Measurement of the coefficient of seepage characteristics in pore-crushed coal bodies around gas extraction boreholes

Pang, Mingkun; Zhang, Tianjun; Ji, Xiang; Wu, Jinyu; Song, Shushu

doi:10.1016/j.energy.2022.124276

Cited by 20 publications

(6 citation statements)

References 21 publications

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“…The modulus of elasticity is a common method for detecting damage counts with the modulus of elasticity damage equation [ 33 , 34 ]: Where: D is the elastic modulus damage variable, E denotes the elastic modulus of the coal rock material at the time of damage, and E 0 is the elastic modulus of the coal rock material at the time of no damage.…”

Section: Resultsmentioning

confidence: 99%

Experimental investigation of the creep damage evolution of coal rock around gas extraction boreholes at different water contents

et al. 2023

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The creep process of the coal rock around the extraction boreholes under stress-water coupling is an important factor affecting the stability of the boreholes. To study the influence of the water content of perimeter of the coal rock around the boreholes on its creep damage, a creep intrinsic model considering water damage was established by introducing the plastic element model from the Nishihara model. To study the steady-state strain and damage evolution of coal rocks containing pores, and verify the practicality of the model, a graded loading water-bearing creep test was designed to explore the role of different water-bearing conditions in the creep process. The following conclusions were obtained: 1) water has a physical erosion and softening water wedge effect on the perimeter of the coal rock around the boreholes, which affects the loading axial strain and displacement of the perforated specimens; 2) an increase in water content reduces the time taken for perforated specimens to enter the creep phase, making the accelerated creep phase come earlier; 3) the parameters of the water damage model are considered to be exponentially related with the water content. The experimental data are similar to the results of the model parameters, and the model shows some practicality; 4) the damage variables in the accelerated creep phase increase rapidly throughout the creep process, leading to local instability in the borehole. The findings of the study provide important theoretical implications for the study of instability in gas extraction boreholes.

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Section: Resultsmentioning

confidence: 99%

Experimental investigation of the creep damage evolution of coal rock around gas extraction boreholes at different water contents

et al. 2023

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“…On this basis, it was obtained that the relationship between permeability, non-Darcy coefficient, and porosity of crushed sample can be fitted using an exponential function . Gas permeability experiments with different stress carried out on crushed coal and rock were used to construct a stress-permeability fitting model by varying the stress conditions and the number of cycles of loading and unloading. , Under constant total stress, permeability to sorption gas increases with a decrease of pressure due to crushed coal and rock swelling , and decreases with increasing pressure due to matrix shrinkage. , Pang et al and Zhang et al , studied the permeability evolution of crushed coal with different porosities and found that porosity is the main factor determining the permeability of crushed coal samples.…”

Section: Introductionmentioning

confidence: 99%

“… 36 , 37 Under constant total stress, permeability to sorption gas increases with a decrease of pressure due to crushed coal and rock swelling 38 , 39 and decreases with increasing pressure due to matrix shrinkage. 40 , 41 Pang et al and Zhang et al 42 , 43 studied the permeability evolution of crushed coal with different porosities and found that porosity is the main factor determining the permeability of crushed coal samples.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study on Compaction Deformation and Gas Permeability Properties for Crushed Limestone

Yang,

Li,

Wang

et al. 2024

ACS Omega

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The mining goaf is enriched in coalbed methane (CBM) resources, and it is imperative to realize its efficient extraction. The gas permeability properties of the crushed coal and rock in the caved zone of mining goaf are the basis for the study of its internal CBM migration and enrichment law. In this study, the compaction deformation and gas permeability properties of crushed limestone with different particle sizes were revealed. The results show that (1) the deformation resistance capacity of the crushed limestone increased with increasing stress. The decreasing trend of porosity of samples with different particle sizes in the early and later compression periods is significantly different. Particle RR of the lower layer is smaller than that of the other layers. (2) The permeability of the sample decreases with decreasing porosity and nitrogen pressure, and it is between 10 −12 and 10 −10 m 2 . Nitrogen migration within the crushed limestone requires the pseudo-threshold pressure gradient, which ranges from 64.86 to 311.42 Pa/m. (3) The average permeability growth amplitude of the sample shows a logarithmic decreasing trend with the decrease of porosity. The average permeability growth amplitude of the 5− 10 mm sample at the same porosity was 15.9−22.3 times that of the 0.315−0.63 mm sample. (4) The permeability of crushed limestone on both sides of the lower layer in the caved zone is much larger than that of other locations. The results are of great practical significance for accurately predicting the CBM enrichment area of mining goaf and then selecting the final position of the extraction drilling hole.

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“…Coal bodies around boreholes are affected by different moisture contents and exhibit distinct force characteristics. The crack sprouting, expansion and development processes in each stage are more complex and difficult to observe and characterize, especially regarding their influences on borehole sealing technology and the extraction effect [1][2][3][4][5]. Therefore, it is of great engineering significance to perform research on the image grayscale characteristics of coal bodies around boreholes with different moisture contents.…”

Section: Introductionmentioning

confidence: 99%

“…The rising trend of the moisture-containing specimen curve is slower, the surface strain is larger, and the stress is smaller than those of Stage II. With increasing moisture content, the specimen ratio σ cd /σ f obviously decreases by 5.1~11.3%, which indicates that water affects the crack initiation and stable expansion stage of the specimen and results in hysteresis in the specimen deformation behavior 4. Stage IV-crack nonstable extension stage.…”

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Study on the Grayscale Characteristics of Borehole Images of Progressive Failure of Coal Bodies with Different Moisture Contents

Pan

et al. 2022

Processes

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The failure process of a coal body around a borehole has progressive characteristics. Image characteristics can visually characterize the stress and failure characteristics of the coal body around a borehole during progressive failure. To investigate the effect of the moisture content on the progressive failure of the coal body around the borehole, an image test system for the deformation and fracture of coal rock was used, and progressive failure tests of coal body specimens with different moisture content conditions around boreholes were performed. We acquired images of the deformation field during the entire process of specimen failure. Based on the grayscale image theory, the variation in the grayscale characteristic parameters of the progressive failure process was analyzed. The results show that throughout the progressive failure of coal bodies with different moisture contents around a borehole, the main specimen failure can be divided into six stages: compression density, elastic deformation, crack initiation and stable extension, crack nonstable extension, post-peak softening, and post-peak failure. With increasing moisture content, the σcd/σf values of the 20%- and 40%-moisture-content specimens were 5.1% and 11.3% lower than those of the dry specimens, respectively, and the maximum uniaxial compressive strength σf was 5.1% and 17.4% lower than those of the dry specimens, respectively. The number of cracks that developed decreased. The grayscale histogram had a reduced grayscale peak at each stage, and the surface distortion diminished. The declining grayscale mean curve indicates a lagging development of stress concentration zones. The declining grayscale entropy curve indicates that macroscopic cracks form. The rising grayscale standard deviation curve indicates the delayed development of strain localization zones and weakening of specimen damage. The study explains the deformation and failure characteristics of the coal body around the borehole and the variation in grayness.

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Measurement of the coefficient of seepage characteristics in pore-crushed coal bodies around gas extraction boreholes

Cited by 20 publications

References 21 publications

Experimental investigation of the creep damage evolution of coal rock around gas extraction boreholes at different water contents

Experimental investigation of the creep damage evolution of coal rock around gas extraction boreholes at different water contents

Experimental Study on Compaction Deformation and Gas Permeability Properties for Crushed Limestone

Study on the Grayscale Characteristics of Borehole Images of Progressive Failure of Coal Bodies with Different Moisture Contents

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