Discrete element simulation model of pulsating hydraulic fracturing considering fatigue damage

Zhu, Guangjun; Dong, Shimin

doi:10.1007/s40948-022-00424-z

Cited by 8 publications

(4 citation statements)

References 36 publications

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“…It is found that the PHF was able to create a more extensive network of fractures in shale, which draws a lot of interest from many researchers. Numerical methods have been used to predict and optimize the formation of hydraulic fractures during pulsating hydraulic fracturing with a fluid–structure interaction method . The mechanical properties of rocks can be evaluated to predict new fractures.…”

Section: Introductionmentioning

confidence: 99%

“…Fatigue is a key degradation form of rock under pulsed/cyclic loading, resulting in a reduction in the breakdown pressure during the PHF process. However, among the limited literature with numerical and experimental methods up to date, the fatigue damage of the PHF has not been clearly described . It is difficult to truly evaluate the fatigue damage effect with pulsating water injection.…”

Section: Introductionmentioning

confidence: 99%

“…Numerical methods have been used to predict and optimize the formation of hydraulic fractures during pulsating hydraulic fracturing with a fluid–structure interaction method. 13 The mechanical properties of rocks can be evaluated to predict new fractures. It indicates that under different pumping rates, PHF could significantly increase the pore connectivity of shale gas reservoirs.…”

Section: Introductionmentioning

confidence: 99%

“…However, among the limited literature with numerical and experimental methods up to date, the fatigue damage of the PHF has not been clearly described. 13 It is difficult to truly evaluate the fatigue damage effect with pulsating water injection. The purpose of this paper is to provide a quantitative analysis of the effects of the PHF on the microstructure of coal after hydraulic pulse loading.…”

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

Prediction of the Effects of Pulsating Hydraulic Fracturing on the Porous Structure and Permeability of Coal Based on NMR and AE Spectra

Yu,

Cheng,

Hong

et al. 2024

ACS Omega

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Pulsating hydraulic fracturing has been an environmentally friendly method to improve the permeability of rock formations to stimulate gas production and reduce hazard risks. It has the advantage of fracturing the reservoir with lower cracking pressure and less water volume, as the mechanical strength of rock materials has been reduced by the hydraulic pulse pressure. Many researchers have found significant changes in hard rocks after cyclic loading. However, the existing work still cannot clearly explain the mechanism of the rock damage by pulsating hydraulic fracturing within a short-time experiment. To solve the issue, an investigation of the effects of pulsating hydraulic fracturing on CBM production has been carried out in lab and field applications. Results indicate that the long-term hydraulic pulse pressure can cause a linear decline in cracking pressure directly measured in the lab. It plays an essential role in the permeability enhancement by generating more flow channels for CBM production. The low-field NMR quantitatively evaluates the increase in porosity, which reveals significant incremental ratios of over 20% in the porosity of macropores, mesopores, and micropores of coal caused by fatigue damage. It is first proven that hydraulic pulse pressure has a significant influence on the porosity components of macropores, mesopores, and micropores. To validate the effectiveness of the technique on the field scale, a field application of pulsating hydraulic fracturing has been carried out in a coal mine. It shows that gas production has been largely enhanced with a long and stable production stage and higher gas flux after the applied pulsating load. The gas concentration and gas flux of the fractured boreholes are about 2 times that of the nonfractured boreholes. This work provides an investigation of the effects of pulsating hydraulic fracturing on CBM production, which gives a better understanding of the mechanism for the engineers in the field.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Prediction of the Effects of Pulsating Hydraulic Fracturing on the Porous Structure and Permeability of Coal Based on NMR and AE Spectra

Yu,

Cheng,

Hong

et al. 2024

ACS Omega

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Study on the influence of vertical stress difference coefficient on fracture characteristics of shale under high stress

Chang,

Qiu,

et al. 2024

Energy Science & Engineering

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To study the effect of vertical stress difference coefficient on fracture characteristics of shale fracturing, high stress true triaxial hydraulic fracturing test was carried out. By analyzing the profile after fracturing, it was found that the area of hydraulic fracture increased with the increase of vertical stress difference coefficient, and the probability of shear fracture will increase when the stress difference coefficient was high. A high vertical stress differential coefficient exerts a strong control over the direction of crack propagation, while a low vertical stress difference coefficient is beneficial to improve the roughness of hydraulic fracture surface and promote the formation of complex fracture network. By analyzing the pump pressure curves of different tests, it was found that with the increase of vertical stress difference coefficient, the formation and expansion of hydraulic fractures were more difficult. The surface characteristics of hydraulic fractures were quantified based on three‐dimensional topography scanning technology, combined with fractal dimension and fracture area calculation method, the results showed that with the increase of vertical stress difference coefficient, the fractal dimension and fracture area decreased. Since shale is stratified, and the transformation of reservoir is mainly reflected in the enhancement of fracture complexity through tensile failure, Xsite discrete grid method was used to study the influence of fracture propagation behavior with different bedding strengths. The results showed that when the bedding tensile strength was high, hydraulic fractures were easy to pass through the bedding, and when the bedding tensile strength was low, hydraulic fractures were easy to be captured by natural fractures. In addition, tensile cracks were easy to form when the tensile strength of bedding was low, shear cracks were easy to form when the strength of bedding was high, and the fracture volume was larger when the strength of bedding was low. This study provides a theoretical basis for hydraulic fracturing in engineering.

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A Fatigue Cohesive Law‐Embedded Finite‐Discrete Element Method for Pulsed Hydraulic Fracture Simulation

Wei,

Wang,

et al. 2024

Num Anal Meth Geomechanics

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The pulsed hydraulic fracture (PHF) is a stimulation technique of reservoir, which can lower breakdown pressure by generating fatigue fracture. In this study, a fatigue cohesive law is proposed and embedded into the finite‐discrete element method (FDEM) to describe the fatigue failure of the interface under cyclic loading. The fatigue is assumed to result from the accumulation of plastic deformation, whose increment is related to the traction variation range of each cycle and the total plastic deformation. The proposed fatigue cohesive law is validated by the uniaxial compression and mixed‐mode three‐point bending test simulation. Then this fatigue cohesive law is embedded into a fully hydraulic–mechanical coupled FDEM to simulate the PHF. The influence of loading scheme, flow rate, frequency, viscosity and natural fracture density on PHF behaviors is discussed. The results suggest that both the pressure‐ and injection rate–controlled PHF can reduce the breakdown pressure. The flow rate, frequency, and viscosity have a great impact on the performance of PHF. The natural fractures surrounding a hydraulic fracture (HF) can be gradually activated under cyclic injection. The activated natural fractures contribute to the complicated HF network. These results indicate that the proposed fatigue cohesive model can effectively simulate the fatigue fracture of rock and HF propagation under cyclic injection.

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Discrete element simulation model of pulsating hydraulic fracturing considering fatigue damage

Cited by 8 publications

References 36 publications

Prediction of the Effects of Pulsating Hydraulic Fracturing on the Porous Structure and Permeability of Coal Based on NMR and AE Spectra

Prediction of the Effects of Pulsating Hydraulic Fracturing on the Porous Structure and Permeability of Coal Based on NMR and AE Spectra

Study on the influence of vertical stress difference coefficient on fracture characteristics of shale under high stress

A Fatigue Cohesive Law‐Embedded Finite‐Discrete Element Method for Pulsed Hydraulic Fracture Simulation

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