Normal faults, layering and elastic properties of rocks

Roche, Vincent; Homberg, Catherine; David, Christian; Rocher, M.

doi:10.1016/j.tecto.2014.03.006

Cited by 14 publications

(13 citation statements)

References 54 publications

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“…We used two models for the initial stress: the lithostatic and uniaxial strain models. In the literature most stress predictions are based on an initial uniaxial strain model (Voight and St. Pierre, 1974;Haxby and Turcotte, 1976;Savage, 1992;Blanton and Olson, 1999), and few are based on an initial lithostatic model (McGarr, 1988;Roche et al, 2014;Roche and Van der Baan, 2015). The choice of the initial stress model influences the final stress predictions for several reasons.…”

Section: Initial State Of Stressmentioning

confidence: 99%

“…Likewise, the possible occurrence of strain discontinuities does not appear decisive in disregarding the stress-driven model because strain decoupling likely exists in natural rocks, notably in the case of detachment faults (Cornet and Burlet, 1992;Meixner et al, 2014). Also, a recent study shows that fracturing depends on the contrast in elasticity between layers, as well as the layer thicknesses, rather than solely on the properties of the layer in which fracturing develops (Roche et al, 2014). This tends to support the stress-driven model rather than the strain-driven model.…”

Section: Strain-driven Models Versus Stress-driven Modelsmentioning

confidence: 99%

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Modeling of the in situ state of stress in elastic layered rock subject to stress and strain-driven tectonic forces

Roche

Baan

2017

Solid Earth

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Abstract. In this study we describe and compare eight different strategies to predict the depth variation of stress within a layered rock formation. This reveals the inherent uncertainties in stress prediction from elastic properties and stress measurements, as well as the geologic implications of the different models. The predictive strategies are based on well log data and in some cases on in situ stress measurements, combined with the weight of the overburden rock, the pore pressure, the depth variation in rock properties, and tectonic effects. We contrast and compare stresses predicted purely using theoretical models with those constrained by in situ measurements. We also explore the role of the applied boundary conditions that mimic two fundamental models of tectonic effects, namely the stress-or strain-driven models. In both models, layer-to-layer tectonic stress variations are added to initial predictions due to vertical variation in rock elasticity, consistent with natural observations, yet describe very different controlling mechanisms. Layer-to-layer stress variations are caused by either local elastic strain accommodation for the strain-driven model, or stress transfers for the stressdriven model. As a consequence, stress predictions can depend strongly on the implemented prediction philosophy and the underlying implicit and explicit assumptions, even for media with identical elastic parameters and stress measurements. This implies that stress predictions have large uncertainties, even if local measurements and boundary conditions are honored.

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Section: Initial State Of Stressmentioning

confidence: 99%

Section: Strain-driven Models Versus Stress-driven Modelsmentioning

confidence: 99%

Modeling of the in situ state of stress in elastic layered rock subject to stress and strain-driven tectonic forces

Roche

Baan

2017

Solid Earth

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Section: Initial State Of Stressmentioning

confidence: 99%

Modeling of the in situ state of stress in elastic layered rock subject to stress and strain-driven tectonic forces

Roche¹,

Baan²

2016

Preprint

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Abstract. In this study we describe and compare eight different strategies to predict the depth variation of stress within a layered rock formation. This reveals the inherent uncertainties in stress prediction from elastic properties and stress measurements, as well as the geologic implications of the different models. The predictive strategies are based on well log data and in some cases on in situ stress measurements, combined with the weight of the overburden rock, the pore pressure, the depth variation in rock properties, and tectonic effects. We contrast and compare stresses predicted purely using theoretical models with those constrained by in situ measurements. We also explore the role of the applied boundary conditions mimicking two fundamental models of tectonic effects, namely the stress or strain-driven models. In both models layer to layer tectonic stress variations are added to initial predictions due to vertical variation in rock elasticity, consistent with natural observations, yet describing very different controlling mechanisms. Layer to layer stress variations are caused by either local elastic strain accommodation for the strain-driven model, or stress transfers for the stress-driven model. As a consequence, stress predictions can depend strongly on the implemented prediction philosophy and the underlying implicit and explicit assumptions, even for media with identical elastic parameters and stress measurements. This implies that stress predictions have large uncertainties, even if local measurements and boundary conditions are honored.

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“…In particular shales and coals may exhibit anisotropy due a preferred orientation of minerals or preexisting fracturing [Thomsen, 1986;Sarout et al, 2007;Tsvankin et al, 2010]. The bedding-parallel Young's modulus may be up to 4 times the bedding-normal one [Thury, 2002;Sarout et al, 2007;Roche et al, 2014]. As a consequence, anisotropic Young's moduli tend to reverse the effect of plasticity strain, thus decreasing the likelihood of failure in the shales and coals.…”

Section: Rock Behavior and Estimated Rock Propertiesmentioning

confidence: 99%

The role of lithological layering and pore pressure on fluid‐induced microseismicity

Roche

Baan

2015

JGR Solid Earth

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The success of hydraulic fracturing treatments is often judged by the shape and size of the resulting microseismic cloud. However, it is challenging to predict the anticipated microseismic cloud prior to treatment. We use geomechanical modeling to predict the distribution of the microseismicity prior to the hydraulic fracture treatment. We analyze the likelihood of tensile and shear failure due to 1-D variations in local stresses and rock strengths, induced by layering and pore pressure, for two field cases. The deviation in the local stresses from the regional stress field is induced by vertical variations in stiffness. This promotes failure of the stronger layers instead of the weaker ones since the stronger layers can become essentially load bearing. The simulations and field studies show that (1) microseismic events tend to locate preferentially where layers reach tensile failure due to fluid injection, and the number of events tends to decrease in layers that do not reach tensile failure; (2) shear initiation can occur in different layers from those failing in tension, thereby creating additional fluid migration paths; and (3) reactivation of preexisting fractures may occur due to fluid migration, even if their orientations are unfavorable. Numerical modeling is a significant aid in understanding the interplay of regional and local stresses and associated in situ failure due to variations in rock strength, pore pressure, and stiffnesses. In a wider perspective, it gives fundamental insights into the understanding of earthquakes and fault localization, the mechanisms of fracture development, and the role of fractures on fluid circulation and on the in situ stress field.

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Normal faults, layering and elastic properties of rocks

Cited by 14 publications

References 54 publications

Modeling of the in situ state of stress in elastic layered rock subject to stress and strain-driven tectonic forces

Modeling of the in situ state of stress in elastic layered rock subject to stress and strain-driven tectonic forces

Modeling of the in situ state of stress in elastic layered rock subject to stress and strain-driven tectonic forces

The role of lithological layering and pore pressure on fluid‐induced microseismicity

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