Mechanical controls on horizontal stresses and fracture behaviour in layered rocks: A numerical sensitivity analysis

Boersma, Q.D.; Douma, L.A.N.R.; Bertotti, G.; Barnhoorn, A.

doi:10.1016/j.jsg.2019.103907

Mechanical controls on horizontal stresses and fracture behaviour in layered rocks

Title

Mechanical controls on horizontal stresses and fracture behaviour in layered rocks: A numerical sensitivity analysis

Author

Boersma, Q.D. (TU Delft Applied Geology)
Douma, L.A.N.R. (TU Delft Applied Geophysics and Petrophysics)
Bertotti, G. (TU Delft Applied Geology)
Barnhoorn, A. (TU Delft Applied Geophysics and Petrophysics)

Date

2020

Abstract

In layered materials, the deformation style, orientation, confinement, and 3D connectivity of natural fractures is generally impacted by changes in sedimentary facies and alternations in mechanical properties. In this study we address this effect and perform a numerical sensitivity analysis. Mechanical properties, confining pressures, and interfacial frictions are varied for a three-layered model, to investigate and quantify the relation between contrasting material properties, the principal horizontal stresses and fracture behaviour (i.e. deformation style and orientation). Firstly, the results show that tensile stresses develop in the stiffer layers due to the contrasting elastic parameters. The magnitude of these stresses is dependent on the ratio between the elastic parameters of stiffer and softer layers (i.e. E_stiff/E_soft and ν_stiff/ν_soft). There are no horizontal tensile stresses, when applying a compressive horizontal confining pressure (approx. 1/5 of the applied vertical stress). Implementing an interfacial friction lower than 0.2 will result in decoupling of the layers, resulting in slip on the layer boundaries and no tensile stresses within the stiffer layers. Further, the acquired numerical results are in good agreement with previously conducted laboratory work. Finally, we discuss whether the presented results can be used for better relating contrasting mechanical properties to potential fracture deformation styles and orientations in layered outcrops or subsurface reservoirs.

Subject

Contrasting elastic properties
Layered rock
Mechanical modelling
Natural fractures

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http://resolver.tudelft.nl/uuid:5e540ad9-0f83-4507-9c78-2b441b5b82bb

DOI

https://doi.org/10.1016/j.jsg.2019.103907

ISSN

0191-8141

Source

Journal of Structural Geology, 130

Part of collection

Institutional Repository