The mechanisms of gas generation during coal deformation: Preliminary observations

Xu, Ruijie; Li, Huijun; Guo, Chenchen; Hou, Quanlin

doi:10.1016/j.fuel.2013.09.035

Cited by 55 publications

(47 citation statements)

References 17 publications

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“…The carbonyl fell from the aromatic ring and formed CO, which probably caused the failure of the secondary structure defects rebuilt, resulting in the increasing value of A D . This speculation was supported by the mentioned results calculated by the quantum chemical calculation (Xu et al, 2014).…”

Section: Raman Spectroscopysupporting

confidence: 53%

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The effect of different deformation mechanisms on the chemical structure of anthracite coals

Hou

et al. 2015

Sci. China Earth Sci.

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To study the effect of different deformation mechanisms on the chemical structure of anthracite coals and further understand the correlation between changed chemical structures and coal and gas outburst, ten groups of sub-high-temperature and sub-high-pressure deformation experiments were performed. All samples maintained primary structure, which were collected from the Qudi Mine in the southern Qinshui Basin of China. The samples were analyzed by ultimate analysis, Vitrinite Reflection (VR), Fourier Transform Infrared spectroscopy (FTIR), and Raman spectroscopy both before and after deformation experiments for contrasting. The results showed that the VR values of all samples after experiments were significantly higher than before experiments, which suggested that the metamorphism degree of anthracite coals was increased by deformation. The results also indicated that both temperature and strain rate had significant effects on the chemical structure of anthracite coals. At a high strain rate of 4×10 5 s 1 , the deformation of the samples was mainly brittle in which the mechanical energy was transformed mainly into frictional energy. In this situation, all samples developed several distinct fractured surfaces and the change of chemical structures was not obvious. On the contrary, with the decrease of the strain rates, the ductile deformation was dominated and the mechanical energy was mainly transformed into strain energy, resulting in the accumulation of deformation energy confessed by increasing quantity of dislocation and creep in the coal's interior nucleus. The absorption in the aromatic ring groups increased; otherwise the absorption in the aliphatic structures and ether oxygen groups decreased rapidly. During these experiments, CO was collected from two experimental samples. The number of aromatic rings and the structure defects within the two generated gas samples increased and the degree of molecular structure orders decreased. anthracite coal, deformation experiment, VR, Vitrinite Reflection Indicating surface (VRI), secondary structure defect Citation: Xu R T, Li H J, Hou Q L, et al. 2015. The effect of different deformation mechanisms on the chemical structure of anthracite coals. Science China: Earth Sciences,

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Section: Raman Spectroscopysupporting

confidence: 53%

“…(a) the partial molecular structure of four benzenes, one hexatomic ring and one carbonyl; (b) the partial molecular structure of eight benzenes, one hexatomic ring and one carbonyl. FromXu et al (2014).…”

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confidence: 99%

The effect of different deformation mechanisms on the chemical structure of anthracite coals

Hou

et al. 2015

Sci. China Earth Sci.

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“…The pore properties are related to the complex physical and chemical structures of coals (Bustin et al, 1995;Firouzi et al, 2014;Xu et al, 2014). The flow property and storage capacity of gas in coals vary due to the heterogeneous textural structure of coals.…”

Section: Introductionmentioning

confidence: 99%

Multifractal analysis of Hg pore size distributions of tectonically deformed coals

Liu

Song

2015

International Journal of Coal Geology

177

167

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“…At CBM production sites in most coal mines in China, the vertical stress on the coal seam is in most cases larger than the horizontal stresses [27]. In order to investigate the influence of horizontal stress difference on fracture morphology, the vertical stress for the experiments was set at 15 MPa, the maximum horizontal principal stress was 12 MPa, and the minimum horizontal principal stresses were 6, 7 and 8 MPa.…”

Section: Methodsmentioning

confidence: 99%

A New Tree-Type Fracturing Method for Stimulating Coal Seam Gas Reservoirs

et al. 2017

Energies

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Hydraulic fracturing is used widely to stimulate coalbed methane production in coal mines. However, some factors associated with conventional hydraulic fracturing, such as the simple morphology of the fractures it generates and inhomogeneous stress relief, limit its scope of application in coal mines. These problems mean that gas extraction efficiency is low. Conventional fracturing may leave hidden pockets of gas, which will be safety hazards for subsequent coal mining operations. Based on a new drilling technique applicable to drilling boreholes in coal seams, this paper proposes a tree-type fracturing technique for stimulating reservoir volumes. Tree-type fracturing simulation experiments using a large-scale triaxial testing apparatus were conducted in the laboratory. In contrast to the single hole drilled for conventional hydraulic fracturing, the tree-type sub-boreholes induce radial and tangential fractures that form complex fracture networks. These fracture networks can eliminate the "blank area" that may host dangerous gas pockets. Gas seepage in tree-type fractures was analyzed, and gas seepage tests after tree-type fracturing showed that permeability was greatly enhanced. The equipment developed for tree-type fracturing was tested in the Fengchun underground coal mine in China. After implementing tree-type fracturing, the gas extraction rate was around 2.3 times greater than that for traditional fracturing, and the extraction rate remained high for a long time during a 30-day test. This shortened the gas drainage time and improved gas extraction efficiency.

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The mechanisms of gas generation during coal deformation: Preliminary observations

Cited by 55 publications

References 17 publications

The effect of different deformation mechanisms on the chemical structure of anthracite coals

The effect of different deformation mechanisms on the chemical structure of anthracite coals

Multifractal analysis of Hg pore size distributions of tectonically deformed coals

A New Tree-Type Fracturing Method for Stimulating Coal Seam Gas Reservoirs

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