Modeling and mechanistic interpretation of creep of rock salt below 200°C

Wawersik, W.R.; Zeuch, David H.

doi:10.1016/0040-1951(86)90040-5

Cited by 79 publications

(31 citation statements)

References 33 publications

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“…The conditions investigated in most studies of natural salt cover temperatures in the range 20ø-250øC, strain rates down to around the creep rate probably being controlled by cross slip of screw dislocations at high stresses (i.e., above •-10 MPa at 50ø-150øC [Wawersik and Zeuch, 1986;Skrotzki and Haasen, 1988;Carter et al, 1993]) and by climb of edge dislocations at lower stresses . In addition, experiments on natural rock salt have shown that when brine is present within grain boundaries, dislocation processes can be accompanied by fluid-assisted recrystallization (FARX) [ Urai et al, 1986a;Spiers et al, 1988, irradiation (i.e., precipitation of particulate Na) often reveals evidence for intergranular overgrowth and grain boundary migration, consistent with the operation of both fluid-assisted dynamic recrystallization (FADRX) and pressure solution [Urai et al, 1987;Wanten et al, 1996;Spiers and Carter, 1998].…”

Section: Introductionmentioning

confidence: 99%

Effect of confining pressure on dilatation, recrystallization, and flow of rock salt at 150°C

Peach¹,

Spiers²,

Trimby³

2001

J. Geophys. Res.

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Abstract. Microstructural evidence for fluid-assisted dynamic recrystallization (FADRX) is widespread in naturally deformed rock salt. However, the principal experimental evidence for FADRX in salt has been obtained from stress relaxation experiments, and it is unclear whether the process occurs during steady state dislocation creep and what its effect might be. Here we report deformation experiments performed on natural rock salt at a constant strain rate of 3.5x10 -7s -•, 150øC, and confining pressures Pt. of 3-30 MPa. Samples deformed at Pt. = 3 MPa showed continuous work hardening and minor dilatation. Microstructurally, they exhibited intergranular cracking plus slip band and subgrain structures indicative of dislocation glide/creep. Electron backscatter diffraction analysis revealed a high frequency of boundaries with low-angle misorientations in the range 5 ø-10 ø. In contrast, samples deformed at Pt. > 6.5 MPa showed work hardening followed by steady state flow at strains > 6-7%. These samples compacted slightly, and crystal plastic deformation was accompanied by extensive FADRX, with a predominance of highangle boundaries (300-50 ø) over low-angle boundaries. We infer that FADRX is suppressed by dilatation at low pressures as a result of grain boundary disruption. At pressures high enough to prevent dilatation, however, FADRX acts as a "recovery" mechanism counteracting work hardening. The results offer a possible explanation for rheological variability seen in previous experiments conducted at pressures up to 30 MPa. A simple rate model for diffusion-and interface-controlled FADRX indicates that FADRX should become increasingly important toward natural halokinetic conditions, although the effect on flow stresses is likely to be small.

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Section: Introductionmentioning

confidence: 99%

Effect of confining pressure on dilatation, recrystallization, and flow of rock salt at 150°C

Peach¹,

Spiers²,

Trimby³

2001

J. Geophys. Res.

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“…One is the dislocation creep mechanism which means crystal defects lead to a dislocation effect. The creep controlled by dislocation mechanisms is widely investigated in laboratory experiments (Carter and Hansen 1983;Carter et al 1993;Rutter 1983;Urai et al 1986;Wawersik and Zeuch 1986;Heard and Ryerson 1986;Senseny et al 1992;van Keken et al 1993;Franssen 1994;Peach and Spiers 1996;Weidinger et al 1997;De Meer et al 2002;Hampel et al 1998;Brouard and Bérest 1998;Bérest et al 2005;Ter Heege et al 2005a, b). The creep equations mainly used in the salt mining industry are based on dislocation creep processes quantified in laboratory experiments (Ottosen 1986;Haupt and Schweiger 1989;Aubertin et al 1991;Cristescu 1993;Munson 1979Munson , 1997Jin and Cristescu 1998;Hampel et al 1998;Hampel and Schulze 2007;Hunsche and Hampel 1999;Peach et al 2001;Fossum and Fredrich 2002).…”

Section: Deformation Mechanisms Of Rock Saltmentioning

confidence: 99%

“…The purpose of these studies is to design safe salt mines and develop the design and performance assessment for nuclear waste disposal and oil and gas storage (Wawersik and Zeuch 1986;Cristescu 1998;Hunsche and Hampel 1999).…”

Section: Introductionmentioning

confidence: 99%

Rheology of rock salt for salt tectonics modeling

Urai

2016

Pet. Sci.

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Numerical modeling of salt tectonics is a rapidly evolving field; however, the constitutive equations to model long-term rock salt rheology in nature still remain controversial. Firstly, we built a database about the strain rate versus the differential stress through collecting the data from salt creep experiments at a range of temperatures (20-200°C) in laboratories. The aim is to collect data about salt deformation in nature, and the flow properties can be extracted from the data in laboratory experiments. Moreover, as an important preparation for salt tectonics modeling, a numerical model based on creep experiments of rock salt was developed in order to verify the specific model using the Abaqus package. Finally, under the condition of low differential stresses, the deformation mechanism would be extrapolated and discussed according to microstructure research. Since the studies of salt deformation in nature are the reliable extrapolation of laboratory data, we simplified the rock salt rheology to dislocation creep corresponding to power law creep (n = 5) with the appropriate material parameters in the salt tectonic modeling.

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“…The opening of a dilatant fault changes the vertical stress in the salt directly above the dilatant fault, producing high differential stresses of more than 20 MPa in 2.5 km depth. Considering steady-state dislocation creep (Wawersik & Zeuch, 1986), effective salt viscosities down to 10 14 Pa s can be expected at the depth and temperatures of the present-day base of the Zechstein above dilatant faults.…”

Section: Salt Flow In Fracturesmentioning

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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Modeling and mechanistic interpretation of creep of rock salt below 200°C

Cited by 79 publications

References 33 publications

Effect of confining pressure on dilatation, recrystallization, and flow of rock salt at 150°C

Effect of confining pressure on dilatation, recrystallization, and flow of rock salt at 150°C

Rheology of rock salt for salt tectonics modeling

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

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