Research on main controlling factors and its influencing laws on hydraulic fracture network in the fractured soft and low-permeability coal

Li, Hao; Liang, Weiguo; Wang, Jianmei; Cao, Wei; Wu, Pengfei; Ma, Kai; Wei, Jie; Li, Jing

doi:10.1016/j.jngse.2021.104147

Cited by 11 publications

(9 citation statements)

References 24 publications

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“…It was suggested that the size effect of the sample, shape of the prefabricated crack, temperature and loading rate could affect the test results, which need further study. Yang et al [42] [43] .…”

Section: Testing Methods For the I/ii Mixed Mode Cohesive Crack Const...mentioning

confidence: 99%

“…By the secondary development of the Python language, cohesive elements are embedded between solid units to model natural weak surfaces such as natural cleats and cracks of coal (Figure 7(d)) to simulate a complex fracture network [42] . Considering the 3D network model of coal discontinuities based on CT data (Figure 7(e)), the constitutive equation of ductile failure and mixed mode fracture, numerical simulation of indirect fracturing in crushed soft and low-permeability coal was performed [43] .…”

Section: Research Progress Of Hydraulic Fracturing Numerical Simulationmentioning

confidence: 99%

“…(a) Interface cohesive element [37] (b) Monte Carlo simulation [39] (c) RVE with rigid particle inclusions [40] (d) Natural fracture in coal [5] (e) 3D fracture network (Chen, 2018) (f) 3D discontinuities network model of fractured soft coal [43] Figure 7. Typical cases of complex fracture network simulation with CZM Currently, artificial intelligence (AI) and machine learning (ML) have been widely applied in the oil and gas industry, such as artificial neural network (ANN), support vector machine, k-nearest neighbor algorithm, decision tree algorithm and random forest.…”

Section: Research Progress Of Hydraulic Fracturing Numerical Simulationmentioning

confidence: 99%

“…The cohesive element method is used to simulate the 2D fracture propagation of hydraulic fracturing in coal seams based on the built cohesive crack constitutive model. Li et al (2021) obtained the constitutive equations of mixed mode ductile fractureseepage of the coal matrix by three-point bending experiments and DCT tests and used these equations to model indirect fracturing in fractured soft and low-permeability coal seams[43] .…”

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confidence: 99%

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A review on the application of cohesive zone model in hydraulic fracturing

Zhao

et al. 2023

IOP Conf. Ser.: Earth Environ. Sci.

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Hydraulic fracturing is an effective measure to increase production and injection and blockage removal in oil and gas field development. Accurate prediction of fracture morphologies is the key to the optimized design of hydraulic fracturing. The cohesive zone model (CZM) has been widely used in the numerical simulation of fracture initiation and propagation during hydraulic fracturing. The fractures formed by the numerical simulation vary significantly with different CZMs. In the current numerical simulation, the CZM generally adopts the bilinear model, which is more suitable for describing brittle fracture, while rocks are quasi-brittle materials and have nonlinear CZMs. This deviation should be corrected. Moreover, the CZM parameters are generally determined based on experience, without a reliable basis and standard determination method. This article focused on the CZM, systematically introduced its concept and classification, and clarified the correlation between the types of CZMs and the brittleness, quasi-brittleness, and ductility of rock fracture. The application of CZM in hydraulic fracturing was reviewed, and the existing problems, corresponding countermeasures and future research trends were presented. An integrated method of combining laboratory experiments, data mining and numerical simulation to determine the CZMs of mode I, mode II, and I/II mixed mode cohesive cracks was proposed.

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Section: Testing Methods For the I/ii Mixed Mode Cohesive Crack Const...mentioning

confidence: 99%

Section: Research Progress Of Hydraulic Fracturing Numerical Simulationmentioning

confidence: 99%

Section: Research Progress Of Hydraulic Fracturing Numerical Simulationmentioning

confidence: 99%

mentioning

confidence: 99%

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A review on the application of cohesive zone model in hydraulic fracturing

Zhao

et al. 2023

IOP Conf. Ser.: Earth Environ. Sci.

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“…Based on theoretical knowledge such as changes in the permeability of structural coal, − stress distribution and roof and floor deformation laws, − and gas adsorption and migration laws, − domestic and foreign scholars have proposed many structural coal gas control technologies. − Zhang et al used hydraulic punching technology to relieve pressure and increase the permeability of structural coal, reducing the number of boreholes by 66.7% and increasing gas extraction concentration by three times. Xiao et al used hydraulic fracturing technology for structural coal gas control, and research showed that the gas extraction concentration in the fracturing area is relatively stable, increasing by 18–37% compared to the non-fracturing area.…”

Section: Introductionmentioning

confidence: 99%

Research on Directional Hydraulic Coal Cutting and Outburst Prevention Technology in Soft and Hard Composite Coal Seams

Shan

Zhong

et al. 2023

ACS Omega

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Affected by tectonics, soft and hard composite coal seams are widely distributed in China; the soft stratification in the soft and hard composite coal seam is the key to controlling the occurrence of coal and gas outburst accidents. Based on this, for soft and hard composite coal seams, in order to accurately extract soft layers, a directional hydraulic coal mining equipment has been developed, including a drilling rig pump truck system, a directional coal wireless measurement system, and a cutter drill pipe system. By constructing a mathematical model and conducting numerical simulations, it was found that the vertical stress, horizontal stress, and gas pressure of the coal body around the borehole after coal extraction decreased significantly compared to normal borehole conditions; the on-site test results indicate that the hydraulic coal extraction volume of directional hydraulic coal extraction boreholes reaches 0.25 m3 per meter. The total amount of coal extracted accounts for more than 3‰ of the total amount of coal within the coverage area. The average concentration of gas extraction in the coal extraction area is 80.15%, and the net amount of gas extraction from 100 m boreholes reaches 0.17 m3/(min·hm). After extraction, the measured residual gas content in the coal extraction and non-extraction areas decreased by 59.27 and 40.38%, respectively. Directional hydraulic coal mining technology can effectively solve the problem of coal and gas outburst prevention in soft and hard composite coal seams and has good application prospects.

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Study and application of reasonable parameters for hydraulic punching of layer penetration boreholes in Changping Coal Mine

Min,

Chen,

Wang

et al. 2023

Energy Science & Engineering

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Aiming at the application of hydraulic punching technology in soft, low permeability, and high gas coal seams in Changping Coal Mine, there are problems such as large workload, poor permeability enhancement effect, and the formation of “blank zones” in the pressure relief and permeability enhancement areas caused by workers' blind construction. By using a combination of theoretical analysis, numerical simulation, and on‐site practice, the threshold pressure for punching and breaking coal was calculated. The simulation analysis determined the reasonable key parameters for hydraulic punching through layered drilling, providing theoretical support for engineering applications; and the application effect of key parameters was investigated in the 5302 bottom extraction roadway of Changping Coal Mine. The research results show that the threshold value of incident pressure for punching and breaking coal in the No. 3 coal seam of Changping Coal Mine is 4.26 MPa, the reasonable hydraulic punching water pressure is 15 MPa, the punching angle is 60°, the diameter of the punching hole is not more than 0.8 m, and the punching time is 120 min; when the punching water pressure is lower than 4.0 MPa, effective coal flushing cannot be achieved. When the water pressure is between 4.0 and 15.0 MPa, the total amount of coal flushing is positively correlated with the punching water pressure; under the determined reasonable parameter punching conditions, the extraction influence radius is 8.9 m, the effective extraction radius is 5 m, and the average pure gas extraction volume is 0.089 m3/min. Under this parameter, hydraulic punching technology effectively improves the permeability characteristics of coal seams, which is conducive to long‐term gas extraction and has a significant effect on pressure relief and drainage promotion.

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Research on main controlling factors and its influencing laws on hydraulic fracture network in the fractured soft and low-permeability coal

Cited by 11 publications

References 24 publications

A review on the application of cohesive zone model in hydraulic fracturing

A review on the application of cohesive zone model in hydraulic fracturing

Research on Directional Hydraulic Coal Cutting and Outburst Prevention Technology in Soft and Hard Composite Coal Seams

Study and application of reasonable parameters for hydraulic punching of layer penetration boreholes in Changping Coal Mine

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