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

Zhai, Cheng; Yu, Xu; Xiang, Xianwei; Li, Quangui; Wu, Shiliang; Xu, Jizhao

doi:10.1016/j.jngse.2015.04.027

Cited by 76 publications

(35 citation statements)

References 22 publications

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“…e parameters of permeability and porosity play an important role in the study of accumulation and development of coalbed methane [2][3][4]. To increase the permeability of those coal seams, underground hydraulic fracturing technology to transform the seam structure is an effective way to achieve this goal [5][6][7][8][9][10][11].…”

Section: Introductionmentioning

confidence: 99%

An Elastoplastic Softening Damage Model for Hydraulic Fracturing in Soft Coal Seams

Yang

Mao

et al. 2018

Advances in Civil Engineering

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In order to improve the permeability of soft coal seams with low intensity and permeability by hydraulic fracturing, an elastoplastic softening damage model of soft coal seams has been established, which takes into consideration the lower elastic modulus and tensile strength and higher pore compressibility and plastic deformation. e model then was implemented to FLAC3D finite difference software to be verified with the on-site results of the Number 2709 coalface in Datong coal mine, China. e modelling results of fracture-influenced radius show good consistency with on-site results. en the parameters of water injection rate and time on fracture-influenced radius were studied. e results indicate that the fracture-influenced radius increases rapidly with an increased injection rate initially. After reaching the maximum value, fracture-influenced radius decreases slowly with further increase of the injection rate. Finally, it remains constant. e fracture-influenced radius rapidly increases initially at a certain time and then slowly increases with the injection time. e novel model and numerical method could be used to predict the radius of hydraulic fracture-influenced area and choose the suitable injection parameters to help the on-site work more efficiently.

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Section: Introductionmentioning

confidence: 99%

An Elastoplastic Softening Damage Model for Hydraulic Fracturing in Soft Coal Seams

Yang

Mao

et al. 2018

Advances in Civil Engineering

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“…In the cylindrical-coordinate system of the borehole, the stress state of a specific point around the borehole wall can be described by Equation (3): When the borehole is perpendicular to the coal seam, γ = 0 and the stress state of the borehole and the coal seam are as is shown in Figure 2. The stress state on the borehole wall can be obtained by converting the Cartesian coordinates of the in situ rock stress [18], as shown in Equation (2): 2 β`σ h sin 2 β˘cos 2 α`σ v sin 2 α σ y " σ H sin 2 β`σ h cos 2 β σ z "`σ H cos 2 β`σ h sin 2 β˘sin 2 α`σ v cos 2 α τ xy "`σ h´σH˘c osαcosβsinβ τ yz "`σ h´σH˘s inαcosβsinβ τ zx "`σ H cos 2 β`σ h sin 2 β´σ v2 sin2α (2) where σ x , σ y , σ z , τ xy , τ yz , and τ zx are the normal and shear stresses in the local coordinate system (x,y,z); σ v is the vertical principal stress (MPa); σ H and σ h are the major and minor horizontal principal stresses (MPa); and β is the azimuth of the major principle stress (˝). When the borehole is perpendicular to the coal seam, γ = 0 and the stress state of the borehole and the coal seam are as is shown in Figure 2.…”

Section: Initiation Location In a Coal Seammentioning

confidence: 99%

“…At present, to enhance gas drainage efficiency in a low-permeability coal seam, hydraulic fracturing (HF) is used as a standard practice [1][2][3]. It achieves good results draining coal bed methane in most coal mines.…”

Section: Introductionmentioning

confidence: 99%

Determination of Fracture Initiation Locations during Cross-Measure Drilling for Hydraulic Fracturing of Coal Seams

Cheng

et al. 2016

Energies

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When drilling coal-bearing sequences to enhance coal seam permeability by hydraulic fracturing (HF), the location where fractures are initiated is important. To date, most research on fracture initiation has studied the problem in two dimensions. In this study, a three-dimensional model to assess initiation location is developed. The model analyzes the stress state of both the borehole wall and the coal-rock interface and the model shows that the fracture initiation location is affected by in situ stress, the dip of the coal seam, and the angle between the borehole and the coal seam. How the initiation location changes near different types of geological faults is calculated by assuming typical in situ stresses for the faults. Following these calculations, physical experiments were carried out to emulate cross-measure hydraulic fracturing under stress conditions equivalent to those in the Chongqing Tonghua coal mine, China. Fracture initiation during the experiments was monitored by an acoustic emission system. The experimental results were consistent with the theoretical calculations. This implies that the three-dimensional model for assessing the locations of fracture initiation can be applied to forecast the initiation location of fractures generated by cross-measure drilling. The assessment model provides reference values for this type of drilling in underground mines.

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“…China is rich in coalbed methane (CBM) resources, and has a high content of CBM; however, in most cases the conditions in which CBM occurs are complex and the permeability of the coal seam is very low [2]. CBM in China is obtained largely by underground gas extraction in coal mines.…”

Section: Introductionmentioning

confidence: 99%

“…Presently, high-pressure hydraulic fracturing is used in industrial experiments in some Chinese mines [3]. Widespread research has been carried out on the process and effects of hydraulic fracturing, and the related technologies and equipment used in underground coal mines [2][3][4][5][6][7]. Hydraulic fracturing is an extremely complex fluid-solid coupling process of fractured rock mass; because of the complexity of the scale effect and site conditions, the evolution of fractures in coal and rock is difficult to study in laboratory experiments, and field tests are costly and non-repeatable.…”

Section: Introductionmentioning

confidence: 99%

Numerical study of hydraulic fracturing fracture area changing rules in underground coal mine

Ge¹,

Zhang²,

Lu³

et al. 2017

Vib. proced.

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Abstract. To investigate the relationship between the fractured area created by hydraulic fracturing and various fracturing parameters of underground coal mines, we applied fracture and porous media fluid-solid coupling theory to establish a numerical model of hydraulic fracturing. Three-dimensional numerical simulation of hydraulic fracturing of coal seam in a coalmine was performed using the proposed numerical model. We examined the relations between the fractured area and the injection volume, injection rate, and viscosity of the fracturing fluid. The results showed that the fractured area increased with increasing injection rate, however, the extension rate slowed down; the fractured area initially increased then decreased with increasing viscosity; the fractured area increases rapidly with the increase of the water injection volume at the beginning, then begin to slow, eventually approximate linear growth.

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

Cited by 76 publications

References 22 publications

An Elastoplastic Softening Damage Model for Hydraulic Fracturing in Soft Coal Seams

An Elastoplastic Softening Damage Model for Hydraulic Fracturing in Soft Coal Seams

Determination of Fracture Initiation Locations during Cross-Measure Drilling for Hydraulic Fracturing of Coal Seams

Numerical study of hydraulic fracturing fracture area changing rules in underground coal mine

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