Articles | Volume 8, issue 2
https://doi.org/10.5194/se-8-479-2017
https://doi.org/10.5194/se-8-479-2017
Research article
 | 
12 Apr 2017
Research article |  | 12 Apr 2017

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

Vincent Roche and Mirko van der Baan

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 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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Short summary
Knowledge of in situ stress magnitudes and their spatial variability is critical for various topics, but local information on the stress field is often sparse and incomplete. In this case, analytic formulations, or numerical models, have to be used. 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.