Paleo-deviatoric stress magnitudes from calcite twins and related structural permeability evolution in minor faults: Example from the toarcian shale of the French Causses Basin, Aveyron, France

2007 ◽  
Vol 429 (1-2) ◽  
pp. 79-97 ◽  
Author(s):  
Joël Constantin ◽  
Philippe Laurent ◽  
Pierre Vergély ◽  
Justo Cabrera
Keyword(s):  
Deviatoric Stress ◽  
Permeability Evolution

scholarly journals Creep Rupture and Permeability Evolution in High Temperature Heat-Treated Sandstone Containing Pre-Existing Twin Flaws

Energies ◽  
2021 ◽  
Vol 14 (19) ◽  
pp. 6362
Author(s):  
Sheng-Qi Yang ◽  
Jin-Zhou Tang ◽  
Derek Elsworth
Keyword(s):  
Creep Strain ◽  
Stress Level ◽  
Stress Ratio ◽  
Deviatoric Stress ◽  
Threshold Temperature ◽  
Critical Threshold ◽  
Plastic Strains ◽  
Permeability Evolution ◽  
Heat Treated ◽  
Pre Treatment

Utilizing underground coal gasification cavities for carbon capture and sequestration provides a potentially economic and sustainable solution to a vexing environmental and energy problem. The thermal influence on creep properties and long-term permeability evolution around the underground gasification chamber is a key issue in UCG-CCS operation in containing fugitive emissions. We complete multi-step loading and unloading creep tests with permeability measurement at confining stresses of 30 MPa on pre-cracked sandstone specimens thermally heat-treated to 250, 500, 750 and 1000 °C. Observations indicate a critical threshold temperature of 500 °C required to initiate thermally-induced cracks with subsequent strength reduction occurring at 750 °C. Comparison of histories of creep, visco-elastic and visco-plastic strains highlight the existence of a strain jump at a certain deviatoric stress level—where the intervening rock bridge between the twin starter-cracks is eliminated. As the deviatoric stress level increases, the visco-plastic strains make up an important composition of total creep strain, especially for specimens pre-treated at higher temperatures, and the development of the visco-plastic strain leads to the time-dependent failure of the rock. The thermal pre-treatment produces thermal cracks with their closure resulting in increased instantaneous elastic strains and instantaneous plastic strains. With increasing stress ratio, the steady-state creep rates increase slowly before the failure stress ratio but rise suddenly over the final stress ratio to failure. However, the pre-treatment temperature has no clear and apparent influence on steady creep strain rates. Rock specimens subject to higher pre-treatment temperatures exhibit higher permeabilities. The pre-existing cracks close under compression with a coplanar shear crack propagating from the starter-cracks and ultimately linking these formerly separate cracks. In addition, it is clear that the specimens pre-treated at higher temperatures accommodate greater damage.

scholarly journals The Role of the Reverse Fault on the Permeability Evolution in Mining Coal

Geofluids ◽  
2021 ◽  
Vol 2021 ◽  
pp. 1-15
Author(s):  
Rui Zhou ◽  
Yujin Qin ◽  
Yang Hu
Keyword(s):  
Coal Sample ◽  
Axial Strain ◽  
Deviatoric Stress ◽  
Reverse Fault ◽  
Permeability Evolution ◽  
Concentration Coefficient ◽  
Stress Peak ◽  
Gas Seepage ◽  
Mining Coal ◽  
Stress Concentration Coefficient

To prevent and control the coal seam gas disaster affected by the reverse fault, we performed gas seepage tests, which consider stress-loading and unloading schemes, to investigate the stress change and coal permeability of the mining coal with reverse fault. The experimental results show that the mechanical behavior and permeability change of the mining coal are related to the distance between the coal and the reverse fault. The stress concentration coefficient of the coal body gradually increases. The closer is the distance between the coal and the reverse fault, the larger are the deviatoric stress peak and strain. In comparison with the coal sample M1 that is 5 m away from the reverse fault, the deviatoric stress peak and axial strain of the coal sample M3, 35 m away from the reverse fault, increase by 40.74% and 26.73%, respectively. In this stage, the permeability of M1, M2, and M3 coal samples increases by 22.1%, 28.0%, and 36.7%, respectively. In another stage, the stress concentration coefficient of coal increases to the peak and then decreases, causing the deviatoric stress peak and strain of coal to rise first and then fall. In comparison with the coal sample M4 that is 65 m away from the reverse fault, the deviatoric stress peak and axial strain of coal sample M6, 5 m away from the reverse fault, decrease by 29.48% and 5.55%, respectively. The permeability of coal samples M4, M5, and M6 increases by 23.6%, 37.2%, and 20.8%, respectively. Based on the gas seepage test results, we established the permeability model of mining-induced coal under the influence of a reverse fault, with consideration of the volume changes of coal fractures induced by adsorption and desorption. In the model, the variations of permeability in both stages of the prepeak and postpeak were deduced, which was verified with the experimental data. The verification results demonstrate that the proposed model has the capacity to predict the permeability evolution of mining coal under the influence of a reverse fault.

scholarly journals Porosity and Permeability Evolution with Deviatoric Stress of Reservoir Sandstone: Insights from Triaxial Compression Tests and In Situ Compression CT

Geofluids ◽  
2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Cong Hu ◽  
Franck Agostini ◽  
Yonggang Jia
Keyword(s):  
Triaxial Compression ◽  
Deviatoric Stress ◽  
Permeability Evolution ◽  
Compression Tests ◽  
Confining Stress ◽  
Porosity Reduction ◽  
Porosity And Permeability ◽  
Deviatoric Stresses ◽  
Triaxial Compression Tests

Porosity and permeability are the two most important characteristics of underground gas storage in sandstone reservoirs. Injection of gas into reservoir rocks will cause rock deformation. The deformation will influence the porosity and permeability properties of the rocks. We investigate the evolution of these two properties of storage sandstone by triaxial compression tests and a uniaxial in situ compression CT test. As the deviatoric stress increases, the sandstone is compressed firstly (porosity reduction) and then dilates (porosity enhancement). With the increase in confining stress, the occurrence of volumetric dilation will be delayed. Trapped porosity of this sandstone at different deviatoric stresses is very small (0.122%-0.115%) which indicates that nearly all pores are connected. During the compression stage, the decrease in permeability is related to compression of pores and microcracks. During the volumetric dilation stage, it is related to increase in tortuosity. This interpretation can be confirmed by observations of in situ compression CT. The permeability evolution estimated by pore network modeling is consistent with macroscopic testing results.

scholarly journals Coupled Effects of Stress, Moisture Content and Gas Pressure on the Permeability Evolution of Coal Samples: A Case Study of the Coking Coal Resourced from Tunlan Coalmine

Water ◽  
2021 ◽  
Vol 13 (12) ◽  
pp. 1653
Author(s):  
Guofu Li ◽  
Yi Wang ◽  
Junhui Wang ◽  
Hongwei Zhang ◽  
Wenbin Shen ◽  
...  
Keyword(s):  
Moisture Content ◽  
Coalbed Methane ◽  
Gas Permeability ◽  
Axial Stress ◽  
Gas Pressure ◽  
Pressure Curve ◽  
Permeability Evolution ◽  
Confining Stress ◽  
Qinshui Basin ◽  
Gas Seepage

Deep coalbed methane (CBM) is widely distributed in China and is mainly commercially exploited in the Qinshui basin. The in situ stress and moisture content are key factors affecting the permeability of CH4-containing coal samples. Therefore, considering the coupled effects of compressing and infiltrating on the gas permeability of coal could be more accurate to reveal the CH4 gas seepage characteristics in CBM reservoirs. In this study, coal samples sourced from Tunlan coalmine were employed to conduct the triaxial loading and gas seepage tests. Several findings were concluded: (1) In this triaxial test, the effect of confining stress on the permeability of gas-containing coal samples is greater than that of axial stress. (2) The permeability versus gas pressure curve of coal presents a ‘V’ shape evolution trend, in which the minimum gas permeability was obtained at a gas pressure of 1.1MPa. (3) The gas permeability of coal samples decreased exponentially with increasing moisture content. Specifically, as the moisture content increasing from 0.18% to 3.15%, the gas permeability decreased by about 70%. These results are expected to provide a foundation for the efficient exploitation of CBM in Qinshui basin.

Effect of initial deviatoric stress on anisotropy of marine clay during principal stress rotation

2020 ◽  
pp. 1-14
Author(s):  
Heng Zhuang ◽  
Xiuqing Hu ◽  
Lin Guo ◽  
Li Mingfeng ◽  
Wang Chaoliang ◽  
...  
Keyword(s):  
Principal Stress ◽  
Deviatoric Stress ◽  
Principal Stress Rotation ◽  
Marine Clay ◽  
Stress Rotation

Mining‐disturbed coal damage and permeability evolution: Model and validation

2021 ◽  
Author(s):  
Chao Xu ◽  
Mingyue Cao ◽  
Kai Wang ◽  
Qiang Fu ◽  
Liangliang Qin
Keyword(s):  
Evolution Model ◽  
Permeability Evolution ◽  
Coal Damage

scholarly journals A permeability evolution model of coal particle from the perspective of adsorption deformation

2021 ◽  
Vol 9 (4) ◽  
pp. 577-587
Author(s):  
Wei Liu ◽  
Deyao Wu ◽  
Hao Xu ◽  
Xiangyu Chu ◽  
Wei Zhao ◽  
...  
Keyword(s):  
Coal Particle ◽  
Evolution Model ◽  
Permeability Evolution ◽  
Adsorption Deformation

Earth's energy “Golden Zone”: a synthesis from mineralogical research

Clay Minerals ◽  
2011 ◽  
Vol 46 (1) ◽  
pp. 1-24 ◽  
Author(s):  
P. H. Nadeau
Keyword(s):  
Oil And Gas ◽  
Gulf Coast ◽  
Clay Mineralogy ◽  
Sedimentary Basins ◽  
Entrapment Efficiency ◽  
Permeability Evolution ◽  
Reservoir Temperature ◽  
Fundamental Particle ◽  
Geological Processes ◽  
The Impact

AbstractThe impact of diagenetic processes on petroleum entrapment and recovery efficiency has focused the vast majority of the world's conventional oil and gas resources into relatively narrow thermal intervals, which we call Earth's energy “Golden Zone”. Two key mineralogical research breakthroughs, mainly from the North Sea, underpinned this discovery. The first is the fundamental particle theory of clay mineralogy, which showed the importance of dissolution/precipitation mechanisms in the formation of diagenetic illitic clays with increasing depth and temperature. The second is the surface area precipitation-rate-controlled models for the formation of diagenetic cements, primarily quartz, in reservoirs. Understanding the impacts of these geological processes on permeability evolution, porosity loss, overpressure development, and fluid migration in the subsurface, lead to the realization that exploration and production risks are exponential functions of reservoir temperature. Global compilations of oil/gas reserves relative to reservoir temperature, including the US Gulf Coast, have verified the “Golden Zone” concept, as well as stimulated further research to determine in greater detail the geological/mineralogical controls on petroleum migration and entrapment efficiency within the Earth's sedimentary basins.

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