The role of bedding in the evolution of meso- and microstructural fabrics in fault zones

Ishii, Eiichi

doi:10.1016/j.jsg.2016.05.007

Cited by 13 publications

(2 citation statements)

References 38 publications

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“…The occurrence of the dilatant shear failure indicates that fault B had cohesion. Although the detail of the cohesive part is unknown, healing by pressure solution or sealing by carbonates (Gratier 2011) might yield cohesion in the fault around the test section because the studied siliceous mudstone contains abundant opal-CT, which is susceptive to pressure solution (Ishii 2016b). Faults sealed by carbonates are also observed (Ishii 2016b).…”

Section: Hydromechanical Evolution Of Fault B During Injection Into F...mentioning

confidence: 99%

Constant-head step-injection tests using a conventional straddle-sliding-packer system for investigating the shear compliances of minor faults

Ishii

2024

Preprint

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Low-permeability rock is suitable as the host rock of an underground repository for radioactive waste disposal; however, minor faults might develop there. Investigating the shear compliance of those faults is crucial because they could be elastically sheared by the thermal effect of the waste to damage the waste’s engineered barriers. This study performed constant-head step-injection tests along with a recently developed packer-pressure-based extensometer method for assessing the applicability of this method to investigate the shear compliance of minor faults. Herein, two neighboring minor faults (A and B) in siliceous mudstone were evaluated. The results showed that fault A, with centimeter-thick fault breccia, exhibited high shear compliance, whereas fault B, with millimeters or less-thick fault breccia, displayed low shear compliance despite containing an incohesive fault rock. An elastic shear displacement occurred for fault A during injection and reached 15–66 mm when the test-section pressure increased from 4.1 MPa to 4.3 MPa. Here, the shear compliance was 101 mm/MPa or more. Conversely, fault B had cohesion, and shear displacement was undetected even when the test-section pressure increased from 4.0 MPa to 6.0 MPa. In this case, the shear compliance was 10− 1 mm/MPa or less. The estimated shear compliances were consistent with the results from previous shear experiments, and therefore, the applied method helps investigate the shear compliances of minor faults.

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Section: Hydromechanical Evolution Of Fault B During Injection Into F...mentioning

confidence: 99%

Constant-head step-injection tests using a conventional straddle-sliding-packer system for investigating the shear compliances of minor faults

Ishii

2024

Preprint

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“…Multi-scale bedding fractures, including km-scale regional bedding fractures and cm-scale lamina-induced fractures, are caused by lamina dissolution or induced by regional tectonic stress [1][2][3][4][5][6][7][8][9][10]. The formation of sedimentary lamina and bedding underground exerts a strong control on the following fracture propagation [11][12][13], so the term lamina-induced fractures is used to indicate the cm-scale fractures forming along the core lamina under the influence of external forces and internal rock mechanical properties [14]. Moreover, the lamina-induced fractures also correspond to the km-scale regional bedding fractures, which are induced by the formation beddings.…”

Section: Introductionmentioning

confidence: 99%

Finite Element Simulation of Multi-Scale Bedding Fractures in Tight Sandstone Oil Reservoir

Wang

Yang

et al. 2019

Energies

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Multi-scale bedding fractures, i.e., km-scale regional bedding fractures and cm-scale lamina-induced fractures, have been the focus of unconventional oil and gas exploration and play an important role in resource exploration and drilling practice for tight oil and gas. It is challenging to conduct numerical simulations of bedding fractures due to the strong heterogeneity without a proper mechanical criterion to predict failure behaviors. This research modified the Tien–Kuo (T–K) criterion by using four critical parameters (i.e., the maximum principal stress (σ1), minimum principal stress (σ3), lamina angle (θ), and lamina friction coefficient (μlamina)). The modified criterion was compared to other bedding failure criteria to make a rational finite element simulation constrained by the four variables. This work conducted triaxial compression tests of 18 column samples with different lamina angles to verify the modified rock failure criterion, which contributes to the simulation work on the multi-scale bedding fractures in the statics module of the ANSYS workbench. The cm-scale laminated rock samples and the km-scale Yanchang Formation in the Ordos Basin were included in the multi-scale geo-models. The simulated results indicate that stress is prone to concentrate on lamina when the lamina angle is in an effective range. The low-angle lamina always induces fractures in an open state with bigger failure apertures, while the medium-angle lamina tends to induce fractures in a shear sliding trend. In addition, the regional bedding fractures of the Yanchang Formation in the Himalayan tectonic period tend to propagate under the conditions of lower maximum principal stress, higher minimum principal stress, and larger stratigraphic dip.

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Biofilm Formation on Excavation Damaged Zone Fractures in Deep Neogene Sedimentary Rock

Hirota,

Kouduka,

Fukuda

et al. 2024

Microb Ecol

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Deep underground galleries are used to access the deep biosphere in addition to mining and other engineering applications, such as geological disposal of radioactive waste. Fracture networks developed in the excavation damaged zone (EDZ) are concerned with accelerating mass transport, where microbial colonization might be possible due to the availability of space and nutrients. In this study, microbial biofilms at EDZ fractures were investigated by drilling from a 350-m-deep gallery and subsequent borehole logging at the Horonobe Underground Research Laboratory (URL). By using microscopic and spectroscopic techniques, the dense colonization of microbial cells was demonstrated at the surfaces of the EDZ fractures with high hydraulic conductivity. 16S rRNA gene sequence analysis revealed the dominance of gammaproteobacterial lineages, the cultivated members of which are aerobic methanotrophs. The near-complete genomes from Horonobe groundwater, affiliated with the methanotrophic lineages, were fully equipped with genes involved in aerobic methanotrophy. Although the mediation of aerobic methanotrophy remains to be demonstrated, microbial O2 production was supported by the presence of genes in the near-complete genomes, such as catalase and superoxide dismutase that produce O2 from reactive oxygen species and a nitric oxide reductase gene with the substitutions of amino acids in motifs. It is concluded that the EDZ fractures provide energetically favorable subsurface habitats for microorganisms.

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The role of bedding in the evolution of meso- and microstructural fabrics in fault zones

Cited by 13 publications

References 38 publications

Constant-head step-injection tests using a conventional straddle-sliding-packer system for investigating the shear compliances of minor faults

Constant-head step-injection tests using a conventional straddle-sliding-packer system for investigating the shear compliances of minor faults

Finite Element Simulation of Multi-Scale Bedding Fractures in Tight Sandstone Oil Reservoir

Biofilm Formation on Excavation Damaged Zone Fractures in Deep Neogene Sedimentary Rock

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