Fracture and vein patterns as indicators of deformation history: a numerical study

Koehn, Daniel; Arnold, Jochen; Passchier, Cees W.

doi:10.1144/gsl.sp.2005.243.01.03

Cited by 15 publications

(14 citation statements)

References 25 publications

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“…Especially extension and strike slip deformation were accompanied by several generations of regional fractures and faults, which are cemented with calcite and minor quartz. Bedding perpendicular vein sets often follow stress oriented anastomosing patterns with regular spacing showing single extensional or conjugate extensional shear patterns [59]. These regularly spaced patterns seem to be overprinted by chaotic and very closely spaced veins that indicate the existence of high fluid pressure gradients.…”

Section: Resultsmentioning

confidence: 99%

“…Natural disorder in geological media corresponds to the ubiquitous presence of Griffith's microcracks, variation in their densities and lengths and other defects, which are present at the grain scale. It has been demonstrated that fracture patterns that are observed both in the field and laboratory can be numerically reproduced by implying realistic normal distributions of breaking strength in DEM models [57][58][59][60]. The overall breaking strength of the model material, and its failure mode, is sensitive to the lower values of the quenched distribution [61][62][63].…”

Section: Methodsmentioning

confidence: 97%

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Dynamics of hydrofracturing and permeability evolution in layered reservoirs

Ghani¹,

Koehn

Toussaint

et al. 2015

Front. Phys.

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International audienceA coupled hydro-mechanical model is presented to model fluid driven fracturing in layered porous rocks. In the model the solid elastic continuum is described by a discrete element approach coupled with a fluid continuum grid that is used to solve Darcy based pressure diffusion. The model assumes poro-elasto-plastic effects and yields real time dynamic aspects of the fracturing and effective stress evolution under the influence of excess fluid pressure gradients. We show that the formation and propagation of hydrofractures are sensitive to mechanical and tectonic conditions of the system. In cases where elevated fluid pressure is the sole driving agent in a stable tectonic system, sealing layers induce permutations between the principal directions of the local stress tensor, which regulate the growth of vertical fractures and may result in irregular pattern formation or sub-horizontal failure below the seal. Stiffer layers tend to concentrate differential stresses and lead to vertical fracture growth, whereas the layer-contact tends to fracture if the strength of the neighboring rock is comparably high. If the system has remained under extension for a longer time period, the developed hydrofractures propagate by linking up confined tensile fractures in competent layers. This leads to the growth of large-scale normal faults in the layered systems, so that subsequently the effective permeability is highly variable over time and the faults drain the system. The simulation results are shown to be consistent with some of the field observations carried out in the Oman Mountains, where abnormal fluid pressure is reported to be a significant factor in the development of several generations of local and regional fracture and fault sets

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Section: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 97%

Dynamics of hydrofracturing and permeability evolution in layered reservoirs

Ghani¹,

Koehn

Toussaint

et al. 2015

Front. Phys.

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“…1 The numerical scheme is built on a 2D hybrid Particle-Lattice model of unit dimension 2 that utilizes a small-scale triangular discrete spring network code inherited from the software 3 'Latte' (part of the modeling environment 'Elle', [Bons et al, 2007;Koehn et al, 2005]) as a 4 deformation isotropic porous material. The discrete lattice is then coupled with a continuum fluid 5 phase presented by a stationary square grid of equivalent or larger dimension (figure 2).…”

Section: 1) Methodologymentioning

confidence: 99%

“…Inspired by [Flekkøy et al, 2002] we extended the work of [Koehn et al, 2005] to a 3 hybrid discrete-continuum constitutive modeling approach. The scheme emphasizes the 4 evolution of rock failure in the light of underlying synergistic evolution of rock permeability 5 upon fracture growth and the consequent change in interstitial pore pressure.…”

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confidence: 99%

Dynamic Development of Hydrofracture

Ghani

Koehn

Toussaint

et al. 2013

Pure Appl. Geophys.

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23Many natural examples of complex joint and vein networks in layered sedimentary rocks are 1 hydro-fractures that form by a combination of pore fluid overpressure and tectonic stresses. In 2 this paper, a two-dimensional hybrid hydro-mechanical formulation is proposed to model the Darcy based pore-pressure diffusion as continuum description for the fluid. This combination 6 yields a porosity controlled coupling between an evolving fracture network and the associated 7 hydraulic field. The model is tested on some basic cases of hydro-driven fracturing commonly 8 found in nature i.e., fracturing due to local fluid overpressure in rocks subjected to hydrostatic 9 and nonhydrostatic tectonic loadings. In our models we find that seepage forces created by 10 hydraulic pressure gradients together with poroelastic feedback upon discrete fracturing play a 11 significant role in subsurface rock deformation. These forces manipulate the growth and [Fyfe et al., 1978]. A number of fluid expansion mechanisms e.g., The mechanism of hydrofracturing has great implications in the interpretation of field 21 observations and for the prediction of natural or industrial problems in a broad range of research 22 disciplines. After pioneering work of [Hubbert and Willis, 1957;Hubbert and Rubey, 1959] 23 which explored pore fluid pressure as an important factor for small scale hydrofracturing in 1 tectonic processes, significant efforts have been made in the development of theoretical 2 fundamentals [Biot et al., 1986; J M Cleary and Illinois State Geological Survey., 1958; 3 Daneshy, 1973;Secor, 1965;Valkó and Economides, 1995]. Apart from theoretical aspects, a 4 significant amount of analytical and numerical solutions have also been put forward by many 5 investigators to address this coupled process in a qualitative and quantitative manner [M P 6 Cleary and Wong, 1985;Flekkøy et al., 2002;Gordeyev and Zazovsky, 1992;Meyer, 1986; 7 Tzschichholz et al., 1994;Yu.N, 1993]. 15Some porosity controlled models [Boone and Ingraffea, 1990;Flekkøy et al., 2002; Mourgues 16 and Cobbold, 2003;Olson et al., 2009;Wangen, 2002] revealed that the potential response of 17 inherent poroelastic mechanics is an important parameter in hydro-driven rock failure, where the 18 seepage forces caused by pore pressure gradients [Engelder and Lacazette, 1990;Rozhko, 2010; 19 Rozhko et al., 2007] in porous rocks affect the driving stress for fracture initiation and growth. 20Regardless of the underlying driving agent hydrofracturing is a complex process which 21 incorporates the dynamic coupling of at least three sub-processes [Adachi et al., 2007]; 1) 22Restructuring of rock skeleton upon elastic/in-elastic strain. 2) Corresponding alteration of both 23

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“…The net force F acting on a node within the network is given by (Monette and Anderson 1994;Malthe-Sørenssen et al 1998;Koehn et al 2005).…”

Section: Forces Related To Elasticitymentioning

confidence: 99%

Faulting of the lithosphere during extension and related rift-flank uplift: a numerical study

Sachau¹,

Koehn²

2010

Int J Earth Sci (Geol Rundsch)

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In this contribution, we present a new model of passive rifting and related rift-flank uplift. The numerical model is based on a lattice spring network coupled with a viscous particle model so that we can simulate visco-elasto-plastic behaviour with dynamic fault development. In our model, we show that rift-flank uplift can be achieved best when extension in the crust is localized and the lower crust is strong so that major rift faults transect the whole crust. Uplift of rift flanks follows a smooth function whereas down-throw in the rift basin takes place in steps. The geometry of the developing faults has also an influence on the uplift; in this case, displacement along major rift faults produces higher flanks than distributed displacement on many faults. Our model also shows that the relative elastic thickness of the crust has only a minor influence on the uplift since fault depth and elastic thickness are not independent. In addition, we show with a second set of simulations and analytically that a strain misfit between the upper and lower boundaries of a stretched crust, which is created by the horizontal extension, leads to an active uplift driven by elastic forces. We compare the numerical simulations, the analytical solution and real surface data from the Albertine rift in the East African Rift System and show that our new model can reproduce realistic features. Our two-layer beam model with strain misfit can also explain why a thick crust in the simulations can have an even higher rift flank than a thin crust even though the thin crust topography has a higher curvature. We discuss the implications of our simulations for real rift systems and for the current theory of rift-flank uplift.

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Fracture and vein patterns as indicators of deformation history: a numerical study

Cited by 15 publications

References 25 publications

Dynamics of hydrofracturing and permeability evolution in layered reservoirs

Dynamics of hydrofracturing and permeability evolution in layered reservoirs

Dynamic Development of Hydrofracture

Faulting of the lithosphere during extension and related rift-flank uplift: a numerical study

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