Effects of caprock sealing capacities on coalbed methane preservation: Experimental investigation and case study

Tian, Fuchao; Liang, Yuntao; Wang, Biao; Jin, Kan

doi:10.1007/s11771-019-4061-3

Cited by 7 publications

(4 citation statements)

References 22 publications

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“…QGP coal on the air-dried basis was used as the raw material which was repeatedly crushed and sieved by a crusher and a screen mesh for preparing the coal sample with a particle size of more than 200 meshes. Then, 200 g of sample were randomly selected for testing 12 .…”

Section: Coal Sample Preparation and Experimental Methodsmentioning

confidence: 99%

Structural characterization analysis and macromolecular model construction of coal from Qinggangping coal mine

Li,

Qin,

Ren

2023

Sci Rep

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Understanding the molecular structure characteristics of coal at the molecular level is of great significance to realize the rational utilization and efficient conversion of coal. This paper gives insights into the acquisition of characterization parameters of coal molecular microstructure by testing and analyzing the long flame coal from Qinggangping (QGP) Coal Mine through proximate analysis, ultimate analysis, vitrinite reflectance determination, fourier transform infrared Spectroscopy test (FTIR), X-ray photoelectron epectroscopy test (XPS), carbon nuclear magnetic resonance (13C-NMR) and X-ray diffraction (XRD). The results show that benzene rings in the QGP coal are mainly connected in a disubstituted way, accounting for 36.48%. Oxygen atoms mainly exist in the oxygen-containing functional groups such as the ether C–O, C=O and –COO. Aliphatic hydrocarbons in the aliphatic group are mainly of symmetrical -CHx stretching vibration. Hydroxyl groups are mainly composed of OH–OH and OH–O hydrogen bonds, accounting for 29.21% and 21.53%, respectively. Nitrogen atoms exist in the form of C4H5N. The coal molecular is mainly of aromatic carbon structure, where the ratio of bridge aromatic carbon to peripheral carbon is 0.198. There are benzene, naphthalene and anthracene in the coal molecular structure, and the former two chemicals play a dominating role. According to the analysis results, the molecular formula of the QGP coal is finally determined as C205H181O29N3S. On this basis, the two-dimensional and three-dimensional macromolecular models are constructed with the assistance of simulation software. In addition, the 13C-NMR spectra and densities of the constructed molecular models are calculated, which verifies the rationality of the models. The macromolecular structure model of bituminous coal constructed in this study provides a theoretical model basis for the optimal surfactant.

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Section: Coal Sample Preparation and Experimental Methodsmentioning

confidence: 99%

Structural characterization analysis and macromolecular model construction of coal from Qinggangping coal mine

Li,

Qin,

Ren

2023

Sci Rep

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“… 69 , 70 Due to the drop of reservoir pressure of the coal seam or the increase of the temperature of the coal seam, etc., the adsorption capacity of coal for gas weakens. Then the adsorbed CBM is desorbed and accumulated in the microstructures, 71 generating a pressure gradient that leads to CBM escape by diffusion 72 , 73 and viscous flow. 74 − 76 The escape of CBM is mainly controlled by the coal permeability 76 and concentration gradient of the gas phase.…”

Section: Geological Controls Of the Gas Contentmentioning

confidence: 99%

“…Coal beds are both the source rock and the reservoir rock for CBM. − The coal thickness variation is closely linked with depositional setting and tectonic activities, which have strong influences on the distribution and migration pathways of CBM. ,,, The CBM mainly exists on the micropore surface of the coal matrix in the adsorbed state. , Due to the drop of reservoir pressure of the coal seam or the increase of the temperature of the coal seam, etc., the adsorption capacity of coal for gas weakens. Then the adsorbed CBM is desorbed and accumulated in the microstructures, generating a pressure gradient that leads to CBM escape by diffusion , and viscous flow. − The escape of CBM is mainly controlled by the coal permeability and concentration gradient of the gas phase . Wei et al demonstrated that the greater the coal seam thickness, the longer it will take to reach the median concentration or the end of diffusion.…”

Section: Geological Controls Of the Gas Contentmentioning

confidence: 99%

Geological Controls on the Gas Content and Permeability of Coal Reservoirs in the Daning Block, Southern Qinshui Basin

et al. 2022

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The gas content and permeability of the coal reservoir are the key factors affecting coalbed methane (CBM) productivity. To investigate the geological controls on the permeability and gas content of coal reservoirs in the Daning block, southern Qinshui Basin, geological surveys combined with laboratory experiments, including coal petrology analysis, proximate analysis, and methane isothermal adsorption experiments, were carried out. The results show that the gas content of coals in the Daning block ranges from 5.56 to 17.57 (avg. 12.83) m 3 /t, and the coal permeability is generally above 0.1 mD, averaging 0.96 mD. The gas content of coal reservoirs shows decreasing trends with the increase in ash yield and moisture content, while tends to increase with the increase of vitrinite content; however, the correlation coefficients are all extremely low. The gas content presents a strong positive correlation with the burial depth of coal seams, but overall poorly correlates with the coal thickness. The CBM-rich areas are generally located at the hinge zones of secondary synclines, while the lower gas content areas commonly occur at the hinge zones of secondary anticlines. The normal faults are developed in the Daning block, and as expected, the gas content of coal seams that are near the normal faults is commonly lower. It was found that the well testing permeability of coal reservoirs in the Daning block decreases exponentially with the increase of the minimum horizontal stress (σ h ) and the maximum horizontal principal stress (σ H ). With the increase of the burial depth, the coal permeability also decreases exponentially. The primary and cataclastic structure coals generally have a higher hydro-fracturing permeability than the granulitic and mylonitic structure coals. This work can serve as a guide for the target area selections of CBM enrichment and high production in the Daning block.

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“…Simultaneously, the advancement of mining technology must align with the geological occurrence and structural characteristics of coal seams. For example, the cap rock plays a vital role in trapping coalbed methane reservoirs [26]. It is worth noting that coal seams buried at depths exceeding 1000 m are commonly referred to as deep coalbed methane reservoirs.…”

mentioning

confidence: 99%

Geomechanics for Energy and the Environment

Feng,

Xie,

Liu

et al. 2023

Energies

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Effects of caprock sealing capacities on coalbed methane preservation: Experimental investigation and case study

Cited by 7 publications

References 22 publications

Structural characterization analysis and macromolecular model construction of coal from Qinggangping coal mine

Structural characterization analysis and macromolecular model construction of coal from Qinggangping coal mine

Geological Controls on the Gas Content and Permeability of Coal Reservoirs in the Daning Block, Southern Qinshui Basin

Geomechanics for Energy and the Environment

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