The characteristics and origins of cleat in coal from Western North China

Su, Xinming; Feng, Yinchang; Chen, Jiangfeng; Pan, Jienan

doi:10.1016/s0166-5162(01)00026-x

Cited by 139 publications

(73 citation statements)

References 6 publications

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“…This is in contrast to hard coal, which are intensively examined, among other reasons because they contain coalbed methane -CBM (e.g. McCulloch et al, 1974McCulloch et al, , 1976Close & Mavor, 1991;Close, 1993;Law, 1993;Karacan & Okandan, 2000;Su et al, 2001;Solano-Acosta et al, 2007;Dawson & Esterle, 2010;Paul & Chatterjee, 2011). The present contribution is the first to focus purely on discontinuities within the Miocene MPLS-1 of central Poland.…”

Section: Introductionmentioning

confidence: 85%

“…McCulloch et al, 1974;Laubach et al, 1998;Su et al, 2001). Cleats are natural opening-mode fractures that are almost perpendicular to the bottom and roof of the coal seam.…”

Section: Cleat Definitionmentioning

confidence: 99%

“…In contrast, the latter type represents cleats resulting from external forces such as tectonics. Regardless of the suggested 'endogenic' processes, at least the cleat orientation seems to be controlled by the tectonic stress field (Laubach et al, 1998;Su et al, 2001;Solano-Acosta et al, 2007;Dawson & Esterle, 2010;Paul & Chatterjee, 2011; and references therein).…”

Section: Genetic Cleat Classificationmentioning

confidence: 99%

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What are cleats? Preliminary studies from the Konin lignite mine, Miocene of central Poland

Widera

2014

Geologos

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Cleats (fractures, joints) are discontinuities in coals, including lignites. They are important in mining activity because of their gas and water permeability in hard coal, and mainly because of their water permeability in lignites. As opposed to hard-coal cleats, lignite cleats have not been studied in detail before. The present contribution does so, using as an example the 1st Middle-Polish Lignite Seam (MPLS-1) in the Jóźwin IIB opencast mine in central Poland. It should be mentioned here that any remarks in the present contribution concerning MPLS-1 refer exclusively to this lignite seam in the Jóźwin IIB opencast mine.The investigated discontinuities consist of two sets, i.e. the face and butt cleats, which are roughly oriented NW-SE and NE-SW, respectively. The mean spacing of the face cleats is ~12.4 cm, while the mean spacing of the butt cleats is ~12.8 cm. The maximum average aperture is ~4.9 mm for the face cleats and ~4.1 mm for the butt cleats. The cleat spacing and aperture do not depend on the lignite thickness, but the cleat spacing increases with increasing mineral-matter and xylite content, whereas the aperture increases when the contents decrease. The regional folding and local salt diapirism tentatively explain the formation of the orthogonal system of the lignite cleats, partly because of the parallelism of the face cleats and the major tectonic directions in central Poland.

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Section: Introductionmentioning

confidence: 85%

“…McCulloch et al, 1974;Laubach et al, 1998;Su et al, 2001). Cleats are natural opening-mode fractures that are almost perpendicular to the bottom and roof of the coal seam.…”

Section: Cleat Definitionmentioning

confidence: 99%

Section: Genetic Cleat Classificationmentioning

confidence: 99%

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What are cleats? Preliminary studies from the Konin lignite mine, Miocene of central Poland

Widera

2014

Geologos

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“…Natural fractures of coal seam can be divided into horizontal bedding fracture and vertical cleat fracture. Methane is mainly stored in the pores by adsorbing on the micropore surface accounting for 70-95% [20,21] of the total reserves. Free methane mainly migrates in coal seam fractures following the convectiondiffusion equation.…”

Section: Background Of the Experimental Minementioning

confidence: 99%

The Migration of Coalbed Methane under Mining Pressure and Air Injection: A Case Study in China

Zhang

et al. 2018

Geofluids

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Gas outburst has always affected the safety of coal mining. To eliminate this risk by high-efficiency extraction of coalbed methane (CBM) in 4102 working face of number 3 coal seam in Hebi Number 3 coal mine, a model of CBM extraction in working face was established which was considering the mining impact of adjacent 4101 working face. In this model, the coupling relationships between stress, desorption, and migration of methane were analyzed. Moreover, we also studied the changes of methane pressure, plastic failure scope, and permeability of coal during the mining and then verified the results with the field data. And on this basis, a stimulation solution for methane extraction by injecting air into coal seam was presented, and the extraction effect was simulated. The simulation results show that the injection of air decreases the effective stress of coal which increases the permeability of coal and promotes the methane migration within the coal seam fractures. Besides, affected by the velocity of gas migration, the pressure drop between fractures and matrix will reduce with time while air injection can provide extra power for gas migration in fractures which causes the desorption and diffusion of methane in the matrix. So this stimulation solution can enhance the efficiency of gas extraction of coal seam and prevent gas outburst of the working face.

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“…The relative permeability behaviour of gas and water in the cleats of a coal seam gas (CSG) reservoir is dependent on many factors including fluid pressure, phase saturations, effective stress, the geometry of individual cleats, the interconnectedness of the cleat network, and the wettability of the coal (Saghafi et al, 2014;Su et al, 2001). Most laboratory studies that report relative permeability in coals measured by steady state or unsteady state core flooding methods derive a crossover point water saturation fraction (S w ) exceeding 0.5, which is usually interpreted as the coal being water wet or hydrophilic (Conway et al, 1995;Durucan et al, 2013;Ham and Kantzas, 2011;Purl et al, 1991;Rahman and Khaksar, 2007;Shen et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

The effect of rank, lithotype and roughness on contact angle measurements in coal cleats

Mahoney

Rufford

Johnson

et al. 2017

International Journal of Coal Geology

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The characteristics and origins of cleat in coal from Western North China

Cited by 139 publications

References 6 publications

What are cleats? Preliminary studies from the Konin lignite mine, Miocene of central Poland

What are cleats? Preliminary studies from the Konin lignite mine, Miocene of central Poland

The Migration of Coalbed Methane under Mining Pressure and Air Injection: A Case Study in China

The effect of rank, lithotype and roughness on contact angle measurements in coal cleats

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