Acoustic emission and velocities associated with the formation of compaction bands in sandstone

Fortin, Jérôme; Stanchits, Sergei; Dresen, Georg; Guéguen, Yves

doi:10.1029/2005jb003854

Cited by 198 publications

(194 citation statements)

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“…The damage almost linearly increases with increasing axial strain: Microcracks accumulate as shear bands are formed, but the sample keeps its integrity. To our knowledge, our data set is the first to show such a linear relationship between crack density and deformation; typically, brittle rocks accumulate microcracks nonlinearly prior to localization [Schubnel et al, 2003;Fortin et al, 2006].…”

Section: Micromechanics Of Deformationmentioning

confidence: 99%

“…Indeed, from a material science point of view, deformation is always localized at some particular length and timescale. AE signals have been used to characterize damage during rock deformation [e.g., Scholz, 1968;Mogi, 1968;Lockner et al, 1992] even in the ductile regime and in the absence of stick-slip [e.g., Baud et al, 2004;Fortin et al, 2006]. Thus, the record of AE during deformation cannot be systematically understood as the signature of a seismic behavior.…”

Section: Introductionmentioning

confidence: 99%

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Damage and rupture dynamics at the brittle-ductile transition: The case of gypsum

2011

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[1] Triaxial tests on gypsum polycrystal samples are performed at confining pressure (P c ) ranging from 2 to 95 MPa and temperatures up to 70°C. During the tests, stress, strain, elastic wave velocities, and acoustic emissions are recorded. At P c ≤ 10 MPa, the macroscopic behavior is brittle, and above 20 MPa the macroscopic behavior becomes ductile. Ductile deformation is cataclastic, as shown by the continuous decrease of elastic wave velocities interpreted in terms of microcrack accumulation. Surprisingly, ductile deformation and strain hardening are also accompanied by small stress drops from 0.5 to 6 MPa in amplitude. Microstructural observations of the deformed samples suggest that each stress drop corresponds to the generation of a single shear band, formed by microcracks and kinked grains. At room temperature, the stress drops are not correlated to acoustic emssions (AEs). At 70°C, the stress drops are larger and systematically associated with a low-frequency AE (LFAE). Rupture velocities can be inferred from the LFAE high-frequency content and range from 50 to 200 m s −1 . The LFAE amplitude also increases with increasing rupture speed and is not correlated with the amplitude of the macroscopic stress drops. LFAEs are thus attributed to dynamic propagation of shear bands. In Volterra gypsum, the result of the competition between microcracking and plasticity is counterintuitive: Dynamic instalibilities at 70°C may arise from the thermal activation of mineral kinking.

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Section: Micromechanics Of Deformationmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Damage and rupture dynamics at the brittle-ductile transition: The case of gypsum

2011

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“…Olsson et al [5,6], Wong et al [7], Haimson et al [8][9][10][11], Baud et al [2] and Fôrtin et al [12] observed three different pat-terns of compaction bands in laboratory experiments [3]. Olsson and Holcomb [5,6] observed wide compaction bands in Castlegate sandstone, which grew in thickness with increasing axial load until the entire specimen was covered.…”

Section: Introductionmentioning

confidence: 99%

“…The bands spread across the specimen with increasing applied load, and were interlayered with less deformed materials. Fôrtin et al [12], Stanchits et al [15] and Charalampidou et al [16] conducted experiments with notched specimens, and observed compaction bands under lower stress levels. The third pattern of compaction bands was observed in specimens with a hole which created a heterogeneous stress field.…”

Section: Introductionmentioning

confidence: 99%

Experimental study on formation mechanism of compaction bands in weathered rocks with high porosity

Han

Liu

Wang

2013

Sci. China Technol. Sci.

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Since Mollema and Antonellini observed compaction bands in the field in 1996, different patterns of compaction bands have been found in laboratory experiments. There are some discrepancies between the laboratory experiments and the field observations: compared to the field observation, the stress levels required to induce compaction bands in laboratory experiments are usually higher than the inferred in the field, and the grain crushing are more intense in the laboratory experiments. In this paper, compaction bands were observed at the maximal principal stresses below 8 MPa, which is lower than the stress level inferred in the field, and there was no severe comminution inside the compaction bands. Experimental results indicate that the porosity and confining pressure have great impacts on the types of localization bands. Lower porosity and confining pressure can promote the growth of shear bands and high-angle shear bands. Higher porosity and confining pressure can promote the growth of discrete compaction bands. Intermediate porosity and confining pressure are favorable for the growth of hybrid modes involving two of the three, i.e., discrete compaction band, diffuse compaction band and high-angle shear band. The formation of discrete compaction bands is more unstable compared to diffuse compaction bands. The two types of compaction bands can appear in the same type rocks, and diffuse compaction bands are formed under lower confining pressure compared to discrete compaction bands. The reduction of permeability was within 2 orders of magnitude in this study, and it is 23 orders of magnitude lower than those obtained by other researchers. porous rock, compaction band, permeability evolution Citation:Han G F, Liu X L, Wang E Z. Experimental study on formation mechanism of compaction bands in weathered rocks with high porosity.

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“…To avoid the conditions leading to the formation of compaction bands, which can produce destructive compartmentalization of reservoirs, one has to better understand how the occurrence of localized zones of compaction is related to the stress state and the constitutive properties of the rock. Development of this phenomenon has been investigated in the laboratory, primarily in sandstones with porosities ranging from 13% to 28% (DiGiovanni et al 2000;Klein et al 2001;Fortin et al 2006). The data show that localized failure in compactant rock is commonly associated with stress states in the transitional regime from brittle faulting to cataclastic flow , with the mode of localization associated with a broad spectrum of complexity Ngwenya et al 2003).…”

Section: Geomechanical Effects In Produced Reservoirsmentioning

confidence: 99%

Rock physics and geomechanics in the study of reservoirs and repositories

David

Ravalec-Dupin

2007

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Reservoir management for hydrocarbon extraction and repositories design for radioactive waste storage are two different areas in which rock physics and geomechanics provide valuable information. Although the targets and objectives are different, similar approaches and common attributes exist in both fields: safety assessment, short-to long-term prediction, integration of various scales of investigation, and remote monitoring, among others. Nevertheless, there are also important differences: reservoirs at depth are investigated through remote geophysical studies, well-logging and/or core samples retrieval, whereas direct access to repositories is possible through excavation in the host formation in which underground research laboratories can be constructed. We review a number of studies focusing on geomechanics and rock physics applied to the characterization of reservoirs and repositories, including laboratory experiments and predictive models, at different scales.Reservoir management and assessment of repository performance require the integration of different fields in Earth sciences, including geochemistry, geophysics, structural geology, and, in the case of interest here, rock physics and geomechanics. We present recent advances in the studies of reservoirs and repositories with the aim of emphasizing how rock physics and geomechanics help to obtain a better insight into important issues linked to reservoir management for exploitation of natural resources, and to repository safety assessment for hazardous waste storage in the geological environment.In the area of reservoir management, the importance of geomechanics in problems such as wellbore stability, hydraulic fracturing and subsidence is well known. Recently, there has been a growing interest in the development of a link between fluid flow simulators and geomechanical models. Several approaches have been proposed to incorporate the correct physics and to account for physical phenomena usually neglected in reservoir simulation. New techniques developed in laboratory studies provide relevant data for this integration. The approaches differ in the degree of coupling. The stronger the coupling, the more computationally demanding the simulation. Numerical experiments showed that coupling is of interest for poorly consolidated reservoirs such as chalk reservoirs. In other cases, one may wonder whether a more accurate modelling of production processes justifies the required computation cost. Complementary sensitivity studies have to be performed to better estimate the conditions in which the coupling is worthwhile.In the area of underground waste storage, the key issue is to design a repository as safe as possible for human activity and for the environment at the near surface, on time scales of the order of hundreds of years. This challenging task requires us to identify favourable geological targets for the storage, and to develop extensive scientific research in different fields, so as to obtain eventually a predictive model of the repository evolu...

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Acoustic emission and velocities associated with the formation of compaction bands in sandstone

Cited by 198 publications

References 41 publications

Damage and rupture dynamics at the brittle-ductile transition: The case of gypsum

Damage and rupture dynamics at the brittle-ductile transition: The case of gypsum

Experimental study on formation mechanism of compaction bands in weathered rocks with high porosity

Rock physics and geomechanics in the study of reservoirs and repositories

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