scholarly journals Anisotropic transport and frictional properties of simulated clay-rich fault gouges

2020 ◽  
Author(s):  
Elisenda Bakker ◽  
Johannes H. P. de Bresser
Keyword(s):  
Co2 Storage ◽  
Shear Displacement ◽  
Direct Shear ◽  
Shale Formations ◽  
Frictional Properties ◽  
Effective Normal Stress ◽  
Storage Reservoirs ◽  
Order Of Magnitude ◽  
Fault Gouges ◽  
Frictional Behaviour

Abstract. We aimed to evaluate various factors that control the frictional and transport properties of gouge-filled faults cutting carbonate-bearing shales or claystone formations. The research experimentally determined the effect of shear displacement, dynamic shearing, static holding, and effective normal stress on fault gouge permeability, both parallel and perpendicular to the fault boundaries, as well as on frictional behaviour. The simulated gouge was prepared from crushed Opalinus Claystone (OPA), on which we performed direct shear experiments. The direct-shear experiments (σneff = 5–50 MPa, Pf = 2 MPa, and T ≈ 20 °C) showed ~1 order of magnitude decrease in permeability with shear displacement (up to ~6 mm), for both along- and across-fault fluid flow orientation. Moreover, our data showed an initial, pre-shear permeability anisotropy of up to ~1 order of magnitude, which decreased with increasing shear displacement (maturity) to ~0.5, with the along-fault permeability being consistently higher. Our results have important implications for calcite-rich claystones and shale formations, and in particular any pre-existing faults therein, that seal hydrocarbon reservoirs and potential CO2 storage reservoirs, as the current results point to a higher leakage potential of pre-existing faults compared to the intact caprock.

scholarly journals Frictional slip weakening and shear-enhanced crystallinity in simulated coal fault gouges at subseismic slip rates

2020 ◽  
Author(s):  
Caiyuan Fan ◽  
Jinfeng Liu ◽  
Luuk B. Hunfeld ◽  
Christopher J. Spiers
Keyword(s):  
Steady State ◽  
Normal Stress ◽  
Hold Time ◽  
Shear Bands ◽  
Fluid Pressure ◽  
Organic Content ◽  
Local Conditions ◽  
Frictional Properties ◽  
Effective Normal Stress ◽  
Fault Gouges

Abstract. Previous studies show that organic-rich fault patches may play an important role in promoting unstable fault slip. However, the frictional properties of rock materials with near 100 % organic content, e.g. coal, and the controlling microscale mechanisms, remain unclear. Here, we report seven velocity stepping (VS) and one slide-hold-slide (SHS) friction experiments performed on simulated fault gouges prepared from bituminous coal, collected from the upper Silesian Basin of Poland. These experiments were performed at 25–45 MPa effective normal stress and 100 °C, employing sliding velocities of 0.1–100 μm s−1, using a conventional triaxial apparatus plus direct shear assembly. All samples showed marked slip weakening behaviour at shear displacements beyond ~ 1–2 mm, from a peak friction coefficient approaching ~ 0.5 to (near) steady state values of ~ 0.3, regardless of effective normal stress or whether vacuum dry flooded with distilled (DI) water at 15 MPa pore fluid pressure. Analysis of both unsheared and sheared samples by means of microstructural observation, micro-area X-ray diffraction (XRD) and Raman spectroscopy suggests that the marked slip weakening behaviour can be attributed to the development of R-, B- and Y- shear bands, with internal shear-enhanced coal crystallinity development. The SHS experiment performed showed a transient peak healing (restrengthening) effect that increased with the logarithm of hold time at a linearized rate of ~ 0.006. We also determined the rate-dependence of steady state friction for all VS samples using a full rate and state friction approach. This showed a transition from velocity strengthening to velocity weakening at slip velocities > 1 μm s−1 in the coal sample under vacuum dry conditions, but at > 10 μm s−1 in coal samples exposed to DI water at 15 MPa pore pressure. This may be controlled by competition between dilatant granular flow and compaction enhanced by presence of water. Together with our previous work on frictional properties of coal-shale mixtures, our results imply that the presence of a weak, coal-dominated patch on faults that cut or smear-out coal seams may promote unstable, seismogenic slip behaviour, though the importance of this in enhancing either induced or natural seismicity depends on local conditions.

scholarly journals Frictional slip weakening and shear-enhanced crystallinity in simulated coal fault gouges at slow slip rates

Solid Earth ◽  
2020 ◽  
Vol 11 (4) ◽  
pp. 1399-1422
Author(s):  
Caiyuan Fan ◽  
Jinfeng Liu ◽  
Luuk B. Hunfeld ◽  
Christopher J. Spiers
Keyword(s):  
Steady State ◽  
Normal Stress ◽  
Hold Time ◽  
Shear Bands ◽  
Fluid Pressure ◽  
Organic Content ◽  
Local Conditions ◽  
Frictional Properties ◽  
Effective Normal Stress ◽  
Fault Gouges

Abstract. Previous studies show that organic-rich fault patches may play an important role in promoting unstable fault slip. However, the frictional properties of rock materials with nearly 100 % organic content, e.g., coal, and the controlling microscale mechanisms remain unclear. Here, we report seven velocity stepping (VS) experiments and one slide–hold–slide (SHS) friction experiment performed on simulated fault gouges prepared from bituminous coal collected from the upper Silesian Basin of Poland. These experiments were performed at 25–45 MPa effective normal stress and 100 ∘C, employing sliding velocities of 0.1–100 µm s−1 and using a conventional triaxial apparatus plus direct shear assembly. All samples showed marked slip-weakening behavior at shear displacements beyond ∼ 1–2 mm, from a peak friction coefficient approaching ∼0.5 to (nearly) steady-state values of ∼0.3, regardless of effective normal stress or whether vacuum-dry or flooded with distilled (DI) water at 15 MPa pore fluid pressure. Analysis of both unsheared and sheared samples by means of microstructural observation, micro-area X-ray diffraction (XRD) and Raman spectroscopy suggests that the marked slip-weakening behavior can be attributed to the development of R-, B- and Y-shear bands, with internal shear-enhanced coal crystallinity development. The SHS experiment performed showed a transient peak healing (restrengthening) effect that increased with the logarithm of hold time at a linearized rate of ∼0.006. We also determined the rate dependence of steady-state friction for all VS samples using a full rate and state friction approach. This showed a transition from velocity strengthening to velocity weakening at slip velocities >1 µm s−1 in the coal sample under vacuum-dry conditions but at >10 µm s−1 in coal samples exposed to DI water at 15 MPa pore pressure. The observed behavior may be controlled by competition between dilatant granular flow and compaction enhanced by the presence of water. Together with our previous work on the frictional properties of coal–shale mixtures, our results imply that the presence of a weak, coal-dominated patch on faults that cut or smear out coal seams may promote unstable, seismogenic slip behavior, though the importance of this in enhancing either induced or natural seismicity depends on local conditions.

Constraining Leakage Pathways Through the Overburden Above Sub-Seafloor Co2 Storage Reservoirs

2019 ◽  
Author(s):  
Jonathan Bull ◽  
Christian Berndt ◽  
Timothy Minshull ◽  
Timothy Henstock ◽  
Gaye Bayrakci ◽  
...  
Keyword(s):  
Co2 Storage ◽  
Storage Reservoirs

scholarly journals Time-Dependent Response of a Recycled C&D Material-Geotextile Interface under Direct Shear Mode

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 3070
Author(s):  
Fernanda Bessa Ferreira ◽  
Paulo M. Pereira ◽  
Castorina Silva Vieira ◽  
Maria de Lurdes Lopes
Keyword(s):  
Shear Stress ◽  
Stress Relaxation ◽  
Shear Displacement ◽  
Time Dependent ◽  
Shear Behaviour ◽  
Displacement Rate ◽  
Shear Mode ◽  
Direct Shear ◽  
Constant Displacement ◽  
Shear Box

Geosynthetic-reinforced soil structures have been used extensively in recent decades due to their significant advantages over more conventional earth retaining structures, including the cost-effectiveness, reduced construction time, and possibility of using locally-available lower quality soils and/or waste materials, such as recycled construction and demolition (C&D) wastes. The time-dependent shear behaviour at the interfaces between the geosynthetic and the backfill is an important factor affecting the overall long-term performance of such structures, and thereby should be properly understood. In this study, an innovative multistage direct shear test procedure is introduced to characterise the time-dependent response of the interface between a high-strength geotextile and a recycled C&D material. After a prescribed shear displacement is reached, the shear box is kept stationary for a specific period of time, after which the test proceeds again, at a constant displacement rate, until the peak and large-displacement shear strengths are mobilised. The shear stress-shear displacement curves from the proposed multistage tests exhibited a progressive decrease in shear stress with time (stress relaxation) during the period in which the shear box was restrained from any movement, which was more pronounced under lower normal stress values. Regardless of the prior interface shear displacement and duration of the stress relaxation stage, the peak and residual shear strength parameters of the C&D material-geotextile interface remained similar to those obtained from the conventional (benchmark) tests carried out under constant displacement rate.

Bionic Concave Pit-Like Metal Surface and Soil Direct Shear Test

2012 ◽  
Vol 569 ◽  
pp. 451-454 ◽  
Author(s):  
Ya Ming Tang ◽  
Yang Tian
Keyword(s):  
Metal Surface ◽  
Shear Force ◽  
Smooth Surface ◽  
Direct Shear Test ◽  
Shear Test ◽  
Shear Displacement ◽  
Direct Shear ◽  
Typical Soil

In order to test the reducing adhesion and resistance effect of bionic metal non-smooth surface, the direct shear test is experimented on a kind of bionic dredging tools with typical soil and bionic concave pit-like metal surface.The relation of shear force and shear displacement on a certain pressure is presented. The result will help to design the structure of cutting soil tools’ surfaces with less adhesion and resistance.

scholarly journals An image-based equation for estimating the prospective CO2 storage resource of organic-rich shale formations

2020 ◽  
Vol 98 ◽  
pp. 103038
Author(s):  
Alexander Azenkeng ◽  
Blaise A.F. Mibeck ◽  
Bethany A. Kurz ◽  
Charles D. Gorecki ◽  
Evgeniy M. Myshakin ◽  
...  
Keyword(s):  
Co2 Storage ◽  
Shale Formations ◽  
Storage Resource

scholarly journals Frictional properties between geocells filled with granular material

2021 ◽  
Vol 20 (2) ◽  
pp. 332-345
Author(s):  
Gökhan Altay ◽  
◽  
Cafer Kayadelen ◽  
Taha Taskiran ◽  
Baki Bagriacik ◽  
...  
Keyword(s):  
Granular Material ◽  
Normal Stress ◽  
Granular Materials ◽  
Direct Shear ◽  
Shear Tests ◽  
Direct Shear Tests ◽  
Frictional Properties ◽  
Geotechnical Structures ◽  
Series Of Experiments ◽  
Restricted Volume

The parameters concerning the interaction between geocell and granular materials is required for the design of many geotechnical structures. With this in mind, a series of experiments using simple direct shear tests are conducted in order to understand the frictional properties between geocells filled with granular materials. The 54 test samples are prepared by filling the geocell with granular materials having three different gradations. These samples are tested at three different relative densities under three different normal stress levels. As a result, it was observed that interface resistance between the geocells filled with granular material is found to be generally greater than in the samples without geocells. Additionally, these samples with geocells are found to be stiffer; this is due to the fact that the samples with geocell gained more cohesion because geocells confined the grains within a restricted volume.

scholarly journals Element mobilization and immobilization from carbonate rocks between CO2 storage reservoirs and the overlying aquifers during a potential CO2 leakage

Chemosphere ◽  
2018 ◽  
Vol 197 ◽  
pp. 399-410 ◽  
Author(s):  
Amanda R. Lawter ◽  
Nikolla P. Qafoku ◽  
R. Matthew Asmussen ◽  
Ravi K. Kukkadapu ◽  
Odeta Qafoku ◽  
...  
Keyword(s):  
Carbonate Rocks ◽  
Co2 Storage ◽  
Co2 Leakage ◽  
Storage Reservoirs ◽  
Element Mobilization

Integration of Geophysical Technologies in the Petroleum Industry

2021 ◽  
Keyword(s):  
Co2 Storage ◽  
Petroleum Industry ◽  
Petroleum Exploration ◽  
Reflection Seismology ◽  
Seismic Reflection Data ◽  
Reflection Data ◽  
Advanced Students ◽  
Storage Reservoirs ◽  
Magnetic Resistivity ◽  
Exploration And Production

The most utilized technique for exploring the Earth's subsurface for petroleum is reflection seismology. However, a sole focus on reflection seismology often misses opportunities to integrate other geophysical techniques such as gravity, magnetic, resistivity, and other seismicity techniques, which have tended to be used in isolation and by specialist teams. There is now growing appreciation that these technologies used in combination with reflection seismology can produce more accurate images of the subsurface. This book describes how these different field techniques can be used individually and in combination with each other and with seismic reflection data. World leading experts present chapters covering different techniques and describe when, where, and how to apply them to improve petroleum exploration and production. It also explores the use of such techniques in monitoring CO2 storage reservoirs. Including case studies throughout, it will be an invaluable resource for petroleum industry professionals, advanced students, and researchers.

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