Effect of Unloading Direction on Rock Failure under True Triaxial Stress Conditions

2021 ◽  
Vol 50 (1) ◽  
pp. 20200298
Author(s):  
Peng Jia ◽  
Nan Yang ◽  
Dong-qiao Liu
Keyword(s):  
Rock Failure ◽  
Stress Conditions ◽  
Triaxial Stress ◽  
True Triaxial ◽  
True Triaxial Stress

Shale permeability model considering bedding effect under true triaxial stress conditions

2019 ◽  
Vol 68 ◽  
pp. 102908 ◽  
Author(s):  
Chao Liu ◽  
Guangzhi Yin ◽  
Minghui Li ◽  
Bozhi Deng ◽  
Zhenlong Song ◽  
...  
Keyword(s):  
Stress Conditions ◽  
Triaxial Stress ◽  
Permeability Model ◽  
True Triaxial ◽  
True Triaxial Stress ◽  
Shale Permeability

A preliminary experimental study on sand production under true triaxial stress conditions

2011 ◽  
Vol 51 (1) ◽  
pp. 567
Author(s):  
Ahmadreza Younessi ◽  
Vamegh Rasouli
Keyword(s):  
Laboratory Experiments ◽  
Test Procedure ◽  
Experimental Studies ◽  
Stress Conditions ◽  
Triaxial Stress ◽  
Cylindrical Shape ◽  
Sand Production ◽  
True Triaxial ◽  
Unconsolidated Sands ◽  
True Triaxial Stress

Sand production prediction is becoming a regular study in reservoirs with weak or unconsolidated sands. Three main approaches for sanding prediction are analytical, numerical and experimental methods. Laboratory experiments have proven to provide more realistic results, with these being used to understand sanding mechanisms and validate analytical and numerical methods. A large number of experimental studies have been carried out by researchers worldwide—most of which have been performed on cylindrical-shape samples under uniaxial (i.e. σ1 ≠ 0, σ2 = σ3 = 0) or triaxial (i.e. σ1 ≠ 0, σ2 = σ3 ≠ 0) stress conditions. In general, a sanding experiment under true-triaxial stresses (i.e. σ1 ≠ σ2 ≠ σ3 ≠ 0) is more realistic in simulating downhole conditions. This stress condition can be simulated in the laboratory on a cubic sample. The first part of this paper provides a comprehensive but brief literature review on past sanding laboratory experiments. This will be followed by the introducition of a unique true-triaxial stress cell (TTSC) which was modified and used for sanding simulations in the laboratory. The applied modifications will be illustrated and the test procedure described. The sample preparation for testing synthetic samples will be explained and some preliminary results obtained will be presented.

Permeability evolution under true triaxial stress conditions of Longmaxi shale in the Sichuan Basin, Southwest China

2019 ◽  
Vol 354 ◽  
pp. 601-614 ◽  
Author(s):  
Yufei Chen ◽  
Changbao Jiang ◽  
Guangzhi Yin ◽  
Dongming Zhang ◽  
Huilin Xing ◽  
...  
Keyword(s):  
Sichuan Basin ◽  
Southwest China ◽  
Stress Conditions ◽  
Triaxial Stress ◽  
Permeability Evolution ◽  
True Triaxial ◽  
Longmaxi Shale ◽  
True Triaxial Stress ◽  
The Sichuan Basin

scholarly journals Effect of Intermediate Principal Stress on the Strength, Deformation, and Permeability of Sandstone

Energies ◽  
2018 ◽  
Vol 11 (10) ◽  
pp. 2694 ◽  
Author(s):  
Zhenlong Song ◽  
Minghui Li ◽  
Guangzhi Yin ◽  
Pathegama Ranjith ◽  
Dongming Zhang ◽  
...  
Keyword(s):  
Pressure Drop ◽  
Principal Stress ◽  
Intermediate Principal Stress ◽  
Stress Conditions ◽  
Triaxial Stress ◽  
Mechanical Behaviors ◽  
Seepage Velocity ◽  
True Triaxial ◽  
Gas Seepage ◽  
True Triaxial Stress

Although the mechanical behaviors and flow aspects of sandstone have been previously investigated, studies of the effect of the intermediate principal stress (σ2) on the strength, deformation, and permeability of sandstone are lacking. In this work, the mechanical behaviors and permeability of sandstone under true triaxial stress conditions were investigated using a newly developed true triaxial geophysical apparatus. The experimental results showed that with increasing σ2, the peak strength, octahedral effective normal stress, and octahedral effective shear stress of the sandstone increased, and the rate of increase decreased. This is because a larger intermediate principal stress coefficient b has an inhibitory effect on rock strength. In our study, as the ratio of σ2/σ3 increased, the specimen entered compressive strain in the σ2 direction during the first stress drop. The stress and strain path deviations occur during rock failure. The amount of deviation increased as the σ2 increased before the peak stress. This phenomenon indicates that elastic mechanics are not suitable for understanding this sandstone rock during its failure. The permeability evolution of the sandstone under true triaxial stress conditions was measured and analyzed to investigate the effect of σ2. During the complete true triaxial stress-strain experiments, the variation we found in gas seepage velocity could be divided into two stages. Before the first pressure drop, the gas seepage velocity was mainly affected by volume strain. After the first pressure drop, the seepage velocity was affected by the deviator strain, which can change the seepage channels.

Permeability evolution of shale under anisotropic true triaxial stress conditions

2016 ◽  
Vol 165 ◽  
pp. 142-148 ◽  
Author(s):  
Minghui Li ◽  
Guangzhi Yin ◽  
Jiang Xu ◽  
Jie Cao ◽  
Zhenlong Song
Keyword(s):  
Stress Conditions ◽  
Triaxial Stress ◽  
Permeability Evolution ◽  
True Triaxial ◽  
True Triaxial Stress

scholarly journals Influence of principal stress effect on deformation and permeability of coal containing beddings under true triaxial stress conditions

2019 ◽  
Vol 6 (2) ◽  
pp. 181438 ◽  
Author(s):  
Jiahui Dai ◽  
Chao Liu ◽  
Minghui Li ◽  
Zhenlong Song
Keyword(s):  
Mechanical Behaviour ◽  
Volumetric Strain ◽  
Bedding Plane ◽  
Stress Conditions ◽  
Triaxial Stress ◽  
Stress Effect ◽  
Direction Parallel ◽  
True Triaxial ◽  
Bedding Planes ◽  
True Triaxial Stress

In situ stress is generally an anisotropic/true triaxial stress ( σ 1 > σ 2 > σ 3 ). Bedding weakens the continuity and integrity of coal. It is critical to understand the mechanical behaviour and gas migration of coal under true triaxial stress conditions. We performed experiments of cubic coal samples to investigate the permeability evolution and mechanical behaviour of coal under true triaxial stress conditions by using newly developed true triaxial geophysical apparatus. We analysed the effect of principal stresses on deformation and permeability characteristics of coal containing bedding planes. The results show that volumetric strain, stress states and bedding directions determine the permeability comprehensively. The variable quantity of strain was the largest in the direction normal to the bedding plane. The expansion or compression degree was characterized by the difference between the major and minor principal strain ( ɛ 1 − ɛ 3 ). Essentially, this represents the difficulty degree with regard to coal being compressed at the initial stress state and the deformation degree in ɛ 1 and ɛ 3 direction. The variation of ( ɛ 1 − ɛ 3 ) was consistent with that of permeability. Under an identical true triaxial stress condition, permeability was smaller when larger stress was applied in the direction normal to the bedding plane. Additionally, stress level in the direction parallel to the bedding planes and the directions between stresses in the direction parallel to the bedding planes and the flow direction also affect the permeability and strain. By solving lateral expansion coefficient, coal also exhibited anisotropic properties.

Fractional-order creep model for soft clay under true triaxial stress conditions

2020 ◽  
Vol 13 (17) ◽  
Author(s):  
Liu Jiashun ◽  
Jing Hongwen ◽  
Meng Bo ◽  
Wang Laigui ◽  
Yang Jianjun ◽  
...  
Keyword(s):  
Fractional Order ◽  
Soft Clay ◽  
Stress Conditions ◽  
Triaxial Stress ◽  
Creep Model ◽  
True Triaxial ◽  
True Triaxial Stress
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