Anisotropy of seismic and mechanical properties of Opalinus clay during triaxial deformation in a multi-anvil apparatus

Popp, T.; Salzer, K.

doi:10.1016/j.pce.2006.04.022

Cited by 63 publications

(32 citation statements)

References 6 publications

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“…Popp and Salzer [] studied dilatancy in Opalinus clay and developed conceptual models relating porosity changes, stress induced deformation, permeability, and P wave and S wave velocities. Their discussion seeks to relate these independently measured physical parameters with compactive, dilatant, and failure behavior of this clay rich rock.…”

Section: Introductionmentioning

confidence: 99%

Helium release during shale deformation: Experimental validation

Bauer

Gardner

Heath

2016

Geochem Geophys Geosyst

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This work describes initial experimental results of helium tracer release monitoring during deformation of shale. Naturally occurring radiogenic 4He is present in high concentration in most shales. During rock deformation, accumulated helium could be released as fractures are created and new transport pathways are created. We present the results of an experimental study in which confined reservoir shale samples, cored parallel and perpendicular to bedding, which were initially saturated with helium to simulate reservoir conditions, are subjected to triaxial compressive deformation. During the deformation experiment, differential stress, axial, and radial strains are systematically tracked. Release of helium is dynamically measured using a helium mass spectrometer leak detector. Helium released during deformation is observable at the laboratory scale and the release is tightly coupled to the shale deformation. These first measurements of dynamic helium release from rocks undergoing deformation show that helium provides information on the evolution of microstructure as a function of changes in stress and strain.

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Section: Introductionmentioning

confidence: 99%

Helium release during shale deformation: Experimental validation

Bauer

Gardner

Heath

2016

Geochem Geophys Geosyst

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“…The crack pattern would be mainly influenced by (i) macroscopic lamination in the sediment, and (ii) magnitude and orientation of the applied stress system. As already described by (Dewhurst & Siggins 2006) for the Muderong Shale and (Popp & Salzer 2007) for the Opalinus Clay, deviatoric loading induces marked changes in the physical properties of the tested shale: bedding-parallel loading favours dilatancy along sedimentary surfaces and pre-existing fractures therefore increasing elastic anisotropy, while bedding normal loading tends to close such bedding parallel fissure and reduce the elastic wave anisotropy.…”

Section: Discussionmentioning

confidence: 62%

Stress-induced anisotropy in brine saturated shale

Piane¹,

Dewhurst²,

Siggins

et al. 2010

Geophysical Journal International

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S U M M A R YThis paper reports the intrinsic and crack-induced anisotropic properties of a set of preserved, brine-saturated shale samples and their response to external stresses. We used undrained multistage triaxial tests to evaluate how the ultrasonic wave velocities and their anisotropy changed with increasing isotropic and differential stress conditions. In addition, the impact of stress orientation with respect to fabric orientation was evaluated. An array of ultrasonic transducers allowed to measure five independent wave velocities which were used to calculate the elastic properties of the shale. Results indicate that in this shale P-and S-wave velocities vary with stress in a different manner dependent on the maximum principal stress orientation with respect to the fabric. Where the maximum stress is normal to bedding, V pv and V s1 increase monotonically with increasing effective stress. However V ph and V sh decrease during individual loading stages but increase from stage to stage as confining pressure increases. The reverse occurs when the microfabric is parallel to the maximum principal stress. Where the maximum stress is bedding normal, velocity anisotropy decreases as differential stress increases; when maximum stress is fabric parallel, anisotropy increases. Elastic anisotropy is related to the initial composition and the spatial distribution of the different minerals (fabric) in the sediment and the presence of microfractures, while changes in elastic anisotropy result from the applied stresses, their orientation with respect to the rock fabric and the degree of stress anisotropy.

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“…Sarout et al (2007) extended the study of elastic anisotropy with the measurement of S-wave velocity, and their study of seismic velocity evolution with increasing effective stress revealed the interplay between damage and variation of water saturation in the COX argillite samples tested in triaxial experiments. A similar study has been conducted by Popp & Salzer (2007) using a multi-anvil apparatus, to define the dilatancy boundary for the Opalinus clay formation. A theoretical model for the anisotropy of C. DAVID & M. LE RAVALEC-DUPINseismic-wave velocity for a cracked solid with an anisotropic crack distribution has been proposed by Wong & Zhu (2007).…”

Section: Repositories In Soft Rock Formationsmentioning

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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Anisotropy of seismic and mechanical properties of Opalinus clay during triaxial deformation in a multi-anvil apparatus

Cited by 63 publications

References 6 publications

Helium release during shale deformation: Experimental validation

Helium release during shale deformation: Experimental validation

Stress-induced anisotropy in brine saturated shale

Rock physics and geomechanics in the study of reservoirs and repositories

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