Geometry and Filling Features of Hydraulic Fractures in Coalbed Methane Reservoirs Based on Subsurface Observations

Li, R.; Wang, S. W.; Lyu, Shuaifeng; Lu, Weicong; Li, G. F.; Wang, J. C.

doi:10.1007/s00603-020-02046-x

Cited by 11 publications

(9 citation statements)

References 25 publications

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“…The width of the main fracture after hydraulic fracturing is much larger than that of the natural fracture, with a range of 1–20 cm . The hydraulic fracturing area is also filled with proppant, a material that has no adsorption or desorption effect. ,, Therefore, the effect of the strain induced by adsorption/desorption on the permeability of hydraulic fractures was negligible in this study, and the increase of the effective stress caused by the reduction of reservoir pressure was the main factor affecting the permeability. Based on this, the permeability of the area dominated by hydraulic fractures can be simplified as follows where k f0 is the permeability of the hydraulic fracturing area, in m 2 ; and C ff represents the fracture compressibility of the hydraulic fracturing area, in MPa –1 .…”

Section: Model Developmentmentioning

confidence: 77%

“…The width of the main fracture after hydraulic fracturing is much larger than that of the natural fracture, with a range of 1−20 cm. 36 The hydraulic fracturing area is also filled with proppant, a material that has no adsorption or desorption effect. 3,19,36 Therefore, the effect of the strain induced by adsorption/desorption on the permeability of hydraulic fractures was negligible in this study, and the increase of the effective stress caused by the reduction of reservoir pressure was the main factor affecting the permeability.…”

Section: Model Developmentmentioning

confidence: 99%

“…36 The hydraulic fracturing area is also filled with proppant, a material that has no adsorption or desorption effect. 3,19,36 Therefore, the effect of the strain induced by adsorption/desorption on the permeability of hydraulic fractures was negligible in this study, and the increase of the effective stress caused by the reduction of reservoir pressure was the main factor affecting the permeability. Based on this, the permeability of the area dominated by hydraulic fractures can be simplified as follows…”

Section: Model Developmentmentioning

confidence: 99%

“…from Chen et al16 and Li et al,36 the half-length of hydraulic fractures ranges from 8 to 115 m.2.3. Relative Permeability.…”

mentioning

confidence: 93%

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Two-Phase Flow Model of Coalbed Methane Extraction with Different Permeability Evolutions for Hydraulic Fractures and Coal Reservoirs

et al. 2021

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Fluid flow modeling of coalbed methane (CBM) wells is effective in predicting gas production and designing appropriate depressurization schemes. Moreover, hydraulic fracturing is an important measure for improving the permeability of CBM reservoirs. In this work, we assumed the hydraulic fracture area near the main fracture to be rectangular. We developed a gas–water two-phase flow model considering the difference in stress sensitivity between the hydraulic fracturing area and the original coal reservoir. The numerical simulation results indicate that our model can accurately predict the production of CBM wells. In the early stage of CBM extraction, gas production increased with the increase of gas relative permeability. When the water saturation was below 0.7, the relative permeability of the gas phase was difficult to increase. At this time, the absolute permeability of the hydraulic fracturing area continued to decrease, leading to a decrease in gas production. Thus, if the difference of permeability evolution between the two areas is not considered, the production of CBM wells will be overestimated. In the process of CBM extraction, both reservoir pressure and water saturation decreased, but the distribution was inconsistent. The variation in reservoir pressure was mainly affected by absolute permeability and gas desorption, while the variation of water saturation was further affected by the distribution of relative permeability and initial water saturation. Therefore, the evolution of water saturation is generally more complex than that of reservoir pressure. In the hydraulic fracturing area, the effect of fracture compressibility on gas production was greater than the initial permeability. In the original coal reservoir, the larger initial permeability was more beneficial than the fracture compressibility for improving the production of CBM wells.

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Section: Model Developmentmentioning

confidence: 77%

Section: Model Developmentmentioning

confidence: 99%

Section: Model Developmentmentioning

confidence: 99%

“…from Chen et al16 and Li et al,36 the half-length of hydraulic fractures ranges from 8 to 115 m.2.3. Relative Permeability.…”

mentioning

confidence: 93%

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Two-Phase Flow Model of Coalbed Methane Extraction with Different Permeability Evolutions for Hydraulic Fractures and Coal Reservoirs

et al. 2021

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“…The main mineable coal seam in Xinyuan Coal Mine is No. 3 coal seam in the middle of Permian Shanxi Formation (Li et al., 2020; Lyu et al., 2020). The thickness of the coal seam ranges from 0.40 to 4.75 m with an average of 2.80 m. The buried depth is 500–800 m (Figure 1a).…”

Section: Materials and Methodologymentioning

confidence: 99%

Microstructure Analysis on the Fracture Network in High‐Rank Coals

Lyu

Chen

Li³

et al. 2021

Earth and Space Science

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Microfractures in the coal matrix have complex spatial structure because of the joint effects of coalification and tectonism. The accurate modeling and characterization of microfractures directly affect mechanism analysis of coal rock fracturing and mining. In this study, taking the high-rank coal in the north of Qinshui Basin, structural characteristics of microfracture in intact and tectonic coals were analyzed systematically using 2D thin section, 3D micro-CT modeling and mercury intrusion based on digital image analysis and fractal theory. Result indicates that response sensitivity of fractal parameters obtained from different methods to microfractures from two types of coal structures is different greatly. Single fractal dimension (Df) in tectonic coal is higher than that of intact coal. Specially, for 2D thin sections, the indicative effect on the Df of manually-corrected images is better than that of automaticallyextracted and linear ones. Df has a positive correlation with the pixel-based microfracture porosity, as well as generalized fractal parameters. Moreover, microfracture permeability based on the Cubic-Law increases with the increase of Df. For 3D micro-CT modeling, the classical Watershed algorithm cannot segment the spatial microfracture network, which however can be segmented and characterized by the self-developed FracSC3D program. Spatial microstructural parameters including volume, surface and length at three-axis directions meet bi-fractal characteristics.Specially, for 2D micro-CT slices, with the increase of porosity, the multifractal spectrum width Δα also increased.

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Experimental Study on the Damage and Cracking Characteristics of Bedded Coal Subjected to Liquid Nitrogen Cooling

Gao

Cai

et al. 2021

Rock Mech Rock Eng

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Geometry and Filling Features of Hydraulic Fractures in Coalbed Methane Reservoirs Based on Subsurface Observations

Cited by 11 publications

References 25 publications

Two-Phase Flow Model of Coalbed Methane Extraction with Different Permeability Evolutions for Hydraulic Fractures and Coal Reservoirs

Two-Phase Flow Model of Coalbed Methane Extraction with Different Permeability Evolutions for Hydraulic Fractures and Coal Reservoirs

Microstructure Analysis on the Fracture Network in High‐Rank Coals

Experimental Study on the Damage and Cracking Characteristics of Bedded Coal Subjected to Liquid Nitrogen Cooling

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