Investigating Hydraulic Fracturing Complexity in Naturally Fractured Rock Masses Using Fully Coupled Multiscale Numerical Modeling

Zhang, Fengshou; Damjanac, Branko; Maxwell, Shawn

doi:10.1007/s00603-019-01851-3

Cited by 207 publications

(67 citation statements)

References 84 publications

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“…To analyze the impact of fractures cracking on slope stability before excavation, the fractures were modeled by the contact surface unit in FLAC3D software; while for slope after coal excavation, the null model in FLAC3D software was used to simulate the slope excavation process and to analyze the impact of fractures on slope stability before and during coal excavation. [19,20]. e strata were divided into 8 layers through reasonable simplification ( Table 2).…”

Section: Simulation Method Principle and Modelmentioning

confidence: 99%

Effect of Coalbed Methane Well Fracturing on Slope Stability of Open‐Pit Coal Mine: A Case Study of Shengli East No. 2 Open‐Pit Coal Mine

Zhu¹,

Wang

Zhao

et al. 2020

Advances in Civil Engineering

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The impact of hydraulic fracture from CBM well fracturing on slope stability of the Shengli East No. 2 open-pit coal mine is analyzed by numerical simulation and limit equilibrium methods. The interference effect of coalbed methane (CBM) well fracturing on slope stability of the open-pit coal mine promotes the coordinated development of CBM, and open-pit coal is discussed before and after coal mining. It shows that nearly horizontal fractures are formed in the coal seam due to CBM well fracturing, of which the dynamic facture length and propping fracture length are 137.2 m and 105.2 m, respectively. Moreover, the dynamic fracture height is 137.2 m and propping fracture height is 130.6 m. At the location of perforation, the dynamic fracture width is 0.873 cm and average propping fracture width is 0.111 cm. The CBM well fracturing barely imposed any effect on slope stability before open-pit coal mining. The maximum vertical displacement at the toe of slope induced by fracturing is 0.293 mm. In situations with and without CBM well fracturing, vertical stress distributions in the toe, top, and interior of slope have no obvious difference. There is some extent of vertical stress increase within the interior of slope, which is merely 0.2 MPa higher than that in the condition of initial in situ stress equilibrium. The presence of hydraulic fractures has little effect on the overall displacement of slope during coal mining; and there is no obvious difference between the slope stability during coal mining and the slope stability impacted by fracturing. According to the results of limit equilibrium method and numerical simulation, the overall slope stability coefficient is 1.5–1.97, which accords with the requirements of the Design Code for Open-Pit Mine of Coal Industry (GB50197-2015). Therefore, more attentions should be paid to the ways of excavation and sloping during coal mining, avoiding slope instability caused by excavation.

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Section: Simulation Method Principle and Modelmentioning

confidence: 99%

Effect of Coalbed Methane Well Fracturing on Slope Stability of Open‐Pit Coal Mine: A Case Study of Shengli East No. 2 Open‐Pit Coal Mine

Zhu¹,

Wang

Zhao

et al. 2020

Advances in Civil Engineering

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“…Its core is to deal with the intersection and extension behavior of many HFs and hundreds of NFs. 21 As the number of natural cracks increases exponentially, the division and processing of model grids and the optimization and upgrading of numerical calculation methods are all major challenges for complex nonplanar fracture models. As the frontier of fracture extension, complex nonplanar fracture model has become the focus of research in recent years.…”

Section: Introductionmentioning

confidence: 99%

Study on induced stress of hydraulic fracturing in fractured‐porous elastic media

Wang

Zhao

et al. 2020

Energy Science & Engineering

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The study on induced stress of hydraulic fracturing is an important part of hydraulic fracturing design, temporary plugging and steering fracturing design, and completion design in oil and gas development. Based on fracture continuum method (FCM), cohesive unit method, and finite volume method (FVM), the propagation behavior of multiple hydraulic fractures (HFs) in fractured‐porous media reservoir is simulated from the perspective of fluid and geological stress coupling. The influence of natural fractures (NFs) on stress distribution and stress inversion sensitive factors are studied. NFs in the model are equivalent to physical models controlled by tension and shear bonds. The proposed model can deal with any number of NFs, which greatly improves the computational efficiency of the model. Then PKN analytic solution and Abaqus software results were used to verify the correctness of our model. The results show that the NF will make the reservoir stress show strong heterogeneity after fracturing, and the prominent feature is the regional stress mutation. The sudden change of stress shows the sudden increase or decrease in stress; with the increase in the initial stress difference, the stress inversion becomes more difficult. When the stress difference exceeds 3 MPa, the stress inversion area is almost 0. The stress interference increases with the decrease in cluster spacing. The stress inversion region between HFs decreases, while the external stress inversion region increases; Biot coefficient has great influence on stress and stress inversion. With the decrease in Biot coefficient, stress inversion region will decrease obviously. When the Biot coefficient is 0.4, there is no stress inversion area in the whole reservoir. Poisson's ratio has little influence on stress inversion. When Poisson's ratio changes between 0.1 and 0.3, the change range of stress is within 1 MPa, and the stress inversion area is almost unchanged. Our results can be helpful for understanding the stress distribution after hydraulic fracturing in fractured‐porous media.

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Section: Introductionmentioning

confidence: 99%

“…Hydraulic fracturing, as one of the most effective stimulation methods to exploit oil and gas, plays an important role in the development of different type of reservoirs worldwide. [1][2][3][4][5][6][7][8][9][10][11] As an emerging technology for the enhancement of well production, pulsating fracturing shows its outstanding potential in the exploitation of unconventional oil and gas reservoirs (such as coal bed methane formation). Compared with the traditional hydraulic fracturing technology, pulsating fracturing is more likely to cause damage to the rock, reduce the strength of the rock, [12][13][14] and facilitate the propagation of fractures in the rock.…”

Section: Introductionmentioning

confidence: 99%

Rock damage evolution model of pulsating fracturing based on energy evolution theory

Zhao²,

Tang

et al. 2019

Energy Science & Engineering

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Pulsating fracturing, as a new technology for unconventional oil and gas exploration, enables to enhance stimulated reservoir volume (SRV) effectively, which further helps to improve well performance. It is of great importance for the evaluation of fracturing performance and optimization of fracturing parameters by accurately calculating variables from formation impairment during pulsating fracturing treatment. Based on the principle of conservation of energy, a novel theoretical model describing the evolution of rock damage was proposed by analyzing energy evolutionary characteristics from the hysteresis loop of rock stress‐strain curve while the treatment. This model was in a good agreement with experimental data. In this paper, our study indicates that the rock damage is caused by the accumulation of damage in each cyclic loading and unloading process during pulsating fracturing. Moreover, the cumulative rock damage would increase with the increment of the number of cyclic loading and unloading. Conversely, the rock strength is negatively correlated with cyclic number. The cumulative damage variable approximates to one as the rock breaks. Additionally, the frequency and the stress level of pulsating fracturing have an obvious impact on the evolution of rock damage. The optimization of these parameters can help to accelerate the rock damage and reduce the corresponding rock strength. The speed of rock damage can be accelerated with the enhancement of the stress level at the later period of the step loading, which facilitates the increment of cumulative damage variable. Our new model provides a guideline for predicting the initial rock damage during pulsating treatment.

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Investigating Hydraulic Fracturing Complexity in Naturally Fractured Rock Masses Using Fully Coupled Multiscale Numerical Modeling

Cited by 207 publications

References 84 publications

Effect of Coalbed Methane Well Fracturing on Slope Stability of Open‐Pit Coal Mine: A Case Study of Shengli East No. 2 Open‐Pit Coal Mine

Effect of Coalbed Methane Well Fracturing on Slope Stability of Open‐Pit Coal Mine: A Case Study of Shengli East No. 2 Open‐Pit Coal Mine

Study on induced stress of hydraulic fracturing in fractured‐porous elastic media

Rock damage evolution model of pulsating fracturing based on energy evolution theory

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