Numerical Simulation of Hydraulic Fracture Propagation in Coal Seams with Discontinuous Natural Fracture Networks

Wang, Shen; Li, Huamin; Li, Dongyin

doi:10.3390/pr6080113

Cited by 43 publications

(19 citation statements)

References 85 publications

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“…The computational fluid dynamics method is used to investigate the flow and loss characteristics under different Reynolds number and different groove depth. Moreover, the structural stress analysis where the valve failure might occur is also done while using a numerical method that is proven by the previous studies [27][28][29][30][31]. This work is helpful for the understanding of the flow characteristics of the gate valve and the judgment of the reason for valve failure in the future.…”

Section: Introductionmentioning

confidence: 95%

Flow Characteristics and Stress Analysis of a Parallel Gate Valve

Wu¹,

Li²,

Gao

2019

Processes

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Gate valves have been widely used in the piping system and have attracted a lot of attention from researchers. In this paper, a wedge-type double disk parallel gate valve is chosen to be analyzed. The Reynolds number varying from 200 to 500,000, and the valve opening degree varying from 20% to 100%, and the groove depth varying from 2.3 mm to 9 mm are chosen to investigate their effects on the flow and loss coefficients of the gate valve. The results show that the loss coefficient decreases and the flow coefficient increases with the increase of the Reynolds number and the valve opening degree, while with the increase of the groove depth, the loss coefficient barely changes, but the flow coefficient increases if the Reynolds number is larger than 10,000. In addition, the effects of the gaps between the disk and the limit stop on the stress distribution of the bolt are also investigated, and the results show that if the gaps are negative, high stress will act on the bolt at the contact position between the bolt and the limit stop.

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Section: Introductionmentioning

confidence: 95%

Flow Characteristics and Stress Analysis of a Parallel Gate Valve

Wu¹,

Li²,

Gao

2019

Processes

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“…In past studies, average pore pressure mainly depended on pressure build-up test results, which have a high cost and need a long testing time, so it is not conducive to utilize. Pressure build-up test data of a single well can also only reflect the average pore pressure of the formation near the test well, not the formation pore pressure of the far area [7,8]. Consequently, these problems make it difficult to evaluate the average formation pressure in many oilfields.…”

Section: Introductionmentioning

confidence: 99%

An Improved New Convolutional Neural Network Method for Inverting the Pore Pressure in Oil Reservoir by Surface Vertical Deformation

Wang

et al. 2021

Lithosphere

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Average pore pressure in oil formation is an important parameter to measure energy in the formation and the capacity of injection–production. In past studies, average pore pressure mainly depends on pressure build-up test results, which have a high cost and need a long testing time, so it is not conducive to utilize. In this paper, the vertical deformation of the Earth’s surface was used to calculate changes in reservoir pore pressure. We set up the marker stake for measuring ground displacement and measured the vertical deformation at the in situ position. Furthermore, we provided an improved new convolutional neural network (CNN), which adopted image-to-image mode, removed pooling layers and full connection layers, and used a new loss function considering the boundary influence coefficient matrix. Then, the machine learning method was used to invert surface vertical deformation to change pore pressure in the oil reservoir. The method was tested in the block of the Sazhong X development zone, in the Daqing Oilfield of China. The average pore-pressure change values of 20 grids whose area was 900×900 m each were determined by the inversion of the corresponding surface vertical deformation at 27 marker stakes. The pore pressure change accuracy reached 82.34%. This study provides a new method for calculating average pore pressure in terms of an oil block. At the same time, it also provides a new technical method for inversion calculations.

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“…Coal bed methane exploitation can not only prevent coal and gas outburst, but also provide clean energy. With the increase of mining depth, the in-situ stress becomes larger, the permeability of coal seam becomes lower, and the difficulty of coalbed methane exploitation increases [5][6][7]. Therefore, how to effectively improve the permeability and prevent gas disaster is one of the most important problems in the development of coalbed methane [8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

Simulation Study on the Effect of Coal Seam Hydraulic Fracturing to Increase Permeability

Wang

Zhang

Wang

et al. 2021

Preprint

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Hydraulic fracturing is mainly used to improve coal seam permeability, extract coal seam gas and prevent coal-gas outburst. However, in the aspect of anti-reflection effect, it is judged by the method of field inspection, and there is no good prediction method before the engineering application. In this work, PFC2D software is used to simulate the process of coal seam hydraulic fracturing, and the results are introduced into the mathematical coupling model of the interaction between coal seam deformation and gas flow for analysis. The results show that the particles are moving towards the direction of the minimum principal stress, the moving speed of the particles at the crack tip increases, and the crack will finally expand towards the direction of the maximum principal stress. The gas pressure decline rate and permeability increase rate of the fractured model are both higher than that of the unfractured model. With the increase of extraction time, the decrease rate of gas pressure and the increase rate of permeability both decrease rapidly and gradually approach 0. The longer the hydraulic fracturing time is, the more complex the fracture network is, and the faster the gas pressure drops. However, the difference between the horizontal and vertical gas pressure drops will become larger and larger, and the impact of fracturing on gas drainage effect will gradually become smaller. With the increase of fracturing time, the difference of permeability increase at different monitoring points becomes larger and larger, but with the increase of gas drainage time, the difference will gradually decrease. The higher the initial void pressure is, the faster the gas pressure drops and the greater the permeability increase. However, the influence of the initial void pressure on the permeability increase will gradually become smaller. The research results could provide certain guidance for the prediction of anti-reflection effect of hydraulic fracturing in underground coal mines.

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Numerical Simulation of Hydraulic Fracture Propagation in Coal Seams with Discontinuous Natural Fracture Networks

Cited by 43 publications

References 85 publications

Flow Characteristics and Stress Analysis of a Parallel Gate Valve

Flow Characteristics and Stress Analysis of a Parallel Gate Valve

An Improved New Convolutional Neural Network Method for Inverting the Pore Pressure in Oil Reservoir by Surface Vertical Deformation

Simulation Study on the Effect of Coal Seam Hydraulic Fracturing to Increase Permeability

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