation effects due to applying a general power-law scaling become relevant when considering the role that different fracture sets may have in the definition of the net permeability of a fractured crystalline basement, as highlighted by field studies (Ceccato et al, 2021b, a;Gabrielsen and Braathen, 2014;Torabi et al, 2018).…”

Section: Spatial Organization and Scaling Limitationsmentioning

confidence: 99%

“…As constrained by field studies, each lineament/fracture set may contribute differently to the bulk permeability of a fractured crystalline basement block (Ceccato et al, 2021b, a;Gabrielsen and Braathen, 2014;Torabi et al, 2018). The effects of the background fracturing of the Rolvsnes granodiorite on permeability is secondary (Ceccato et al, 2021a), it being mainly composed of minor sealed faults and mineralized fractures belonging to Set 2-4 lineaments.…”

Section: Constraints On the Multiscale Permeability Structure Of Crys...mentioning

confidence: 99%

“…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). One way to obtain quantitative constraints upon the scale dependency of fracture and fault network attributes is to perform a multiscale analysis of, for example, their length and spacing distributions.…”

Section: Introductionmentioning

confidence: 99%

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Multiscale lineament analysis and permeability heterogeneity of fractured crystalline basement blocks

et al. 2022

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Abstract. The multiscale analysis of lineament patterns helps define the geometric scaling laws and the relationships between outcrop- and regional-scale structures in a fracture network. Here, we present a novel analytical and statistical workflow to analyze the geometrical and spatial organization properties of the Rolvsnes granodiorite lineament (fracture) network in the crystalline basement of southwestern Norway (Bømlo Island). The network shows a scale-invariant spatial distribution described by a fractal dimension D≈1.51, with lineament lengths distributed following a general scaling power law (exponent α=1.88). However, orientation-dependent analyses show that the identified sets vary their relative abundance and spatial organization and occupancy with scale, defining a hierarchical network. Lineament length, density, and intensity distributions of each set follow power-law scaling laws characterized by their own exponents. Thus, our multiscale, orientation-dependent statistical approach can aid in the identification of the hierarchical structure of the fracture network, quantifying the spatial heterogeneity of lineament sets and their related regional- vs. local-scale relevance. These results, integrated with field petrophysical analyses of fracture lineaments, can effectively improve the detail and accuracy of permeability prediction of heterogeneously fractured media. Our results also show how the geological and geometrical properties of the fracture network and analytical biases affect the results of multiscale analyses and how they must be critically assessed before extrapolating the conclusions to any other similar case study of fractured crystalline basement blocks.

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Section: Constraints On the Multiscale Permeability Structure Of Crys...mentioning

confidence: 84%

Section: Spatial Organization and Scaling Limitationsmentioning

confidence: 99%

Section: Constraints On the Multiscale Permeability Structure Of Crys...mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Multiscale lineament analysis and permeability heterogeneity of fractured crystalline basement blocks

et al. 2022

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“…In total, nine normal faults were studied (Figs 4 & 11) with dip-slip displacement ranging from a few centimetres to several metres (Torabi et al 2018). The main set of fractures and faults, which are predominantly filled with epidote, are captured in scanlines 1 and 2 ( Fig.…”

Section: Sotra Island Outcrop Datamentioning

confidence: 99%

Fault zone architecture and its scaling laws: where does the damage zone start and stop?

Torabi

Ellingsen

Johannessen

et al. 2019

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Damage zones of different fault types are investigated in siliciclastics (Utah, USA), carbonates (Majella Mountain, Italy) and metamorphic rocks (western Norway). The study was conducted taking measurements of deformation features such as fractures and deformation bands on multiple 1D scanlines along fault walls. The resulting datasets are used to plot the frequency distribution of deformation features and to constrain the geometrical width of the damage zone for the studied faults. The damage-zone width of a single fault is constrained by identifying the changes in the slope of cumulative plots made on the frequency data. The cumulative plot further shows high deformation frequency by a steep slope (inner damage zone) and less deformation as a gentle slope (outer damage zone). Statistical distributions of displacement and damage-zone width and their relationship are improved, and show two-slope power-law distributions with a break point at c. 100 m displacement. Bleached sandstones in the studied siliciclastic rocks of Utah are associated with a higher frequency of deformation bands and a wider damage zone compared to the unbleached zone of similar lithology. Fault damage zones in the carbonate rocks of Majella are often host to open fractures (karst), demonstrating that they can also be conductive to fluid flow.

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Contribution of bedrock structures to the bedrock surface topography and groundwater flow systems within deep glaciofluvial aquifers in Kurikka, Western Finland

Ruuska

Skyttä

Putkinen

et al. 2023

Earth Surf Processes Landf

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One of the key challenges related to glaciofluvial aquifers is understanding how the underlying bedrock structures and the associated bedrock surface topography contributed to the deposition of the glaciofluvial sediments and the generation of groundwater flow pathways. In this study from Western Finland, we present a new digital elevation model of the Precambrian crystalline bedrock surface buried up to 100 m beneath the glaciofluvial sediments along the Kurikka depression. We link bedrock topography to structural anisotropy using additional data from rock outcrops, boreholes and gravity data. Brittle deformation zones are seen in the bedrock‐digital elevation model (DEM) as sharp breaks in the rock surface. These vertical fracture zones contributed to the development of interlinked elongate bedrock depressions and delimit rock blocks with different elevations. A narrow, zigzagging trench, with a stepped floor, follows WNW‐ESE and NE‐SW oriented fracture zones and forms a major hydraulic connection between two major parts of the aquifer. Furthermore, the conductive fracture zones are conduits which connect the shallow glacifluvial aquifer system to deep groundwater in the bedrock. Understanding bedrock structures and buried topography is critical for successful groundwater modelling in crystalline, fractured bedrock.

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Faults and fractures in basement rocks, their architecture, petrophysical and mechanical properties

Cited by 28 publications

References 18 publications

Multiscale lineament analysis and permeability heterogeneity of fractured crystalline basement blocks

Multiscale lineament analysis and permeability heterogeneity of fractured crystalline basement blocks

Fault zone architecture and its scaling laws: where does the damage zone start and stop?

Contribution of bedrock structures to the bedrock surface topography and groundwater flow systems within deep glaciofluvial aquifers in Kurikka, Western Finland

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