Impact of coal matrix strains on the evolution of permeability

Peng, Yan; Liu, Jishan; Pan, Zhejun; Connell, Luke D.; Chen, Zhongwei; Qu, Hao

doi:10.1016/j.fuel.2016.10.086

Cited by 73 publications

(57 citation statements)

References 40 publications

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“…e relationships between w c , w θ , w ψ , and volumetric plastic shear strain ε sp v are shown in Table 2. In order to verify the on-site test results, the injection rate was set at 2 * 10 −3 m 3 /s, and the water injection volume was xed at 150 m 3 and was applied directly at the fracture Advances in Civil Engineering 7…”

Section: Modelling Descriptionmentioning

confidence: 99%

“…is study undertakes quantitative analysis of only two major factors: the injection rate and injection time to simulate the impact on crack growth. erefore, the water injection volume was xed at 150 m 3 and was applied directly at the fracture hole. e injection rate and injection time varied from 1 * 10 −3 m 3 /s to 1 * 10 −2 m 3 /s and 0 hour to 10 hours, respectively.…”

Section: Sensitivity Studymentioning

confidence: 99%

“…Hence, conventional methods cannot effectively drain gas from those seams [1]. 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%

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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: Modelling Descriptionmentioning

confidence: 99%

Section: Sensitivity Studymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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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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“…CO2 adsorption-induced volume strain has been studied by many researchers under unconfined conditions or uniaxial strain conditions [28,38,42]. In this section, we consider the adsorption-induced strain from the perspective of unconfined conditions.…”

Section: Adsorption-induced Swelling Strainmentioning

confidence: 99%

Strength Reduction of Coal Pillar after CO2 Sequestration in Abandoned Coal Mines

Liu

Wang

et al. 2017

Minerals

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CO 2 geosequestration is currently considered to be the most effective and economical method to dispose of artificial greenhouse gases. There are a large number of coal mines that will be scrapped, and some of them are located in deep formations in China. CO 2 storage in abandoned coal mines will be a potential option for greenhouse gas disposal. However, CO 2 trapping in deep coal pillars would induce swelling effects of coal matrix. Adsorption-induced swelling not only modifies the volume and permeability of coal mass, but also causes the basic physical and mechanical properties changing, such as elastic modulus and Poisson ratio. It eventually results in some reduction in pillar strength. Based on the fractional swelling as a function of time and different loading pressure steps, the relationship between volumetric stress and adsorption pressure increment is acquired. Eventually, this paper presents a theory model to analyze the pillar strength reduction after CO 2 adsorption. The model provides a method to quantitatively describe the interrelation of volumetric strain, swelling stress, and mechanical strength reduction after gas adsorption under the condition of step-by-step pressure loading and the non-Langmuir isothermal model. The model might have a significantly important implication for predicting the swelling stress and mechanical behaviors of coal pillars during CO 2 sequestration in abandoned coal mines.

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“…Some models considered the variation of stress and just focused on gas flow principles. Cao et al [2] and Peng et al [21] developed a model considering the deformation induced by the changes in effective stress. In these studies, only the matrix mechanical deformation is taken into account and the mechanical interactions between the matrix and kerogen/micro-fracture induced by the differential pressure are ignored.…”

Section: Introductionmentioning

confidence: 99%

Impact of Local Effects on the Evolution of Unconventional Rock Permeability

Ma¹,

Li²,

Zhang

et al. 2019

Energies

Self Cite

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When gas is extracted from unconventional rock, local equilibrium conditions between matrixes and fractures are destroyed and significant local effects are introduced. Although the interactions between the matrix and fracture have a strong influence on the permeability evolution, they are not understood well. This may be the reason why permeability models in commercial codes do not include the matrix-fracture interactions. In this study, we introduced the local force to define the interactions between the matrix and the fracture and derived a set of partial differential equations to define the full coupling of rock deformation and gas flow both in the matrix and in the fracture systems. The full set of cross-coupling formulations were solved to generate permeability evolution profiles during unconventional gas extraction. The results of this study demonstrate that the contrast between the matrix and fracture properties controls the processes and their evolutions. The primary reason is the gas diffusion from fractures to matrixes. The diffusion changes the force balance, mass exchange and deformation.

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Impact of coal matrix strains on the evolution of permeability

Cited by 73 publications

References 40 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

Strength Reduction of Coal Pillar after CO2 Sequestration in Abandoned Coal Mines

Impact of Local Effects on the Evolution of Unconventional Rock Permeability

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