Numerical Investigation of Acoustic Emission Events of Argillaceous Sandstones under Confining Pressure

Chong, Zhaohui; Li, Xuehua; Lu, Jingzheng; Chen, Tian; Zhang, J.; Chen, Xiangyu

doi:10.1155/2017/7676417

Cited by 7 publications

(2 citation statements)

References 32 publications

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“…In the proposed model, the micro-properties of intact specimens were firstly calibrated through a trial and error method. According to the authors' previous works [41], the calibrated micro-properties are listed in Table 1. The comparison between the numerical simulation results and physical experimentation results of rock formation under different CPRs is shown in Figure 13.…”

Section: Model Validationmentioning

confidence: 99%

Numerical Investigation into the Effect of Natural Fracture Density on Hydraulic Fracture Network Propagation

Chong

Chen

et al. 2017

Energies

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Hydraulic fracturing is an important method to enhance permeability in oil and gas exploitation projects and weaken hard roofs of coal seams to reduce dynamic disasters, for example, rock burst. It is necessary to fully understand the mechanism of the initiation, propagation, and coalescence of hydraulic fracture network (HFN) caused by fluid flow in rock formations. In this study, a coupled hydro-mechanical model was built based on synthetic rock mass (SRM) method to investigate the effects of natural fracture (NF) density on HFN propagation. Firstly, the geometrical structures of NF obtained from borehole images at the field scale were applied to the model. Secondly, the micro-parameters of the proposed model were validated against the interaction between NF and hydraulic fracture (HF) in physical experiments. Finally, a series of numerical simulations were performed to study the mechanism of HFN propagation. In addition, confining pressure ratio (CPR) and injection rate were also taken into consideration. The results suggested that the increase of NF density drives the growth of stimulated reservoir volume (SRV), concentration area of injection pressure (CAIP), and the number of cracks caused by NF. The number of tensile cracks caused by rock matrix decrease gradually with the increase of NF density, and the number of shear cracks caused by rock matrix are almost immune to the change of NF density. The propagation orientation of HFN and the breakdown pressure in rock formations are mainly controlled by CPR. Different injection rates would result in a relatively big difference in the gradient of injection pressure, but this difference would be gradually narrowed with the increase of NF density. Natural fracture density is the key factor that influences the percentages of different crack types in HFN, regardless of the value of CPR and injection rate. The proposed model may help predict HFN propagation and optimize fracturing treatment designs in fractured rock formations.

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Section: Model Validationmentioning

confidence: 99%

Numerical Investigation into the Effect of Natural Fracture Density on Hydraulic Fracture Network Propagation

Chong

Chen

et al. 2017

Energies

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“…Based on a widely accepted viewpoint, a piece of coal, if containing water, will go through creep damage, which also damages coal strength [19,20]. Auxiliary monitoring means are generally adopted by many scholars to indirectly reflect the strength loss relation of coal [21,22].…”

Section: Introductionmentioning

confidence: 99%

Experimental Study of the Influence of Moisture Content on the Mechanical Properties and Energy Storage Characteristics of Coal

Liu

Feng

et al. 2021

Geofluids

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Rock burst occurs frequently as coal mining depth goes deeper, which seriously impacts the safety production of underground coal mines. Coal seam water injection is a technique commonly used to prevent and control such accidents. Moisture content is a critical factor tightly related to rock burst; however, an in-depth insight is required to discover their relationship. In this study, the influence of moisture content on the mechanical properties of coal and rock burst tendency is explored via multiple measurement techniques: uniaxial compression test, cyclic loading/unloading test, and acoustic emission (AE) test. These tests were performed on coal samples using the MTS-816 rock mechanics servo testing machine and AE system. The testing results showed that with the increase in moisture content, the peak strength and elastic modulus of each coal sample are reduced while the peak strain increases. The duration of the elastic deformation phase in the complete stress-strain curves of coal samples is shortened. As the moisture content increases, the area of hysteretic loop and elastic energy index W ET of each coal sample are reduced, and the impact energy index K E is negatively correlated with the moisture content, whereas dynamic failure time is positively correlated with the moisture content, but this variation trend is gradually mitigated with the continuous increase of moisture content. The failure of the coal sample is accompanied by the sharp increase in the AE ring-down count, whose peak value lags behind the peak stress, and the ring-down count is still generated after the coal sample reached the peak stress. With the increase in moisture content, the failure mode of the coal sample is gradually inclined to tensile failure. The above test results manifested that the strength of the coal sample is weakened to some extent after holding moisture, the accumulative elastic energy is reduced in case of coal failure, and thus, coal and rock burst tendency can be alleviated. The study results can provide a theoretical reference for studying the fracture instability of moisture-bearing coal and prevention of coal and rock burst by the water injection technique.

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Fracture evolution of transversely isotropic rocks with a pre-existing flaw under compression tests based on moment tensor analysis

Tang

et al. 2021

Acta Geotech.

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Numerical Investigation of Acoustic Emission Events of Argillaceous Sandstones under Confining Pressure

Cited by 7 publications

References 32 publications

Numerical Investigation into the Effect of Natural Fracture Density on Hydraulic Fracture Network Propagation

Numerical Investigation into the Effect of Natural Fracture Density on Hydraulic Fracture Network Propagation

Experimental Study of the Influence of Moisture Content on the Mechanical Properties and Energy Storage Characteristics of Coal

Fracture evolution of transversely isotropic rocks with a pre-existing flaw under compression tests based on moment tensor analysis

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