Wave motion in a viscous fluid-filled fracture

Ashour, Ahmed

doi:10.1016/s0020-7225(99)00045-2

Cited by 17 publications

(17 citation statements)

References 11 publications

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“…Based on the theorem of Helmholtz decomposition, the same wave equation also can be expressed by the scalar potential φ and vector potential ψ of particle displacement (J.d.achenbach 1975;Ashour 2000):…”

Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

Numerical modelling of acoustic stimulation induced mechanical vibration enhancing coal permeability

Jiang

Xing

2016

Journal of Natural Gas Science and Engineering

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Mechanical vibration is a major effect generated by acoustic stimulation inside a coal sample for enhancing its permeability. The numerical simulation based on the staggered-grid finite differential method (FDM) is applied to simulate 3D wave propagation in a fractured coal. Two parameters, shear wave energy (SE) and variable width of cleat (DW), are introduced and implemented in the numerical model to explicitly visualise and evaluate the acoustic stimulation effects. The polarized wave induced wave dynamics in a coal sample with a cleat/fracture is numerically simulated and analysed. Especially, the energy trapping and dynamic variation of fracture width in coal for the cleat/fracture with three different filled media (i.e. air, water and weak mineral) are numerically analysed and compared with each other subjected to different incident wave angles, and the optimal stimulation parameters are obtained through such sensitivity analysis. Simulation results show that the coal property (i.e. cleat and its filled media) and incident wave angles are crucial for acoustic stimulation to produce physical damages around coal cleats and enhance the permeability of fractured coal samples.

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Section: A C C E P T E D Accepted Manuscriptmentioning

confidence: 99%

Numerical modelling of acoustic stimulation induced mechanical vibration enhancing coal permeability

Jiang

Xing

2016

Journal of Natural Gas Science and Engineering

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“…When PHF is implemented in a coal mine, the PWP propagates in a wave-form through the water medium and is affected by the fissure size changes and blockage state (Ashour, 2000;Ionov, 2007). When mining or drilling occurs in an underground coal mine, crustal stress is redistributed, and coal particles flow into the fissures, causing coal fissure size and shape changes.…”

Section: Introductionmentioning

confidence: 99%

Experimental study of pulsating water pressure propagation in CBM reservoirs during pulse hydraulic fracturing

Zhai

Xiang

et al. 2015

Journal of Natural Gas Science and Engineering

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“…Hence at the initial stimulating stage of the experiment, the ultrasonic wave propagation at the interfaces of a cleat model, or around its surrounding medium, is governed by the elastic wave equation. The elastic wave equation without external body force is expressed by particle displacement vector u as (Ashour, 2000) :…”

Section: Governing Equations Of Elastic Wavementioning

confidence: 99%

“…Based on the theorem of Helmholtz decomposition, the same wave equation also can be expressed by the scalar potential φ and vector potential ψ of particle displacement (Achenbach, 1999;Ashour, 2000):…”

Section: Governing Equations Of Elastic Wavementioning

confidence: 99%

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Numerical simulation of acoustic stimulation for enhancing coal seam gas reservoir permeability

Jiang¹

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Acoustic stimulation method has been recognized as one of the most effective methods for enhancing coal permeability and improving the production amount of gas. Laboratory data has proved that the geometrical parameters (width and length) of coal cleats, which are the crucial pathway for gas migration, could be highly increased by acoustic field stimulation. The main reason for this positive effect is that acoustic energy could induce the mechanical vibration effect around coal cleats. However, the basic mechanism of this effect is still poorly understood due to the limitation of experimental facilities; the progress and details about this effect cannot be directly observed. It is imperative to conduct proper numerical simulation for the technology to improve the understanding of mechanical vibration. And only based on the conclusion of simulation results, the engineering parameters for optimal stimulation effect could be found. This thesis addresses this key issue and demonstrates how exactly the mechanical vibration is induced and affect the original coal cleat system. This thesis focuses on conducting numerical simulation for acoustic wave induced mechanical vibration around the coal cleats. The primary contributions are summarized as follows:(1) The numerical simulation based on the staggered-grid finite differential method (FDM) is applied to simulate 3D wave propagation in a single coal cleat model. Two parameters, shear wave energy (SE) and variable width of cleat (DW), are introduced and implemented in the numerical model to explicitly evaluate the acoustic stimulation effects. The results indicate that these parameters could accurately represent the variations of acoustic energy and geometrical parameters of the coal cleat model.(2) The polarized wave induced wave dynamics in a coal sample with a single cleat model is numerically simulated and analyzed; the energy trapping and dynamic variation of fracture width in coal for the cleat model with three different filled media (i.e. air, water and weak mineral) are numerically analyzed and compared with each other subjected to different incident wave angles, and the optimal stimulation parameters are obtained through such sensitivity analysis. Simulation results show that the mechanical vibration is induced by the energy trapping effect; coal property (i.e. cleat and its filled media) and incident wave angles are crucial for acoustic stimulation to produce physical damages around coal cleats and enhance the permeability of fractured coal samples. II (3)The numerical simulation is further applied to simulate the viscoelastic wave propagation in 3D coal sample with a coal cleat system. Two kinds of coal cleat system model, orthogonal cleat sets (OCS) and T-junction cleat sets (TCS), are adopted to investigate the influence of coal cleats special structure for mechanical vibration. A stochastic model building process, which includes Monte Carlo method and von-Ká rmá n function, is proposed to better represent the structure of coal cleat system and hete...

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Wave motion in a viscous fluid-filled fracture

Cited by 17 publications

References 11 publications

Numerical modelling of acoustic stimulation induced mechanical vibration enhancing coal permeability

Numerical modelling of acoustic stimulation induced mechanical vibration enhancing coal permeability

Experimental study of pulsating water pressure propagation in CBM reservoirs during pulse hydraulic fracturing

Numerical simulation of acoustic stimulation for enhancing coal seam gas reservoir permeability

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