Effect of Pore Fluid Pressure on the Normal Deformation of a Matched Granite Joint

Zhang, Qiang; Li, Xiaochun; Bai, Bing; Hu, Shaobin; Shi, Lu

doi:10.3390/pr6080107

Cited by 12 publications

(4 citation statements)

References 32 publications

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“…We have already used the same cores to study the influence of the intermediate principal stress (σ 2 ) on the permeability evolution during true triaxial compression [41]. Although this paper emphasizes the effect of confining pressure (P c ) on the strain-permeability behavior of mudstone, which can be tested by a conventional triaxial apparatus with a cylindrical specimen, the true triaxial apparatus for rocks [41][42][43][44][45] at the Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, which can exert three stresses independently, was still employed in this study because the specimen usually failed with a relatively flat fault parallel to σ 2 [42,[46][47][48]; the flow in the σ 2 direction can still be regarded as a one-dimensional flow. In contrast, the fault of the specimen in the CTC is not only very rough but also oblique to the flow direction [40,49] and the fluid flow inside the specimen near or after failure cannot be approximated as a one-dimensional flow; therefore, the cores in this study were also processed into cuboid specimens of 5 cm square by 10 cm long ( Figure 1) and the permeability in the σ 2 direction was monitored during deviatoric loading.…”

Section: Specimen Apparatus and Experimental Proceduresmentioning

confidence: 99%

Investigation of the Effect of Confining Pressure on the Mechanics-Permeability Behavior of Mudstone under Triaxial Compression

et al. 2019

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Injecting CO 2 into a reservoir disturbs the geostress field, which leads to variations in the permeability of caprock and affects its sealing performance. In this paper, the evolution characteristics of the permeability of Yingcheng mudstone were experimentally studied during deviatoric compression under different confining pressures. As the confining pressure increased, the strength of the mudstone increased bilinearly, the angle between the fault and the maximum principle stress increased, and the fault became flatter. During compression, the permeability of mudstone first decreased and then increased and the turning point of the permeability was between the onset of dilatancy and the turning point of volumetric strain; when the fault formed, the permeability increased sharply and the fault-induced increment was reduced exponentially with increasing confining pressure. In addition, the mudstone transformed to the ductile failure mode when the effective confining pressure was greater than 35 MPa, which means that the permeability did not jump within a small strain. Finally, a practical strain-based model of permeability evolution that separately considers compaction and dilatancy was proposed, and the predicted permeability values were in good agreement with the experimental results. This study revealed the effect of confining pressure on permeability evolution during compression and can help evaluate the sealing ability of mudstone caprock.

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Section: Specimen Apparatus and Experimental Proceduresmentioning

confidence: 99%

Investigation of the Effect of Confining Pressure on the Mechanics-Permeability Behavior of Mudstone under Triaxial Compression

et al. 2019

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“…The effective stress principle is essential in stress-seepage field coupling [39]. A great deal of research has been conducted on this: Terzaghi [40] first proposed the concept of effective stress to describe the geotechnical medium via the coupling of external stress and pore water pressure. The formulation is as follows:…”

Section: Effective Stress Analysis Under Stress-seepage Couplingmentioning

confidence: 99%

“…The literature [40] suggests that an exponential model can be used to describe the relationship between permeability and effective stress in porous rocks:…”

Section: Effective Stress Analysis Under Stress-seepage Couplingmentioning

confidence: 99%

Experimental Study on the Pre-Peak Mechanical and Seepage Characteristics of Granite

Zeng,

Lin,

Chen

et al. 2024

Applied Sciences

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The Sanshandao Gold Mine is currently in the deep mining stage. The ground pressure on the surrounding rocks is gradually becoming more considerable, and at the same time, threatened by the overlying seawater, the possibility of mine water inrush accidents is increasing. In this study, the MTS815 rock triaxial seepage test system was employed for the triaxial compression testing and stress–seepage coupled testing of granite under different confining pressures. The results show that granite’s pre-peak mechanical evolution under different confining pressures is divided into four stages (the crack closure stage, linear elasticity stage, stable crack expansion stage, and unstable crack expansion stage). With the increase in the confining pressure, the crack initiation threshold, crack damage threshold, and peak threshold gradually increased, but the closure threshold had no corresponding change. Moreover, in the loading process, the permeability curve first decreased and then increased, and the confining pressure suppressed the peak permeability of granite. Finally, based on the test results, stress sensitivity analysis was carried out, and it was found that polynomials fit the relationship between permeability and effective stress better. Granite’s permeability showed strong stress sensitivity at medium confining pressures. The stress sensitivity of the permeability of granite decreased with increasing effective stress at medium and high confining pressures, while it tended to increase at low confining pressures.

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“…Based on orthogonal triaxial stress experiments with CH 4 seepage, the complete stress-strain relationship and the corresponding evolution of the volumetric strain and permeability were obtained. Zhang et al (2018) investigated the effect of pore-fluid pressure on normal deformation through laboratory experiments. The results indicated that the pore-fluid pressure significantly affects the normal deformation of a jointed sample.…”

Section: Introductionmentioning

confidence: 99%

Calculation of Average Reservoir Pore Pressure Based on Surface Displacement Using Image-To-Image Convolutional Neural Network Model

Wang

2021

Front. Earth Sci.

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The average pore pressure during oil formation is an important parameter for measuring the energy required for the oil formation and the capacity of injection–production wells. In past studies, the average pore pressure has been derived mainly from pressure build-up test results. However, such tests are expensive and time-consuming. The surface displacement of an oilfield is the result of change in the formation pore pressure, but no method is available for calculating the formation pore pressure based on the surface displacement. Therefore, in this study, the vertical displacement of the Earth’s surface was used to calculate changes in reservoir pore pressure. We employed marker-stakes to measure ground displacement. We used an improved image-to-image convolutional neural network (CNN) that does not include pooling layers or full-connection layers and uses a new loss function. We used the forward evolution method to produce training samples with labels. The CNN completed self-training using these samples. Then, machine learning was used to invert the surface vertical displacement to change the pore pressure in the oil reservoir. The method was tested in a block of the Sazhong X development zone in the Daqing Oilfield in China. The results showed that the variation in the formation pore pressure was 83.12%, in accordance with the results of 20 groups of pressure build-up tests within the range of the marker-stake measurements. Thus, the proposed method is less expensive, and faster than existing methods.

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Effect of Pore Fluid Pressure on the Normal Deformation of a Matched Granite Joint

Cited by 12 publications

References 32 publications

Investigation of the Effect of Confining Pressure on the Mechanics-Permeability Behavior of Mudstone under Triaxial Compression

Investigation of the Effect of Confining Pressure on the Mechanics-Permeability Behavior of Mudstone under Triaxial Compression

Experimental Study on the Pre-Peak Mechanical and Seepage Characteristics of Granite

Calculation of Average Reservoir Pore Pressure Based on Surface Displacement Using Image-To-Image Convolutional Neural Network Model

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