Compaction and Failure in High Porosity Carbonates: Mechanical Data and Microstructural Observations

Baud, Patrick; Vinciguerra, Sergio; David, Christian; Cavallo, Andrea; Walker, E.; Reuschlé, Thierry

doi:10.1007/978-3-0346-0122-1_7

Cited by 33 publications

(80 citation statements)

References 48 publications

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“…Water weakening has also been reported for sandstone [Chester and Logan, 1986;Rutter and Mainprice, 1978;Baud et al, 2000Baud et al, , 2015, granite [Hadizadeh and Law, 1991], porous carbonates [Baud et al, 2009], and tuff [Zhu et al, 2011]. Overall, the water-weakening effect in basalt seems to be smaller than sandstones.…”

Section: Weakening In the Presence Of Watermentioning

confidence: 79%

Micromechanics of brittle faulting and cataclastic flow in Mount Etna basalt

et al. 2016

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Understanding how the strength of volcanic rocks varies with stress state, pressure, and microstructural attributes is fundamental to understanding the dynamics and tectonics of a volcanic system and also very important in applications such as geothermics or reservoir management in volcanic environments. In this study we investigated the micromechanics of deformation and failure in basalt, focusing on samples from Mount Etna. We performed 65 uniaxial and triaxial compression experiments on nominally dry and water‐saturated samples covering a porosity range between 5 and 16%, at effective pressures up to 200 MPa. Dilatancy and brittle faulting were observed in all samples with porosity of 5%. Water‐saturated samples were found to be significantly weaker than comparable dry samples. Shear‐enhanced compaction was observed at effective pressures as low as 80 MPa in samples of 8% porosity. Microstructural data revealed the complex interplay of microcracks, pores, and phenocrysts on dilatant failure and inelastic compaction in basalt. The micromechanics of brittle failure is controlled by wing crack propagation under triaxial compression and by pore‐emanated cracking under uniaxial compression especially in the more porous samples. The mechanism of inelastic compaction in basalt is cataclastic pore‐collapse in agreement with a recent dual‐porosity model.

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Section: Weakening In the Presence Of Watermentioning

confidence: 79%

Micromechanics of brittle faulting and cataclastic flow in Mount Etna basalt

et al. 2016

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“…Further, there are a couple of extra ideas to consider. First, high porosity limestones are also prone to inelastic compaction (grain crushing and pore collapse), termed P*, at elevated pressures (Baud et al, 2009). Baud et al (2009) showed that, for Majella limestone (30% porosity) and Saint-Maximin limestone (37% porosity), P* was about 26.5 MPa and 13 MPa (both pressures represent depths above that of the Hyblean Plateau) for wet conditions, respectively.…”

Section: Accepted M Manuscriptmentioning

confidence: 99%

Thermal weakening of the carbonate basement under Mt. Etna volcano (Italy): Implications for volcano instability

Heap

Mollo

Vinciguerra

et al. 2013

Journal of Volcanology and Geothermal Research

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The physical integrity of a sub-volcanic basement is crucial in controlling the stability of a volcanic edifice. For many volcanoes, this basement can comprise thick sequences of carbonates that are prone to significant thermally-induced alteration. These debilitating thermal reactions, facilitated by heat from proximal magma storage volumes, promote the weakening of the rock mass and likely therefore encourage edifice instability. Such instability can result in slow, gravitational spreading and episodic to continuous slippage of unstable flanks, and may also facilitate catastrophic flank collapse. Understanding the propensity of a particular sub-volcanic basement to such instability requires a detailed understanding of the influence of high temperatures on the chemical, physical, and mechanical properties of the rocks involved. The juxtaposition of a thick carbonate substratum and magmatic heat sources makes Mt. Etna volcano an ideal candidate for our study. We investigated experimentally the effect of temperature on two carbonate rocks that have been chosen to represent the deep, heterogeneous sedimentary substratum under Mt. Etna volcano. This study has demonstrated that thermalstressing resulted in a progressive and significant change in the physical properties of the two rocks. Porosity, wet (i.e., water-saturated) dynamic Poisson's ratio and wet Vp/Vs ratio all increased, whilst P-and S-wave velocities, bulk sample density, dynamic and static Young's modulus, dry Vp/Vs ratio, and dry dynamic Poisson's ratio all decreased. At temperatures of 800 °C, the carbonate in these rocks completely dissociated, resulting in a total mass loss of about 45% and the release of about 44 wt.% of CO 2 . Uniaxial deformation experiments showed that high in-situ temperatures (> 500°C) significantly reduced the strength of the carbonates and altered their deformation behaviour. Above 500 °C the rocks deformed in a ductile manner and A C C E P T E D M A N U S C R I P T ACCEPTED MANUSCRIPTthe output of acoustic emissions was greatly reduced. We speculate that thermally-induced weakening and the ductile behaviour of the carbonate substratum could be a key factor in explaining the large-scale deformation observed at Mt. Etna volcano. Our findings are consistent with several field observations at Mt. Etna volcano and can quantitatively support the interpretation of (1) the irregularly low seismic velocity zones present within the sub-volcanic sedimentary basement, (2) the anomalously high CO 2 degassing observed, (3) the anomalously high Vp/Vs ratios and the rapid migration of fluids, and (4) the increasing instability of volcanic edifices in the lifespan of a magmatic system. We speculate that carbonate sub-volcanic basement may emerge as one of the decisive fundamentals in controlling volcanic stability.

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“…Within porous granular carbonate rocks there is a growing body of documentation covering the structure, mechanics and kinematics of natural deformation bands (Tondi et al 2006Tondi 2007;Antonellini et al 2008Antonellini et al , 2014bAgosta et al 2009;Cilona et al 2012;Rustichelli et al 2012) as well as laboratoryinduced deformation bands (Baxevanis et al 2006;Baud et al 2009;Vajdova et al 2010;Zhu et al 2010;Cilona et al 2012Cilona et al , 2014Ji et al 2015). Studies reporting permeability, on the other hand, are scarce but suggest that deformation bands in carbonate rocks are associated with a permeability reduction of 1 -3 orders of magnitude relative to host rock (Rath et al 2011;Antonellini et al 2014a, b;Tondi et al 2016).…”

mentioning

confidence: 99%

Do deformation bands matter for flow? Insights from permeability measurements and flow simulations in porous carbonate rocks

Rotevatn

Fossmark

Bastesen

et al. 2016

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We investigate the permeability and flow effects of deformation bands in porous granular carbonate rocks in Malta and use results from flow simulations to discuss the practical implications of deformation bands in carbonate and siliciclastic reservoirs rocks in general. Image-and laboratory-based analyses of deformation bands show permeabilities that are 1 -2 orders of magnitude lower than the adjacent host rocks. Small-scale outcrop-based flow models (1 × 1 m) focus on the effect of deformation band on flow at the scale of individual bands. Two-phase flow simulations (water displacing oil) show that at the local scale a decrease in deformation band permeability led to increasing flow complexity, reduced and irregular waterfront propagation and reduction in sweep efficiency. A reduction in host rock permeability is associated with increased sensitivity to deformation bands. In low-permeable host rocks, a single magnitude-order reduction of deformation band permeability significantly delays flow, whereas in higher-permeable host rocks the effect is less pronounced. Hence, in some cases, deformation bands may represent a significant impediment to flow already when they are only 1 -2 orders of magnitude less permeable than host rock. Consequently, deformation bands may have greater practical implications than previously thought, particularly in reservoir rocks with moderate to low host rock permeability.

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Compaction and Failure in High Porosity Carbonates: Mechanical Data and Microstructural Observations

Cited by 33 publications

References 48 publications

Micromechanics of brittle faulting and cataclastic flow in Mount Etna basalt

Micromechanics of brittle faulting and cataclastic flow in Mount Etna basalt

Thermal weakening of the carbonate basement under Mt. Etna volcano (Italy): Implications for volcano instability

Do deformation bands matter for flow? Insights from permeability measurements and flow simulations in porous carbonate rocks

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