Evolution of fault zones in carbonates with mechanical stratigraphy – Insights from scale models using layered cohesive powder

Gent, H. W. van; Holland, Marc; Urai, János L.; Loosveld, R.

doi:10.1016/j.jsg.2009.05.006

Cited by 81 publications

(70 citation statements)

References 47 publications

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“…The set-up consists of a mechanically layered model deforming above a rigid basement fault. We used sand to simulate the sandstones of the Permian and Carboniferous, and cohesive hemihydrate powder (Holland et al, 2006(Holland et al, , 2011van Gent et al, 2010;Kettermann et al, 2016) to simulate the Zechstein anhydrites and carbonates (Fig. 4).…”

Section: Physical Modelsmentioning

confidence: 99%

The effect of salt in dilatant faults on rates and magnitudes of induced seismicity – first results building on the geological setting of the Groningen Rotliegend reservoirs

Kettermann

Abe

Raith

et al. 2017

Netherlands Journal of Geosciences

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The presence of salt in dilatant normal faults may have a strong influence on fault mechanics in the Groningen field and on the related induced seismicity. At present, little is known of the structure of these fault zones. This study starts with the geological evolution of the Groningen area, where, during tectonic faulting, rock salt may have migrated downwards into dilatant faults. These fault zones therefore may contain inclusions of rock salt. Because of its rate-dependent mechanical properties, the presence of salt in a fault may introduce a loading-rate dependency into fault movement and affect the distribution of magnitudes of seismic events. We present a first-look study showing how these processes can be investigated using a combination of analogue and numerical modelling. Full scaling of the models and quantification of implications for induced seismicity in Groningen require further, more detailed studies: an understanding of fault zone structure in the Groningen field is required for improved predictions of induced seismicity. The analogue experiments are based on a simplified stratigraphy of the Groningen area, where it is generally thought that most of the Rotliegend faulting has taken place in the Jurassic, after deposition of the Zechstein. This suggests that, at the time of faulting, the sulphates were already transformed into brittle anhydrite. If these layers were sufficiently brittle to fault in a dilatant fashion, rock salt was able to flow downwards into the dilatant fractures. To test this hypothesis, we use sandbox experiments where we combine cohesive powder as analogue for brittle anhydrites and carbonates with viscous salt analogues to explore the developing fault geometry and the resulting distribution of salt in the faults. Using the observations from analogue models as input, numerical models investigate the stick-slip behaviour of fault zones containing ductile material qualitatively with the discrete element method (DEM). Results show that the DEM approach is suitable for modelling the seismicity of faults containing salt. The stick-slip motion of the fault becomes dependent on shear loading rate with a modification of the frequency-magnitude distribution of the generated seismic events.

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Section: Physical Modelsmentioning

confidence: 99%

The effect of salt in dilatant faults on rates and magnitudes of induced seismicity – first results building on the geological setting of the Groningen Rotliegend reservoirs

Kettermann

Abe

Raith

et al. 2017

Netherlands Journal of Geosciences

Self Cite

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“…The set-up chosen in all models is a graben bounded by normal faults with a dip of 60° [12,16]. However, in the numerical models, this angle can be varied [18][19] down by a motor, with a constant velocity, two side tables are pushed symmetrically to the sides, forming a master graben.…”

Section: Analogue Modelmentioning

confidence: 99%

“…However, in the numerical models, this angle can be varied [18][19] down by a motor, with a constant velocity, two side tables are pushed symmetrically to the sides, forming a master graben. The maximum horizontal elongation is 11% (see also [12,16] for more details).…”

Section: Analogue Modelmentioning

confidence: 99%

“…The material properties of this powder are previously described [12,16]. One particularly relevant property of this powder is that due to compaction (i.e.…”

Section: Analogue Modelmentioning

confidence: 99%

“…The mechanical background of open fault formation can studied in analogue models using cohesive materials (see for example [5][6][13][14][15][16][17]) as well as with numerical methods, like the Discrete Elements Method [18][19][20]. Here we will attempt to integrate these results as well as present some new insight on the progradation direction of these faults.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

The formation of open fractures in cohesive materials, results of scaled analogue and numerical modelling on fault zone porosity development

Gent

Abe

Urai

et al. 2010

EPJ Web of Conferences

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Abstract. We compare analogue and numerical models of dilatational fractures at low confining stress. These structures form an effective conduit for fluid flow in the field, but are difficult to model since they form in cohesive materials at low stresses. We use a truly cohesive powder for the analogue models and a Discrete Element Model (DEM) with brittle-elastic bonds for the numerical modelling. We show that despite variations in the model type, small differences in the location of initial fractures and the way these structures link-up to control the evolution of the model, the observed structures are robust. Three structural zones develop where different fault types dominate. In 3D numerical models we show an increase of the porosity on the fault zone with increasing deformation. The progradation direction is shown to be controlled by the position of the fracture. The combination of analogue models with cohesive powder and DEMs with internal cohesion is an excellent tool to study the evolution of open fractures.

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Tectonic and gravity extensional collapses in overpressured cohesive and frictional wedges

2015

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Two modes of extensional collapse in a cohesive and frictional wedge of arbitrary topography, finite extent, and resting on an inclined weak décollement are examined by analytical means. The first mode consists of the gravitational collapse by the action of a half-graben, rooting on the décollement and pushing seaward the frontal part of the wedge. The second mode results from the tectonics extension at the back wall with a similar half-graben kinematics and the landward sliding of the rear part of the wedge. The predictions of the maximum strength theorem, equivalent to the kinematic approach of limit analysis and based on these two collapse mechanisms, not only match exactly the solutions of the critical Coulomb wedge theory, once properly amended, but generalizes them in several aspects: wedge of finite size, composed of cohesive material and of arbitrary topography. This generalization is advantageous to progress in our understanding of many laboratory experiments and field cases. For example, it is claimed from analytical results validated by experiments that the stability transition for a cohesive, triangular wedge occurs with the activation of the maximum length of the décollement. It is shown that the details of the topography, for the particular example of the Mejillones peninsula (North Chile) is, however, responsible for the selection of a short length-scale, dynamic instability corresponding to a frontal gravitational instability. A reasonable amount of cohesion is sufficient for the pressures proposed in the literature to correspond to a stability transition and not with a dynamically unstable state.

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Evolution of fault zones in carbonates with mechanical stratigraphy – Insights from scale models using layered cohesive powder

Cited by 81 publications

References 47 publications

The effect of salt in dilatant faults on rates and magnitudes of induced seismicity – first results building on the geological setting of the Groningen Rotliegend reservoirs

The effect of salt in dilatant faults on rates and magnitudes of induced seismicity – first results building on the geological setting of the Groningen Rotliegend reservoirs

The formation of open fractures in cohesive materials, results of scaled analogue and numerical modelling on fault zone porosity development

Tectonic and gravity extensional collapses in overpressured cohesive and frictional wedges

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