Study of the borehole hydraulic fracturing and the principle of gas seepage in the coal seam

Wang, Peng; Mao, Xianbiao; Jin-bin, Lin; Du, Chunzhi

doi:10.1016/j.proeps.2009.09.241

Cited by 22 publications

(5 citation statements)

References 3 publications

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“…With the development of numerical simulation technology, many scholars have adopted the method to study the change in morphology and expansion of hydraulic fractures in different reservoirs. The numerical simulation methods include finite element method (FEM) [11][12][13], twodimensional particle flow code (PFC) [14][15][16][17], continuousdiscontinuous coupling method [18][19][20], and discrete element method (DEM) [21][22][23], which can visualize and quantify the fracture morphology and fracturing process. Among these methods, the finite element method is the most widely used one.…”

Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Simulation Study of Hydraulic Fracture Propagation during Coalbed Methane Development

et al. 2021

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The extraction of low-permeability coalbed methane (CBM) has the dual significance of energy utilization and safe mining. Understanding hydraulic fracturing mechanism is vital to successful development of CBM. Therefore, it is important to improve the law of hydraulic fracture propagation in coal and rigorously study the influencing factors. In this paper, laboratory experiments and numerical simulation methods were used to investigate the hydraulic fracture propagation law of coal in coalbed methane reservoir with natural fractures. The results show that the maximum and minimum horizontal in situ stress and the difference in stress significantly affect the direction of crack propagation. The elastic modulus of coal, the mechanical properties of natural fractures, and the injection rate can affect the fracture length, fracture width, and the amount of fracturing fluid injected. To ensure the effectiveness of hydraulic fracturing, a reservoir environment with a certain horizontal stress difference under specific reservoir conditions can ensure the increase of fractured reservoir and the controllability of fracture expansion direction. In order to increase the volume of fractured reservoir and fracture length, the pumping speed of fracturing fluid should not be too high. The existence of stress shadow effect causes the hydraulic fracture to propagate along the main fracture track, where the branch fracture cannot extend too far. Complex fractures are the main hydraulic fracture typology in coalbed methane reservoir with natural fractures. The results can provide a benchmark for optimal design of hydraulic fracturing in coalbed methane reservoirs.

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Section: Introductionmentioning

confidence: 99%

Experimental and Numerical Simulation Study of Hydraulic Fracture Propagation during Coalbed Methane Development

et al. 2021

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“…On the one hand, the slot is equivalent to an extremely thin protective layer mined within the coal seam, which provides favorable conditions for stress release in a coal seam . On the other hand, the slots provide channels for desorption and flow of gas, thus improving the efficiency of gas drainage …”

Section: Introductionmentioning

confidence: 99%

“…17,18 On the other hand, the slots provide channels for desorption and flow of gas, thus improving the efficiency of gas drainage. [19][20][21] To investigate the mechanism of high-pressure water jets in breaking coal (rock) and eliminating outbursts, various engineers have carried out a series of experiments: Lin et al [22][23][24] analyzed coal and gas outbursts in coal roadways and proposed the concept of integral pressure relief to allow further slotting of working faces. The results showed that slotting can be applied to prevent gas outbursts in coal seams owing to slots being able to connect boreholes to relieve gas pressure in a coal mass.…”

Section: Introductionmentioning

confidence: 99%

Elimination of coal and gas outburst risk of low‐permeability coal seam using high‐pressure water jet slotting technology: A case study in Shihuatian Coal Mine in Guizhou Province, China

Xie

Zou

et al. 2019

Energy Science & Engineering

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Coal seams in China are mainly characterizsed by low permeability and high risk of coal and gas outburst. Therefore, the elimination of coal and gas outburst risk of low‐permeability coal seam remains a hard challenge. Taking Shihuatian Coal Mine in Guizhou Province, China as an example, boreholes were slotted using high‐pressure water jet to relieve the gas pressure inside the coal seam and increase the permeability of coal mass, which thus improves the gas drainage efficiency and eliminate the outburst risk. The results show that the gas drainage efficiency of the slotted boreholes significantly increases. Compared with the conventional boreholes, the average gas concentration and flow velocity improved by 1.6 and 7.5 times, respectively. Moreover, the prediction index of outburst risk is less than the critical value after high‐pressure water jet slotting, which indicate that the coal and gas outburst risk has been effectively eliminated. The measured values of gas desorption index of drilling cuttings are all lower than the critical value after the application of the high‐pressure water jet slotting technology. The research achievements could provide a practical reference for the effective gas disaster prevention and control in low‐permeability coal seams.

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“…In numerical simulation research, a three-dimensional (3D) finite element model was established by Guangqing and Mian [11] to study the factors that influence the fracture shape in orientated hydraulic fracturing based on rock mechanical tests and practical data interpretation. To analyze the initiation and propagation mechanism of a crack, the principle of gas seepage in cracks and the hydraulic fracturing process were analyzed synthetically through numerical simulation [12], the results of which showed that the rock stress state greatly affects the crack propagation and the crack propagated randomly with bifurcation when the two ground stresses on the horizontal plane were equal. e influences of various complex factors, such as geostress, rock mechanic characteristics, and fracturing fluid characteristics, on hydraulic fracturing expansion were investigated [13], and the initiation pressure, maximum crack width, and crack propagation length were obtained under different maximum horizontal stress conditions.…”

Section: Introductionmentioning

confidence: 99%

Numerical Investigation on Rock‐Fracturing Mechanism by Using Splitter under Hole Assistance

Liu

Guo

2019

Shock and Vibration

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In this work, a numerical model of rock breaking under hole assistance was established based on the finite element method (FEM) coupling with smoothed particle hydrodynamics (SPH) to reveal rock-breaking mechanisms and analyze the reasons for crack formation and propagation under hole assistance. In addition, the numerical model was verified by experiment with and without a hole, and the simulation results are basically consistent with the experimental results in rock breaking. During the process of rock fracturing, the hydraulic splitter was first inserted into the predrilling hole, and then the wedges were pushed into the rock under the action of the hydraulic pressure. In this process, the splitter wedge was separated from the two sides, and the transverse bursting force was transmitted to the rock. Finally, the main fracture formed and the rock mass broke due to the bursting force. The results show that the cracks propagate along the approximately straight lines OO1 (the distance between the auxiliary holes and the left predrilled fracturing hole) and OO2 (the distance between the auxiliary holes and the right predrilled fracturing hole) before extending to the auxiliary hole which is unlike the crack propagation in rock without auxiliary holes, and the crack propagating direction gradually approaches horizontally and is vertical to the side after passing through the auxiliary holes. Moreover, when the auxiliary holes are located at the prefabricated angles α = 40° and 45°, the crack propagation can be well induced and the cracks pass through the auxiliary holes. However, at α = 50°, the auxiliary holes can no longer well induce the crack propagation in the process of rock breaking; however, the fracturing pressure is still less than that with no auxiliary holes, indicating that the auxiliary holes play a positive role in guiding rock breaking.

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Study of the borehole hydraulic fracturing and the principle of gas seepage in the coal seam

Cited by 22 publications

References 3 publications

Experimental and Numerical Simulation Study of Hydraulic Fracture Propagation during Coalbed Methane Development

Experimental and Numerical Simulation Study of Hydraulic Fracture Propagation during Coalbed Methane Development

Elimination of coal and gas outburst risk of low‐permeability coal seam using high‐pressure water jet slotting technology: A case study in Shihuatian Coal Mine in Guizhou Province, China

Numerical Investigation on Rock‐Fracturing Mechanism by Using Splitter under Hole Assistance

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